Chapter 6 NutritionChapter 6 Nutrition
6.1 Types Of Nutrition
Learning Outcomes
• State the types of nutrition• Explain autotrophic nutrition• Explain heterotrophic nutrition• Classify organisms according to the types
of nutrition
Types of Nutrition• Nutrition is the entire process by which
organisms obtain energy from food, for growth, maintenance and repair of damaged tissues.
• The substances that are required for the nourishment of an organism are called nutrients.
• Living organisms can be divided into two main groups based on their nutritional habits : autotrophs and heterotrophs.
Chapter 6 Nutrition
Types Of Nutrition
Nutrition
Autotrophs(autos: self;
trophos : feed)
Heterotrophs(heteros: other)
1) Autotrophic nutrition• Autotrophs (autos: self; trophos: feed) are
organisms which practice autotrophic nutrition.
• Autotrophs synthesise complex organic compounds from raw, simple inorganic substances, such as air and water, by using light or chemical energy.
• Autotrophs manufacture their own food, either by photosynthesis or by chemosynthesis.
a) Photosynthesis • (photo: light) is the process in which green
plants, called photoautotrophs, produce organic molecules from carbon dioxide and water using sunlight as a source of energy.
b) Chemosynthesis • (chemo : chemical) is the process in which
chemoautotrophs synthesise organic compounds by oxidising inorganic substances such as hydrogen sulphide and ammonia.
1) Autotrophic nutrition
Examples of autotrophs
Photoautotrophs - Trees
Chemoautotrophs- Bacteria
2) Heterotrophic nutrition• Heterotrophs (hetero: other) are organisms that
cannot synthesise their own nutrients but must obtain the nutrients from other organisms.
• Heterotrophic nutrition is a type of nutrition in which an organism obtains energy through the intake and digestion of organic substances, usually plant and animal tissues.
• Heterotrophs may practise holozoic nutrition, saprophytism or parasitism.
a) Holozoic nutrition• A type of nutrition which the organisms feed
by ingesting solid organic matter which is subsequently digested and absorbed into their bodies.
• Some examples are humans, herbivores, carnivores and some carnivorous plants such as pitcher plants and Venus flytraps.
2) Heterotrophic nutrition
Examples of heterotrophs
Carnivorous plants (Holozoic nutrition-Pitcher plants
Holozoic nutrition - Carnivores
b) Saprophytism• A type of nutrition which the organisms, called
saprophytes, feed on dead and decaying organic matter.
• Examples are bacteria and fungi which digest their food externally before absorbing the nutrients into their bodies.
2) Heterotrophic nutrition
Saprophytes-Fungi
c) Parasitism • Is a close association in which an
organism, the parasite, obtains nutrients by living on (ectoparasite) or in the body (endoparasite) of another living organism, the host.
• The parasite absorbs readily digested food from its host.
• Examples of parasites include fleas and lice, various bacteria, fungi and the worms which infest the human intestinal tract.
2) Heterotrophic nutrition
Parasites Lice‑
Chapter 6 Nutrition
Types Of Nutrition
Nutrition
Autotrophs
Photosynthesis
Chemosynthesis
Process of synthesis of food by using light energy
Process of synthesis of food by using chemical energy
Chapter 6 Nutrition
Types Of Nutrition
Nutrition
Heterotrophs
SaprophytismHolozoic Paratism
Hunts and eat other organisms.
Absorbs nutrient from dead and decaying organic matter.
• Absorb nutrient from living hosts.
• Ectoparasites and endoparasites.
Chapter 6 NutritionChapter 6 Nutrition
6.2 Balanced Diet
Learning Outcomes• State the necessity for a balanced diet• explain the factors affecting the daily energy requirement
of the human body• Determine the energy value and nutrient content in food
samples• Explain the functions and sources of vitamins and minerals
in diet to maintain health• Explain the functions and sources of roughage or dietary
fibre in a diet • Explain the functions of water in the body• Justify the selection of an appropriate balanced diet for a
target group
Chapter 6 Nutrition
Balanced Diet
Contains correct proportions of all classes of food according to the needs of body.
Contains correct proportions of all classes of food according to the needs of body.
Balanced Diet
The Necessity for a
Balanced Diet
For various metabolic reactions.
Source of energy.
For growth and repair of damaged body tissue.
Chapter 6 Nutrition
Balanced Diet
Daily Energy Requirement
Energy value is quantity of heat released from the combustion of 1 gram of food.
During respiration, the energy is released in an oxidation process, which is similar to the combustion (burning) of food.
When the food is burnt, it releases energy, mainly in the form of heat
The assumption made is that respiration releases the same amount of energy as combustion does.
Chapter 6 Nutrition
Balanced Diet
Daily Energy Requirement
Unit of energy value = joule per gram (Jg-1).
Energy Content/ Value of food
• The amount of heat generated from the combustion of one gram of food is known as the energy value of the food.
• The unit used to describe energy values in food is joule per gram (J g-1).
• The amount of energy in food can also be expressed in terms of calories.
Energy content of food• Table 1 shows the calorific values for the three
main food classes.
Which class of food has the highest energy value?
Energy Content / Value of food• The energy content of a
particular food can be measured by burning a known mass of the food completely in the presence of oxygen in a bomb calorimeter
(Figure 1).• The bomb calorimeter is
used to calculate the energy value of various types of food samples.
• It consists of a container in which the food sample is sealed with excess oxygen.
• The electrical coil ignites the food sample.
Figure 1 : A food calorimeter or a bomb calorimeter
Figure 2: Apparatus set-up to determine the energy value in a food sample in the lab
• The energy content of a sample of food can be determined by first weighing the sample and then completely burning the food in an atmosphere of oxygen.
• The heat released by the burning food is transferred to a known volume of water, causing a rise in the temperature of the water.
• The energy value of food can be calculated as follows:
Energy Content / Value of food
• The following data show the results of an experiment to determine the energy value of a peanut.
Energy content of food
Nutrient Content in Food
• The nutrient content of different food samples can be determined by carrying out food tests.
• Certain foods are rich sources of a particular nutrient, for example, starch, proteins or lipids.
ITeach – Biology Form 4
Chapter 6 Nutrition
Balanced Diet
Nutrient Content in Food
VitaminsVitamins
Fat Soluble VitaminsWater Soluble
Vitamins
For maintenance of good health and efficient metabolism
Can be stored in body fat
Can be stored in body fat
Vitamins A, D,E,K Vitamins A, D,E,K
Obtained from daily diet
Obtained from daily diet
Vitamin B and C Vitamin B and C
ITeach – Biology Form 4
Chapter 6 Nutrition
Balanced Diet
Nutrient Content in Food
MineralsMinerals
Macrominerals Microminerals
• Vital for maintenance of good health
• Must be obtained through diet
Ex: Calcium, phosphorus
Required in large quantity 100mg / day
Required less than 20 mg / day
Ex: Ferum, iodine,zinc
Chapter 6 Nutrition
Balanced Diet
Roughage or Dietary Fibre
Made up of cellulose.
Stimulate peristalsis and prevent constipation
Eliminate toxic substances which can cause bowel cancer
Constipation result from deficiency of roughage.
ITeach – Biology Form 4
Chapter 6 Nutrition
Balanced Diet
WaterWater
Act as medium of transport for nutrients
Act as medium of transport for nutrients
Healthy adults need 2 to 2.5 litres of water a day.
Healthy adults need 2 to 2.5 litres of water a day.
Water loss need to be replaced to prevent dehydration.
Water loss need to be replaced to prevent dehydration.
Chapter 6 Nutrition
Balanced Diet
Selection of an Appropriate Balanced Diet
Lipids, salt and sugar
Meat and alternatives
Fruits and vegetables
Rice and alternatives
Level 4
Level 3
Level 2
Level 1
Which level we should take in a large quantity?
Chapter 6 NutritionChapter 6 Nutrition
6.3 Malnutrition
ITeach – Biology Form 4
Chapter 6 Nutrition
Malnutrition
MalnutritionOccurs when a person’s diet is not balanced.
