Digestion and Absorption

Question 1

Oesophagus

Answer 1

transports food from mouth to stomach

Question 2

Stomach

Answer 2

muscular sac, inner layer produces enzymes, stores and digests food (particularly protein)

Question 3

Ileum (small intestine)

Answer 3

further enzyme digestion, enzymes produced in the wall of the ileum villi and microvilli

Question 4

Large Intestine

Answer 4

mostly absorbs water and nutrients

Question 5

Salivary glands

Answer 5

secretions via a duct into the mouth, containing amylase

Question 6

Pancreas

Answer 6

contains pancreatic juices which contain various enzymes

Question 7

What are the exchange features in the ileum? (5)

Answer 7

1. Villi and microvilli increase surface area
2. Villi lining and capillary endothelium are one cell thick
3. Ileum contain muscle which contracts.
4. Well supplied with blood vessels.
5. Epithelial cells are dense with carrier proteins for amino acids and glucose

Question 8

How is many villi and microvilli in the ileum beneficial?

Answer 8

creates a large SA:V ratio

Question 9

How is the villi lining and capillary endothelium of the ileum being one cell thick beneficial?

Answer 9

Shorter diffusion distance

Question 10

How is the ileum containing muscles that contract beneficial?

Answer 10

This movement mixes the contents of the ileum and so maintains concentration gradients.​

Question 11

How is the ileum being supplied with blood vessel beneficial?

Answer 11

Blood circulates to maintain concentration gradient

Question 12

How is the epithelial cells being dense in the ileum with carrier proteins for amino acids and glucose beneficial?

Answer 12

selectively permeable

Question 13

Role of carbohydrases

Answer 13

Hydrolyses polysaccharides to disaccharides​

Question 14

Role of disaccharidases

Answer 14

Hydrolyse disaccharides to monosaccharides ​

Question 15

Role of Lipases

Answer 15

Hydrolyses lipids into monoglycerides and fatty acids​

Question 16

Role of Proteases/ Peptidases (2)

Answer 16

Hydrolyses polypeptides to dipeptides​Hydrolyses dipeptides to amino acids

Question 17

Where are all these digestive enzymes found?

Answer 17

in the epithelial surface membrane

Question 18

Outline the process of Carbohydrate digestion (7)

Answer 18

1. Saliva enters mouth and is mixed with food.​
2. Salivary amylase starts hydrolysing starch to maltose.​
3. Mineral salts in the saliva maintain the pH at neutral.
4. The food enters the stomach and amylase is denatured.
5. The food is passed into the small intestine and mixed with pancreatic juices (containing pancreatic amylase)​
6. Epithelial lining of small intestine produces maltase.
7. Maltase hydrolyses maltose to alpha glucose.

Question 19

Describe how a molecule of starch is digested into glucose (4 marks)​

Answer 19

1. Salivary amylase hydrolyses starch into maltose​2. Pancreas makes pancreatic amylase which further hydrolyses starch into maltose​3. Membrane-bound maltase hydrolyses maltose into glucose​4. Glycosidic bonds are broken​

Question 20

Role of the disaccharidase Sucrase?

Answer 20

breaks the glycosidic bond in a sucrose molecule, producing glucose and fructose.​

Question 21

Role of the disaccharidase Lactase?

Answer 21

breaks the glycosidic bond in a lactose molecule, producing glucose and galactose.​

Question 22

What happens when you add lipids in water? Why?​

Answer 22

An emulsion is formed.
Fatty acids are hydrophobic – insoluble in water.​

Question 23

Outline the process of triglyceride digestion (7)

Answer 23

1. Emulsification must occur to aid digestion
   ​2. Bile salts are produced by the liver and stored in the gall bladder
   ​3. Large lipid droplets are split up into tiny droplets called micelles by bile salts.​4. This increases the lipids surface area, increasing the activity of lipases​
2. Now lipid digestion can occur at an increased rate​6. Lipases in pancreatic juice hydrolyse triglycerides into monoglycerides and fatty acids. Break ester bond.
   ​7. Micelles carry monoglycerides/fatty acids to the epithelial cell membrane

Question 24

What is a micelle?

