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biology > paper 2: Homeostasis > Flashcards

paper 2: Homeostasis Flashcards

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1
Q

define the term homeostasis

A

maintaining a constant internal environment within restricted limits

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2
Q

why does homeostasis take place

A

to prevent damage to cells

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3
Q

explain what happens to enxymes when core body temperature is too high

A
  • hydrogen bonds break within enzymes
  • changing thier tertiary structure and the shape of the active site
  • less enzyme-substrate complexes form
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4
Q

explain what happens to enzymes when core body temperature is too low

A
  • eznymes have too low kinetic energy
  • less enzyme-substrate complexes form
  • metabolic rate is reduced
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5
Q

explain what happens to enzymes when blood pH is too high

A
  • hydrogen bonds break within proteins
  • chaning the tertiary structure
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6
Q

explain what happens to enzymes when blood pH is too low

A
  • hydrogen bonds break within enzymes
  • changeing their tertiary structure
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7
Q

what happens to water potential when blood glucose concentration is too high

A
  • blood has lower water potential than cells
  • water leaves cells into blood by osmosis
  • cells lack water for metabolic reactions such as hydrolysis and as a solvent
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8
Q

what happens when blood glucose concentration is too low

A
  • glucose is not provided to cells fast enouugh for anhigh enough rate of respiration
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9
Q

what happens when blood water potential is too high

A
  • water enters cells by osmosis
  • too much can cause cell lysis
  • lots of water in blood causes high blood pressure
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10
Q

what happens when blood water potential is too low

A
  • water leaves cells by osmosis
  • cells lack ater for metabolic recations such as hydrolysis and as a solvent
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11
Q

define negative feedback

A

reverses the direction of change back to its original level

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12
Q

how is regulation of the body temperature an example of negative feedback

A
  • when body is too high, the body responds to decrease it back to original
  • when body temperature is too low, the body responds to increase it back to its original
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13
Q

what is the advantage of having separate mechanisms to increase or decrease the factor

A
  • separate mechanisms are used to increase or decrease the factor, as this gives a greater degree of control
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14
Q

define positive feedback

A

where a change in one direction is amplified
(an increase leads to a further increase)

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15
Q

give an example of positive feedback

A

sigmoid curve for oxygen dissociation

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16
Q

what type of messenger is a hormone

A

chemical messenger

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17
Q

where are hormones secreted from

A

glands

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18
Q

how are hormones transported around the body

A

in the blood stream

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19
Q

where do specific hormones act and why

A

target cells as they have complimentary hormone receptors

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20
Q

describe the effect of hormones. how is this different to the nervours sytem

A
  • effect of hormones is widespread and longlasting
    WHEREAS
  • effect of nervous system is local and short term
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21
Q

what will make blood glucose rise

A
  • eating foods high in glucose and starch as g;uvose is absorbed into the bloodstream
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22
Q

what will cause blood glucose to fall

A
  • increase in cell respiration
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23
Q

when is insulin released

A

when blood glucose is high

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24
Q

when is glucagon released

A

when blood glucose is too low

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25
Q

which cells produce insulin

A

beta cells in islets of Langerhans in the pancreas

26
Q

which cells produce glucagon

A

alpha cells in islets of Langerhans in the pancreas

27
Q

what effect does insulin have on blood glucose

A

decrease blood glucose levels

28
Q

what effect does glucagon have on blood glucose

A

increase blood glucose levels

29
Q

what are the target cells for insulin

A

liver and muscle cells

30
Q

what are the target cells for glucagon

A

liver cells

31
Q

how does insulin decrease blood glucose levels

A
  • inserting more glucose channel proteins into the cell membrane, glucose enters the cell by facilitated diffusion
  • activating enzymes to convert glucose into glycogen for storage (glycogenesis)
32
Q

how does glucagon increase blood glucose levels

A
  • activates enzymes to hydrolyse glycogen into glucose (glycogenolysis)
  • activates enzymes to convert glycerol/ amino acds into glucose (gluconeogenesis)
33
Q

what is the role of adrenalin in the body

A

increase blood glucose

34
Q

how does adrenaline increase blood glucose

A
  • adrenalin release from adrenal glands
  • binds receptors on liver cells
  • enzymes are activated which hydrolyse glycogen to glucose (glycogenolysis)
35
Q

dra wand label a diagram showing the secondary messenger pathway of glucagon and adrenaline

A
36
Q

describe type 1 diabetes

A
  • cant produce insulin due to the death of beta cells in the islets of Lagerhans
37
Q

describe type 2 diabetes

A

insulin is produced by the beta cells but the insulin receptors do not respond to the insulin
- blood glucose decreases more slowly
- can be causes by obesity

38
Q

what 2 ways can a type 1 diabetic control their blood glucose levels

A
  1. inject insulin
  2. eat complex carbs over sugars
39
Q

how does injecting insulin help control the blood glucose of a type 1 diabetic

A
  • as insulin cannot be produced due to beta cells being destoryed
  • insulin (protein) cannot be taken orally as it will be digested or denatured by stomach acid
40
Q

how does eating complex carbs instead of sugars help control blood glucose of a type 1 diabetic

