Nutrient Digestion 1 (Carbohydrates and Proteins)

Question 1

What are the 6 main principal dietary constituents?

Answer 1

Carbohydrate
Protein
Fat
Vitamins
Minerals
Water

Question 2

What are the 3 hexose sugars?

Answer 2

Glucose
Galactose
Fructose

Question 3

What absorbs monosaccharides?

Answer 3

Small intestine

Question 4

What are disaccharides?

Answer 4

2 monosaccharides linked together by glycosidic bond

Question 5

What happens to disaccharides?

Answer 5

Broken down to constituent monomers by brush border enzymes in small intestine

Question 6

What is lactose?

Answer 6

Glucose + galactose

Question 7

What is sucrose?

Answer 7

Glucose + fructose

Question 8

What is maltose?

Answer 8

Glucose + glucose

Question 9

What is starch?

Answer 9

Plant storage form of glucose

Question 10

What is alpha-amylose?

Answer 10

Glucose linked in straight chains

Question 11

What is amylopectin?

Answer 11

Glucose monomers linked by alpha-1,4 glycosidic bods - hydrolysed by amylases (saliva, pancreas)

Question 12

What is cellulose?

Answer 12

Constituent of plant cell walls

Unbranched, linear chains of glucose monomers linked by beta-1,4 glycosidic bonds

Question 13

Why can’t vertebrates use cellulase to break down beta-1,4 glycosidic bonds?

Answer 13

Vertebrates cannot produce cellulase which is the only enzyme that can break down beta-1,4 glycosidic bonds
Vertebrates can only digest through bacteria

Question 14

What is glycogen?

Answer 14

Animal storage form of glucose

Glucose monomers linked by alpha-1,4 glycosidic bonds

Question 15

What do you need in order to absorb glucose?

Answer 15

Sodium

Question 16

What is SGLT1?

Answer 16

Transporter that has a binding site for Na and a binding site for glucose but they need to bind simultaneously to cause a conformational change

Question 17

What is GLUT2?

Answer 17

Expressed in epithelial cells - facilitated diffusion process since glucose cannot move out of the cell on its own

Question 18

What happens after sodium and glucose move into the cell?

Answer 18

Glucose moves into the blood (via GLUT2)
Na–> blood, potassium moves into cell (via Na-K pump) which creates an osmotic gradient allowing water to travel from lumen –> blood

Question 19

How does fructose move through cells?

Answer 19

Fructose moves from lumen into cell via GLUT-5 and moves into blood via GLUT-2
Na not required

Question 20

What are proteins?

Answer 20

Polymers of amino acids linked together by peptide bonds with large variations in length

Question 21

What are small proteins classed as and what are they called?

Answer 21

3-10 amino acids in length

Called peptides

Question 22

What are the enzymes called that hydrolyse peptide bonds and reduce proteins/peptides to amino acids?

Answer 22

Proteases or peptidases

Question 23

How does an amino acid move through a cell?

Answer 23

Needs a symporter to pull amino acid into cell
SAAT1 has binding sites for Na and amino acid which binds to both simultaneously which causes a conformational change
Creates water absorption effect due to Na moving onto Na-K pump

Question 24

Describe the process of di/tri-peptides moving into cell?

Answer 24

Process which takes peptides instead of full amino acid
H and the dipeptide both move into the cell via PepT1
H moves back out the cell at the same time Na moves in via NHE3
Involves Na-K pump

Question 25

What is it called when a H ion is involved?

Answer 25

Proton motive force

Question 26

What is NHE3?

Answer 26

Sodium hydrogen exchanger

Takes Na in and H ion out and acidifies it