Homeostasis

Question 1

Definition of negative feedback

Answer 1

A change to the normal level triggers a response which reverses / reduces the effect of the change.

Question 2

Definition of positive feedback.

Answer 2

A change to the normal level triggers a response which increases the effect of the change.

Question 3

Explain why it is so important to regulate blood glucose concentration (5 points).

Answer 3

1. Glucose is a respiratory substrate for cells.
2. Respiration provides ATP for cells.
3. If no / little glucose, then the cell has no ATP.
4. Cell cannot carry out metabolic reactions, for example: aerobic respiration.
5. Causing cell death.

Question 4

Definition of tissue.

Answer 4

A group of cells with similar adaptations.

Question 5

What two cells do the Islets of Langerhans in the pancreas consist of?

Answer 5

1. B-cells.
2. A-cells

Question 6

Describe the function of the B-cells in the Islets of Langerhans.

Answer 6

Secrete the hormone insulin, which decreases blood glucose concentration.

Question 7

Describe the function of A-cells in the Islets of Langerhans.

Answer 7

Secrete the hormone glucagon which increases blood glucose concentration.

Question 8

Describe and explain 3 adaptations for B-cells and A-cells in the Islets of Langerhans.

Answer 8

1. Many ribosomes and rough endoplasmic reticulum. For proteinsynthesis, production of hormones.
2. Many mitochondria. Movement of hormone out the cell and inside the cell. Use of ATP for movement for aerobic respiration.
3. Golgi apparatus- large and many vesicles. Movement of proteins / amino acids inside the cell. Modifies proteins.

Question 9

Describe glycogenesis.

Answer 9

The conversion of glucose to glycogen. Causes the liver to remove glucose from blood. Converted to glycogen inside liver cells.

Question 10

Describe glycogenolysis.

Answer 10

The breakdown of glycogen to glucose.
Occurs when blood glucose concentration is lower than normal. Causes liver to hydolyse glycogen into glucose. Glucose diffuses into blood from liver cells.

Question 11

Describe the action of insulin. (3 points)

Answer 11

1. Increase in number of glucose transport channel proteins in plasma membrane.
2. So more glucose diffuses into cell by facilitated diffusion.
3. Activation of enzymes that convert glucose into glycogen (glycogenesis) and fat.

Question 12

What triggers the release of insulin? (3 points).

Answer 12

1. Detected by B-cells in the Islets of Langerhans.
2. Secretes insulin into the blood.
3. Binds to receptors on liver and muscle cells.

Question 13

Describe the consequences of insulin release in the blood (3 points).

Answer 13

1. Absorption of glucose into muscle/liver cells as membrane is more permeable.
2. Increased respiration.
3. Conversion of glucose into glycogen (glycogenesis) in muscle and liver cells.

Question 14

Describe the trigger of release for glucagon (3 receptors).

Answer 14

1. Detected by A-cells in the Islets of Langerhans.
2. Secretes glucagon into the blood.
3. Binds to specific receptors on liver cells.

Question 15

Describe the action of glucagon in the blood.

Answer 15

1. Decrease in number of glucose transport channel proteins in plasma membranes.
2. More glucose diffuses out the cell.
3. Activation of enzymes that convert glycogen to glucose (glycogenolysis) and conversion of amino acids / glycerol to glucose (gluconeogenesis).

Question 16

What is the result of insulin release in the blood?

Answer 16

Decrease in blood glucose concentration.

Question 17

What is the result of glucagon release in the blood?

Answer 17

Increase in vlood glucose concentration.

Question 18

Definition of first messenger.

Answer 18

Molecules that bind to receptors in the plasma membrane of target cells and cause changes to happen inside the target cell.

Question 19

Definition of second messenger.

Answer 19

Molecules found inside the target cell that are affected by the binding of a first messenger to a receptor.

Question 20

Describe the mechanism of adrenaline
(5 points).

Answer 20

1. The hormone: adrenaline, approaches the transmembrane protein.
2. Adrenaline fused to the receptor causing it to change shape on the inside of the membrane activating an enzyme, called; adrenaline cyclase inside the membrane.
3. The activated adrenaline cyclase converts ATP to cyclic AMP whoch acts as a second messenger.
4. The cAMP, in turn changes the shape of and, activates protein kinase enzyme.
5. The active protein kinase enzyme catalyses the conversion of glycogen to glucose: glycogenolysis.

Question 21

Describe diabetes.

Answer 21

Diabetes is a disease where the body cannot control its blood glucose concentration traction. This can lead to very high blood glucose concentrations- hypoglycaemia.

Question 22

Compare type 1 and type 2 diabetes (7 points).

Answer 22

1. Type 1 is insulin dependent, type 2 is non-insulin dependent.
2. Type 1 starts an early age (in childhood)- can be juvenile onset. Type 2 develops with increasing age.
3. Type 1 develops quickly. Type 2 develops slowly.
4. Type 1: signs and symptoms are usually obvious. Type 2’s signs and symptoms are less severe and may go unnoticed.
5. Type 1: beta cells do not make insulin. Type 2: beta cells still secrete insulin but at low concentrations.
6. Type 1: not linked to obesity, poor diet and sedentary lifestyle. Type 2: linked to obesity, poor diet and sedentary lifestyle.
7. Type 1: may be due to an autoimmune response where the immune system attacks its own beta cells. Type 2: glycoproteins receptors on target cells lose their responsiveness to insulin.

Question 23

How is type 1 diabetes treated?

Answer 23

Insulin injections.

Question 24

What’s the treatment for type 2 diabetes?

Answer 24

Controlled by regulating the intake of carbohydrate into the diet. Matching to the amount of exercise taken. Supplemented by injections of insulin or by the use of drugs that stimulate insulin production.