Ch06

NSS Biology_Ch06 Nutrition in humans

Quick check (p.6-9)

Directions: Questions 1 and 2 refer to the diagram,

which shows the vertical section of a human tooth:

1. Which structures are hard and rigid?

A. 1, 2 and 3

B.B 1, 2 and 4

C. 1, 3 and 5

D 2, 4 and 5 HKCEE Biology 2004 II Q28

2. Which structures receive a continuous supply of nutrients?

A. 1, 2 and 3 only

B. 3, 4 and 5 only

C. 1, 2, 4 and 5 only

D.D 2, 3, 4 and 5 only HKCEE Biology 2004 II Q29

Quick check (p.6-11)The diagram below shows the

movement of food along the

oesophagus. Which line in the

table below correctly describes

the state of the circular muscles at

points 1, 2 and 3 on the diagram?

Circular musclesPoint 1 Point 2 Point 3

A. contracted relaxed contractedB. relaxed contracted contractedC.C contracted relaxed relaxedD. relaxed contracted relaxed

SQA Intermediate 2 Biology 2003 Section A Q6

p.1 / Nutrition in humans

Quick Check (p.6-16)Directions. Questions 1 and 2 refer to the diagram below,

which shows the alimentary canal and its associated

structures:

1. Which structures are responsible for producing secretions that help the digestion of fat?

A. 1 and 3 only

B. 1 and 5 only i

C. 2 and 3 only

D.D 4 and 5 only HKCEE Biology 2006 II Q1

2. Which of the following operations may help an obese (過胖的) person to control body

weight?

(1) decrease the volume of 1

(2) decrease the length of 2

(3) decrease the length of 3

A. (1) and (2) only

B.B (1) and (3) only i

C. (2) and (3) only

D. (1), (2) and (3) HKCEE Biology 2006 II Q2

Quick Check (p.6-21)

The diagram shows the longitudinal section of a villus長茸毛.

Which food substances are absorbed into structures P and Q

respectively after taking a meal containing lipids and starch?

P Q

A. glucose lipids

B. amino acids glucose

C. glucose water

D. lipids glucose


Quick check (p.6-24)

The liver is regarded as a digestive gland because it

A. converts stored glycogen into glucose.

B. breaks down excess amino acids.

C.C produces bile(膽汁)

D. stores iron. HKCEE Biology 2002 IIQ14


NSS Biology_Ch06_Exercise (p.6-27) Nutrition in humans

Multiple-choice questions

1. Which of the following comparisons between the milk dentition and the permanent

dentition of humans is/are correct?

Milk dentition Permanent dentition

(1) fewer molars more molars

(2) no canines with canines

(3) serves babies whose main diet is milk serves adults whose main diet is solid food

A.A (1) only

B. (3) only

C. (1) and (2) only

D. (2) and (3) only HKCEE Biology 2002 II Q22

Directions: Questions 2 and 3 refer to the diagram

below, which shows the human alimentary canal and its

associated structures:

2. Which of the following structures are responsible for producing secretions that help the

digestion of proteins?

A. 1 and 2 only

B. 1 and 3 only

C. 2 and 3 only

D.D 1, 2 and 3 HKCEE Biology 2007 II Q19

3. Which of the following would be the possible effect of removing part of structure 4 in an

operation?

A. Less faeces will be produced.

B. Oily faeces will be produced.

C. Hard faeces will be produced.

D.D Watery faeces will be produced. HKCEE Biology 2007 II Q20


Directions: Questions 4 and 5 refer to the diagram below, which

shows the alimentary canal and its associated structures:

4. Chemical digestion of carbohydrate occurs in

A. 1 and 2 only.

B.B 1 and 4 only.

C. 2 and 3 only.

D. 3 and 4 only. HKCEE Biology 2005 II Q19

5. If structure 5 of a person were blocked, which of the following would occur?

A.A His faeces would contain a lot of fat.

B. His faeces would become hard and dry.

C. His blood insulin level would decrease.

D. He would produce a large volume of dilute urine. HKCEE Biology 2005 II Q20

6. Which of the following statements about the digestion in the stomach is incorrect?

A. The stomach churns to break down food into smaller pieces.

B. Proteins are digested into polypeptides and peptides.

C. Hydrochloric acid is secreted to provide an optimum pH for the enzymes to work.

D.D Gastric juice can neutralize the acidic bolus.

