Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-Level Biology > 5.1.2 Excretion as an example of homeostasis > Flashcards

5.1.2 Excretion as an example of homeostasis Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

substances that need to be excreted

A

carbon dioxide (from respiration)
nitrogen-containing compounds (ammonia, urea, uric acid)
bile pigments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

excretion definition

A

removal of metabolic waste from the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

excretory organs

A

lungs (removal of CO2 from respiring tissue, brought from bloodstream mostly as HCO3- which diffuses into the alveoli to be breathed out)
liver (lots of metabolic roles e.g. deamination)
skin (not primary function, secretes ammonia, urea, uric acid (toxic), water and salt for homeostasis of body temperature and water potential)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

why nitrogenous compounds are excreted

A

body cannot store excess amino acids
deamination: AA + oxygen -> keto acid + ammonia
formation of urea (less toxic and soluble than ammonia): ammonia + CO2 -> urea + H2O
NH4 + CO2 -> (NH2)2CO + H2O
urea transported to kidneys for excretion
keto acid used in respiration or converted to fat/carbohydrate for storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

why CO2 is excreted

A

excess CO2 is toxic as..
H+ ions from CO2 form haemoglobinic acid, competed with O2 for space on haem.
CO2 join with haemoglobin to form carbaminohaemoglobin (lower affinity for O2 than haemoglobin)
both result in less O2 carriage
if pH of blood drops too low, respiratory acidosis occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

respiratory acidosis symptoms

A

slow breathing
headaches
confusion
rapid heart rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

structure of liver

A

divided into lobes

divided into lobules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

structure of lobule

A

centre of lobule has hepatic vein
hepatic artery and hepatic portal vein run parallel into lobule
their blood mixes in sinusoid
Kupffer cells move around in sinuosood
canalicalus carries bile produced by hepatocytes to gall bladder

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

hepatic artery function + characteristic

A

brings oxygenated blood from heart to supply hepatocytes with oxygen needed for aerobic respiration
thicker wall, smaller lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

hepatic portal vein function + characteristic

A

brings deoxygenated blood from intestines
may contain toxic compounds need detoxification or produces of digestion for storage
thin wall, larger lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

bile canaliculus role + characteristic

A

bile made by hepatocytes secreted into bile canaliculi delivered to bile duct
stored in gall bladder until release in small intestine
enclosed space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

bile function

A

emulsifies lipids

neutralises acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why does blood mix in sinusoid

A

increase oxygen content for hepatocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Kupffer cell function

A

resident macrophage at sinusoid
breaks down RBCs
products of this breakdown released into bile duct to be sent into digestive system for excretion e.g. bilirubin from haemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

liver functions

A

detoxification of alcohol
storage of glycogen (by converting glucose into glycogen)
formation of urea from excess amino acids (deamination)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

detoxification definition

A

conversion of toxic molecules into less toxic or non-toxic molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

why detoxification occurs

A

prevents accumulation of toxic substances which may kill us

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

detoxification in the liver

A

hydrogen peroxide (made by WBCs) by catalase
drugs by a group of enzymes called cytochrome P450
alcohol by ethanol dehydrogenase and ethanal dehydrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

detoxification of alcohol

A

ethanol dehydrogenated into ethanal (catalysed by ethanol dehydrogenase, NAD into NADH)
ethanal dehydrogenated ethanoic acid (catalysed by ethanal dehydrogenase, NAD into NADH)
ethanoic acid forms acetyl coenzyme A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

why alcohol is detoxified

A

alcohol is toxic (depresses nerve activity)

can be broke down into useful products (contains chemical potential energy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

why too much alcohol ingested is bad

A

NAD accept hydrogen atoms in detoxification of ethanol
also used in oxidising and breaking down fatty acids for respiration
too much alcohol = not enough NAD = too many fatty acids
fatty acids -> lipids stored in liver cells -> liver cirrhosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

why freshwater fish secrete ammonia

A

highly toxic / very soluble in water

must be diluted in large volume of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

