3.2 Carbohydrates and fat metabolism

Question 1

Metabolism

Answer 1

All biochemical reactions that occur within an organism

Question 2

Anabolism

Answer 2

Energy requiring reactions whereby molecules are built up into larger ones.

Question 3

Catabolism

Aerobic vs Anaerobic

Answer 3

Chemical reactions that break down complex organic compounds into simpler ones, with the net release of energy.

In presence of O2 vs in the absence of O2

Question 4

State what glycogen is and its major storage sites

Answer 4

Highly branched chain of glucose monomers

Liver and skeletal muscle

Question 5

State major sites of triglyceride storage

Answer 5

Adipose tissue and skeletal muscle

Question 6

Explain the role of insulin in the formation of glycogen and the accumulation of body fat

Answer 6

Glycogen Formation: Insulin promotes glucose uptake into liver and muscle cells, facilitating glycogen synthesis and storage.

Blood Sugar Regulation: Insulin helps maintain normal blood glucose levels by encouraging glucose storage as glycogen.

Body Fat Accumulation: High insulin levels inhibit fat breakdown, leading to increased fat storage if energy intake exceeds expenditure.

Long-term Effects: Chronic high insulin levels can contribute to obesity and insulin resistance, impairing glucose and fat regulation.

Question 7

Outline glycogenolysis

Answer 7

Glycogenolysis:

Definition: The breakdown of glycogen into glucose.

Process: Initiated when blood glucose levels drop, such as between meals or during exercise.

Purpose: Provides a quick source of glucose for energy, particularly important for maintaining blood sugar levels and fueling muscle activity.

Question 8

Outline lipolysis

Answer 8

Definition: The breakdown of stored fats (triglycerides) into fatty acids and glycerol.

Process: Triggered by hormonal signals such as adrenaline and low insulin levels, often during fasting or prolonged exercise.

Purpose: Provides an alternative energy source, especially during prolonged periods when glycogen stores are depleted, and helps mobilize fat reserves for energy.

Question 9

Outline the functions of glucagon during fasting and exercise

Answer 9

Glucagon:

Fasting:

Function: Stimulates glycogenolysis in the liver to increase blood glucose levels.
Mechanism: Promotes the breakdown of liver glycogen into glucose, which is released into the bloodstream to maintain normal blood sugar levels during fasting.

Exercise:

Function: Supports glucose supply to working muscles.
Mechanism: Enhances glycogenolysis and, in some cases, stimulates gluconeogenesis (production of glucose from non-carbohydrate sources) to provide additional glucose for energy.

Question 10

Outline the functions of adrenaline during fasting and exercise

Answer 10

Adrenaline:

Fasting:

Function: Mobilizes energy stores to support immediate energy needs.
Mechanism: Increases lipolysis (breakdown of fat) and glycogenolysis (breakdown of glycogen) to release fatty acids and glucose into the bloodstream, helping to maintain energy levels during fasting.

Exercise:

Function: Enhances performance by increasing energy availability.
Mechanism: Stimulates glycogenolysis in muscles and liver, increases lipolysis to release fatty acids, and elevates heart rate and blood flow to deliver more oxygen and nutrients to active muscles.

Question 11

Explain the role of insulin and muscle contraction on glucose uptake during exercise

Answer 11

Insulin:

Role During Exercise:

• less direct facilitation of glucose uptake into cells.
• reduces insulin levels to increase glucose availability for working muscles.

Mechanism:
- Lower insulin levels during exercise
- prevent excessive glucose uptake by non-active tissues
-allows more glucose to be available for muscles.
- less critical as muscle contraction itself helps increase glucose uptake.

Muscle Contraction:

Role During Exercise:

• plays a crucial role in glucose uptake
• independent of insulin.
• stimulate the translocation of glucose transporters (specifically GLUT4) to the cell membrane.

Mechanism:
- As muscles contract, they increase glucose uptake through these transporters directly
- allows for more efficient glucose use

• while insulin helps regulate overall glucose levels and facilitates glucose uptake under normal conditions
• muscle contraction significantly enhances glucose uptake during exercise through direct mechanisms that do not rely on insulin.