Glucose Homeostasis

Question 1

Where is energy stored?

Answer 1

1. Glycogen: - stored in the liver & skeletal muscle
2. Fat :- Triglycerides stored in adipose tissue Triglycerides stored in adipose tissue
3. Protein :- Stored in skeletal muscle

Question 2

Describe the role of insulin and its structure

Answer 2

• Glucose metabolism main hormone
• Peptide hormone made of alpha & beta chain linked by S-S
• Secreted from β-cells in the Islets of Langerhans in
  the endocrine pancreas
• Act at tyrosine recpetors

Question 3

Describe the synthesis of insulin

Answer 3

• Done at ribosome on RER
• The protein is then modified in the golgi where the folding anf disulfide bond are formed
• C peptide cleaved o give 2 chains (A - 21αα and B
  30αα) linked by disulphide bonds
  *

Question 4

Describe insulin secretion regulation

Answer 4

**Negative feedback system
**
1. After food, glucose levels increase
2. Glucose enters via GLUT2 transporter - passivly goes in
3. Glucose stimulates metaboilism and ATP production
4. K+ channel is inhibited from ATP
5. The increase positive charge leads to depolarization
6. Depolarisation leads to CA2+ channel activation —> Ca2+ enters

7. Ca2+ in the cell leads to to exocytosis from the secretory glands of insulin into blood

Question 5

Describe the process of less insulin production

Answer 5

• Sympathetic system - alpha adrenergic agonist inhibit adenyl cyclase —> inhibit cyclic AMP meaning decrease in insuling release

Question 6

Describe moa of insulin

Answer 6

1. Bind tyrosine kinase coupled receptor
2. homodimer comes together –> cross phosphorelats
3. IRS is phosphorelated
4. Key enzyme phosphorelation (MAP kinase) leads to recruitemnt of glucose transporters - e.g GLUT 4
5. GLUT 4 allows glucose into cells

There is also increase in increased formation in protein fat and glycogen

Decreased blood glucose

Question 7

What is Glucagon ?

Answer 7

Hormone with antagonist of insulin

Question 8

Describe the moa of of glucagon

Answer 8

1. Increases cAMP within the cell (Gαs)
   * Secreted during times of fasting (between meals) from
   the α-cells of the islets of Langerhans –

• The liver is the major target organ

Secreted into the hepatic portal vein

Question 9

How does the glucagon affect carbohydrate metabolism

Answer 9

1. Increased glycogenolysis —-> increased blood sugar

Question 10

How does the glucagon affect protein and fat metabolism

Answer 10

1. Effects on fat metabolism
   < Levels of fatty acids in blood

<Lipolysis

2. Effects on protein metabolism – on liver only –

<Proteolysis (in liver)

> Protein synthesis (in liver)