7.D Cooked egg white cubes and an enzyme obtaining from the stomach are put in four test

tubes. The mixture will become clear if the egg white is digested. Which of the following

tubes will become clear first?


8. Humans cannot digest fibre. This means that fibre

A. cannot pass along the intestines.

B.B makes up most of the faeces.

C. creates acid conditions in the stomach.

D. stimulates the release of enzymes from the liver.Edexcel IGCSE Biology May 2005 Paper 1F Q1i

9 The diagram below shows the blood supply of the liver

and the small intestine. Which blood vessel has the

greatest fluctuation in blood glucose concentration within

a day?

A. vessel 1

C.C vessel 3

B. vessel 2

D. vessel 4HKCEE Human Biology 2004 II Q16

Short questions

10. Compare phvsical digestion and chemical digestion. (4 marks)

Physical digestion breaks down food into fine pieces to increase its surface area to enhance chemical digestion. Chemical digestion breaks down large food molecules into smaller molecules.The products after chemical digestion are small enough for absorption but those formed after physical digestion are not.Physical digestion is done by physical actions whereas chemical digestion is done by the action of digestive enzymes.Chemical digestion involves changes in the chemistry of the food but physical digestion does not.


11. The function of the pancreas in some

people may become impaired due to

the blockage of the pancreatic duct.

The diagram below shows the pancreas

and part of the alimentary canal:


(a) The faeces produced by such patients usually have a high fat content. Explain why.

The pancreas is the major organ that produces lipase.Due to blockage of the pancreatic duct, pancreatic lipase cannot reach the duodenum.Thus fat in the food cannot be digested and is egested in the faeces

(3 marks)

(b) In these patients, tissue of the pancreas may get digested. How would you account

for this? (2 marks)

Due to the blockage of the pancreatic duct, digestive enzymes accumulate / become active in the Pancreas.The protease accumulated digests the tissue ofthe pancreas / the lipase accumulated digests the cell membrane of pancreatic tissue cells

HKCEE Biology 2003 I Q2c

12. Complete the table. (4

marks)

Part of gut where digestion occurs

Enzyme Substrate Product

Stomach Protease Protein Polypeptides / peptides

Duodenum Lipase Lipase / fat

Fatty acids and glycerol

Duodenum Amylase Starch Maltose

Ileum Carbohydrase / maltase

Maltose Glucose

AQA GCE (AS) Unit 1 Jun 2005 Q4a

13. The table below shows the average amount of water entering the alimentary canal and

the average amount being absorbed in the intestine of a person each

day:


Water entering the alimentary canal Water absorbed by the intestine

Source Volume (mL) Site Volume (mL)Ingestion 2000 Small intestine 9000Secretions along the alimentary canal 8000 Large intestine 850

(a) Based on the above information, how much water is egested with the faeces each

day? (Note: Neglect the amount of water absorbed in the other parts of the

alimentary canal.)

(1 mark)

150 mL(b) Give two examples of secretions that enter the alimentary canal. (2

marks)saliva, mucus, gastric juice, pancreatic juice, bile, intestinal juice (any two)

(c) (i) Based on one structural difference between the small intestine and the large

intestine, explain why a much larger volume of water is absorbed in the

small intestine. (2

marks)

The small intestine is longer than the large intestine so the time for water absorption is longer / surface area for water absorption is larger

(ii) Explain how the absorption of digested food facilitates the absorption of water in

the small intestine. (2

marks)

The absorption of digested food into blood increases the water potential of the gut content. As a result, water is drawn into the blood by osmosis

HKCEE Biology 2006 I Q2

14 The diagram below shows a cross section of a part of the ileum.


(a) What is the function of X? (2 marks)

Absorbs / transports lipids / fats

(b) What is the importance of having muscle cells in the ileum? (2 marks)

Enables villi to moveIncreased contact with food


15. The diagram shows part of the small intestine, the liver and associated blood vessels.

(a) Explain why shortly after eating a meal containing protein, the concentration of amino

acids in the blood in the portal vein rises. (4

marks)

Proteins are digested / broken down into amino acids in the stomach and small intestines by the action of proteases.The amino acids are then absorbed into blood capillaries of the villi, and carried to other parts of the body by the blood.

(b) Why does a high concentration of amino acids in the liver result in a high

concentration of urea in blood in the hepatic vein? (1 mark)

The liver deaminates excess amino acids by removing and converting the amino groups into urea.

