Topic 6C - Homeostasis

Question 1

What is homeostasis?

Answer 1

The mechanisms involved in the maintenance of a stable internal environment

Question 2

What factors affect enzyme activity?

Answer 2

Temperature
pH
Blood glucose concentration

Question 3

What is negative feedback?

Answer 3

Mechanism that restores the level to the normal

Question 4

How does negative feedback work?

Answer 4

Normal level
Level changes from normal
Receptors detect change
Communication (via nervous or hormanal system)
Effectors response
Level brought back to normal

Question 5

Why is having multiple negative feedbacks important?

Answer 5

Means you can actively increase or decrease a level so it returns to normal

Question 6

Why is one negative feedback bad? (2)

Answer 6

Slow response
Less control

Question 7

What is positive feedback?

Answer 7

Amplifies a change away from the normal

Question 8

How does positive feedback work?

Answer 8

Normal level
Normal level changes
Receptors detect change
Communication (via nervous or hormonal system)
Effectors respond
Change is amplified

Question 9

Why is positive feedback useful?

Answer 9

Positive feedback is useful to rapidly activate processes in the body

Question 10

What organ controls blood glucose concentration?

Answer 10

Pancreas

Question 11

What are the 2 hormones used when controlling blood glucose concentration?

Answer 11

Insulin
Glucagon

Question 12

What type of cells secrete insulin?

Answer 12

B cells

Question 13

What type of cells secrete glucagon?

Answer 13

A cells

Question 14

What is the process converting glycogen into glucose?

Answer 14

Glycogenesis

Question 15

What hormone activates glycogenesis?

Answer 15

Insulin

Question 16

What is the role of insulin?

Answer 16

Lowers blood glucose concentration when its too high

Question 17

What is the process called when glycogen is broken down into glucose?

Answer 17

Glycogenolysis

Question 18

What is the process when glycerol and amino acids are broken down into glucose?

Answer 18

Gluconeogenesis

Question 19

What hormone activates glycogenolysis?

Answer 19

Glucagon

Question 20

What hormone activates gluconeogenesis?

Answer 20

Glucagon

Question 21

What is the purpose of glucagon?

Answer 21

Raises blood glucose concentration when its too low

Question 22

How does negative feedback mechanisms control the rise in blood glucose concentration? (6)

Answer 22

Normal blood glucose conc
Rise in blood glucose conc
Pancreas detects change
Secretes insulin, stops glucagon secretion
Liver and muscle cells respond by:
Cells take up more glucose
Glycogenesis is activated
Cells respire more glucose
This causes blood glucose concentration to fall

Question 23

How does negative feedback mechanisms control the fall in blood glucose concentration? (6)

Answer 23

Normal blood glucose conc
Fall in blood glucose con
Pancreas detects change
Pancreas secretes glucagon, stops insulin secretion
Liver cells respond:
Glycogenolysis is activated
Gluconeogenesis is activated
Cells respire less glucose

Question 24

What are glucose transporters?

Answer 24

Channel proteins that allow glucose to be transported across a cell membrane

Question 25

What occurs when insulin levels are low? (Glucose transporters)

Answer 25

GLUT4 stored in vesicles of cytoplasm Insulin binds to receptor on the cytoplasm membrane, triggering movement of GLUT4 to membrane Glucose enters the cell via facilitated diffusion

Question 26

Where is adrenaline secreted from? Why is it secreted?

Answer 26

Adrenal glands When there is a low conc of glucose in your blood, when your stressed or when you’re exercising

Question 27

How does adrenaline increase blood glucose concentration? (2 ways)

Answer 27

Activates glycogenolysis Inhibits glycogenesis

Question 28

What is the second messenger model?

Answer 28

Binding of hormone to cell receptors activates an enzyme on the inside of the cell membrane which produces a second messenger

Question 29

What does the second messenger do?

Answer 29

Activates other enzymes in the cell and brings about a response

Question 30

How is glycogenolysis activated?

Answer 30

Adrenaline and glucagon bind to their receptors and activate the enzyme adenlyate cyclase

Question 31

What does adenylate cyclase do?

Answer 31

Converts ATP into cyclic AMP (cAMP) (which is a second messenger)

Question 32

What does cAMP do?

Answer 32

Activates an enzyme called protein kinase A

Question 33

What does protein kinase A do?

Answer 33

Activates a cascade that breaks down glycogen into glucose

Question 34

What is diabetes?

Answer 34

A condition where blood glucose concentration cant be controlled properly

Question 35

What is type 1 diabetes?

Answer 35

Immune system attacks the b-cells in the islets of langerhans so they can’t produce any insulin After eating, the blood glucose level rises and stays high The kidneys cant re absorb all the glucose so some of it is secreted in urine

Question 36

What is hyperglacaemia?

Answer 36

When after eating the blood glucose level rises and stays high

Question 37

How can you get type 2 diabetes?

Answer 37

Often linked with obesity, lack of exercise, age and poor diet

Question 38

What is type 2 diabetes?

Answer 38

Occurs when b-cells dont produce enough insulin or when the body’s cells dont respond properly to insulin

Question 39

Why would the body’s cells not respond properly to insulin? What is the effect of this?

Answer 39

Because the insulin receptors on the cells membrane dont work properly, meaning the cell can’t take up enough glucose Means that the concentration of blood glucose is higher than normal

Question 40

How can type 2 diabetes be treated? (5)

Answer 40

Healthy, balanced diet Losing weight Regular exercise Glucose-lowering medication can be taken aswell as insulin injections

Question 41

How can you determine the concentration of a glucose solution? (3)

Answer 41

Using colorimetry Perform a quantitive benedicts test After this, use a colourimeter to determine the light absorbance The higher the concentration of glucose, the more blue will have been lost, decreasing the absorbance of light

Question 42

What is ultrafiltration?

Answer 42

As blood passes through the capillaries in the cortex, substances are filtered out of blood and into long tubules that surround the capillaries

Question 43

What is selective reabsorbption?

Answer 43

Useful substances, such as glucose and the right amount of water, are then re absorbed back into the blood. The remaining unwanted substances pass along to the bladder and are excreted as urine

Question 44

What are nephrons?

Answer 44

Long tubules along with the bundles of capillaries where the blood is filtered