why mammals excrete urea

A

less toxic
can be more concentrated
less water needed to get rid of it
can be safely stored before being released from body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

why birds excrete uric acid

A

loss of very little water

smaller mass of water is an advantage in flight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

stages in making urea

A

deamination

ornithine cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

why deamination occurs

A

amino acids can’t be stored (toxic)

can be used to release energy (waste to directly excrete them)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

deamination

A

removal of the amine group from amino acid
forms a keto acid and ammonia
keto acid can be used directly in respiration
amino acid + oxygen -> keto acid + ammonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

why ornithine cycle happens

A

ammonia must be removed
too toxic and too soluble to transport and excrete
if excreted, large amount of water required and it would dehydrate us
urea less soluble and less toxic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

ornithine cycle steps

A

ammonia + CO2 + ornithine combine to form citrulline + water in mitochondria
citrulline moves out into cytoplasm
converted to argininosuccinic acid then arginine and water by adding more ammonia (requires ATP -> AMP)
converted back to ornithine by adding water to arginine to remove urea and moves back into mitochondria
ammonia + CO2 -> urea + water
2NH3 + CO2 -> CO(NH2)2 + H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

main function of kidney

A

remove waste from blood and make urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

urine passage through body

A

formed in kidney
through ureter
stored in bladder
moves out of body to urethra

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

nephron definition

A

functional unit of kidney

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

kidney structure

A

outside to inside
capsule (very outer layer)
cortex (dark outer layer where filtering takes place)
medulla (lighter in colour, collecting ducts)
branch of renal vein (deoxygenated blood without waste or excess water, leaves kidney)
branch of renal artery (oxygenated blood with waste and excess water, enter kidney)
pelvis (not the bone lol)
ureter (carries urine to bladder)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

ultrafiltration definition

A 
filtration at a molecular level
smaller molecules (urea, water, glucose, amino acids, ions) filtered out of the blood into lumen of Bowman’s capsules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

arterioles, glomerulus and Bowman’s capsule pressure in ultrafiltration

A

afferent arteriole lumen is wider than efferent arteriole lumen
provides hydrostatic ultrafiltration pressure needed for ultrafiltration
pressure in glomerulus higher than in Bowman’s capsule, forces substances from blood into Bowman’ capsule to form filtrate

36
Q

filter of Bowman’s capsule

A

there are many gaps in between cells of the capillary (fluid can pass between these)
podocytes inside of Bowman’s capsule lifts cells away from the capillary to allow filtrate to pass beneath them rather than through them

37
Q

why selective reabsorption occurs

A

a lot of molecules need to bereabsorbed in the blood (as they are vital)
around 85% reabsorbed

38
Q

what happens to filtrate as it moves through the nephron method

A

glucose, amino acids, hormones, vitamins, Na+ actively transported out of filtrate at proximal convoluted tubule
filtrate is isotonic compared to blood in surrounding capillaries
water potential becomes less negative
water exits proximal convoluted tubule via osmosis
chlorine diffuses out of the convoluted tubule

more water moves out of filtrate at descending Loop of Henley (impermeable to ions)
concentration of Cl- and Na+ increases, filtrate is hypertonic compared to blood in surrounding capillaries
Na+ and Cl- ions leave the filtrate at ascending Loop of Henley (AT) (impermeable to water)
via diffusion initially, then active transport due to changing concentrations
filtrate is isotonic in comparison to blood in surrounding capillaries

H2O leaves at distal convoluted tubule via osmosis (controlled by ADH)
Na+ and Cl- leave (AT, then diffusion)

more H2O is reabsorbed at the collecting duct

39
Q

ADH stands for

A

anti-diuretic hormone

40
Q

where ADH is produced and secreted

A

produced in neurosecretory cells in hypothalamus

passes down axon of these cells to terminal bulb in posterior pituitary gland for storage

41
Q

when ADH secreted

A

osmoreceptors in hypothalamus monitor water potential of blood
low w.p. = osmoreceptors shrink, triggers action potentials down axon of neurosecretory cells in hypothalamus
stimulates release of ADH into blood