Protein deficiency will lead to Kwashiorkor and Marasmus problems.
Deficiency diseases caused by inadequate intake of mainly vitamins, minerals and amino acids.
Osteoporosis result from a diet lacking in calcium.
Obesity will result in cardiovascular disease and diabetes mellitus.
Processing food can cause high blood pressure.
Kwashiorkor
Marasmus
Chapter 6 NutritionChapter 6 Nutrition
6.4 Food Digestion
ITeach – Biology Form 4
6.4 Food Digestion• The food we consume are complex organic
molecules which are too large to pass through plasma membranes and enter body cells.
• In order for food substances to be used by the human body, they have to be converted into a form that can be readily absorbed by the body cells.
• Digestion is the process that breaks down complex food substances into simpler, soluble molecules that are small enough for the body to absorb.
• Food digestion takes place in the alimentary canal, a long, muscular tract which extends from the mouth to the anus.
• The alimentary canal consists of the: • mouth• oral cavity • Pharynx• Oesophagus• Stomach• small intestine (duodenum, jejunum and ileum)• large intestine (appendix, caecum, colon,
rectum) • anus.
The Human Digestive System
• The small intestine constitutes two thirds of the length of the alimentary canal.
• Digestion breaks down:
carbohydrates into glucose moleculesproteins into amino acidslipids into glycerol and fatty acids.
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Breaks down of larger food substances to simpler soluble molecules, tiny enough for body to assimilate.
Food Digestion
Starchdigest
Glucose
Protein Amino Acids
Lipids Glycerol + Fatty Acids
digest
digest
• These essential substances are required by the body cells to carry out metabolic processes.
• For example:glucose is oxidised to generate energyamino acids are used to synthesise
proteins such as enzymes and hormoneslipids form a major component of
plasma membranes.
• As the food passes through the alimentary canal, it is broken down in stages until the digestible material is dissolved and absorbed.
• The indigestible residue is removed through the anus.
• Digestion involves both physical and chemical processes.
1) Physical digestion
• involves the breaking down of large pieces of food into smaller pieces by mechanical means. It starts in the mouth with the slicing and chewing action of the teeth.
• continues to a smaller extent in the stomach by the churning action brought about by the contraction of the muscles of the stomach wall.
2) Chemical digestion
• Process of breaking down of complex food molecules into simple soluble molecules by digestive enzymes.
• This process normally involves hydrolysis reactions. (involved/need water)
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Human Digestive System
Takes place in alimentary canal with aid of digestive juices.
Physical digestion - breaking down of large pieces of food into smaller pieces.
Chemical digestion - break down of complex food molecules by digestive enzymes into smaller molecules.
Oral cavity
Liver
Gall bladder
Rectum
Small intestine
Large intestine
Pancreas
Stomach
Oesophagus
PharynxSalivary glands
(A) Digestion in the mouth
• The digestive process starts in the mouth.
• The chewing action breaks down the food into smaller pieces and increases the surface area of the food for digestive enzymes to act on.
• The presence of food in the mouth triggers secretion of saliva by three pairs of salivary glands.
• Saliva contains the enzyme salivary amylase which begins the hydrolysis of starch to maltose.
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Digestion in the Mouth
Peristalsis: A series of wave-like muscular contraction along oesophageal wall.
Starch + watersalivary
maltoseamilase
• The thoroughly chewed food is rolled into a mass called a bolus in preparation for swallowing.
• During swallowing, a cartilage flap called the epiglottis temporarily closes the airway to prevent food from entering the trachea.
• Next, the bolus enters the oesophagus, a muscular tube lined with epithelium and mucous glands.
• The mucus :lubricates the bolus aids the movement of the bolus along the
oesophagus by peristalsis, a series of wave-like muscular contractions along the oesophageal wall (Diagram 1).
• When the cardiac sphincter relaxes, the bolus enters the stomach.
• Cardiac sphincter is a ring of muscles which control the opening of the stomach.
Diagram 2 :Secretion of gastric juice in the stomach
Diagram 1: Peristalsis along the oesophagus
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Digestion in the Mouth
Peristalsis: A series of wave-like muscular contraction along oesophageal wall.
Starch + watersalivary
maltoseamilase
(B) Digestion in the stomach• The stomach is a thick-walled, sausage-
shaped organ situated below the diaphragm.
• It is a muscular sac with a highly folded inner wall.
• The epithelial lining of the stomach contains gastric glands that secrete gastric juice (Diagram 2).
• Gastric juice contains mucus, hydrochloric acid and the enzymes pepsin and rennin.
Diagram 2 :Secretion of gastric juice in the stomach
(a) Hydrochloric acid• Creates an acidic condition (pH 1.5- 2.0)
which is optimal for the action of the enzymes in the stomach.
• Stops the activity of salivary amylase.• Helps to kill bacteria in food.
(b) Pepsin • starts the hydrolysis of large protein
molecules into smaller chains of
polypeptides by breaking specific peptide
bonds.
(c) Rennin • coagulates milk by converting the soluble
milk protein, caseinogen, into insoluble casein.
• Mucus, secreted by the goblet cells of the gastric gland, protects the stomach wall from the action of hydrochloric acid and digestive enzymes.
• Food stays in the stomach for a number of hours.
• During this period, the food is thoroughly churned and mixed with the gastric juice by the peristaltic contractions of the stomach wall.
• Eventually, the contents of the stomach become a semi-fluid called chyme.
• Relaxation of the pyloric sphincter allows the chyme to gradually enter the duodenum.
Food
Oesophagus
LungLung
Stomach
Diaphragm
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Gastric glands secrete gastric juice.
Gastric juice consists of mucus, hydrochloric acid, enzyme pepsin and rennin.
High acidity (pH 2) - sufficient to destroy existence bacteria in food.
Digestion in the Stomach
Protein + waterpepsin
polypeptides
Caseinogenrennin
casein
Finally, chyme is produced.
stomach
(C) Digestion in the small intestine
• The small intestine consists of the duodenum, jejunum and the highly coiled ileum.
• The duodenum, the first part of the small intestine, receives chyme from the stomach and secretions from the gall bladder and pancreas.
2) Digestion in the ileum
• Glands in the wall of the ileum secrete intestinal juice which contains digestive enzymes needed to complete the digestion of peptides and disaccharides.
• The intestinal enzymes require an alkaline medium to act at an optimum rate.
• At the end of the digestive process, all carbohydrates are digested into monosaccharides such as glucose, fructose and galactose.
• Proteins are digested into amino acids and lipids into fatty acids and glycerol.
* Show summary
• Vitamins and minerals are extremely small and soluble and need not be digested.
• Dietary fibre cannot be digested in the human body as the enzyme cellulase is not produced in the human alimentary canal.
* Show summary
Ileum
Liver
PancreasDuodenum
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Digestion in Small Intestine
Starch, protein and lipids are digested here
Receives chyme from stomach Produced bile that helps neutralise acidic chyme and optimises pH for enzyme action in duodenum
Secrete intestinal juice
Major site of nutrient absorption
Ileum
Liver
Pancreas
Secretes pancreatic juice that contains enzyme amylase, trypsin and lipase
Duodenum
Digestion of cellulose in ruminants and rodents
(a) The digestive system of ruminants• Herbivores like ruminants and rodents feed on
plants which contain a high percentage of cellulose, a polysaccharide which is extremely insoluble.
• Therefore, much of the energy in their diets is stored in this complex carbohydrate. The breakdown of cellulose requires the enzyme cellulase.
• Ruminants obtain most of their energy from the breakdown of cellulose of plant cell walls by cellulase.
Ruminants
• The herbivors that regurgitate food and rechew the food.
• Although ruminants do not produce cellulase, their digestive systems are specially adapted to carry out cellulose digestion.
• Ruminants like cows and goats have stomachs which are divided into four chambers, namely rumen, reticulum, omasum and abomasum.
