3.2 Carbohydrate and Fat Metabolism

Question 1

Outline metabolism, anabolism, catabolism: aerobic catabolism and anaerobic catabolism.

2.1

Answer 1

Metabolism: All the biochemical reactions that occur within an organism, including anabolic and catabolic reactions.

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

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

• Aerobic catabolism: Compounds breaking down in the presence of oxygen
• Anaerobic catabolism: Compounds breaking down in the absence of oxygen

Question 2

State what glycogen is and its major storage sites.

2.2

Answer 2

When body has more glucose than neeeded, it’s stored as glycogen predominantly in liver & muscle tissue.

Question 3

State the major sites of triglyceride storage.

2.3

Answer 3

Adipose tissue and skeletal muscle

Question 4

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

2.4

Answer 4

Insulin: tells body to store excess glucose as glycogen & stimulates lipogenisis/ formation & storage of triglycerides:
1. Uptake of fatty acids by fat cells, which are converted to triglycerides
2. Triglycerides stored for future use in adipose tissue as body fat
3. Conversion of excess glucose into triglycerides, which are also stored as body fat in adipose tissue

Question 5

Outline glycogenolysis and lipolysis.

2.5

Answer 5

Glycogenolysis- Glyogen Breakdown into Glucose
When body needs more glucose than it obtains from diet, glycogen (stored in liver & muscle) is broken down back into glucose.

• liver glycogen used to maintian blood-glucose levels to meet needs of entire individual
• muscle glycogen used to meet needs of muscles only

Lypolysis- Fat Breakdown
1. Triglycerides are released into bloodstream & broken down into fatty acids & glycerol via lipolysis
2. Fatty acids transported to mitochondria
3. BETA oxidation of fatty acids to produce ATP
4. Fatty acids slowly broken down over 4 repeated stages, reducing carbon bonds each time -> produces ACETYL-CoA
5. Acetyl-CoA further metabolized in KREBS Cycle to produce large ATP amounts

Question 6

Outline the functions of glucagon and adrenaline during fasting and exercise.

2.6

Answer 6

Energy metabolism controlled by hormones including: glucagon, adrenaline (insulin, cortisol, growth hormones)

Glucagon
During exercise or prolonged time w/ no food caused drop in blood glucose which is detected by pancreas -> glucagon released by α-cells of pancreas to simulate glycogenolysis to increase blood glucose levels & use.

Adrenaline also increases w/ low glucose levels & promotes glycogenolysis & lipolysis

Question 7

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

2.7

Answer 7

Insulin: Meal eaten and glucose levels rise which is detected by pancreas -> secretes insulin from β-cells to increase transport of glucose into cells (muscle and liver), while glycogenesis promoted & lipolysis inhibited. Results in decreased blood glucose levels.

Muscle Contraction: When insulin binds to its receptors on the skeletal muscle cell, a translocation of GLUT 4 (glucose transporter) from within the vesicles to the cell wall occurs. Muscle contraction causes the same translocation to happen. The translocation of GLUT 4 channel to the cell membrane allows glucose uptake into the cell from the bloodstream via facilitated diffusion.