42
Q

how ADH makes cells of walls of collecting duct more permeable to water

A

ADH binds to receptor on cell
enzyme-controlled reactions caused a vesicle to be made containing aquaporins
vesicle fuses with membrane, more aquaporins = more permeable to H2O
water reabsorbed from collecting duct via osmosis into capillaries

43
Q

ADH 6 marker perfect answer (hot days)

A

pituitary gland makes and secretes ADH
ADH travels in blood
target cells = cells lining collecting duct in nephrons of kidneys
ADH binds to receptors on cell surface membranes of target cells
triggers series of enzyme-controlled reactions
causes vesicles containing aquaporins to fuse with membranes
increases permeability to H2O
more ADH = more aquaporins = collecting duct is more permeable to water = more reabsorption of water from collecting duct (osmosis) = smaller volume of more conc. urine

44
Q

ADH 6 marker model answer (cold days)

A

pituitary gland makes and secretes less ADH
less ADH travels in blood
target cells = cells lining collecting duct in nephrons of kidneys
less ADH binds to receptors on cell surface membranes of target cells
triggers series of enzyme-controlled reactions
causes less vesicles containing aquaporins to fuse with membranes
less permeability to H2O
less ADH = less aquaporins = collecting duct is less permeable to water = less reabsorption of water from collecting duct (osmosis) = larger volume of less conc. urine

45
Q

advantages of kidney transplant

A

no need to dialysis (time-consuming)
diet less limited
better quality of life - can travel (not tied to hospital visits)

46
Q

disadvantages of kidney transplant

A

may be rejected by the body
have to take immunosuppressants (increase likelihood of infections)
risks of major surgery (high likelihood of infection)

47
Q

kidney failure causes

A

diabetes mellitus
hyper tension
infection

48
Q

why kidney failure bad

A

build up of urea in blood (toxic to cells)

unable to regulate ion and water levels in blood

49
Q

what protein in urine suggests has gone wrong

A

damage to basement membrane (caused by hypertension), allowing large substances like protein during ultrafiltration into nephron

50
Q

haemodialysis method

A

blood from artery removed
blood pump keeps blood moving
heparin (anticoagulant) prevents clotting
blood passes into passed into machine with partially permeable artificial dialysis membrane
other side of membrane is dialysis fluid with correct conc. of glucose, ions, urea
blood and dialysis fluid flow in opposite direction to one another
urea diffuses from blood to dialysis fluid
air trap and air detector needed to remove any bubbles is returned to vein
takes 3-4 hours, 2-4 times a week

51
Q

peritoneal dialysis method

A

tube surgically implanted into abdomen
bag connected, sends dialysis solution through tube into peritoneal cavity surrounding organs
abdominal membrane acts as filter
solution drained after few hours

52
Q

adv. of peritoneal dialysis

A

treats kidney failure
keeps patients alive long enough to receive kidney transplant
can be done from home (better quality of life)

53
Q

disadv of peritoneal dialysis

A

risk of infection post surgery

must carefully control diet

54
Q

monoclonal antibodies method

A

inject mouse with target antigen to generate immune response
collect b-lymphocytes and combine with tumour cells to form hybridoma
produce lots of antibodies, collected and purified

55
Q

pregnancy testing method

A

embryo secretes hCG, released during pregnancy
hCG (acts as antigen) binds to mobile monoclonal antibodies (anti-hCG) with coloured beads on them, complementary in shape
hCG-antibody complex moves along test strip with urine and binds to immobilised antibodies specific to the complex, producing blue line
control antibodies binds with any urine and bind to immobilised antibodies on control line to form coloured strip
indicates test is working

56
Q

hCG stands for

A

human chorionic gonadotropin

57
Q

assessing kidney failure

A

test urine for substances e.g. protein

measuring glomerular filtration rate (GFR)

58
Q

GFR

A

glomerular filtration rate

59
Q

sodium citrate

A

anticoagulant used in dialysis
removes calcium ions from blood
calcium ions are cofactor for blood clotting

60
Q

why haemodialysis needs to be done for less time overall than peritoneal dialysis

