3.3.3 Digestion & absorption

Question 1

What enzymes are involved in the hydrolysis of protein?

Answer 1

Endopeptidase, exopeptidase, dipeptidase

Question 2

What enzymes are involved in the hydrolysis of carbohydrates?

Answer 2

Amylase, maltase, lactase, sucrase

Question 3

What enzymes are involved in the hydrolysis of triglycerides?

Answer 3

Lipase

Question 4

What are disaccharidases / dipeptidases and where are they made?

Answer 4

Enzymes that hydrolysis bond between two monossacharide / amino acids
Made and embedded in cell membrane of ileum

Question 5

What is the function of endopeptidases?

Answer 5

Hydrolyse peptide bonds within polypeptide chains, producing shorter polypeptide chains with more terminal peptide bonds

Question 6

What is the function of exopeptidases?

Answer 6

Hydrolyse terminal peptide bonds, working from outside towards middle
Cannot hydrolyse peptide bond of a dipeptide - hydrolysed by dipeptidase

Question 7

What is the process of triglyceride hydrolysis?

Answer 7

1. Triglyceride is hydrolysed into a diglyceride and a fatty acid via lipase by breaking ester bond between fatty acid and glycerol
2. Diglyceride is hydrolysed into a monoglyceride and two fatty acids
3. Monoglyceride can be absorbed - no longer need to be hydrolysed

Question 8

What is the function of bile salt?

Answer 8

Emulsify triglycerides from having a lower SA to vol. ratio to a higher SA to vol. ratio
This makes hydrolysis of triglycerides by lipase easier

Question 9

What bond do carbohydrases hydrolyse?

Answer 9

Glycosidic bonds between monosaccharides

Question 10

What bond do lipases hydrolyse?

Answer 10

Ester bond between glycerol and fatty acid

Question 11

What bond do peptidases hydrolyse?

Answer 11

Peptide bond between amino acids

Question 12

Where is the site of absorption?

Answer 12

Ileum in the small intestine

Question 13

How is the ileum adapted to absorption of monomers?

Answer 13

Lined with a single layer of epithelial cells which has microvilli to further increase surface area and shortens diffusion pathway to increase rate of diffusion
Good blood supply
Presence of lacteal for the absorption of chylomicron

Question 14

How do monomers move across membrane of epithelial cells of ileum?

Answer 14

Co-transport (amino acids and monosaccharides - not lipid soluble)
Simple diffusion (monoglycerides and fatty acids - lipid soluble)

Question 15

What is the process of amino acids and monosaccharides absorption in the ileum?

Answer 15

1. Na+ ions leave cell via active transport, K+ ions enter cells. Concentration of Na+ is lowered inside cell, concentration gradient increases between lumen and cell
2. Na+ diffuse into epithelial cells via facilitated diffusion, co-transporting monosaccharides/ amino acids with them
3. Monosaccharides/amino acids concentration inside cell increases, they will leave cell via facilitated diffusion down concentration gradient into blood stream to be transported
4. Concentration gradient is maintained by constant blood flow

Question 16

What is the process of triglyceride absorption in the ileum?

Answer 16

1. Monoglycerides and fatty acids are grouped as micelles (stuck with bile salt)
2. As micelles come in contact with microvilli, they release their content - monoglycerides and fatty acids and they diffuse across the membrane of epithelial cells via simple diffusion
3. Monoglyceride and fatty acids are reformed back into triglycerides in the sER (synthesis) and packaged (+transported) in the golgi apparatus

4.Triglycerides bundle together and they are protected by phosolipids (phosphate head on the outside, tails on the inside), apolipoproteins and cholesterols (strengthens)

5. They form a structure called Chylomicron which leaves the cell through exocytosis

6.Chylomicron enters the lacteal which will be transported through the lymph system into the blood to be transported