Rumen
Omasum
Reticulum
Abomasum
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Digestive System in Ruminants
Rumen
Cellulose is broken down by cellulase.
Omasum
Cellulose is hydrolysed.
Cud is swallowed again into mouth and chewed to break down cellulose.
Reticulum
Reswallowed cud is moved to omasum.
Large particle of food are broken down into smaller pieces by peristalsis.
Abomasum
Proteins and food substances are digested by digestive enzymes.
The food then passes through small intestine.
• This adaptation enables ruminants to carry out rumination, the process of regurgitating food and rechewing it.
• The first two chambers, the rumen and reticulum, are specialised compartments which have large communities of bacteria and protozoa.
• These microorganisms are able to secrete cellulase to digest cellulose.
• In many cases, the microorganisms also use the sugars and other products of cellulose digestion along with minerals to synthesise certain nutrients, such as vitamins and amino acids, which are essential to the ruminants.
• Diagram 4 shows the processes involved a cellulose digestion in the digestive system of a cow.
b) The digestive system of rodents and other Herbivores
• In rodents like rats and herbivores like rabbits, the caecum and appendix are enlarged to store the cellulase-producing bacteria.
• In herbivores like, the breakdown products pass through the alimentary canal twice.
• The faeces in the first batch are usually produced at night, and are soft and watery.
The digestive system of rodents and other Herbivores
• These are eaten again to enable the animals to absorb the products of bacterial breakdown as they pass through the alimentary canal for the second time.
• The second batch of faeces become drier and harder.
• This adaptation allows rabbits to recover the nutrients initially lost with the faeces.
Diagram 4: Digestion of cellulose by the digestive system of a rabbit
1
2
3
4
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
RodentsRodents
Have long and large caecum.Have long and large caecum.
Cellulose is digested in the caecum by bacteria.Cellulose is digested in the caecum by bacteria.
caecum
ileum
ITeach – Biology Form 4
Chapter 6 Nutrition
Food Digestion
Comparison of Digestive Process in Humans, Ruminants and Rodents
Human
Cannot digest cellulose
No enzyme cellulase
Stomach has one chamber
Caecum is short
Ruminant
Digest cellulose in stomach
Enzyme cellulose is secreted in the stomachStomach has four
chambers
Caecum is short
Rodent
Digest cellulose in the caecum
Enzyme cellulose is secreated in the caecumStomach has one
chamberCaecum is long and
large
Problems associated with food digestion
• The function of the digestive system depends largely on proper nutrition.
• Proper nutrition can help the digestive system functions at its best.
• There are many problems associated with the digestion of food.
(1)Incomplete digestion
• Incomplete digestion of food may cause severe pain in the abdomen followed by nausea, vomiting and a bloated stomach.
• Incomplete digestion of food is caused by excessive intake of food, eating too much oily food or eating too fast.
(1) Incomplete digestion
• If the food is not chewed properly before swallowing, the stomach cannot digest the food properly and this decreases the effectiveness of the digestive enzymes.
• Eating moderately and chewing food properly help prevent incomplete digestion of food.
(2) Reduced production of specific digestive enzymes
• Reduced production of specific digestive enzymes can cause digestive problems.
• Adults usually find it difficult to digest lactose (milk sugar) compared to a baby or a child because of the lack of lactase. This condition is known as lactose intolerance.
(2) Reduced production of specific digestive enzymes
• Damage to organs such as the pancreas causes reduced production of digestive enzymes for the digestion of starch, proteins and lipids.
• As a result, digestion of these foods will be disrupted and the body will not be able to obtain sufficient nutrients.
(3) Gallstone preventing the flow of bile
• A person who often eats fatty food encourages the formation of gallstones in the bile duct and gall bladder.
• Gallstones are formed through the hardening of cholesterol. It is also caused by the excessive secretion of bilirubin and bile salts.
• The size of the gallstones may be as small as a grain of sand or as big as a golf ball.
(3) Gallstone preventing the flow of bile
• When the gallstones block the bile duct, bile cannot be channelled out. As a result, lipids cannot be emulsified and are difficult to digest.
• Formation of gallstones usually occurs in obese people.
Chapter 6 NutritionChapter 6 Nutrition
6.5 Absorption And Assimilation Of Digested Food
ITeach – Biology Form 4
Absorption And Assimilation Of Digested Food
• Digested food consists of small molecules which can pass through the plasma membranes of the body cells.
• To enter the body cells, nutrients in the lumen of the small intestine must be transported across the intestinal lining into the bloodstream.
• Ileum, the last part of the small intestine is the major site of nutrient absorption.
Adaptive Characteristics of the Small Intestines for Absorption
It is the longest section of alimentary canal (about 6m) for longer digestion time and greater absorption of nutrients.
The intestinal lining (inner wall) is highly folded and covered by tiny finger-like projections called villi.
The epithelial cells of a villus have a lining of microscopic projections called microvilli. Villi and microvilli increase the surface area for absorption of nutrients.
Villus, microvilli, blood capillaries and lacteal increase the rate of nutrient absorption and assimilation.
Chapter 6 Nutrition
Absorption And Assimilation Of Digested Food
Absorption And Assimilation Of Digested Food
Epithelial cells
Blood capillaries
Lacteal
Microvilli
Epithelial cell
Adaptive Characteristics of the Small Intestines for Absorption
The epithelial lining is only one cell thick to make the absorption of nutrients easy.
Each villus also has a network of blood capillaries and lymphatic vessel called lacteal ( blood vessels) to increase absorption and transportation of nutrients.
Villus, microvilli, blood capillaries and lacteal increase the rate of nutrient absorption and assimilation.
Chapter 6 Nutrition
Absorption And Assimilation Of Digested Food
Absorption And Assimilation Of Digested Food
Epithelial cells
Blood capillaries
Lacteal
Microvilli
Epithelial cell
(A) Absorption of Digested Food
Nutrient absorption involves both diffusion and active transport.
(a) In the blood capillaries:
(1) Absorption of glucose and amino acids
• Initially, they diffuse (facilitated diffusion) into the epithelial cells and are absorbed into the capillaries.
• Subsequently, the transport of the remaining nutrients across the epithelial lining involves active transport which energy is used.
(A) Absorption of Digested Food
(2) Absorption of mineral ions and water soluble vitamins B and C • Are absorbed by diffusion (facilitated
diffusion) into the blood capillaries.
(b) In the lacteals:
(1)Absorption of fatty acids and glycerols• Fatty acids and glycerol diffuse into the
epithelial cells of the villi and then they recombine to form droplets of lipid before enter the lacteals.
(A) Absorption of Digested Food
(b) In the lacteals:
(2) Absorption of fat soluble vitamins (ADEK)• Are also diffused (simple diffusion) and
absorbed into the lacteals.
(c) In the colon:
(1) 90% of water and some remaining mineral ions are reabsorbed into the cells lining the colon and subsequently into the bloodstream.
(A) Absorption of Digested Food
(c) In the colon:
(2) Vitamin K that is synthesized by the bacteria in the colon is also absorbed.
The absorbed nutrients are transported to body tissues or organs to be assimilated or to be stored.
Chapter 6 Nutrition
Absorption And Assimilation Of Digested Food
Absorption of Digested Food
Capillary network- allows transport nutrient to liver
Epithelial cell- allows rapid diffusion of nutrients
Lacteal- allows absorptions of fat
To liver – (glucose, amino acids, minerals)
To thoracic duct(fat droplets, Vitamin A,D,E,K)
(B) Assimilation of Digested Food
Assimilation: is a metabolic process where the
nutrients are used (utilised) to form complex compounds or structural components.
Happens in the liver and in the body cell.
(B) Assimilation of Digested FoodGlucose, amino acids, water soluble
vitamin B and C and minerals are transported by the blood vessels to the hepatic portal vein. (Textbook, page 119)
The hepatic portal vein then transports these nutrients to the liver to be processed for assimilation or metabolic processes.
The blood circulatory system transports the nutrients from the liver to the body cells for assimilation.