Answer 24

an association of bile salts, monoglycerides and fatty acids​

Question 25

Describe what happens during emulsification.​

Answer 25

Large insoluble lipid droplets are split into smaller molecules called micelles

Question 26

How do micelles increase the digestion and absorption of lipids? (2 ways)​

Answer 26

Increase SA for action of lipasescarry them to epithelial lining and make them soluble​

Question 27

What are the three types of peptidases?

Answer 27

endopeptidases, exopeptidases and dipeptidases​

Question 28

endo

Answer 28

in

Question 29

exo

Answer 29

out

Question 30

Outline the process of protein digestion (3)

Answer 30

1. Endopeptidases hydrolyse the central region of a protein molecule forming a series of peptide molecules.​2. Exopeptidases progressively release dipeptides and single amino acids by breaking peptide bonds on terminal amino acids ​3. Dipeptidases break the bond between the 2 amino acids of a dipeptide​

Question 31

What is the function of endopeptidase?

Answer 31

hydrolyses the central region of a protein molecule

Question 32

What is the function of exopeptidases?

Answer 32

progressively release dipeptides and single amino acids by breaking peptide bonds on terminal ends of the polypeptide chain

Question 33

What is the function of dipeptidases?

Answer 33

break the bond between the 2 amino acids of a dipeptide​

Question 34

Where are peptidases produced in the body? (3 organs)​

Answer 34

stomach, small intestine and pancreas

Question 35

How are glucose and amino acids absorbed?

Answer 35

co transport

Question 36

Outline the process of cotransport of glucose absorption in the ileum (4)

Answer 36

1. Sodium ions are actively transported out of ileum epithelial cell into blood. There are now less Na+ ions inside the cell.​2. This forms a diffusion gradient for sodium to enter epithelial cell from the lumen.​3. As sodium moves into cell, glucose enters by facilitated diffusion with sodium ions via the co-transporter protein.​4. Glucose moves into blood via facilitated diffusion through a channel protein.​

Question 37

Outline the process of cotransport of amino acid absorption in the ileum (4)

Answer 37

1. Sodium ions are actively transported out of ileum epithelial cell into blood. There are now less Na+ ions inside the cell.​2. This forms a diffusion gradient for sodium to enter epithelial cell from the lumen.​3. As sodium moves into cell, amino acids enter by facilitated diffusion with sodium ions via the co-transporter protein.​4. Amino acids move into the blood via facilitated diffusion through a channel protein.​

Question 38

What is lacteal?

Answer 38

Tiny lymphatic vessels ​Transport fat and slowly release them into the bloodstream​

Question 39

What do epthelial cells make?

Answer 39

Chylomicrons. These lipoproteins are adapted for transporting dietary lipids from intestines to other parts of the body.​

Question 40

Describe how triglycerides/lipids are absorbed (6)

Answer 40

1. Micelles come into contact with epithelial cell membrane and break down, releasing the monoglycerides and fatty acids.​2. MGs and FAs diffuse across the phospholipid bilayer into the epithelial cells.​3. MGs and FAs move to endoplasmic reticulum where they are recombined to form triglycerides.​4. Triglycerides move to Golgi apparatus, where they associate with cholesterol and lipoproteins to form chylomicrons.​5. Chylomicrons move out of epithelial cells by exocytosis.​​6. Chylomicrons enter lacteals (lymphatic capillaries) and are transported away from intestine.​

Question 41

what is the role of micelles in the absorption of lipids. (5)

Answer 41

1. Micelles include bile salts and fatty acids2. Make the fatty acids (more) soluble in water;3. Release fatty acids to cell/lining (of the ileum)4. Maintain high(er) concentration of fatty acids to cell/lining (of the ileum)5. Fatty acids (absorbed) by diffusion