Lecture 5

Question 1

What are the macronutrients?

Answer 1

Protein, lipid, carbohydrates

Question 2

What is the predominant type of carbohydrate in our diet?

Answer 2

monosaccharides, predominantly D-glucose

Question 3

What is the mammalian store of glucose?

Answer 3

Glycogen in the liver and muscle

Question 4

What is the store of glucose in plants?

Answer 4

Starch

Question 5

What is the cellular structural component in plants?

Answer 5

Cellulose

Question 6

What does pop have a high percentage of?

Answer 6

High fructose corn syrup.

Question 7

Why does fructose contribute to obesity?

Answer 7

It is not metabolised in the same way glucose is.

Question 8

What is the sweetest type of sugar?

Answer 8

Fructose

Question 9

What is the average carbohydrate intake daily?

Answer 9

300g.

Question 10

What are the different types of carbohydrate in our diet?

Answer 10

Polysaccharides (45-60%), disaccharides (30-40%) like sucrose or lactose. Monosaccharides (5-10%)

Question 11

What is the main type of polysaccharide?

Answer 11

Vegetable starch which is amylose and amylopectin.

Question 12

What is amylose?

Answer 12

A straight chain polymer of glucose with alpha-1,4 bonds

Question 13

What is amylopectin?

Answer 13

branched chain glucose polymer with alpha-1,4 bonds and alpha-1,6 bonds between branches every 20-30 glucose monomer.

Question 14

What is animal starch in meat?

Answer 14

Glycogen.

Question 15

What are the two stages of carbohydrate digestion?

Answer 15

Intraluminal hydrolysis and membrane digestion

Question 16

Describe intraluminal digestion of starch

Answer 16

Broken down into oligosaccharides (3-10 glucose) by salivary and pancreatic amylase

Question 17

Describe membrane digestion

Answer 17

Oligosaccharides are broken down by brush border enzymes such as maltase, sucrase and isomaltase.

Question 18

What are the three monosaccharides that can be absorbed?

Answer 18

D-glucose, D-fructose, D-galactose

Question 19

Why is fibre indigestible?

Answer 19

We do not have an enzyme capable of breaking the beta-1,4 linkage within cellulose and hemicellulose.

Question 20

At what points can amylase break down amylose and what are the products?

Answer 20

Any bond except the end bonds. This produces maltose and maltotriose. (2 or 3 glucose monomers).

Question 21

What are the products of amylase digestion of amylopectin?

Answer 21

Maltose, maltotriose and alpha-limit dextrins.

Question 22

What are the three enzymes present at the membrane?

Answer 22

Lactase, maltase and sucroisomaltase

Question 23

What does lactase do?

Answer 23

Breaks down lactose into glucose and galactose.

Question 24

What does maltase do?

Answer 24

Breaks down maltose and maltotriose into 2 or 3 glucose

Question 25

What is maltase also called?

Answer 25

glucoamylase

Question 26

What is sucroisomaltase?

Answer 26

It is a dimer of both sucrase and isomaltase.

Question 27

What does sucrase do?

Answer 27

Breaks down sucrose into glucose and fructose

Question 28

What does isomaltase do?

Answer 28

Breaks down all the products of amylase amylopectin digestion.

Question 29

What are glucose and galactose absorbed by?

Answer 29

SGLT1

Question 30

What is fructose absorbed by?

Answer 30

GLUT5

Question 31

What is the basolateral transporter for all of the monomers?

Answer 31

GLUT2