(B) Assimilation of Digested Food
The lipid droplets and fat soluble vitamins ADEK are transported by the thoracic duct to the left subclavian vein.
The nutrients then enter the blood circulatory system.
Assimilation in the Body Cells
Amino acids which enter the cells are used for the:
• Synthesis of new protoplasm • Repair the damaged tissues• Important building blocks in the
synthesis of enzymes and hormones.
Glucose is used to produce energy in cellular respiration.
Lipids represent the major energy store of the body. Excess lipids are stored in the adipose tissue.
Some lipids, eg: phospholipids and cholesterols are major components of plasma membranes.
Assimilation in the Body Cells
Functions of the LiverThe liver acts as a checkpoint which controls
the amount of nutrients released into the blood circulatory system.
(a) Regulation of blood glucose levels:• Excess glucose is converted by insulin to
glycogen and stored in the liver.• When the glycogen store in the liver is full,
excess glucose is converted into lipids by the liver.
• When the blood glucose level decreases, glycogen is converted by glucagon to glucose.
Functions of the Liver
(a) Regulation of blood glucose levels:
• Glucose is distributed throughout the body by the circulatory system.
• When the glucose molecules reach the cells, they are oxidized to release energy during cellular respiration.
(Textbook pg 119, Figure 6.12)
• When there is short supply of glucose and glycogen, the liver converts amino acids to glucose.
Functions of the Liver(b) Deamination:
• Excess amino acids cannot be stored in the body and are broken down in the liver by a process called deamination.
• Excess amino acids are converted to ammonia which is then converted to urea to be excreted.
Functions of the Liver(c) Detoxification:
• The liver cells remove the harmful substances from the blood. Bacteria are killed by phagocytic cells in the liver.
• The liver cells convert harmful substances to a compound which are less toxic by modified chemically and are eliminated.
Functions of the Liver
(d) Storage Function:• Stores fat soluble vitamins A and D, water
soluble vitamin B12 and mineral ions.
(e) Production of Bile:• Bile is transported to the duodenum to
emulsify fats.(f) Synthesis of Plasma Protein:• Site of synthesis fibrinogen and
prothrombin (components in blood clotting)
ITeach – Biology Form 4
Chapter 6 Nutrition
Absorption And Assimilation Of Digested Food
Assimilation Of Digested Food
Assimilation is where nutrients are used to form complex compounds.
Deamination – Broken down process of excess amino acid in liver.
Detoxification - liver cells remove harmful substances from blood or convert them to less toxic compounds.
•Glucose --> Glycogen
•Glycogen -->Glucose
•Excess glucose --> Lipids
•Amino acid --> Plasma protein
Chapter 6 NutritionChapter 6 Nutrition
6.6 Formation Of Faeces And Defaecation
Formation Of Faeces And DefaecationAfter absorption of nutrients has taken place in the
small intestine, the intestinal content enter the colon.
The intestinal contents are mixture of:
~water
~undigested food substances
~indigestible fibre (most is cellulose from plant
cell walls)
The movement of these undigested materials along the colon is slow and helped by peristalsis.
Formation Of Faeces And Defaecation
In the colon, about 90% of the water and mineral ions are reabsorbed from the undigested materials into the bloodstream.
Vitamin B12 and K that are synthesized by the symbiotic bacteria in the colon are also absorbed.
Finally, the remaining food residue is known as faeces.
Formation Of Faeces And Defaecation
Faeces consists of:
~undigested food residue
~dead epithelial cells (membranes of
intestine)
~bile pigments (bring colour to the faeces)
~toxic substances / bacteria
~water
~fibre
Formation Of Faeces And Defaecation
The wall of the colon secretes mucus to smoothen the movement of the faeces.
The faeces is kept in the colon for 12-14 hours.
The faeces is pushed into the rectum which is the temporary storage place.
Formation Of Faeces And Defaecation
When the rectum is full, pressure in the rectum increases, causing a desire to expel the faeces from the body.
Spinchter muscles relax and the rectal wall contracts.
The faeces are eliminated through the anus in a process called defecation.
Formation Of Faeces And Defaecation
Defecation is important to:
~eliminate undigested substances
~eliminate toxic substances
produced during fermentation by
bacteria.
ITeach – Biology Form 4
Chapter 6 Nutrition
Formation Of Faeces And Defaecation
Formation of Faeces and Defaecation
Avoid toxicity in human body.
Excrete wastes and unwanted toxic substances.
Defective defaecation may lead to headache and lost appetite.
The formation of faeces in the colon
colon
rectum
solid waste
Role of Microorganism in the Colon The colon also serves as a habitat for a flourishing
population of bacteria.
The symbiotic microorganisms living in the human colon, eg:
~ Escherichia coli
1) synthesise vitamin B12 and K that can be
absorbed through the colon wall
2) maintain a stable environment in the alimentary
canal.
The microbial population in the colon can be killed due to excessive consumption of antibiotics.
Problem Related to Defecation1. Constipation • Difficulty elimination of feaces as the faeces become dry and
hard.
• This is caused by the extremely slow movement of faeces
through the colon.
• As a result, a greater amount of water is reabsorbed in the colon, making the faeces hard.
• Can be avoided :
~by drinking a lot of water
~by taking dietary fibre
• Chronic constipation can cause piles, which can cause bleeding during defecation.
Problem Related to Defecation
2. Haemorrhoids • Swollen veins in the rectum or anus due to
excessive pressure exerted to eliminate faeces.
3) Colon cancer• The symptoms are irregular frequency of
bowel (usus) movement and blood in faeces.
Chapter 6 NutritionChapter 6 Nutrition
6.7 Evaluating Eating Habits
ITeach – Biology Form 4
Earlier, we learned the importance of a balanced diet. It is also important that we practise good eating habits.
In recent times, we hear of increasing cases of eating disorders. Most cases of eating disorders reflect a disruption in normal eating habits.
Good eating habits mean taking food in the correct quantity at the correct time.
We should refrain from overeating or eating too little during a meal. For example, a balanced breakfast is essential as it provides all the nutrients required by the body.
Evaluating Eating Habits
A normal person should take in three meals a day: breakfast, lunch and dinner. He or she must also eat a variety of food to satisfy the body's nutrient requirement.
Sufficient amounts of fibre from fruits and vegetables must be included in the meals.
Drinking at least 2 to 3 litres of water a day is essential. This helps to flush out toxins from the body.
One should also avoid taking excessive fatty food and food rich in sugar.
Improper eating habits are associated with various health problems which affect a large number of the population.
Evaluating Eating Habits
ITeach – Biology Form 4
Chapter 6 Nutrition
Evaluating Eating Habits
Good eating habits mean taking food in the adequate quantity at the right time.
Evaluating Eating Habits
Health Problem
Related to Bad Eating
Habits
Health Problem
Related to Bad Eating
Habits
Bulimia
Obesity
Anorexia nervosa
Gastritis
Health Problems Related To Eating Habits
(A) Gastritis
is a condition where the epithelial lining of the stomach becomes inflamed.
The stomach lining is normally covered with a layer of mucus which protects it from hydrochloric acid and digestive enzymes.
Gastric juice is secreted into the lumen of the stomach whenever one feels hungry.
If food is not taken at regular times, the absence of food in the stomach results in the acidic gastric juice acting on the epithelial lining of the stomach wall.
(A) Gastritis
Gastritis occurs when the protective mechanism in the stomach is disrupted and this results in damage to the stomach lining.
When the breach in the stomach lining develops into a hole, gastric ulcer may result.
For most types of gastritis, treatment involves taking medication such as antacids to reduce or neutralise stomach acids.
Health Problems Related To Eating Habits
Health Problems Related To Eating Habits
Excessive alcohol consumption and stress:
• can damage the stomach lining.
Taking aspirin and other pain relievers regularly:
• can also cause the stomach lining to become inflamed.
(B) Obesity
is defined as the excessive storage of energy in the form of fat.