Edexcel GCSE Biology B Higher Tier Jun 2003 Q3

Structured questions


16. The X-ray photograph below shows a human molar.

(a) Using the letters in the photograph, state

all the structures that is/are

(i) richly supplied with capillaries,

C

(ii) rich in calcium salts.

A, B, D(2 marks)


(b) Based on the X-ray photograph, make a labelled drawing of this tooth. (4

marks)

(c) Explain how the process of digestion would be affected if a person lost most of this

type of tooth. (3 marks)

Food could not be ground or crushed into small Pieces /there would be less mechanical digestionThe surface area for the action of digestive enzymes would not be large enough. It would take longer time for the food to be broken down into simple soluble forms.

HKCEE Biology 2001 I Q1c

17. The diagram below shows the alimentary canal and

its associated structures:

The table on the right shows the extent of digestion

of certain food substances in various regions of the

alimentary canal.

Percentage of undigested food substances present

Region X Region Y Region ZProtein 100 0 60Starch 85 0 85

Fat 100 0 100

(a) Based on the table above, which region (X, Y

or Z) corresponds to part A of the alimentary

canal? Explain your answer. (4 marks)

Region XThis is because food in A has passed through the mouth cavity. The salivary amylase will digest some of the starch in the food, but there is no


enzyme to digest rat and protein.


(b) If structure B of a person is removed in a surgical operation, he is advised to reduce

the intake of fat in his diet. Explain why. (5

marks)

Bile produced in the liver cannot be stored after the removal of B. When food enters the duodenum, insufficient amount of bile is released for emulsifying fats in the food.Thus the surface area for the action of lipase decreases and fat cannot be digested efficiently.

HKCEE Human Biology 2004 I Q1C

18 Read the paragraph below and answer the questions that follow.Gastric reflux describes a backflow of the gastric juice from the stomach into the

oesophagus. This can irritate and sometimes damage the lining of the oesophagus, giving

a feeling of heartburn. In Hong Kong, the rate of patient suffering from gastric reflux rose

from 2.3 per 10 000 in 1996 to 6.2 per 10 000 in 2005. It is believed that the alarming

rise is related to the lifestyles of people in Hong Kong. These include having midnight

snack right before sleeping, excessive fatty foods, large meals, irregular mealtime, and

drinking a lot of alcohol or coffee.

(a) (i) With reference to the content of gastric juice, suggest a probable reason for

its damage to the oesophagus. (1 mark)

Gastric juice contains hydrochloric acid

(ii) Food entering the small intestine carries some gastric juice from the stomach.

Explain why the gastric juice does not normally damage the small intestine.

(3 marks)Pancreatic juice / bile / intestinal juice in the small intestine are alkaline which neutralizes the gastric juice

(b) Suggest why the backflow of gastric juice is more likely to occur if a person has a

meal just before sleeping. (3

marks)

After meal, the release of gastric juice


increases and the pressure inside the stomach increasesAlso, the stomach and oesophagus are at the same level while sleeping. These increase the chance of gastric reflux

(c) A patient siiflering from severe gastric reflux will also likely to have tooth decay.

Give an explanation for this. (2

marks)

The acid in the gastric content dissolves the enamel / calcium salts of the tooth.

HKCEE Biology 2007 I Q619. (a) Describe the digestion of carbohydrate in the alimentary canal. (5 marks)

The digestion of carbohydrates starts in the mouth.Saliva contains amylase which catalyses the conversion of starch to maltose.Further digestion of carbohydrates takes place in the small intestine.Amylase from pancreas catalyses the breakdown of remaining starch to maltose.Carbohydrases in small intestine catalyse the breakdown of disaccharides (e.g. maltose) into monosaccharides (e.g. glucose).

(b) State two functions of the acid secreted in the stomach. (2 marks)

Kills bacteriaProvides an acidic medium for the enzyme to work properly.

WJEC GCE (A) Biology Module BI4 Jan 2007 Q3


20. The photomicrograph

below shows a cross

section of the small

intestine of a mammal:

(a) With reference to

two features of X

observable from the

photomicrograph,

explain how these

features facilitate

the absorption of

digested food

substances.

(4 marks)

X is a finger-like projection of the intestinal wall. This feature provides a large surface area for food absorption.The epithelium of X is very thin / one-cell thick.This shortens the distance of diffusion / transport of digested food substances.

(b) Use a flowchart to show how amino acids are transported to the heart after entering X.

