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Biology Y13 > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

Homeostatis definition

A

Maintaining a constant internal environment within restricted limits

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2
Q

What happens when core body temperature becomes too high?

A

Hydrogen bonds break within enzymes - changes tertiary structure and shape of active site so less enzyme-substrate complexes

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3
Q

What happens when core body temperature becomes too low?

A

Enzymes have too low kinetic energy so less enzyme-substrate complexes so reduced metabolic rate

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4
Q

What happens when blood pH becomes too high?

A

Hydrogen bonds break within proteins - changes tertiary structure

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5
Q

What happens when blood pH becomes too low?

A

Hydrogen bonds break within proteins - changes tertiary structure

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6
Q

What happens when blood glucose concentration becomes too high?

A

Blood has lower water potential than cells so water leaves cells into blood via osmosis and cells lack water for hydrolysis reactions and as a solvent

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7
Q

What happens when blood glucose concentration becomes too low?

A

Glucose not provided to cells fast enough for a high enough rate of respiration

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8
Q

What happens when blood water potential becomes too high?

A

Water enters cells by osmosis - too much can cause cell lysis, too much water in blood causes high blood pressure

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9
Q

What happens when blood water potential becomes too low?

A

Water leaves cells into blood via osmosis so cells lack water for hydrolysis and as a solvent

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10
Q

What is an example of a biological negative feedback mechanism?

A

Regulating body temperature through vasodilation/constriction

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11
Q

What is an example of a biological positive feedback mechanism?

A

Depolarisation causing Na+ channels to open so more Na+ ions diffuse in which causes more depolarisation

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12
Q

What type of messenger are hormones and where are they produced/secreted from?

A

Chemical, glands

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13
Q

How are hormones transported around the body?

A

Through the bloodstream

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14
Q

Where do specific hormones act?

A

Protein binding receptors on TARGET cells

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15
Q

What causes blood glucose to increase?

A

Eating foods high in glucose/starch - absorbed into blood

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16
Q

What causes blood glucose to decrease?

A

Increase in cell respiration e.g. during exercise

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17
Q

Which cells produce insulin?

A

β-cells

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18
Q

What does insulin do?

A

Decreases blood glucose

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19
Q

What are the target cells for insulin?

A

Liver and muscle cells

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20
Q

What are the 2 ways insulin decreases blood glucose?

A
  1. Inserts more glucose channel proteins so glucose enters cells via facilitated diffusion
  2. Activates enzymes to convert glucose into glycogen for storage
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21
Q

What is the name of the process where glucose is converted into glycogen?

A

Glycogenesis

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22
Q

Which cells produce glucagon?

A

α-cells

23
Q

Where is adrenaline released from?

A

Adrenal glands

24
Q

What do glucagon and adrenaline do?

A

Increase blood glucose

25
Q

What are the target cells for glucagon and adrenaline?

A

Liver cells

26
Q

What are the 2 ways glucagon and adrenaline increase blood glucose?

A
  1. Activate enzymes that hydrolyse glycogen into glucose
  2. Activate enzymes that convert glycerol/amino acids into glucose
27
Q

What is the name of the process when glycogen is hydrolysed into glucose?

A

Glycogenolysis

28
Q

What is the name of the process when glycerol/amino acids are converted into glucose?

A

Gluconeogenesis

29
Q

What is the secondary messenger pathway of glucagon and adrenaline?

A
  1. Binding of glucagon/adrenaline to their receptors activates adenylate cyclase
  2. Converts ATP to cAMP
  3. Activates protein kinase
  4. Activates enzymes for glycogenolysis
30
Q

What is diabetes?

A

Individual is unable to lower blood glucose level

31
Q

What can’t individuals with type 1 diabetes produce and why?

A

Insulin, pancreatic B cells have been destroyed

32
Q

Why can’t people with type 2 diabetes lower their blood glucose level and what is type 2 diabetes caused by?

A

Insulin produced but insulin receptors don’t respond to insulin, caused by obesity

33
Q

Why can’t people with type 1 diabetes take insulin orally?