This results from a lack of balance between food intake and energy expenditure.
Obesity is one of our nation's most critical health problems and is directly responsible for a huge number of deaths each year.
Health Problems Related To Eating Habits
(B) Obesity
Obese people are predisposed to a number diseases including cardiovascular disease, hypertension and diabetes
For many, obesity leads to often life threatening diseases disorder such as anorexia nervosa and bulimia.
Health Problems Related To Eating Habits
(C) Aneroxia nervosa
Experience an intense fear of gaining weight.
They intentionally deprive themselves of food to achieve a severe loss in body weight, often 15% or more below their normal body weight.
This condition is potentially fatal and is recognised as a
psychological disorder.
Individuals with this disorder have a distorted body image which convinces them they are fat.
Health Problems Related To Eating Habits
(C) Aneroxia nervosa
In an attempt to boost their self-esteem, they refrain from eating to the extent that they become extremely emaciated.
They lose both fat and muscle and this eventually leads to disruptions of the functions of the heart, endocrine system and reproductive system.
Early treatment can correct some of the physical symptoms through nutrition and gradual restoration of body mass.
Health Problems Related To Eating Habits
(D) Bulimia
may have a normal body mass.
Bulimia is characterised by sequences of excessive food intake and purging to counteract the effects of the binge.
The victims engage in consuming huge amounts of food within a short period of time.
Health Problems Related To Eating Habits
(D) BulimiaThis is followed immediately by self-induced
vomiting or purging through laxative abuse.
Repeated purging results in serious injury to the digestive tract and can cause an imbalance of mineral ions in the blood.
This can lead to cardiovascular problems and kidney damage.
Health Problems Related To Eating Habits
Nutrient Contents of Food
• Good eating habits also involve choosing the types of food we eat wisely.
• Are you aware of the contents of the food that you consume everyday?
• Do you normally check the food labels for information regarding the nutrient contents of the food you buy?
• Food manufacturers are required to provide nutritional labelling on commercially packaged food.
• The labels of food packets and containers provide complete information about the total calories per serving and the contents of various nutrients.
Nutrient contents of food
• As consumers we are able to make informed choices about the types of food we consume by studying the food labels.
• When buying food, we must consider the nutrients contents, freshness and various safety aspects
~ for example whether the food contains
additives which may have adverse effects
on our health.
• The nutritional information obtained from these sources will help reduce health problems related to poor eating habits.
Chapter 6 NutritionChapter 6 Nutrition
6.8 The Importance Of A Healthy Digestive System
ITeach – Biology Form 4
ITeach – Biology Form 4
Chapter 6 NutritionThe Importance Of A Healthy Digestive System
The Importance Of A Healthy Digestive
System
The Importance Of A Healthy Digestive
System
Effects of a Defective Digestive
System on Health
Indigestion
Constipation
Haemorrhoids
Diarrhoea
Formation of bile stone
Too much spicy food Overeating
Prolonged constipation
Prevent the flow of bile to duodenum
ITeach – Biology Form 4
Chapter 6 Nutrition
The Importance Of A Healthy Digestive System
Ways to Take Care of Digestive System
Good eating habit
Avoid junk food Eat nutritious food
Chapter 6 NutritionChapter 6 Nutrition
6.9 The Importance Of Macronutrients And
Micronutrients In Plants
6.9 The Importance Of Macronutrients And
Micronutrients In Plants
Elements required by plants• Green plants are able to synthesise their own nutrients.
• To do this, they require raw materials in the form of inorganic substances: carbon dioxide, water and mineral nutrients.
• Mineral nutrients are essential chemical elements required by plants to:
1) complete their life cycle
2) achieve optimal growth and development.
• What are the mineral elements required by plants?
ITeach – Biology Form 4
Chapter 6 NutritionThe Importance Of Macronutrients And Micronutrients In Plants
The Importance of Macronutrients and Micronutrients in Plants
To accomplish their life cycle, growth and development.
Ex: Carbon (C), hydrogen (H) and Oxygen (O).
6.9 The Importance Of Macronutrients And
Micronutrients In Plants
Elements required by plants
• Carbon (C), hydrogen (H) and oxygen (O) are three macronutrients that can be easily obtained from carbon dioxide in the atmosphere and water from the soil.
• Therefore, deficiency in these nutrients rarely occurs.
• They are the most abundant elements found in a plant and form the major ingredients of organic compounds, most of which are carbohydrates.
• The remaining mineral nutrients are obtained in the form of inorganic ions from the soil.
6.9 The Importance Of Macronutrients And
Micronutrients In Plants
• The six macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S) are needed by plants in relatively large amounts.
• Micronutrients which include boron (B), copper (Cu), ferum (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn) are needed in very small amounts.
• To determine which elements are required for normal growth, plant seedlings are grown in a complete culture solution, also known as Knop's solution (Table 6.3).
6.9 The Importance Of Macronutrients And
Micronutrients In Plants
• We can investigate whether a plant needs a particular mineral element by eliminating it from Knop's solution.
• Macronutrients and micronutrients are involved in the synthesis of chemical substances essential for the healthy growth of plants.
• They are also required for the various metabolic processes which take place within plants.
• The absence of one or more of these nutrients can lead to mineral deficiency in plants.
6.9 The Importance Of Macronutrients
And Micronutrients In Plants
• The symptoms of mineral deficiency depend on the functions of the mineral in the plant.
• For example, nitrogen (N) is the macronutrient that influences plant growth the most.
• It is a major component of proteins, nucleic acids, chlorophyll and enzymes of photosynthesis and respiration.
6.9 The Importance Of Macronutrients
And Micronutrients In Plants
• Nitrogen is important for the rapid growth of stems and leaves, and increases seed and fruit yield.
• The most common symptoms of nitrogen deficiency are chlorosis and stunted growth.
• In chlorosis, synthesis of chlorophyll is inhibited, resulting in pale yellow leaves.
• Table 6.4 The functions and effects of deficiency of other macronutrients
ITeach – Biology Form 4
Chapter 6 NutritionThe Importance Of Macronutrients And Micronutrients In Plants
Function of Macronutrient in Plants
FunctionFunctionElementElement
Nitrogen
Phosphorus
Potassium
Calcium
Magnesium
To synthesis chlorophyll
Necessary for cell division
Protein synthesis, carbohydrate metabolism
Needed for formation of cell wall
To synthesis chlorophyll and protoplasm
Sulphur To synthesis protein and nucleic acids
ITeach – Biology Form 4
Chapter 6 NutritionThe Importance Of Macronutrients And Micronutrients In Plants
The Effects of Macronutrient Deficiency
P
Mg
S
N
K
Ca Stunted growth Leaves become
distorted
Yellow-edged leaves Plant will die
Leaves turn yellow
Red or purple spots on old leaves
Red spots on leaves surfaces
Poor growth
General yellowing of affected leaves
The Functions And Effects of Deficiency of Micronutrients
• In addition to macronutrients, micronutrients or trace elements, are also essential for plant growth.
• Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients to growing plants.
• Table 6.5 shows the functions and effects of micronutrient deficiency in plants.
ITeach – Biology Form 4
Chapter 6 NutritionThe Importance Of Macronutrients And Micronutrients In Plants
Function of Micronutrients in Plant
FunctionFunctionElementElement
Boron
Copper
Ferum
Manganese
Molybdenum
Necessary for the development of apical meristems
Reproductive growth and flower formation
To synthesis chlorophyll
Activate certain enzymes
For nitrogen metabolism
ZincFormation of leaves, synthesis of auxin
ITeach – Biology Form 4
Chapter 6 NutritionThe Importance Of Macronutrients And Micronutrients In Plants
The Effects of Micronutrient Deficiency
Zn
Mn
BFe
Mo
Cu Brown spots Death of tips of
young shoots
Chlorosis
Yellowing of young leaves
Mottled leaves
Brown spots between the veins
Death of terminal buds, abnormal plant growth
Studying the Effects of Macronutrient Deficiencies In Plants1) Problem statement
• What are the effects of macronutrient decencies in plants?
