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a-level biology (aqa) > Homeostasis > Flashcards

Homeostasis Flashcards

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AP® Biology flashcards
1
Q

What is homeostasis?

A

Maintenance of a stable internal environment

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2
Q

What is the problem of body temperature being too high?

A

Enzymes become denatured. Enzyme’s molecules vibrate too much, which breaks the hydrogen bonds that hold their 3D shape. Active site changes so it is not complementary to substrate anymore so doesn’t act as a catalyst.

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3
Q

What is the problem of body temperature being too low?

A

Enzyme activity reduced, less kinetic energy, slowing rate of metabolic rate.

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4
Q

What is the problem of pH being to high or too low?

A

Enzymes become denatured, hydrogen bonds broken so active site of enzyme is changed so doesn’t act as a catalyst. Metabolic reactions are less efficient. Optimum: pH7

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5
Q

What is the problem of blood glucose concentration being too high?

A

Water potential reduced forcing water to diffuse out of cells by osmosis causing cells to shrivel up and die.

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6
Q

What is the problem of blood glucose concentration being too low?

A

Less glucose available for respiration to provide energy.

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7
Q

What is a negative feedback mechanism?

A

Detect a change from the optimum and respond by bringing the level back to normal.

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8
Q

What is the disadvantage of having a single negative feedback mechanism for one factor being controlled?

A

One negative feedback mechanism means you can only turn it on and off. You could change a level in one direction so it returns to normal. It’s like trying to slow down in a car with only the accelerator, all you can do is take your foot of the accelerator to slow down. More negative feedback mechanisms give more control

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9
Q

What is a positive feedback mechanism and give an example?

A

Amplify a change from the normal level so it’s further away from the normal line. Example: Hypothermia: as body temperature falls the brain doesn’t work properly and shivering stops - this makes temperature fall even more.

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10
Q

Name a factor that increases blood glucose concentration.

A

Eating food containing carbohydrates.

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11
Q

Name a factor that decreases the blood glucose concentration.

A

Exercise: more glucose used to make energy in respiration.

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12
Q

Where is insulin secreted from?

A

Beta cells

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13
Q

Where is glucagon secreted from?

A

Alpha cells

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14
Q

What is insulin?

A

A hormone that lowers blood glucose concentration when it’s too high.

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15
Q

What is glucagon?

A

A hormone that raises the blood glucose levels when it’s too low.

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16
Q

How does insulin work?

A

Binds to specific receptors on cell membrane of liver and muscle cells and increases permeability of muscle-cell membranes to glucose so more glucose is taken up (increasing number of channel proteins). Also activates enzymes to convert glucose to glycogen (energy store). Finally increases rate of respiration.

17
Q

How does glucagon work?

A

Binds to specific receptors in cell membrane of liver cells and activates enzymes that break glycogen into glucose and also activates formation of glucose from glycerol and amino acids. Finally it decreases the rate of respiration.

18
Q

What is glycogenesis?

A

Convert glucose to glycogen

19
Q

What is glycogenolysis

A

Breaking down glycogen in glucose.

20
Q

What is gluconeogenesis?

A

Forming of glucose from glycerol and amino acids.

21
Q

Where are beta and alpha cells found?

A

In the islets of Langerhans in the pancreas.

22
Q

What is adrenaline?

A

A hormone that increases blood glucose concentration. It is secreted from the adrenal glands.

23
Q

How does adrenaline work?

A

Binds to receptors in membrane of liver cells and activates glycogenolysis and inhibits glycogenesis. Also activates glucagon secretion and inhibits insulin secretion.

24
Q

Describe the second messenger model of adrenaline and glucagon action.

A

Activate glycogenolysis outside cell even though they bind to receptors outside of the cell. They bind to complementary receptors in membrane and activate adenylate cyclase which converts ATP into a chemical signal (cyclic AMP). cAMP activates protein kinase A which itself activates cascade (chain of reactions) which causes glycogenolysis.

25
Q

What is type 1 diabetes and what are it’s causes?

A

Immune system attacks the B cells so they can’t produce insulin by unknown reasons (maybe genetic predisposition or triggered by viral infections). Treated by insulin therapy - regular insulin injections or insulin pump. Controlling simple carbohydrates intake.

26
Q

What is hyperglycaemia?

A

Blood glucose level too high.

27
Q

What is type 2 diabetes and what causes it?

A

Acquired later in life usually and linked with obesity and more likely in people with a family history of the condition. Occurs when beta cells don’t produce enough insulin or when body cells don’t respond properly to insulin. Receptors on cell membrane don’t work properly so cells don’t take up enough glucose.

28
Q

How is type 2 diabetes treated?

A

Eating a healthy, balanced diet, losing weight and regular exercise. Glucose-lowering medication. Insulin injections.

29
Q

What test can be conducted to see if, and how much glucose is present in a solution.

A

Benedict’s test.

30
Q

Why is colorimetry conducted?

A

Determine colour of quantitative benedicts reagent with glucose and compare it with other solutions

31
Q

What is the main function of the kidney?

A

To excrete waste products such as urea, and reabsorb useful substances like water and glucose so it isn’t lost from the body (Selective Reabsorption). They also regulate the water potential of the blood.

32
Q

What is the blood vessel that enters the kidney?

A

Renal artery.

33
Q

What is the glomerulus?

A

A bundle of capillaries looped inside the Bowman’s capsule.

34
Q

Which arteriole takes blood into the glomerulus?

A

Afferent Arteriole.

35
Q

Which arteriole has a smaller diameter and why?

A

Efferent is smaller in order to create high pressure in the glomerulus.

36
Q

Name the three layers that the molecules of the glomerular filtrate have to pass through to get to the bowman’s capsule.

A

Capillary wall, the basement membrane and the epithelium of the Bowman’s capsule.

37
Q

Name the molecules that make up the glomerular filtrate.

A

Water, urea, ions, salts, glucose, amino acids.

38
Q

Name the molecules that can’t pass out of the glomerulus and why?

A

RBCs, WBCs, platelets, large proteins, antibodies. Too big

39
Q

Name the five key features of the nephron.

A

Bowman’s capsule, PCT, Loop of Henle, DCT and Collecting Duct

a-level biology (aqa) (7 decks)

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