Digestion and absorption

Question 1

what is amylase?

Answer 1

enzyme produced by the salivary glands and pancreases which hydrolyses starch into the dissacharide maltose

Question 2

what is sucrase?

Answer 2

enzyme that hydrolyses sucrose to form glucose and fructose

Question 3

what is lactase?

Answer 3

enzyme that hydrolyses lactose to for glucose and galactose

Question 4

where is amylase produced?

Answer 4

pancreas and salivary gland

Question 5

How is carbohydrates hydrolysed into monosaccharides?

Answer 5

-amylase hydrolyses polysaccharides into the dissacharide maltose by hydrolysing the glycosidic bonds

-sucrase and lactase are membrane bound enzymes that hydrolyse sucrose and lactose into monosaccharides.

Question 6

how are proteins hydrolysed?

Answer 6

1) endopeptidases: hydrolyse peptide bonds between amino acids in the middle of a polypetide chain

2) exopeptidases: hydrolyse peptide bonds between amino acids at the end of a polpeptide chain

3) membrane - bound dipeptidases : hydrolyse peptide bonds between amino acids

Question 7

where is lipase produced?

Answer 7

pancreas

Question 8

what can lipase hydrolyse?

Answer 8

ester bond in triglycerides to form the monoglycerides and fatty acids

Question 9

what is the role of bile salts?

Answer 9

produced in the liver and can emulsify lipids to form micelles
this can increase the surface area for lipase to act on

Question 10

describe how starch is digested?

Answer 10

glycosidic bonds are hydrolysed
starch is converted into maltose by amylase
maltose is converted into glucose by membrane bound maltase

Question 11

The action of endopeptidases and exopeptidases can increase the rate of protein digestion. Describe how

Answer 11

Exopeptidases hydrolyse peptide bonds at the ends of a polypeptide AND endopeptidases hydrolyse internal peptide bonds within a polypeptide

More surface area;/ more ends

Question 12

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.

Answer 12

1. Micelles contain bile salts and fatty acids/monoglycerides;
2. Make fatty acids/monoglycerides (more) soluble (in water)
3. Fatty acids/monoglycerides absorbed by diffusion;
4. reformed back into triglycerides
5. Vesicles move to the cell membrane

Question 13

Describe and explain two features you would expect to find in a cell specialised for absorption.

Answer 13

microvilli so large surface area (for absorption);
Large number of co-transport/carrier/channel proteins so fast rate (of absorption)

Question 14

Describe the role of micelles in the absorption of fats into the cells lining the ileum.

Answer 14

1.Micelles include bile salts and fatty acids;
2. Make the fatty acids (more) soluble in water;
3.carry 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

Question 15

describe the hydrolysis reaction involved in the digestion of triglycerides

Answer 15

-breaking up the ester bonds
- by the addition of water

Question 16

The movement of Na+ out of the cell allows the absorption of glucose into
the cell lining the ileum.
Explain how. (2)

Answer 16

Maintains/generates) a concentration/diffusion gradient
for Na+ (from ileum into cell);

Na+ moving (in) by co-transport, brings glucose with it;

Question 17

Cells lining the ileum of mammals absorb the monosaccharide glucose by
co-transport with sodium ions. Explain how.

Answer 17

1.Sodium ions actively transported from ileum cell to blood;
2. Maintains / forms diffusion gradient for sodium to enter cells from gut
(and with it, glucose);
3. Glucose enters by facilitated diffusion with sodium ions;