2) Variables• Manipulated variable: Components of mineral elements in each
jar • Responding variable: Condition of the plants• Constant variables: The volume of the solution, the size and
type of maize seedlings, air that is pumped into
the jar
3) Hypothesis• Plant grows healthily in a complete Knop's solution (jar B).
4) Materials• Maize seedlings, potassium nitrate, potassium dihydrogen phosphate,
magnesium sulphate, calcium nitrate, iron(III) phosphate, distilled water, cotton wool and black paper.
The apparatus set-up to study the effects of macronutrient deficiencies in plants
5) Apparatus:• Glass jars, rubber bungs with holes, straight glass
tubes to fit into the holes of the rubber bungs, L-shaped delivery tubes to be connected to an air pump, and a knife.
6) Technique• Observe and record the conditions of seedlings at the
end of one month.
*Note:• The growth of green algae can deplete the nutrient
content of the culture solutions and affect the results of the experiment.
7) Procedure:
1 Eight glass jars labelled A to H are prepared.
2 The jars are filled with the solutions as given in Table 6.9.
3 The jars are wrapped with black paper to prevent the
growth of green algae.
4 Eight maize seedlings of almost the same size are chosen.
5 The glass jars are connected to an air pump to provide
aeration to the roots so that respiration can take place.
6 The culture solutions are replaced every week to replenish
the nutrients absorbed by the maize seedlings.
7 The growth of each seedling is observed at the end of one
month.
8 The colour, number, size and shape of leaves, height of
seedlings, length of roots, the growth of branches and the
strength of the stems are observed and recorded in a
table.
Table 6.9 Nutrient contents of glass jars A to H
Results
8) Discussion: • The maize seedling in jar B grows healthily the jar
contains Knop's solution. • The seedling in jar A does not show any growth as it does
not contain any nutrients.• The maize seedlings in the other jars show the effects of
macronutrient deficiencies. • The symptoms shown are related to the function of each
macronutrients in plants
9) Conclusion
• Plants will only grow healthily when the contents of the nutrient components in the jar are complete (jar B) . If there is a deficiency of a certain nutrient, the plant will have symptoms that show what is lacking. The hypothesis is accepted.
Chapter 6 NutritionChapter 6 Nutrition
6.10 Photosynthesis
ITeach – Biology Form 4
ITeach – Biology Form 4
Chapter 6 NutritionPhotosynthesis
Discovery Of Photosynthesis
Jean Baptiste Van Helmont
1640
Joseph Priestly1772
Jan Ingenhousz1779
Study how plants grow
Show green plant restore O2
Discover plant release O2 in presence of sunlight
Jean Senebier1780
Robert Mayer1845
F.F Blackman1905
Prove plant release O2 when there is CO2 Find light energy convert to chemical energyDetermine photosynthesis involve light and dark reaction
1937Verify photosynthesis require sunlight, water and CO2
Photosynthesis = CO2 + Water light Carbohydrate + O2
(glucose)
Robert Hill
ITeach – Biology Form 4
Chapter 6 Nutrition
Photosynthesis
Leaf Structure and FunctionLeaf Structure and Function
Xylem- Transports water from roots to the leaf
Phloem- Transports organic product away from the leaf
Palisade mesophyll- Contains many chloroplasts.- Absorbs sunlight.
Guard cells- Regulate opening and closures of pores
Spongy mesophyl cell-Allow diffusion of water and gases.
Stomata- Allows gaseous exchange between leaf and environment
Upper epidermis -Prevents loss of water.
Cuticle- Enables the leaf to trap sunlight
ITeach – Biology Form 4
Chapter 6 Nutrition
Photosynthesis
Adaption of Plants from Different Habitats to Carry Out Photosynthesis
Adaption of Plants from Different Habitats to Carry Out Photosynthesis
Land plants Land plants
Plant floating on surface of water Plant floating on surface of water
Adaption of Plants from Different Habitats
Desert plants Desert plants
Ex: Hibiscus
• An abundant chloroplast in palisade cells and spongy mesophyll cells
• More stomata on the lower surface of the leaf
Ex: Water lily
• Chloroplast are found in leaves and stems
• Large, round and flat leaves
Ex: Cactus
• Leaves in thorn form
• Reduced leaves with sunken stomata
Adaptation of Land plants
The distribution of stomata is more on the lower epidermis layer to absorb more carbon dioxide and reduce transpiration
Chloroplasts can be found abundantly in the mesophyll palisade cells and spongy mesophyll cells to absorb more light for photosynthesis
Floating plants such as the lotus, have huge, round and flat leaves to enable them to absorb more sunlight.
The distribution of stomata on the upper layers of the leaves facilitates the absorption of carbon dioxide and the release of oxygen
Submerged plants usually do not have stomata
Chloroplasts are found on the leaves and stem of the plants
Adaptation of Aquatic plants
• Have a few stomata which are sunken to reduce transpiration
• The stomata are usually found on the lower layers of the surface of the leaves
• Chloroplasts can be found on the stems and leaves
Adaptation of Dessert plants
Chapter 6 NutritionChapter 6 Nutrition
6.11 The Mechanism Of Photosynthesis
Two main stages in photosynthesis are light reaction and dark reaction.
Chapter 6 Nutrition
The Mechanism Of Photosynthesis
The Mechanism of Photosynthesis
Granum Stroma
Light reaction occur here.
Two main substances required: H2O,
sunlight
Dark reaction occur here Three main
substances required: hydrogen atom , CO2,
ATP Products: H2O +
Glucose
Products: H2O + O2 +
ATP
Mechanism of Photosynthesis1) Light Reaction
• The chlorophyll in the thylakoids absorbs light energy which excites the molecule of chlorophyll until it releases an electron.
• The light energy is used to break down/ split water molecules to become hydrogen ions (H+) and hydroxide ions (OH-).
• This reaction is known as photolysis of water.
• Electrons combine with the hydrogen ions to produce hydrogen atoms and chemical energy in the form of ATP which will be used in the dark reaction.
Mechanism of Photosynthesis1) Light Reaction
• Hydroxide ions release electrons to the chlorophyll to replace the excited electrons released from chloroplast and form hydroxide group.
• The combination of hydroxide group will form water and oxygen.
Mechanism of Photosynthesis1) Light Reaction
• After the light reaction is completed, the dark reaction takes place.
• The dark reaction does not involve the use of light.
• Try to remember which parts of the chloroplast absorb light. Your answer will explain why the dark reaction does not involve light.
Mechanism of Photosynthesis1) Dark Reaction (Calvin Cycle)
• The dark reaction occurs in the stroma.• Hydrogen atoms from the light reaction
react with carbon dioxide and produce glucose.
• This reaction is known as the reduction of carbon dioxide to glucose.
• This reaction is catalysed by enzymes and involves the use of energy, ATP.
Mechanism of Photosynthesis1) Dark Reaction
6 (CH2O)
• (CH2O) is the basic unit of glucose.
• Six units of (CH2O) combine to form one molecule of glucose.
• The glucose monomers then undergo condensation to form starch.
• Starch is temporarily stored as starch granules in the chloroplasts.
Mechanism of Photosynthesis1) Dark Reaction
• The following is a complete equation for photosynthesis:
• 6H2O + 6CO2 C6H1206+ 6O2
Mechanism of Photosynthesis
Light energy
chlorophyll
A comparison between the light reaction and dark
Use in cellular respiration
Undergoes condensation to form starch
Two main stages in photosynthesis are light reaction and dark reaction.
Chapter 6 Nutrition
Summary
The Mechanism of Photosynthesis
Granum Stroma
Light reaction occur here.
