Digestion and Absorption

Question 1

What is a digestive system?

Answer 1

A tube which extends from the mouth, to the anus. Each section of this tube has a specialised role in the breakdown and absorption of food molecules and water.

Question 2

What are proteins hydrolysed by?

Answer 2

Amino acids and proteases

Question 3

What are carbohydrates hydrolysed by?

Answer 3

Carbohydrases

Question 4

What are fats hydrolysed by?

Answer 4

Lipases

Question 5

What are proteins hydrolysed into?

Answer 5

Amino acids

Question 6

What are carbohydrates hydrolysed into?

Answer 6

Simple sugars

Question 7

What are fats hydrolysed into?

Answer 7

Glycerol, fatty acids and monoglycerides

Question 8

Salivary glands -

Answer 8

Secrete saliva containing amylase which hydrolyses starch to maltose

Question 9

Stomach -

Answer 9

Food is mixed with gastric juice which kills microorganisms and contains endopeptidases and exopeptidases which breaks down proteins

Question 10

Pancreas -

Answer 10

Secretes pancreatic juice containing amylase (and other carbohydrases), protease and lipase

Question 11

Small intestine -

Answer 11

Adapted to provide a larger SA for absorption. Maltase enzymes are embedded

Question 12

What is the first stage in starch digestion?

Answer 12

Salivary amylase starts to hydrolyse glycosidic bonds in the starch producing maltose

Question 13

What is the second stage in starch digestion?

Answer 13

In the stomach the amylase is denatured due to the acidic pH

Question 14

What is the third stage in starch digestion?

Answer 14

In the small intestine, pancreatic amylase continues to hydrolyse the starch to maltose

Question 15

What is the fourth stage in starch digestion?

Answer 15

Maltose is then hydrolysed to glucose by maltase enzymes in the membrane of the epithelial cells. The glucose can then be absorbed

Question 16

Describe the first step of the co-transport of glucose

Answer 16

Sodium ions are actively transported out of the epithelial cell into the blood by a sodium potassium pump (Na+/K+)

Question 17

Describe the second step of the co-transport of glucose

Answer 17

This creates a concentration gradient of the sodium ions between the lumen and of the ilium and the epithelial cell

Question 18

Describe the third step of the co-transport of glucose

Answer 18

Sodium ions and glucose enter by facilitated diffusion

Question 19

Describe the fourth step of the co-transport of glucose

Answer 19

Sodium ions move into the cell down their concentration gradient

Question 20

Describe the fifth step of the co-transport of glucose

Answer 20

Glucose moves into the cell against its concentration gradient

Question 21

Describe the sixth step of the co-transport of glucose

Answer 21

Glucose moves into the blood by facilitated diffusion

Question 22

What is the first step in protein digestion?

Answer 22

It begins in the stomach with endopeptidases hydrolysing the peptide bonds within the protein. This increases the SA for the next enzyme, making digestion faster and more efficient.

Question 23

What is the second step in protein digestion?

Answer 23

In the small intestine endopeptidases continue to hydrolyse the peptide bonds within the protein while exopeptidaes hydrolyse the peptide bonds at the end of the protein. This breaks down the polypeptide chains into amino acids and dipeptides

Question 24

What is the third step of protein digestion?

Answer 24

The dipeptidaes are broken down into amino acids by enzymes embedded into the cell surface membrane of the epithelial cell. Once broken down the amino acids can be absorbed by facilitated diffusion and active transport in co-transport

Question 25

Describe the first step in how amino acids are absorbed through co-transport

Answer 25

Sodium ions are actively transported out of the epithelial cell into the blood by a sodium potassium pump

Question 26

Describe the second step in how amino acids are absorbed through co-transport

Answer 26

This creates a concentration gradient of sodium ions between lumen and the ilium and the epithelial cell

Question 27

Describe the third step in how amino acids are absorbed through co-transport

Answer 27

Sodium ions and amino acids enter by facilitated diffusion

Question 28

Describe the fourth step in how amino acids are absorbed through co-transport

Answer 28

Sodium ions move into the cell down its concentration gradient

Question 29

Describe the fifth step in how amino acids are absorbed through co-transport

Answer 29

Amino acids move into the cell against their concentration gradient

Question 30

Describe the sixth step in how amino acids are absorbed through co-transport

Answer 30

Amino acids move into the blood by facilitated diffusion

Question 31

What happens to lipids before digestion?

Answer 31

In the stomach the lipids are churned into fat droplets. In the lumen of the small intestine the lipids are digested. Bile salts, that are produced in the liver and stored in the gall bladder, are released into the small intestine with the food and emulsify the fat droplets. This increases the SA of the lipids for the action of enzymes to make digestion faster and more efficient. Lipases hydrolyse lipids into glycerol, fatty acids and monoglycerides

Question 32

What is the first step in lipid absorption?

Answer 32

Lipid droplets are mixed with bile salts and make smaller droplets which increase the SA for faster absorption

Question 33

What is the second step in lipid absorption?

Answer 33

Triglycerides are broken down into glycerol and fatty acids which form micelles

Question 34

What is the third step in lipid absorption?

Answer 34

Micelles are small enough to enter the cell by simple diffusion

Question 35

What is the fourth step in lipid absorption?

Answer 35

At the SER fatty acids and glycerol are recombined to tryglycerides

Question 36

What is the fifth step in lipid absorption?

Answer 36

At the golgi apparatus tryglycerides are modified by proteins being added to make lipoproteins (chylomicrons) and packaged into vesicles

Question 37

What is the sixth step in lipid absorption?

Answer 37

Chlomicrons are transported into a lymph vessel by exocytosis, they then enter the blood

Question 38

What is a trigyliceride modified with proteins called?

Answer 38

Chylomicrons/Lipoproteins