A

Insulin is a protein so will be digested by stomach acid

34
Q

Why are people with type 1 diabetes advised to eat complex carbohydrates rather than sugar?

A

Prevents rapid increase in glucose as glycosidic bonds need to be hydrolysed first before absorption

35
Q

Why are people with type 2 diabetes advised to exercise regularly?

A

Glucose will be taken into cells from blood for respiration

36
Q

What happens in the kidney?

A

Substances filtered out of blood, including water - useful substances reabsorbed back into blood, unwanted substances travel to bladder and are excreted

37
Q

What happens in the kidney when blood water potential is too high?

A

Less water reabsorbed, greater volume of urine, less concentrated urine

38
Q

What happens in the kidney when blood water potential is too low?

A

More water reabsorbed, smaller volume of urine, more concentrated urine

39
Q

What are the 7 structures in a nephron?

A

Glomerulus
Basement membrane
Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct

40
Q

Describe the process of ultrafiltration, including what layers molecules pass through

A
  1. High blood pressure in glomerulus so water and small molecules e.g. glucose are forced out of pores in capillary endothelium and basement membrane
  2. Forms the glomerular filtrate in the tubule
  3. Proteins/cells too large to pass through so stay in the blood
41
Q

What causes proteinurea (high quantity of protein in urine)?

A

Damage to the basement membrane

42
Q

What is selective reabsorption?

A

85% of useful molecules and water are reabsorbed at proximal convoluted tubule into the blood

43
Q

What are 3 ways epithelial cells lining the proximal convoluted tubule are adapted for absorption?

A
  1. Microvilli increase surface area for diffusion
  2. Many mitochondria to produce ATP for active transport
  3. Microvilli increases number of carrier proteins for facilitated diffusion
44
Q

How is water reabsorbed at the proximal convoluted tubule and what causes water potential in the blood to be lower?

A

Osmosis, proteins in the blood that weren’t filtered

45
Q

Why is glucose found in the urine of someone with diabetes?

A

High glucose concentration in blood so not all glucose reabsorbed at proximal convoluted tubule as all carrier proteins are occupied

46
Q

What is the Loop of Henle involved in and how does it do this?

A

Involved in reabsorbing more water from glomerular filtrate by producing Na+ conc. gradient in the medulla

47
Q

What happens at the ascending limb in the Loop of Henle?

A

Na+ ions are actively transported out and water remains as the ascending limb is impermeable to water - concentration decreases up the ascending limb

48
Q

What happens at the descending limb in the Loop of Henle?

A

Na+ ions are actively transported in and water moves out via osmosis as the descending limb is permeable to water - concentration increases up the descending limb

49
Q

What increases down the medulla?

A

Na+ concentration gradient

50
Q

What is maintained along the whole length of the collecting duct and why?

A

Water potential gradient, medulla has a lower water potential than collecting duct

51
Q

What does it mean when an organism has a longer Loop of Henle?

A

Greater Na+ concentration gradient so water potential gradient maintained for longer so more water reabsorbed from the collecting duct by osmosis

52
Q

Describe how osmoregulation by ADH occurs when there is a decrease in blood water potential?

A

Water moves OUT OF osmoreceptors in the hypothalamus into the blood by osmosis so the posterior pituitary gland releases MORE ADH into blood so collecting duct becomes MORE permeable to water as MORE aquaporins in membrane so MORE water reabsorbed into blood via osmosis so urine volume DECREASES and becomes MORE concentrated

53
Q

Describe how osmoregulation by ADH occurs when there is an increase in blood water potential?

A

Water moves INTO osmoreceptors in the hypothalamus into the blood by osmosis so the posterior pituitary gland releases LESS ADH into blood so collecting duct becomes LESS permeable to water as LESS aquaporins in membrane so LESS water reabsorbed into blood via osmosis so urine volume INCREASES and becomes LESS concentrated

Biology Y13 (13 decks)

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