Two main substances required: H2O,
sunlight
Dark reaction occur here Three main
substances required: hydrogen atom , CO2,
ATP Products: H2O +
Glucose
Products: H2O + O2 +
ATP
Chapter 6 NutritionChapter 6 Nutrition
6.12 The Factors Affecting Photosynthesis
ITeach – Biology Form 4
Chapter 6 Nutrition
The Factors Affecting Photosynthesis
Factors Affecting Photosynthesis
Factors Affecting Photosynthesis
3 Factors Affecting
Photosynthesis
Light Intensity
Concentration of Carbon Dioxide
Temperature
ITeach – Biology Form 4
Chapter 6 Nutrition
Light Intensity
When the concentration of CO2 and temperature are controlled at constant level, the rate of photosynthesis is directly proportional to light intensity up to a certain point.(P)
Beyond point P, no increase in rate of photosynthesis even if the light intensity increases. Concentration of CO2 or
temperature become the limiting factor because of insufficient.
The rate of photosynthesis will increase again by increasing the concentration of CO2 or temperature.
Light intensity
Rate of photosynthesis
The Factors Affecting Photosynthesis
Refer textbook pg 135, Figure 6.19
Rate of photosynthesis increases when concentration of CO2
increases.
At BC, increasing CO2
concentration will not increase the rate of photosynthesis because light intensity and temperature are limiting factors.
ITeach – Biology Form 4
Chapter 6 Nutrition
The Factors Affecting Photosynthesis
The Factors Affecting Photosynthesis
Concentration of Carbon Dioxide
Rate of photosynthesis
Concentration of carbon dioxide
Refer textbook pg 136, Figure 6.20
Photosynthesis rate is high when light intensity and temperature are high.
ITeach – Biology Form 4
Chapter 6 Nutrition
The Factors Affecting Photosynthesis
TemperatureTemperature
When temperature increase as much as 10oC, rate of photosynthesis increases doubly.
At temperature above 40oC, enzymes are denaturated cause rate of photosynthesis to decrease and stops.
Conclusion:
Optimum temperature: 25oC to 30oC.
Rate of photosynthesis
Temperature
Optimum temperature
Refer textbook pg 136, Figure 6.21
The difference in the rate of photosynthesis in plants throughout the
day• The rate of photosynthesis is not constant
throughout the day.
• In the morning and evening: is low • In the midday: is the highest• At night: stop
The difference in the rate of photosynthesis in plants throughout the
year• The rate of photosynthesis is not constant
throughout the year.
• In the summer: is the highest • In the autumn: is low• During winter: decrease (cease)
Chapter 6 NutritionChapter 6 Nutrition
6.13 A Caring Attitude Towards Plants
ITeach – Biology Form 4
ITeach – Biology Form 4
Chapter 6 Nutrition
A Caring Attitude Towards Plants
The Importance of
A Good Attitude
towards Plants
The Importance of
A Good Attitude
towards Plants
Regulates normal climate
Plays important roles in ecosystem
Produces green foods
Maintains contents of O2 and CO2 in air
Provide wildlife and fish habitat
Chapter 6 NutritionChapter 6 Nutrition
6.14 Technology Used In Food Production
ITeach – Biology Form 4
6.14 Technology Used in Food Production
Introduction The need for improving the quality and quantity of food
• The rapid increase in the country's population imposes a greater demand on food supply.
• There is a need to improve the quality and quantity of food production to meet the demands of the growing population.
• In order to improve the quality and quantity of food, the Agriculture Ministry of Malaysia has drawn up several strategies to sustain the production of food in the country.
• Among these are strategies to raise productivity in food production and support the food industries.
• The ministry has also given priority to the production of food such as rice, fruits, vegetables, fishes and poultry.
The efforts by various agencies to diversify food production
1) Ulam • is a type of salad which includes fresh leaves, fruits and other
plant parts which are eaten raw.
• It is a traditional Malay dish but it is now well accepted by other races.
• Examples of ulam include pegaga (Centella asiatica), shoots of papaya, kacang botor, petai (Parkia speciosa) and kemangi (Ocimum sanctum).
• They are rich in mineral ions, vitamins and fibre. Some of these plants are also used in the preparation of herbal medicines and drinks.
The efforts by various agencies to diversify food production
2) Chicken, fish and meat. • In order to diversify the sources of protein, the government
encourages the consumption of rabbit meat, quail meat, ostrich meat, freshwater fish and prawns.
• Rabbit meat is rich in protein but low in fat and cholesterol. The meat has a soft texture and is suitable for young children.
• Ostrich meat is nutritious, rich in protein and low in fat.• Freshwater fish like tilapia, jelawat and haruan are low in
cholesterol. Fish protein is easily digestible and is much needed by growing children for healthy development.
Photograph 6.8 The diverse sources of food
The efforts by various agencies to diversify food production
3) Mushrooms• Another nutritious source of food is mushrooms.
• There is a wide variety of mushrooms available in our country, for example, button mushrooms, abalone mushrooms and shittake mushrooms.
• These mushrooms have a high nutrient content and some, like the shittake mushrooms, are believed to be able to increase the body's immunity.
Methods used to improve the quality and quantity of food production
• These include:• Direct seeding for rice• Hydroponics for vegetables• Aeroponics for vegetables• Breeding of plants and animals• Tissue culture• Genetic engineering• Crop rotation• Soil management • Biological control.
ITeach – Biology Form 4
Chapter 6 Nutrition
Technology Used In Food Production
Technology Used In Food Production
Method used to improve the quality and
quantity of food production
Crop rotation
Direct seeding
Hydroponics
Aeroponics
Breeding of plant
Animal breeding
Biological control
x
1) Direct seeding • is a method by which seeds are sown directly into the soil by
using special machines.
• The seeds are covered with soil while they are being sown.
• This technique does not involve transplanting of seedlings and therefore results in less damage to the roots of the seedlings.
• The plants achieve faster growth and this increases the yield.
• Less water is needed to irrigate the fields.
• This method is widely used in the planting of paddy to obtain higher yields of rice.
2) Hydroponics
• a commercial technique for growing certain crop plants in culture solutions rather than soil (Photograph 6.9)
• The roots of the plants are immersed in a solution which contains all the macronutrients and micronutrients required by the plants in the correct proportion.
• The plants are supported by a medium such as pebbles.
• The culture solution is aerated to provide sufficient oxygen for respiration.
3) Aeroponics
• is a modified technique of hydroponics. • In this method, the plants are suspended in
a special chamber with the roots exposed to the nutrient are sprayed onto the roots of the plants at suitable intervals.
• This enables the plant roots to absorb more oxygen in between the periods of spraying.
• Almost all types of vegetables like spinach, lettuce, tomatoes and chillies can be cultivated by using hydroponics and aeroponics methods.
• Both methods have a lot of benefits compared to planting in
soil:
1) Light intensity and temperature can be controlled to ensure that the environmental factors are at an optimum level for maximum growth.
2) The plants can be grown all year round and higher yields
can be obtained.
3) Plants achieve faster growth because the culture solutions
provide nutrients in a form that can be readily absorbed by
the roots and used by the plants to carry out living processes.
4) Selective Breeding (in Plants)• In this technique, different plant varieties with certain
beneficial characteristics are selectively bred.• The resulting varieties of plants (hybrid plant)
inherit the beneficial characteristics of both parent plants.
• Beneficial characteristics of hybrid plant:
~ have increased nutritional value
~ higher yields
~ show greater resistance to diseases and
climatic changes.
• In Malaysia, the most widely planted variety of oil palm is Tenera sp.
4) Selective Breeding (in Plants)• It is a variety produced by crossing the
parent varieties of Dura sp. and Pisifera sp.
• Tenera sp. possesses the beneficial characteristics of Dura sp. and Pisifera sp.
• It produces fruit with less fibre and more oil content (Photograph 6.10).
• The fruit do not drop off easily from the bunch.
• Many varieties of paddy, maize, sugar cane and vegetables have also been cross-bred by scientists.
