Lecture 32 - Coordinating metabolism fuel storage

Question 1

Why can’t ATP be stored in the body

Answer 1

ATP can’t be stored or transferred between tissues, so it must be made in the cells that requires at the time

Question 2

What happens to fuel after a meal

Answer 2

After a meal, excess fuel is stored. Glucose is stored as glycogen in the liver and muscle, and fatty acids are stored as TAGs in adipose tissue

Question 3

What are the major fuel reserves in the body

Answer 3

The major fuel reserves are glycogen in the liver and muscle, TAGs in adipose tissue and protein in muscle

Question 4

How much energy is stored in a typical 70Kg person fuel reserves

Answer 4

About 700000 KJ of energy is stored in the body as fuel reserves

Question 5

Why are fat stores necessary for animals like bears and eels

Answer 5

These animals store large amount of fat to survive long periods of fasting, such as during hibernation or migration

Question 6

How does insulin help adipose tissue store fat

Answer 6

Insulin activate LPL to release FAs from Lipoproteins, which are then stored as TAGs in adipose tissue

Question 7

What role does GLUT4 play in fat storage

Answer 7

GLUT4 stimulated by insulin, transports glucose into adipocytes, where it is used for TAG synthesis

Question 8

How does glucose contribute to TAG synthesis in adipose tissue

Answer 8

Glucose is metabolised to glycerol-3-phosphate, which forms the backbone of TAGs

Question 9

What happens to excess glucose after glycogen stores are full

Answer 9

Excess glucose is converted into Acetyl-Coa, which is then used for fatty acid synthesis in the liver and adipose tissue

Question 10

How are fatty acids transported from liver to adipose tissue

Answer 10

Fatty acids synthesised in the liver are packaged as TAGs in VLDL particles and transported to adipose tissue

Question 11

What is the key enzyme for glycogen synthesis and what does it do

Answer 11

Glycogen synthase adds glucose molecules from UDP glucose to a growing glycogen chain, forming a-1,4 glycosidic bonds

Question 12

How is glycogen stored in liver cells

Answer 12

Glycogen is stored as granules in the cytoplasm of liver cells, which helps maintain blood glucose level between meals

Question 13

How is glycogen stored in muscle different from liver glycogen

Answer 13

Muscles glycogen is used only within muscle cells, while liver glycogen maintains blood glucose levels

Question 14

Why is muscle glycogen not available to other tissues

Answer 14

Muscles lacks the enzyme glucose-6-phosphatase, which is required to release glucose into the bloodstream

Question 15

what stimulated glycogen synthesis in the body

Answer 15

Insulin stimulates glycogen synthesis by activating glycogen synthase and inhibiting glycogen breakdown enzymes

Question 16

How does insulin regulate glycogen synthase activity

Answer 16

Insulin inactivates glycogen synthase (GSK3) and activate protein phosphatases (PP1), which keeps glycogen synthase dephosphorylated and active

Question 17

what happens during glycogen synthesis at the molecular level

Answer 17

Glucose-1-phosphate is converted to UDP-glucose, which glycogen synthase uses to form new glycosidic bonds in the growing glycogen molecule

Question 18

Why is glycogen synthesis energy dependent

Answer 18

Glycogen synthesis require ATP and UTP to activate glucose into UDP-glucose, a high-energy precursor for glycogen formation

Question 19

What happens to glucose when liver and muscle glycogen stores are full

Answer 19

Excess glucose is converted to acetyl CoA and then into FAs, which is stored as TAGs in adipose tissure

Question 20

How does insulin stimulate glycolysis in adipocytes

Answer 20

Insulin promoted the activity of hexokinase, which phosphorylates glucose to enter the glycolysis pathway, leading to TAG synthesis

Question 21

What happens to glycogen in muscle during exercise?

Answer 21

Muscle glycogen is broken down to provide energy for muscle contraction, but it remains within the muscle as glucose-6-phosphatase is absent

Question 22

what are glycogen storage diseases

Answer 22

These are inherited disorders that affect enzymes involved in glycogen metabolism, leading to abnormal glycogen accumulation or deficiency in tissues