Unit 3.2 Food

1. What are the functions of the digestive system?

• Takes in food & water - ingestion

• Mechanical processing

• Digestion• Secretion• Absorption• Excretion

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body?

• Oral Cavity, teeth, tongue • Mechanical processing, moistening, mixing with salivary

secretions• Tongue assists with swallowing of bolus = mass of chewed or

partially digested food

• Hard palate & soft palate• Form roof of the oral cavity• With the uvula, the soft palate keeps food from going into nasal

cavity during swallowing

• Salivary Glands • Exocrine glands that secrete lubricating fluid containing enzymes

that break down carbohydrates. • Salivary amylase starts carbohydrate digestion

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body? Cont.

• Pharynx• A hollow tube shared by both the digestive &

respiratory system—allows the passage of food, water & air.

• Epiglottis• Elastic cartilage in the laryngophaprynx that

closes during swallowing to prevent food from traveling into the trachea

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body? Cont.

• Esophagus • Hollow tube• Pushes food & water to the stomach using

peristalsis = muscle contractions• No enzymes are secreted into the esophagus

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body? Cont.• Stomach

• Chemical breakdown of materials by acid and enzymes: protein digestion

• Mechanical processing through muscular contractions

• pH (of 2) and enzymes will decontaminate incoming food matter

• Forms chime• Food mixed with water, HCl and other enzymes

• Parietal cells produce • HCl• Intrinsic factor required for vitamin B12 absorption

• Chief cells secrete pepsinogen which is going to be converted into pepsin in the presence of HCl

• Goblet cells produce mucus to protect stomach lining from being digested by the acid

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body? Cont.

• Liver• Found in the upper right quadrant• It weighs 3.5 lbs• Secretes bile (important for lipid digestion)

which is carried to gall bladder by cystic duct • Stores nutrients• Produces plasma proteins • Removes old RBC• Detoxifies toxic substances• Breaks down glycogen into glucose

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body? Cont.

• Gall bladder• Stores and concentrates bile• Passes bile into the small intestine to help

break down fats • Bile is carried by the common bile duct

into the duodenum• Formed by the union of the common

hepatic duct (from the liver) and the cystic duct

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body? Cont.

• Pancreas• 6 inches long located behind the stomach• Exocrine cells secrete buffers and digestive enzymes:

• trypsin: breaks down proteins• Chymotrypsin and carboxypeptidase: break down

proteins• Pancreatic lipase: breaks down fats• Pancreatic amylase: breaks down carbohydrates• Secretes bicarbonates to deactivate the acid in the

chime exiting the stomach• Endocrine cells secrete hormones

• Beta cells produce insulin – decreases sugar in blood• Alpha cells produce glucagon – increases sugar in

blood

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body? Cont.

• Small intestine• Food moves by peristalsis• Long, narrow, has villi that absorb nutrients into

bloodstream• Enzymatic digestion and absorption of water,

organic substrates, vitamins and ions• Bulk of digestion occurs in the duodenum• Bulk of absorption takes place in the jejunum and

ileum• pH in duodenum is 6 and as it travels through the

small intestine it raises to 7.4 due to the bicarbonate released by the pancreas

• Common bile duct and pancreatic duct enter the duodenum at the hepatopancreatic sphincter

2. How does the structure of each organ in the digestive system relate to its function? 3. How does the digestive system assist in maintaining the water balance in the body?

• Large intestine• Reabsorbs water and salts in the ascending colon and in

the cecum• Dehydration and compaction of undigestible materials

in preparation for elimination

• Cecum• Begins the process of compaction and absorbs water

• Colon• Ascending, transverse, descending• Bears pouches and longitudinal bands of smooth muscle

• Rectum• Terminates in the anal canal• Has internal and external sphincters

4. How do enzymes assist the process of digestion?

• Enzymes are proteins that help speed up or initiate chemical reactions, including digestion.

• Pepsin breaks down proteins• Carbohydrases break down carbohydrates• Lipases break down lipids• Proteases break down proteins• Nucleases break down nucleic acids

5. How do factors such as temperature, pH and concentration of enzyme or substrate affect the rate of enzyme-catalyzed reactions?

• Enzymes work best within a particular range of temperatures & pH values.

• For instance, salivary amylase works best at 37ºC (body temperature) and a pH of 6.8 (barely acidic).

• Pepsin works best at pH 2 and 37 C

• The higher the enzyme, substrate ratio, the more effective the enzyme will be.

• Enzymes have a very narrow optimal temperature and pH above and below which it will cause the enzyme to not work properly

6. What are BMI and BMR? 7. How can BMI and BMR help assess healthy diet and weight?

• Body mass index (BMI) • Ratio of weight (kg) to

height (m)—used to determine whether a person is at a healthy weight

6. What are BMI and BMR? 7. How can BMI and BMR help assess healthy diet and weight? Cont.

• Basal metabolic rate (BMR) • Metabolism (total chemical reactions) while at complete rest. It is

combined with a person’s activity level to plan a healthy caloric intake.

8. What are the health risks associated with being overweight or underweight? 9. What body systems are affected when a person is overweight or underweight?Underweight (BMI of 19 for women, 20 for

men) Overweight (BMI of 25 or more)

• Anemia & nutrient deficiencies (CARDIO)

• Bone loss & osteoporosis (SKELETAL) • Heart irregularities & blood vessels

disease (CARDIO) • Amenorrhea (loss of periods for

women) (REPRODUCTIVE) • Increased vulnerability to

infection/disease (IMMUNE) • Delayed wound healing (IMMUNE)

• Cancers (IMMUNE) • Depression (NERVOUS) • Type II Diabetes (ENDOCRINE) • Sleep Apnea

(RESPIRATORY/NERVOUS) • Asthma (RESPIRATORY) • Osteoarthritis (SKELETAL) • Heart attack or stroke (CARDIO) due to:

High cholesterol, High blood pressure, Arteriosclerosis

10. What is ATP?

• ATP is adenosine triphosphate, the energy molecule used by our bodies to build up tissues (anabolism)

11. How is energy released from ATP and used to do work in the body?

• ATP releases energy by losing a phosphate group and turning into ADP (adenosine diphosphate). The breaking of the bond gives off energy.

• To strip off a phosphate group a molecule of water is added which breaks the hydrogen bonds – Hydrolysis reaction

12. How do the air you breathe and the food you eat relate directly to the production of energy in the form of ATP?

• The release of energy occurs in 3 steps: • Glycolysis • Kreb’s Cycle • Electron Transport

• The process is cellular respiration.• It occurs in the mitochondria of the cell

• You get glucose from the food you eat and the oxygen from the air you breathe

• Together, these steps can make 38 ATP molecules from one glucose molecule (taken in through food) that is in the presence of oxygen (aerobic). If there’s no oxygen (anaerobic), the process is 15x less efficient!