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A2 BIOLOGY > 3.7 homeostasis and the kidney > Flashcards

3.7 homeostasis and the kidney Flashcards

1
Q

homeostasis

A

maintaining an internal environment at a set point despite external changes (keeping environments stable)

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2
Q

negative feedback

A

a series of stages which self-regulates body systems so they return to their original levels if they fluctuate from the optimum
(when something goes up, something else will happen to bring it back down)

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3
Q

example of homeostasis

A

urea

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4
Q

what is wrong with excess amino acid

A

cannot be stored. they must be broken down and excreted

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5
Q

excretion

A

the removal of metabolic waste

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6
Q

what is done with the amine group of an amino acid

A

want to get rid of it (poison)

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7
Q

where is keto acid found

A

carboxyl group

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8
Q

what is done to keto acid

A

kept for respiration (stored in the liver)

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9
Q

explain the amine part of amino acid

A

is removed in a process called deamination (occurs in the liver)

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10
Q

where does deamination occur

A

the liver

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11
Q

what does deamination lead to

A

the formation of urea

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12
Q

what needs to happen to urea in mammals

A

urea needs to be diluted in water to form urine

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13
Q

what is in the nitrogenous waste

A

ammonia (produced as a result of deamination of amino acid)

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14
Q

what is ammonia

A

a small, highly toxic molecule

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15
Q

what do aquatic organisms excrete

A

ammonia directly into water, they don’t need to store it as they are surrounded by water

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16
Q

what do mammals excrete

A

urea (less toxic than ammonia but energy is used to produce it- ATP)

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17
Q

what do birds and insects excrete

A

uric acid (virtually non-toxic, doesn’t harm offspring, low solubility a lot of energy is used to produce it) which is advantageous for flying. they don’t need to use a lot of water to get rid of it (low soluble) so good in dry environment

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18
Q

stage 1- formation of urine

A

ultrafiltration in the Bowman’s capsule

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19
Q

where does ultrafiltration occur

A

in the glomerulus (capillary knot)

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20
Q

explain ultrafiltration in the Bowman’s capsule

A

water and small molecules in the blood plasma are forced out of the blood into the lumen of the Bowman’s capsule (e.g. glucose, amino acid, urea, sodium, chloride, potassium ions)

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21
Q

what forces molecules out of the blood into the lumen (ultrafiltration)

A

high hydrostatic pressure

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22
Q

walls of the bowman’s capsule for ultrafiltration in the bowman’s capsule

A

the capillary walls and the Bowman’s capsule walls have small holes to sieve molecules through

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23
Q

what are too big to filter through the bowman’s molecules
(ultrafiltration)

A

blood cells and blood proteins are too big to pass through the holes and remain in the blood

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24
Q

adaptions for ultrafiltration

A

-there are 3 layers which the filtrate needs to pass through
-walls of glomerulus (capillary)
-basement membrane
-walls of the bowman’s capsule

