lecture 35 - fuel storage & metabolism

Question 1

Is ATP an energy store?

Answer 1

No - energy is stored in glycogen and fat

Question 2

Is ATP transferred between tissues or made in the tissue that needs it?

Answer 2

made in the tissue that needs it

Question 3

In what form is fat stored in tissues?

Answer 3

TAG as fat droplets in adipose tissue

Question 4

What form are fatty acids derived from for TAG synthesis and fuel storage?

Answer 4

fatty acids from chylomicrons and VLDL metabolism

Question 5

Where are the glycerol backbones (glycerol-3-phosphate) sourced from in synthesis and storage of TAGs?

Answer 5

From glucose

Question 6

What is the process of TAG storage mediated by?

Answer 6

The hormone insulin

Question 7

What reaction forms TAGs from glycerol-3-phosphate and free fatty acids?

Answer 7

Esterification, with the fatty acids first converted to fatty acyl-CoA

Question 8

What enzyme is activated by adrenaline and glucagon when TAG stores need to be mobilised?

Answer 8

Hormone-sensitive lipase

Question 9

What hormones activated hormones-sensitive lipase, and in what situations?

Answer 9

Adrenaline (exercise), glucagon (in fasting)

Question 10

What is the function of hormone sensitive lipase?

Answer 10

Acts to hydrolyse TAG molecules to release fatty acids and glycerol when stored energy is required.

Question 11

What is glycerol used by?

Answer 11

The liver

Question 12

What type of bond are glucose units joined by in glycogen?

Answer 12

alpha (1-4) glycosidic bonds with branches introduced by alpha(1-6) glycosidic bonds

Question 13

Where is glycogen stored?

Answer 13

As granules in the cytoplasm of liver and muscle cells, which also contain the enzymes required for their synthesis and degradation.

Question 14

What supplies the energy for glycogen synthesis?

Answer 14

ATP and UTP

Question 15

What is the role of ATP in glycogen synthesis?

Answer 15

Supplies energy for the phosphorylation of glucose to glucose-6-phosphate

Question 16

What is the role of UTP in glycogen synthesis?

Answer 16

Makes the activated high-energy precursor of glycogen, UDP-glucose

Question 17

What is the process of glycogen breakdown?

Answer 17

Glycogenolysis

Question 18

What hormones stimulate glycogenolysis?

Answer 18

Adrenaline and glucagon

Question 19

In what circumstances is stored glycogen released from the liver?

Answer 19

Gradually degraded between meals to maintain a steady concentration of glucose in the blood to fuel the brain and other glucose-dependent tissues

Question 20

In what circumstances is stored glycogen released from muscle?

Answer 20

Degraded mainly during bursts of physical activity to supply fuel for glycolysis to generate ATP for muscle contraction.

Question 21

When would glucose be converted to fatty acids in the liver?

Answer 21

When there is excess carbohydrate intake, beyond what can be stored as glycogen

Question 22

What happens to newly-synthesised fatty acids from glucose in the liver?

Answer 22

They are esterified with glycerol and exported from the liver to adipose tissues as TAGs via VLDL

Question 23

What is the primary source of energy for the brain?

Answer 23

Glucose

Question 24

Why are fatty acids not used by the brain for energy?

Answer 24

Fatty acids cannot efficiently cross the blood brain barrier

Question 25

What is the energy source of red blood cells, and why?

Answer 25

Glucose, because they lack mitochondria so cannot break down fats by beta-oxidation

Question 26

What is a characteristic of tissues that use fatty acids as fuel?

Answer 26

They have oxygen available for fatty acid oxidation