Digestive System

Question 1

What is the role of the large intestine?

Answer 1

Absorb water

Question 2

What are the 2 types of digestion?

Answer 2

Physical and chemical

Question 3

What is the process by which fatty acids and glycerol enter the intestinal epithelial cell?

Answer 3

Diffusion

Question 4

What is the action of salivary amylase?

Answer 4

Hydrolyses glycosisdic bond in starch to convert: starch —> maltose

Question 5

How is the optimum neutral pH for amylase maintained in the mouth?

Answer 5

saliva contains mineral salts

Question 6

Explain why alkaline salts are produced/where

Answer 6

to maintain a neutral pH for pancreatic amylase
-produces in pancreas and intestinal wall

Question 7

What does sucrase hydrolyse/ products of this

Answer 7

sucrose–>
glucose+fructose

Question 8

What does maltase hydrolyse/products of this

Answer 8

maltose –>
glucose+glucose

Question 9

What does lactase hydrolyse/products of this

Answer 9

lactose–>
glucose+galactose

Question 10

what is meant by ‘membrane bound disaccharidase’?

Answer 10

The disaccharidase is bound to Cell surface membrane of epithelial cells lining the ileum rather than being released into the intestine

Question 11

What is the function of lipase/ what products does it form?

Answer 11

hydrolyse the ester bond in triglycerides to form monoglycerides and two fatty acids

Question 12

What is the role of the liver in lipid digestion?

Answer 12

produces bile salts that emulsify fat

Question 13

Explain why emulsification increases the rate of lipid digestion.

Answer 13

increases the surface area for lipase action

Question 14

What is the group of enzymes that hydrolyse proteins?

Answer 14

peptidases

Question 15

What is the function of endopeptidases?

Answer 15

hydrolyse peptide bonds in the centre of a protein molecule forming smaller peptides

Question 16

What is the function of exopeptidases?

Answer 16

hydrolyse peptide bonds on the terminal amino acids of peptides to form dipeptides and single amino acids

Question 17

What is the function of membrane bound dipeptidases?

Answer 17

hydrolyse dipeptides into amino acids

Question 18

What is the structure of the ileum?

Answer 18

Folded, villi containing epithelial cells which contain capillaries and microvilli

Question 19

how is the ileum is adapted for absorption?

Answer 19

-Villi - finger-like projections.
-Many blood capillaries, maintain diffusion gradient. Increase SA for diffusion.
-Thin walls so short diffusion pathway.
-Epithelial cells of villi have microvilli further increasing SA

Question 20

How are triglycerides absorbed

Answer 20

• Micelle collides with the epithelial cell wall which releases monoglyceride, bile salt and fatty acids
• these diffuse into the cell
• go to SER where triglyceride is reformed
• goes to golgi apparatus where triglyceride combines with cholesterol and a lipoprotein to form a chylomicron
• moves out of cell by exocytosis into the lacteal
• transported to capillary
• hydrolysed by a membrane bound enzyme on the endothelium
• monoglyceride and fatty acids then absorbed into cells

Question 21

where are membrane bound dipeptidases often located?

Answer 21

on the cell surface membrane of epithelial cells in small intestine

Question 22

where is amylase produced

Answer 22

-salivary glands-release amylase into mouth
-pancreas-releases amylase into small intestine

Question 23

what two types of enzyme can break down carbohydrates

Answer 23

amylase or membrane bound disacharidases

Question 23

what is the ileum

Answer 23

-section of small intestine covered in villi, which are covered in epithelial cells

Question 24

Where are bile salts produces?

Answer 24

the liver

Question 24

How to bile salts aid in the hydrolysis of lipids by lipase?

Answer 24

-emulsify lipids, breaking them down inot small droplets increasing SA for lipases to work on

Question 25

How are amino acids absorbed?

Answer 25

-sodium ions actively transported out of the ileum epithelial cells into the blood
-this creates a sodium ion conc. gradient
-sodium ions then diffuse from the lumen of the ileum into the epithelial cells through sodium dependant transport proteins, carrying a/a w/ them

Question 26

How are micelles formed

Answer 26

-once the lipid has been broken down, the monoglycerides and fatty acids stick with the bile salts to form micelles

Question 27

How do micelles aid in the absorption of monoglycerides and fatty acids

Answer 27

-micelles help to move monoglycerides and fatty acids towards the ileum
-micelles are constantly breaking and reforming
-this allows monoglycerides and fatty acids to be diffuse directly across the epithelial cell membrae
( as they are lipid-soluble)

Question 28

What happens to the products of digestion

Answer 28

-the products of digestion are absorbed by the ileum epithelium into the blood stream

Question 29

list three organeles/reasons why, that you would expect to be numerous /well developed in the epithelial cell of the ileum

Answer 29

-Endoplasmic reticulum to resynthesize tricglycerides from monoglycerides and fatty acids
-golgi apparatus to form chylomicrons from triglycerides, cholesterol, and lipoproteins
-mitochondria to provide ATP required for for co-transport of glucose and a/a molecules

Question 30

How is glucose/ galactose absorbed

Answer 30

-absorbed into ileum epithelium by active transport with sodium ions via a co-transport protein
-galactose absorbed same way via a different transporter protein

Question 31

how is fructose absorbed

Answer 31

-by facillitated diffusion through a different transporter protein