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25
adaptation:walls of glomerulus for ultrafiltration
the glomerulus walls are made of ENDOTHELIUM and have small pores between the cells called fenestrae. (the filtrate passes through these pores)
26
adaptions of the basement membrane for ultrafiltration
basement membrane is found around the endothelium. it is made of collagen and glycoprotein which cross over each other to form a mesh. acts as a molecular sleve (the selective layer)
27
adaptions of the walls of the bowman's capsule for ultrafiltration
the bowman's capsule is made of specialised epithelial cells called podocytes. they have finger like projections that wrap around the capillaries to increase the surface area to increase filtration rate (can be drawn as a claw clip)
28
stage 2 of formation of urine
selective reabsorption (only certain substances reabsorbed)
29
where does selective reabsorption happen
proximal convoluted tubule
30
explain selective reabsorption
substances that are needed are reabsorbed back into the blood through a blood vessel called the vesa recta
31
how does selective reabsorption happen
by facilitated diffusion and active transport
32
what proteins are involved in FD
channel and carrier proteins
33
what proteins are involved in AT
only carrier proteins (pump)
34
adaptions of selective reabsorption
-walls of the proximal convoluted tubule -mitochondria -brush border of microvilli -tight junctions -basal channels -good blood supply
35
how are the walls of the proximal convoluted tubule adapted for selective reabsorption
walls are 1 cell thick. they are made of cuboidal epithelial cells. so thin walls will mean a short diffusion pathway, increase efficiency. only 1 layer of cells to get through
36
how are the mitochondria in the proximal convoluted tubule adapted for selective reabsorption
the cells are packed with mitochondria so ATP can be made for active transport. (ATPsynthetase) also needed for protein synthesis (for transport proteins)
37
how are the brush border of microvilli in the proximal convoluted tubule adapted for selective reabsorption
the cell membrane in contact with the filtrate has a brush border of microvilli: will increase the SA for absorption
38
how are the tight junctions in the proximal convoluted tubule adapted for selective reabsorption
tight junctions between the cells will prevent diffusion between other cells, preventing molecules being lost/leaked
39
how are the basal channels of the proximal convoluted tubule adapted for selective reabsorption
basal channels at the basement membrane to also increase the SA of the cell membrane for reabsorption
40
how is a good blood supply in the proximal convoluted tubule adaptation for selective reabsorption
vesa recta, makes sure there is a constant gradient maintained
41
how is glucose transported: 1) from inside the nephron to cells of PCT 2) from cells of PCT to the blood
1) Co-transport with Na+ 2) secondary active transport (via a pump)
42
how are amino acids transported: 1) from inside the nephron to cells of PCT 2) from cells of PCT to the blood
1) co-transport with Na+ 2)facilitated difusion
43
how is water transported: 1) from inside the nephron to cells of PCT 2) from cells of PCT to the blood
1) osmosis 2)osmosis
44
how is urea transported: 1) from inside the nephron to cells of PCT 2) from cells of PCT to the blood
1) facilitated difusion 2) Facilitated diffusion
45
how is Na+ transported: 1) from inside the nephron to cells of PCT 2) from cells of PCT to the blood
1) co-transport with glucose and amino acids 2) active transport (via sodium-potassium pump)
46
how is Cl- transported: 1) from inside the nephron to cells of PCT 2) from cells of PCT to the blood
1) facilitated diffusion 2) facilitated diffusion
47
explain the usual process of absorbing glucose- diabetes
all glucose is reabsorbed unless the concentration is too high in the filtrate (in this case some would stay in the urine-sign of diabetes) the glucose stays in the nephron as there isn't enough transport proteins to remove it. (proteins are a limited factor)
48
stage 3 of the formation of urine
water conservation in the loop of Henle
49
what is the role of the loop of Henle
to produce concentrated urine
50
what does the loop of henle have
2 limbs
51
2 limbs of the loop of henle
ascendning/descending
52
what is the ascending limb
impermeable to water, but actively transports Na+ and Cl- into the tissue of the medulla. this creates a high concentration of Na+ and Cl- in the medulla tissue
53
what is the descending limb
is permeable to water so water diffuse out into the medulla tissue by osmosis. as water moves out of the descending limb Na+ and Cl- ions are diffusing in (high concentration to low) this is good as it recycles the ions
54
what is at the bottom of the loop (stage 3)
the filtrate is concentrated (little water and high Na+ and Cl- concentration)
55
explain when the two limbs of the loop of henle flow in opposite ways (stage 3)
the 2 limbs flow at the same time in opposite directions (called a counter current multiplier) causing a change in concentrations
56
the longer the loop of henle........ stage 3
the longer the loop of henle the more concentrated the urine becomes, therefore less water is excreted. this is an adaptation of many animals in dry habitats e.g. desert rats have long loops of henle
57
vasa recta...... stage 3
they are looped thin walled blood vessels that run close to the loops of henle. blood in the vasa recta flows in the opposite direction to the loop of henle; gaining water as it flows from the medulla to the cortex
58
stage 4 of the formation of urine
ion readjustment
59
explain ion readjustment stage 4
if there is an excess/deficiency of ions in the blood, they are returned, usually by active transport. this happens in the distal convoluted tubule (DCT)
60
what is stage 5 of the formation of urine
osmoregulation
61
where does osmoregulation occur
in the walls of the distal convoluted tubule and collecting ducts
62
what is osmoregulation
the homeostatic control of water in the body
63
what is osmeoregulation operated by
negative feedback
64
stimulus of osmoregulation
volume of blood
65
receptors of osmoregulation
osmoreceptors in the hypothalamus
66
co-ordinator of osmoregulation
hypothalamus
67
effector of osmoregulation
posterior lobe of the pituitary gland (it release ADH- anti-diuretic hormone)
68
what is complementary to ADH
glycolipid/glycoprotein is complementary. found in glycocalix
69
properties of ADH
water soluble, carried in the blood to the receptors found on the cells of the DCT and collecting ducts ADH increases the permeability of the walls of the DCT and the collecting duct. this means more water can leave the nephron and return into the vasa recta in the medulla
70
how does ADH increases permeability/how do DCT and collecting duct become permeable
- ADH attaches to the receptors -enzymes called adenyl cyclase catalyses production of AMP -AMP is a second messenger and it causes vesicles containing aquaporins to fuse with the membranes -aquaporins become part of the membrane and water can move in by osmosis
71
aquaporins....
temporary when the AMP levels fall the aquaporins are removes
72
hypertonic solution
=concentrated (ADH present)
73
hypotonic solution
=low concentration (no ADH present)
74
effectsnof kidneys not working
toxic levels of urea in the body (the kidneys are usually involved in the removal of urea) body fluid increases in volume and are diluted compromising metabolic reactions (the kidneys are also involved in removing excess water)
75
problems caused by kidney failure
-urea and ion production -high blood pressure which can stop ultrafiltration -inability to filter blood to remove inorganic ions, water and urea -end-stage renal disease
76
solution: high blood pressure which can stop ultrafiltration
reduce constriction of blood vessels (medication)
76
solution: urea and ion production
reducing intake of certain nutrients e.g. proteins
77
solution: inability to filter blood to remove inorganic ions, water and urea
dialysis
78
solution: end-stage renal failure
kidney transplant
79
potential treatment of kidney disease
eat less protein (less urea so less pressure on the kidney) drugs to reduce blood pressure (high pressure causes damage to the glomerular capillaries preventing ultrafiltration) -drugs to control blood potassium and calcium ion levels -dialysis -kidney transplant
80
what is dialysis
dialysis removes waste, slats and excess fluids from the blood by passing over a dialysis membrane (partially permeable and contains the perfect plasma, correct amount of glucose, water and other substances/ not urea) urea passes into the dialysis membrane by diffusion
81
2 types
haemodialysis peritoneal dialysis
82
haemodialysis
-dialysis contains fibres which mimic basement membrane of Bowman's capsule -heparin is added to act as an anticogulant
83
peritoneal dialysis
-at home -dialysis fluid within abdomen
84
kidney transplant
old kidney remains in the body (unless cancerous or likely to cause an infection) patient would need to take immunosupressants for life

A2 BIOLOGY (16 decks)

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