• Photograph 6.10 The Tenera sp. variety has a big kernel, a thick mesocarp and a thin endocarp
5) Animal breeding • involves the cross breeding of two different
breeds of animals. • Animals have been selectively bred to enhance
the yields of milk, meat and other products. • In Malaysia, the hybrid cattle called Mafriwal is
bred in farms for its milk. • Mafriwal is a cross between a Friesian cow
and a Sahiwal bull. • Mafriwal produces more milk with low fat
content.• Many breeds of goats, sheep, chickens and
ducks have also been cross-bred in Malaysia.
Mafriwal
6) Tissue culture• This process involves tissue culture in which an
entire plant can be regenerated from the cells or tissues of a parent plant.
• The cells or tissues(explant) taken from the parent plant are grown in a sterile culture medium or culture solution which contains the necessary nutrients and growth hormones.
• Plantlets which are produced can then be transplanted to nurseries.
• In Malaysia, tissue culture of plant tissues enables commercial propagation of clones which have all the beneficial characteristics of the parent plants.
• This method helps increase the agricultural yield of many crop plants like papayas, pineapples and starfruits.
Photograph 6.11
Producing clones through tissue culture technique
7) Genetic engineering
• is a technique that has great potential in improving the quality and quantity of food to meet the needs of an increasing world population.
• This technique enables the characteristics of an organism to be altered by changing the genetic composition of the organism.
• It involves the transfer of beneficial genes from one organism to another organism.
• For example, genes from plants can be inserted into the DNA of animal cells and vice versa.
7) Genetic engineering
• The genetically modified organism (GMO) is called a transgenic organism.
• Developments in genetic engineering have enabled transgenic crop plants such as wheat, tomatoes, legumes, soya beans and potatoes to be cultivated commercially.
• These crop plants contain genes from other organisms to enhance growth, nutritional properties and resistance against diseases.
8) Soil Management
• Another method of increasing productivity is to practise proper soil management.
• Soil should be cultivated in a controlled manner
• So that not all minerals are removed from it at any one time.
• Regular addition of organic or inorganic fertilisers returns the nutrients to the soil.
• Ploughing helps increase aeration in the soil.
9) Crop Rotation• Many countries practise crop rotation to maintain
and improve soil fertility and prevent the build-up of pests which are peculiar to certain crop species.
• In this method, different plants are cultivated in succession on the same plot of land over a period of time. In a typical four-stage rotation, legumes are an important source of nitrogen for the soil. Other crops that can be included are leafy plants, plants that bear fruits like watermelons and root plants like onion and garlic.
• Steps must also be taken to reduce soil erosion and the leaching of nutrients from the soil. Addition of organic matter promotes humus formation and improves the soil structure. This helps promote plant growth.
10) Biological control
• Is the control of pests by biological means. • This is achieved by introducing a natural enemy of the pest,
such as a predator or a parasite. • The predator or parasite either feeds on or kills the pest. • In Malaysia, owls and snakes have been used successfully
to control the rat population in oil palm plantations. • In Australia, the population of the prickly pear cactus
(Opuntia sp.) is controlled by introducing the cactus moth (Cactoblastis cactorum).
• This method of pest control is beneficial as it reduces a number of problems associated with chemical control which uses pesticides.
• However, care must be taken to avoid upsetting the natural ecological balance, for example, a particular predator may harm other species which are beneficial.
Chapter 6 NutritionChapter 6 Nutrition
6.15 Technological Development In Food Processing
ITeach – Biology Form 4
ITeach – Biology Form 4
Chapter 6 Nutrition
Technological Development In Food Processing
Technological Development In Food Processing
Technological Development In Food Processing
Process of preparing food to make it more attractive, more edible and last longer
The Necessity for Food Processing
To preserve food from food spoilage
Expanding the uses of food substances
To enhance its commercial value
To withstand long periods of transportation and storage
6.15 Technological Development In Food Processing
The necessity for food processing:• Food processing is the process of preparing
food to make it more attractive, more palatable and to last longer.
• So that it can withstand long periods of transportation and storage
• To preserve food by overcoming the factors that cause food spoilage. This avoids wastage of food and prevents food poisoning due to food spoilage.
• To increase its commercial value.
• Photograph 6.12 The various processed food found on the supermarket shelf
ITeach – Biology Form 4
Chapter 6 Nutrition
Technological Development In Food Processing
Involves methods of preparing food to increase lifespan of food.
Food Preservation
What causes food spoilage?
What causes food spoilage?
Oxidation of foodOxidation of food
The action of microorganism on food
The action of microorganism on food
Infestation by insects and rodents
Infestation by insects and rodents
6.15 Technological Development In Food Processing
• Food preservation involves methods of preparing food to extend the lifespan of food so that it can be stored for future use.
• Food substances are processed in various ways to ensure that there is a continuous supply for the population.
What causes food spoilage? • One of the causes is the action of microorganisms on food,
especially decomposing bacteria and fungi which act on carbohydrates and proteins in food to produce carbon dioxide, water, ammonia, hydrogen sulphide and other organic substances.
• The presence of these substances spoils the food and makes it toxic.
• Food preservation prevents bacterial and fungal decay and contamination of food, which can cause food poisoning.
6.15 Technological Development In Food Processing
• Another cause for food spoilage is the oxidation of food.
• Have you noticed how apples turn brown very quickly when cut and exposed to air?
• This condition is due to oxygen reacting with enzymes and chemicals released by the cells in the fruit.
• What happens to fried food that is exposed to air for an extended period of time?
• Oily food becomes rancid, smells and tastes different as a result of oxidation.
• Rancid food is harmful to the body.
Correlating the food processing methods with factors causing food spoilage
• Microorganisms, like other living organisms, require food, water, oxygen and a suitable temperature for growth and reproduction. In addition, microorganisms can only survive in conditions with optimum pH and solute concentrations.
• Food can be preserved by destroying the microorganisms present in the food or by stopping the activities of these microorganisms.
ITeach – Biology Form 4
Chapter 6 Nutrition
Technological Development In Food Processing
Types of Processing MethodTypes of Processing Method
7 Types of Processing
Method
Cooking
Pickling
Fermentation
Drying
Pasteurisation
Canning
Refrigeration
Correlating the food processing methods with factors causing food spoilage
1) Cooking • is the easiest way to prevent food spoilage. Heating food
at high temperatures can kill microorganisms and denature the enzymes that cause the breakdown of food.
2) Treating food with salt or sugar • causes the microorganisms to lose water due to osmosis. • Pickling food such as chillies with vinegar reduces the pH
and prevents microorganisms from growing. • Vegetables and fruits are normally preserved by using
this method.
3) Fermentation • Fruit juices and other food substances can be fermented by
adding yeast. • Fermentation of fruit juices produces ethanol which, at high
concentrations, prevents the juices from becoming spoiled. • The ethanol produced has great commercial value.
Traditional food such as tapai is produced by the fermentation of pulut rice or tapioca.
4) Drying • Fish, meat and fruits can be dried to preserve them. Drying
under the hot sun removes water from food• This prevents the microorganisms from growing. • The ultraviolet rays of the sun also kill bacteria and many
other microorganisms.
5) Pasteurisation• Milk is preserved by pasteurisation to destroy
bacteria which cause diseases such as those of tuberculosis and typhoid.
• This method of preservation retains the natural flavour of milk.
• Nutrients like vitamin B are not destroyed. In this process, milk is heated to 63°C for 30 minutes or to 72°C for 15 seconds followed by rapid cooling to below 10°C.
• The pasteurised milk can then be refrigerated to last for a few days.
• Fruit juices and soups can also be preserved this way.
6) Canning • Uses heat sterilisation to kill microorganisms
and their spores. • The food is packed in cans and steamed at
high temperatures and pressure to drive out air.
• The cans containing food are then sealed while the food is being cooled.
• The vacuum created within the cans prevents growth of microorganisms.
7) Refrigeration (Freezing)• Is a common method employed at home to
keep food such as meat and fish from spoiling. • Food stored at temperatures below 0°C can
remain fresh for a long period of time. • The extremely low temperatures prevent the
growth of microorganisms or the germination of spores.
Photograph 6.13 Examples of pasteurised milk
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