Digestion and Absorption

Question 1

How are large biological molecules broken down?

Answer 1

Through Hydrolysis reactions

Question 2

What is the use of amylase? and where is it produced?

Answer 2

Amylase is used to catalyse the breakdown of starch (polysaccharide) into maltose (disaccharide), its made in the salivary glands as well as the pancreas

Question 3

What is the use of membrane-bound disaccharidases? where are they located?

Answer 3

They are bound to the cell membranes of epithelial cells lining the ileum, and are used to catalyse the break down of disaccharides (e.g. maltose, lactose, sucrose) into monosaccharides (e.g. glucose, fructose and galactose) by the hydrolysis of glyosidic bonds

Question 4

How are monosaccharides absorbed into the bloodstream?

Answer 4

Glucose and galactose are both absorbed by active transport with sodium ions using a co-transporter protein

Question 5

How are monosaccharides absorbed into the bloodstream?

Answer 5

Glucose and galactose are both absorbed by active transport with sodium ions using a co-transporter protein. Fructose is absorbed by a different transporter protein by facilitated diffusion

Question 6

Describe the step by step process of lipid hydorlysis.

Answer 6

1) Lipase produced in the pancreas catalyses the breakdown of lipids into monoglycerides and fatty acids by hydrolysis of ester bonds
2) Bile salts, produced in the liver, will emulsify the lipid into tiny droplets, increasing its surface area for lipase to work on
3) The products, monoglycerides and fatty acids stick with bile salts to form micelles

Question 7

How are by products of lipid hydrolysis absorbed into the bloodstream?

Answer 7

Micelles, will move towards the ileum epithelium, they can constantly reform and break up to release the products. Micelles themselves are not absorbed but monoglycerides and fatty acids are lipid soluble and so will diffuse through into the bloodstream

Question 8

Name the 2 enzymes involved in protein hydrolysis

Answer 8

Exopeptidases and endopeptidases

Question 9

Explain 2 ways in which proteins are hydrolysed

Answer 9

1) Endopeptidases- hydrolyse the peptide bonds within a protein
2)Exopeptidases - hydrolyse peptide bonds at the end of a protein- they remove single amino acids, dipeptidases are examples of one, they seperate 2 amino acids in a dipeptide

Question 10

How are amino acids absorbed?

Answer 10

Sodium ions are actively transported out of epithelium into ileum, they diffuse back in via sodium dependent co-transporter proteins carrying amino acids with them