Digestive system

Question 1

Which enzymes break down carbohydrates?

Answer 1

ptyalin
pancreatic amylase
maltase
sucrase
lactase

Question 2

Which enzymes break down Protein?

Answer 2

pepsin
trypsin
chymotrypsin
carboxypeptidase
aminopeptidase
dipeptidase

Question 3

Which enzymes break down Lipids?

Answer 3

Pancreatic lipase

Question 4

Which enzymes break down Nucleic acids?

Answer 4

nuclease

nucleosidase

Question 5

Which enzymes are produced in salivary glands?

Answer 5

ptyalin

Question 6

Which enzymes are produced in the stomach wall?

Answer 6

pepsin

Question 7

Which enzymes are produced in the pancreas?

Answer 7

pancreatic amylase
pancreatic lipase
trypsin
chymotrypsin
aminopeptidase
carboxypeptidase
nuclease

Question 8

Which enzymes are produced in the intestinal wall?

Answer 8

maltase
sucrase
lactase
dipeptidase
nucleosidase

Question 9

How and why is the pH changed when food enters the stomach?

Answer 9

In the stomach, the conditions are acidified by adding large amounts of HCl. This activates the enzyme pepsin and starts protein digestion. It also has secondary functions of killing off foreign microorganisms that may enter with the food, and unravelling big complex molecules in the food.

Question 10

How and why is the pH changed when chyme enters the duodenum?

Answer 10

In the duodenum, the acid is neutralized by sodium bicarbonate from the pancreas, and bile salts from the liver. This deactivates pepsin, preventing digestion of the intestines and their enzymes. It also provides the slightly basic conditions under which pancreatic enzymes work.

Question 11

Three divisions of the small intestine

Answer 11

duodenum (mixing of pancreatic juice, bile and chyme)
jejunum (chemical breakdown of macromolecules by enzymes)
ileum (absorption of micronutrients)

Question 12

What are the functions of bile?

Answer 12

The main function of bile is to emulsify (suspend) fats in the intestinal fluid. The hydrophobic ends of the bile salts dissolve in tiny droplets of fat, and the hydrophilic ends then hold the droplets in suspension. This allows a large surface area for lipase to work on. A secondary function of bile salts is to neutralize some of the HCl from the stomach.
Bile also acts a s disposal system for wastes generated by the breakdown of hemoglobin - bile pigments.

Question 13

How would stomach muscles, gastric pits, food, gastrin and enterogastrone interact?

Answer 13

• food stimulates the secretion of gastrin
• gastrin causes chief and parietal cells to release their contents & starts peristalsis
• Peristalsis squirts HCl and pepsinogen into stomach
• If the chyme is high in fat, entergastrone to slow down the release of chyme into the duodenum

Question 14

Why is the inside surface of the jerjunum and ileum so highly folded?

Answer 14

The many layers of folding (ridges, villi, microvilli) provide a huge surface area for the absorption of digested nutrients, allowing food nutrients to move into the circulatory system more rapidly.

Question 15

What is the large blood vessel that carries nutrient poor blood away to the intestine?

Answer 15

The anterior mesenteric artery

Question 16

What is the large blood vessel that carries blood away from the intestine?

Answer 16

The colon is specialised to absorb water from the intestinal fluid. Over the course of a day, you dump several litres of water into the digestive system. If you did not recover it, you would rapidly dehydrate. (This dehydration is what kills cholera sufferers, as the bacterium blocks the protein channels that actively increase the rate of osmosis.) Water soluble vitamins are also absorbed in the colon.

Question 17

What do faeces consist of?

Answer 17

Faeces contain indigestible material (mostly cellulose) from food, as well as bile pigments, dead and living intestinal bacteria, mucus secreted in the colon to bind the waste together, dead cells from the intestinal wall, and about 10% water.

Question 18

What is the function of cellulose in the diet?

Answer 18

Cellulose (fibre) is indigestible for humans, but it is still very important. It stimulates peristalsis, and thus keeps the food moving steadily through the system. (That’s why fibre keeps you regular, but a sudden excess can give you diarrhea.) Without fibre, food would tend to stagnate, especially in the intestine where there is little other solid material for the muscles to push against. Bacterial fermentation can create undesirable byproducts if the intestinal fluid is allowed to stagnate.

Question 19

Which vitamins and minerals play some role in mobilizing and respiring sugars to obtain ATP. Explain why each is necessary.

Answer 19

Niacin, thiamine and riboflavin are all required as coenzymes in cellular respiration. Folacin, B6, iron and copper are all involved in making haemoglobin, which delivers the oxygen for respiration. Pantothenic acid is required for the breakdown of carbohydrates. Phosphorus is an essential ingredient in making ATP. You did not have to get all of these, but you should have had a reasonable list and given justification.

Question 20

Why does your body use many different types of enzyme to accomplish the digestion of a single type of molecule?

Answer 20

several enzymes will create division of labour, which will provide a more complete breakdown of a nutrient in a shorter amount of time.