Carbohydrate Structure/Digestion/Absorption/Use

Question 1

What are disaccharide monomers linked by?

Answer 1

Glycosidic bonds; covalent between carboxyl and an anomeric carbon

Question 2

What makes a sugar reducing?

Answer 2

It had an anomeric carbon that can be oxidised

Question 3

Four ways that polysaccharides can be identified?

Answer 3

• monomers present
• length
• bond types
• amount of branching

Question 4

What two components is starch made up of?

Answer 4

Amylose and amylopectin

Question 5

Why is glycogen stored in polymers?

Answer 5

• compactness
• gives non-reducing ends which allow rapid synthesis/degradation
• form a hydrated gel which keeps them osmotically inactive

Question 6

What is a glycoprotein?

Answer 6

Protein with a covalently attached carbohydrate

For cell/cell communication

Question 7

What is a glycosaminoglycan?

Answer 7

Unbranched polymer of hexuronoc acid and amino sugars

Question 8

What is a proteoglycan?

Answer 8

GAG and a protein, where carb&raquo_space; protein

Question 9

Give an example and symptoms of a mucopolysaccharidoses?

Answer 9

Hurler Syndrome:
Breakdown of cornea
Thickening of arterial wall
Build-up of cerebrospinal fluid

Question 10

Give three areas of carbohydrate digestion and state the enzymes active there

Answer 10

Mouth - salivary amylase
Duodenum - pancreatic amylase
Jejunum - isomaltase/glucoamylase/sucrose/lactase

Question 11

How is glucose absorbed in the small intestine?

Answer 11

1. High [Na+] outside, flows in & pulls glucose w/ it

2. Glucose flows down con. grad. through a transporter to reach blood (works against gradient as well)

Question 12

Give an account of what happens to glucose when it reaches the liver from the small intestine

Answer 12

1. Phosphorylated to give G-6-P

2. Acted on by hexokinase/glucokinase

Question 13

What are the differences between the actions of hexokinase and glucokinase?

Answer 13

Hex. in all tissues, gluc. in the liver
Hex even @ low [glucose]
Gluc @ high [glucose] (excess allows for storage)

Question 14

What happens when a tissue is in need of glucose?

Answer 14

G-6-P in the liver is converted to glucose
Travels to the site of need
Reconverted to G-6-P by hexokinase
Used in glycolysis/pentose pathways
Excess G-6-P converted to glycogen for storage

Question 15

How is glycogen synthesised?

Answer 15

Glucose molecules from UDP binded by glycogenin
Glycogen synthase take over when chain > 8
Glycogen-branching enzyme breaks the chains and reattaches them to give branch points

Question 16

How is glycogen degraded?

Answer 16

Glucose monomers removed one at a time (from non-reducing ends by glycogen phosphorylate)

Glucose near branches removed by de-branching enzymes:

• transferase removes 3 glucose and attaches to non-reducing end
• Glucosidase removes final glucose leaving an unbranched chain