Section 6:Homeostasis

Question 1

Define homeostasis with examples

Answer 1

The maintenance of a constant internal environment. Factors:temperature,concentration of glucose,water potential and concentration of ions (pH)

Question 2

What is the optimum point?

Answer 2

The pont at which system operates best

Question 3

Define feedback mechanism

Answer 3

By which a receptor respondes to a stimuli,created by a change to the system brought about by the effector

Question 4

Involved when gluocse concentration is too high

How does insulin affect glucose concentartion?

Answer 4

1. Insulin binds to specific receptors on cell membrane of liver and msucle cells
2. Increase permability of muscle-cell membranes to glucose=cells take up more glucose~involves increasing no. of channel protwina
3. Insulin activates enzymes liver and msucle cells glucose into glycogen (glycogenesis)
4. Cells able to store glycogen as energy source
5. Increase rate of respiration of glucose

Question 5

How does glucagon affect blood glucose concentration?

Answer 5

1. Glucagon binds to specific receptors on cell membrane of liver cells
2. Glucagon activates enzymes in liver cells which break down glycogen into glucose (glycogenoysis)
3. Glucoagon activates enzymes that are involved in formation of glucose from glycerol
4. Glucoagon decreases the rate of respiration of glucose in cells

Question 6

What is involved in any self-regulating system?

Answer 6

• Optimum point
• Receptor
• Coordinator
• Effector
• Feedback mechanism

Question 7

Describe the characteristics of a hormone

Answer 7

• Produced in glands,which secreate the hormone dircetly into the blood
• Blood plasma to the cells on which they act (target cells)~have specific receptors
• Effective in low concentrations, but often have widespread and long-lasting effects

Question 8

What are the islets of langerhans?

Answer 8

Group of hormone-producing cells
* Alpha cells~larger and produce the hormone glucagon
* Beta cells~smaller and produce the hormone insulin

Question 9

What are the three processes that are associated with regulating blood sugar?

Takes place in the liver

Answer 9

• Glycogenesis=Glucose into glycogen (high blood glucose conc)
• Glycogenolysis=Breakdown of glycogen to glucose (low blood glucose conc)
• Gluconeogenesis=Production of glucose from sources other than carbohydrates

Question 10

Describe the second messenger model

Answer 10

1. Hormone adrenaline approaches transmembrane protein
2. Adrenaline fuses to the receptor=Changes shape on the inside of the membrane~Activates an enzyme within membrane
3. Activated emnzyme converts ATP to cyclicr AMP
4. cAMP in turn changes the shape of and activates protein kinase enzyme
5. The activate protein kinase enzyme catalyses the conversion of glycogen to glucose

Question 11

Describe the role and characteristics

Answer 11

A gland which produces enzymes
Produces the hormones insulin and glucagon (produced by the islets of langerhans)~islets secreate these hormones

Question 12

What are the three sources of glucose?

Answer 12

1. Directly from the diet in the form of glucose~hydrolysis of carbs
2. Hydrolysis of glycogen stored in the liver and muscle cells
3. Gluconeogesis

Question 13

How does insulin lower blood glucose concentration levels?

Answer 13

1. Increased rate of absorption of glucose into cells
2. Increased rate of respiration
3. Increased rate of conversion of glucose to glycogen
4. Increasing the rate of conversion of glucose to fat

Question 14

How does glucagon increase blood glucose concentration levels?

Answer 14

1. Attach to specific proteins on cell surface membrane of liver cells
2. Activates enzymes that convert glycogen to glucose
3. Activates enzymes involved in the conversion of amino acids and glycerol to glucose