Digestion And Absorption

Question 1

Amylase

Answer 1

Starch—-> maltose
Salivary glands, pancreas

Question 2

Membrane bound disaccharidases

Answer 2

Cell membranes of epithelial cells lining the ileum
Disaccharides——> monosaccharides

Question 3

Lipases

Answer 3

Lipids——> monoglycerides and fatty acids
Pancreas

Question 4

Bile salts

Answer 4

Produced by liver
Emulsify lipids
Micelles

Question 5

Endopeptidases

Answer 5

Hydrolyse peptide bonds within a protein

Question 6

Exopeptidases

Answer 6

Hydrolyse binds at the ends of protein molecules, removing single amino acids
Dipeptidases work specifically on dipeptides and are located in the cell surface membrane of epithelial cells in the small intestine

Question 7

Absorption of glucose and galactose (same transporter protein)

Answer 7

Na+ actively transported out of epithelial cell into the blood via the sodium- potassium pump (carrier protein). Creates/maintains concentration gradient
Na+ diffuse from ileum into cell down concentration gradient via sodium-glucose co transporter proteins
Co transporter carries glucose with the Na+. Glucose travelling against concentration gradient
Glucose diffuses out of cell through protein channel by facilitated diffusion
Symport

Question 8

Absorption of fructose

Answer 8

Facilitated diffusion

Question 9

Absorption of amino acids

Answer 9

Co transport
Sodium dependent transporter proteins
(Same as glucose mechanism)

Question 10

Absorption of lipids

Answer 10

Micelles move monoglycerides and fatty acids towards the epithelium
Micelles constantly break up and reform so they can release them for absorption
Monoglycerides and fatty acids are lipid soluble (diffuse across membrane)

Question 11

Micelles and solubility

Answer 11

Micelles contain bile salts and fatty acids, monoglycerides
Make fatty acids/ monoglycerides more soluble in water. Fatty acids are amphiphilic as the COOH is soluble in water. In micelles the fatty acid hydrophobic tail points inwards and the COOH outwards
Maintain higher concentration of fatty acids and monoglycerides outside cell
Absorbed by diffusion

Question 12

How the Golgi apparatus is involved in the absorption of lipids

Answer 12

Modifies the triglycerides then packages them into a vesicle
Combines triglycerides with proteins

Question 13

Describe the mechanism for the absorption of amino acids in the ileum

Answer 13

Co transport
Na+ actively transported from cell to blood
Creating Na+ concentration gradient.
Facilitated diffusion of amino acid into blood

Question 14

The number of copies of the AMY1 gene (associated with concentration of saliva) is unlikely to affect people’s ability to digest starch explain why

Answer 14

Little digestion of starch by salivary amylase/ starch in mouth for short period
Amylase also secreted by pancreas
So most starch digestion occurs in small intestine

Question 15

Describe the complete digestion of starch by a mammal

Answer 15

Hydrolysis
Glycosidic bonds
Maltose by amylase
Maltose to glucose by maltase
Maltase membrane bound