intro to homeostasis + blood glucose regulation

What is homeostasis?

The maintenance of a constant internal environment within restrictive limits

Why could increase in temperature be a problem?

H-bonds in the tertiary structure of proteins (including enzymes) might break

So the tertiary structure changes and the protein can no longer carry out its function

Why could decrease in temperature be a problem?

A decrease in temperature means particles might not have enough kinetic energy for reactions to occur so the rates of reaction are too slow

Why could a change in pH be a problem?

The H-bonding and ionic bonding in proteins will change

This could cause a change in the tertiary structure and thus function of proteins e.g. enzymes

Why could an increase in blood glucose concentration be a problem in terms of water potential of the blood?

Increase in blood glucose → decreases water potential of blood → more water leaves the cells and moves into the blood → cells dehydrate and shrivel

Why could a decrease in blood glucose concentration be a problem in terms of energy transfer and water potential of the blood?

Decrease in blood glucose → lack of glucose available for cells → less respiration in cells Decrease in blood glucose → increases water potential of blood → more water absorbed into cells than they need (could lead to cells bursting)

What is negative feedback?

Where a change triggers a response which reduces the effect of a change.

What is positive feedback?

When talking about an example of positive feedback what should you always include in your answer?

Where a change triggers a response which increases the effect of a change

More X, therefore more Y, therefore more X

Why are there separate mechanisms involving negative feedback to control departures in different directions from the original state?

This allows a greater degree of control

• more control systems = stronger response

What can cause blood glucose concentration to increase?

eating & drinking carb rich foods

What can cause blood glucose concentration to decrease?

exercising

What is glycogenesis? And where does it take place?

conversion of glucose —> glycogen

What is gluconeogenesis? Where does it take place? What causes it to take place?

Glucagon binds to receptors

This causes enzymes to be activated so that amino acids and fatty acids and glycerol are converted into glucose.

It takes place in the liver.

what is glycogenolysis?

hydrolysis of glycogen back into glucose in liver, occurs in liver, occurs when blood glucose levels are lower than normal

Write a flow-chart to describe what happens when blood glucose concentration is too high

1. Detected by beta cells in the islets of langerhan in the pancreas

2. The beta cells release insulin

3. Insulin travels in the blood

4. Insulin binds to receptors on target cells (muscle cells, liver cells, adipose cells)

5. More glucose transporter proteins become embedded in the cell membrane and open

6. More glucose is absorbed into the cells

7. Insulin activates enzymes which convert glucose to glycogen

Write a flow-chart to describe what happens when blood glucose concentrations is too low

1. Detected by alpha cells in the islets of langerhan in the pancreas

2. The alpha cells release glucagon

3. Glucagon travels in the blood

4. Glucagon binds to receptors on target cells in the liver and muscles

5. adenylate cyclase is activated and converts ATP to CAMP

6. CAMP activates protein kinase

7. protein kinase activates other enzymes which converts glycogen to glucose and/or amino acids & fats to glucose

Describe the effect of adrenalin on glycogen break down

1. Adrenalin travels in the blood

2. Adrenalin binds to receptors on target cells in the liver and muscles

3. adenylate cyclase is activated and converts ATP to CAMP

4. CAMP activates protein kinase

5. protein kinase activates other enzymes which converts glycogen to glucose

What's the difference between the effects of glucagon and adrenalin?

Adrenalin causes glycogenolysis

Glucagon can cause glycogenolysis and gluconeogenesis

Glucagon and adrenaline both work by the secondary messenger model.

What is the primary messenger?

Glucagon and adrenaline

What is the secondary messenger in both cases?

Cyclic AMP

When does diabetes occur?

when blood glucose cannot be controlled

Describe Type I diabetes

due to the body being unable to produce insulin, it starts in childhood and could be the result of an autoimmune disease where the beta cells were attacked. Treatment involves injections of insulin

Describe Type Il diabetes

is due to receptors on the target cells losing their responsiveness to insulin, it usually develops in adults because of obesity and poor diet. It is controlled by regulating intake of carbohydrates, increasing exercise and sometimes insulin injections

Describe the role of glucagon in gluceoneogenesis (2)

1. Attaches to receptors on target cells, activating the enzymes

2. glycerol/ amino acids are converted into glucose