Indicate the major organs and blood vessels along the pathway. (2

marks)

X → hepatic portal vein → liver → hepatic vein → vena cava → (heart)

(c) Describe how the muscle layer helps the movement and digestion of food inside the small

intestine. (3 marks)

The peristaltic contraction of the muscle layer pushes food along the small intestine.This also helps to mix food with digestive enzymes.

HKCEE Biology 2004 I Q l


Essays

21. Describe the digestion of protein and the fate of the products of protein digestion. Any

diagrams included in your answer must be fully annotated. (10 marks)

Physical digestion of proteins takes place in mouth and stomach.Chemical / enzyme digestion starts in stomach.One of the proteases in stomach catalyses the breakdown of proteins into peptides.Further digestion of proteins takes place in small intestine.Proteases from pancreas further catalyse the breakdown of proteins into peptides and some peptides into amino acids.Proteases on the wall of the small intestine catalyse the breakdown of some peptides into amino acids.Amino acids are then absorbed into the capillaries of the villi of the small intestine by diffusionand active transport.They are carried to the liver via the hepatic portal vein.Amino acids are used by cells to make different types of proteins for growth and repair.They are also the raw materials for making enzymes, antibodies and some hormones.Excess amino acids cannot be stored in the body and are deaminated in the liver.

WJEC GCE (A) Biology Module BI4 Jan 2006 Q6


22. Explain the likely effects of liver damage on the metabolism of carbohydrate and protein.

(8 marks)

Effects on carbohydrate metabolism:Less glucose absorbed by liver cellsLess glycogen stored / glycogen synthesis(because) liver cells do not respond to insulinLess release of glucose from stored glycogen(if) liver cells do not respond to glucagonLess production of glucose from amino acids / glycerol (can be part of protein metabolism)

Effects on protein metabolism:Less breakdown of proteinLess conversion of amino acids to ammonia / less deaminationLess urea productionReduced synthesis of proteinConsequence of each of the above, such as blood clotting, transport role of proteins, water potential, blood glucose concentration is high / inability to regulate blood glucose / diabetic-like symptoms / need for amino acid supplements

OCR GCE (A) Mammalian Physiology and Behaviour Jan 2004 Q2


Reading to learn

Read the article below and answer the questions.

The real cause of peptic ulcers — bacteria

A healthy stomach can produce mucus to

protect its wall from being damaged by its

own enzymes and hydrochloric acid. When

this protection fails, a peptic ulcer (胃潰瘍)

may result.

In the past, certain drugs, smoking, alcohol,

coffee and stress were thought to be the

main causes of peptic ulcers. However, a few

years ago, an Australian doctor, Barry

Marshall found that most peptic ulcers are

actually caused by the bacteria Helicobacter

pylori (幽門螺旋菌).Fig 6.23 Barry Marshall (1951-) won the

2005 Nobel Prize for his discovery of H.

pylori

H. pylori can survive in the acidic conditions

of the stomach. The bacteria release

substances that can reduce mucus

secretions from the stomach. With

Marshall's discovery, most peptic ulcers can

now be treated with drugs that kill the

bacteria.

Fig 6.24 H. pylori on the stomach wall

(x9000)

Questions

1. How is the stomach wall protected from being damaged by the stomach's own enzymes

and acid? (2

marks)

The stomach produces mucus to cover its inner wall. The mucus protects the stomach wall from being damaged by the stomach's own enzymes and acid.

2. What are the functions of the enzymes and hydrochloric acid secreted by the stomach?


The enzymes catalyse the breakdown of proteins into peptides.The hydrochloric acid provides an acidic medium needed for the action of proteases and kills most bacteria in food. (2 marks)

3. What is the cause of most peptic ulcers? How does it lead to the condition? (2 marks)

Most peptic ulcers are caused by the bacteria Helicobacter pylori. The bacteria release substances that can reduce the mucus secretions from the stomach. The protection by the mucus fails.

4. (a) How does H. pylori behave differently from other bacteria in a low pH medium?

H. pylori can survive in a low pH medium where most other bacteria cannot.

(2 marks)

(b) Suggest how this would have affected scientists' discovery of the presence of H.

pylori in the stomach of patients with peptic ulcers. (2

marks)

Scientists’ preconceived ideas that bacteria cannot survive in a low pH medium may have hindered this discovery because observations are theory laden (i.e. biased by what scientists have expected to see or what other people have seen earlier).


Ch06

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