A
  • prevents a rapid spike in blood glucose
  • absorbed more slowly than monosaccharides because gycosidic bonds need to be hydrolysed first before absorption
41
Q

what are the 3 ways of controlling blood glucose of a type 2 diabetic

A
  1. regular exercise
  2. loss of weight
  3. glucose lowering medication
42
Q

why can a type 2 diabetic not inject insulin to control blood glucose

A

they already produce insulin as beta cells are present but the receptors do not respond

43
Q

how does regular exercise help control the blood glucose of a type 2 diabetic

A

more respration so more glucose used so decreases concentration of glucose in cells so more glucose enters by faciliatated diffusion

44
Q

how does a loss of weight help control blood glucose of a type 2 diabetic

A

due to obesity being a cause of type 2 diabetes

45
Q

what is the function of the kidney

A
  • substances are filtered out of the blood, including water
  • useful substances are reabsorbed back into the blood
  • unwanted substances travel to the bladder where they excreted within urine
46
Q

if water potential is too high what happens at the kidney

A
  • less water reabsorbed
  • greater urine volume
  • lower urine concentation
47
Q

if blood water potential is too low what happens at the kidney

A
  • more water reabsorbed
  • lower urine volume
  • greater urine concentration
48
Q

label a diagram of a nephron

A
49
Q

decsribe how ultrafiltration occurs

A
  • there is a high blood pressure in the glomerulus
  • water and small molecules e.g. glucose and amino acids are forced out
  • this forms the glomerular filtrate in the tubule
  • proteins and cells are too large to pass through so they stay in the blood
50
Q

what are the 3 layers molecules pass through during ultrafiltration

A
  • pores in the capillary endothelium
  • basement membrane
  • the Bowman’s capsule epithelium (made of podocytes)
51
Q

why does proteinurea occur

A
  • damage made to the basement membrane
52
Q

describe selective reabsoption

A

most of the useful molecules and water are reabsorbed at the proximal convuluted tubule into the blood

53
Q

how are the epithelial cell lining the proximal convuluted tubul adapted for absorption

A
  • many mitochondria to provide lots of ATP to be hydrolysed and release energy for active transport
  • microvilli - to provide a large surface area for more diffusion of small molecules
  • microvilli increases number of channel protiens/ carrier proteins for facilitated diffusion
54
Q

what causes water potential of the blood to be lower after ultrafiltration

A
  • the proteins in the blood that were not filtered
55
Q

describe how glucose is reabsorbed in the proximal convuluted tubule

A
  • Na+ ions are actively transported out of the epithelial cell of the convuluted tubule into the blood to maintain the Na+ concentration gradient
  • Na+ ions and glucose are co-transported from the filtrate into the epithelial cell of the proximal convuluted tubule through carrier proteins by facilitated diffusion
  • glucose is then transported from the epithelium into the blood by facilitated diffusion
56
Q

describe the steps of how the loop of Henle reabsorbs water in the ascending limb

A
  • Na+ ions are actively transported out of the ascending limb
  • this creates a lower water potential in the medulla
  • the walls of the ascending limb are impermeable to water so water remains in the tubule
  • filtrate becomes less concentrated
57
Q

describe the steps of how the loop of Henle reabsorbs water in the descending limb

A
  • the walls of te descending limb are permeable to water
  • water moves out by osmosis into the lower water potential of the medulla
  • Na+ actively transported into the descending limb
  • due to the loss of water and Na+ moving in, the filtrate becomes more concentrated down the descending limb
  • this creates an increasing Na+ concentration deeper into the medulla
58
Q

describe the steps of how the loop of Henle reabsorbs water in the collecting duct

A
  • a water potential gradient is maintained along the whole length of the collecting duct
  • water will leave along the whole length of the collecting duct into the medulla
  • water is then reabsorbed into the surrounding capillaries
59
Q

how does the length of the loop of Henle effect the concentration of Na+ ions in the medulla

A
  • the longer the loop of Henle, the greater the Na+ concentration, deeper into the medulla.
  • the water potential gradient is maitained for longer
  • more water is reabsorbed from the collecting duct by osmosis
60
Q

describe osmoregulation by ADH when you are dehydrated

A
  • decrease in blood water potential
  • water moves out of osmoreceptors in the hypothalamus in the brain into blood by osmosis
  • imoulses are sent to the posterior pituitary gland and it releases more ADH into blood
  • more ADH causes collecting duct membrane to become more permeable to water as there are more aquaporins
  • more water is reabsorbed into the blood
  • urine volume becomesless and is more concentrated
61
Q

describe osmoregulation by ADH when you drink too much water

A
  • increase in blood water potential
  • water moves into osmoreceptors in the hypothalamus in the brain out of the blood by osmosis
  • sends impulses to the posterior pituitary gland and releases less ADH into the blood
  • less ADH causes collecting duct membrane to become less permeable to water as there are less aquaporins
  • less water is reabsorbed into the blood
  • urine volume becomes more and is less concentrated

biology (30 decks)

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