Digestion

Question 1

What happens during digestion

Answer 1

large biological molecules are hydrolysed to smaller molecules that can be absorbed across cell membranes.

Question 2

What are the 2 enzymes involved in carbohydrates being broken down and hydrolysed into monosaccharides from them being polysaccharides

Answer 2

Amylase
Membrane bound disaccharidases

Question 3

Describe the role of amylase in carbohydrates (Starch) and how it hydrolyses polysaccharides into disaccharides

Answer 3

-amylase is produced by the pancreas and salivary glands
-amylase is a digestive enzyme which hydrolyses the polysaccharide starch into the disaccharide maltose by hydrolysing the glycosidic bonds in starch

Question 4

Describe the role of membrane bound disaccharidases and how they break down and hydrolyse disaccharides into monosaccharides

Answer 4

-disaccharidases ie Maltase sucrase and lactase are membrane bound enzymes
-that hydrolyse the glycosidic bonds of the disaccharides maltose sucrose and lactose into monosaccharides

Question 5

What are the three monosaccharides produced by membrane bound disaccharidases

Answer 5

Glucose + glucose
Fructose + glucose
galactose + glucose

Question 6

What enzyme and other molecule digest lipids

Answer 6

-lipase enzyme and the action of of bite salts

Question 7

How does lipase break down lipids-chemical stage

Answer 7

-lipase are produced in the pancreas
-and it hydrolyses the ester bonds in triglycerides to form the monoglycerides and fatty acids

Question 8

How do bile salts emulsify lipids-physical stage

Answer 8

-bile salts are produced in the liver and emulsify lipids into small droplets called micelles
-this increases the surface area of lipids for lipase to act on

Question 9

What 3 enzymes hydrolyse the polymer proteins

Answer 9

-endopeptidases
-exopeptidases
-membrane bound dipeptidases

Question 10

Explain the function of endopeptidases

Answer 10

-hydrolyse the peptide bonds between amino acids in the middle of the polypeptide more ends / surface area for exopeptidases

Question 11

Explain the function of exopeptidases

Answer 11

Hydrolyse terminal peptide bonds between amino acids at the end of the polypeptide
They remove single amino acids from proteins

Question 12

Explain the function if membrane bound dipeptidases

Answer 12

Hydrolyse peptide bonds between 2 amino acids

Question 13

Explain the role of micelles for the absorption of the lipids of digestion by cells lining the ileum of mammals

Answer 13

Micelles include bile salts and fatty acids and monoglycerides
Monoglycerides and fatty acids make them soluble in water
-micelles help diffuse the monoglycerides and fatty acids to be across the cell surface membrane to the epithelial cells due to them being lipid soluble and non polar

-once inside the epithelial cell the fatty acids and monoglycerides are modified into triglycerides

Question 14

In mammals where are the products of digestion absorbed

Answer 14

The cells lining the ileum

Question 15

How is the ileum adapted to maximise diffusion

Answer 15

-ileum wall is covered in villi which have thin walls to create a short diffusion pathway
-villi is surrounded by a network of capillaries maintaining a a concentration gradient
- epithelial cells have smaller microvilli - larger surface area to volume ratio

Question 16

Explain the absorption of the monosaccharides(glucose galactose fructose) of digestion by cells lining the ileum of mammals

Answer 16

-glucose/galactose is absorbed by co transport with sodium ions via co-transporter protein
-fructose is absorbed via facilitated diffusion through a transporter protein

Question 17

Explain the absorption of amino acids (products) and monosaccharides of digestion by cells lining the ileum of mammals

Answer 17

Co transport
● sodium ions actively transported from epithelial cells lining ileum to blood
● Establishing a conc. gradient of sodium ions higher in lumen than epithelial cell)

● sodium ions enters epithelial cell down its concentration gradient with glucose against its concentration gradient
● Via a co-transporter protein

● Glucose moves down a conc. gradient into blood via facilitated diffusion

Question 18

Describe the digestion of lipids in mammals, including action of bile salts

Answer 18

● Bile salts (produced by liver) emulsify lipids causing them to form smaller lipid droplets called micelles
● This increases surface area of lipids for increased / faster lipase activity
● Lipase (made in pancreas) hydrolyses lipids (eg. triglycerides) → monoglycerides + fatty acids
● Hydrolysis of ester bond

Question 19

Suggest why membrane-bound enzymes are important in digestion

Answer 19

● Membrane-bound enzymes are located on cell membranes of epithelial cells lining ileum
● (By hydrolysing molecules at the site of absorption they) maintain concentration gradients for absorption

Question 20

Describe the pathway for absorption of products of digestion in mammals

Answer 20

Lumen (inside) of ileum → cells lining ileum (part of small intestine) → blood