A

removes more waste than peritoneal dialysis
fluids moves countercurrent flow (maintains steep concentration gradient)
dialysis fluid is constantly refreshed
instead of allowing fluids to reach equilibrium

61
Q

where selective reabsorption occurs

A

proximal convoluted tubule

62
Q

why longer Loop of Henle is advantageous

A

more ions can be actively transported out of the filtrate with a longer ascending limb
creates a steeper water potential gradient
more water can be reabsorbed via osmosis at the collecting duct

63
Q

symptoms of lack of ADH

A 
frequent need to urinate
large volume of very dilute urine
persistent feeling of thirst/excessive drinking
electrolyte/mineral imbalance
dehydration
64
Q

ectothermic definition

A

organism that relies on external sources of heat to maintain body temperature

65
Q

endothermic definition

A

organism uses heat from metabolic reactions to maintain body temperature

66
Q

what ectotherms do when they are not warm enough

A

move into sunny area
move onto warm surface
expose larger SA to sun

67
Q

what endothermic do when they are too warm

A

move out of sun
move underground
reduce body surface area to the sun

68
Q

advantages of ectothermy

A

less food used up in respiration
more energy and nutrients gained from food can be converted to growth
need to find less food
survive for longer periods without food

69
Q

disadvantages of ectothermy

A

less active in lower temperatures during which:
greater risk from predation (unable to escape)
cannot take advantage of food available

70
Q

exergonic definition

A

releases energy as heat

71
Q

behavioural responses of endotherms when too hot

A

hide away from sun (in shade)
orientated body to reduce SA exposed to sun
remain inactive and spread limbs out (enable greater heat loss)
wet skin (evaporation helps cool body)

72
Q

behavioural responses of endotherms when too cold

A

lie in sun
orientate body to increase SA exposed to sun
move about (heat generated in muscles)
role into ball to reduce SA and heat loss
remain dry

73
Q

physiological responses used by endotherms when too warm (skin)

A

sweat glands secrete fluid (evaporates using heat from blood)
hairs/feather lie flat (reduce insulation from air, greater heat loss)
vasodilation of arterioles near skin (more heat radiates away from body

74
Q

physiological responses used by endotherms when too warm (gaseous exchange system)

A

some animals pant
increases evaporation of water from surface of lungs and airways
using heat from blood

75
Q

physiological responses used by endotherms when too warm (liver/muscles)

A

less respiration/contraction

less heat released

76
Q

physiological responses used by endotherms when too warm (blood vessels)

A

dilation of blood vessels at extremities

more heat can be a lost

77
Q

physiological responses used by endotherms when too cold (skin)

A

less sweat secreted (less evaporation means less heat is lost)
hair/feathers stand erect to trap air (insulates body)
vasoconstriction of arterioles near skin surface (blood diverted away from skin surface, less heat loss)

78
Q

physiological responses used by endotherms when too cold (gaseous exchange system)

A

less panting, less heat lost

79
Q

physiological responses used by endotherms when too cold (liver/skeletal muscles)

A

increased respiration in liver cells (more heat released as byproduct)
spontaneous muscle contractions (shivering releases heat)

80
Q

physiological responses used by endotherms when too cold (blood vessels)

A

constriction to limit blood flow to extremities (blood not cooled too much)

81
Q

advantages of endothermy

A

maintain constant body temperature (no matter external temperature)
remain active even when external temperatures low (take advantage of prey available or escape from predators)
inhabit colder parts of planet

82
Q

disadvantages of endothermy

A

use significant part of energy intake to maintain body temperature in the cold
need more food
lower proportion of energy and nutrients used for growth
may overheat in hot weather

83
Q

role of peripheral temperature receptors

A

early warning that body temperature has changed helps hypothalamus respond more quickly
helps reduce variation in core body temperature
receptors in the skin monitor changes in temperate at extremities, which may affect core body temperature

84
Q

similarities between ultrafiltration and formation of tissue fluid

A
  • small molecules are filtered from/diffuse out of blood
  • both processes occur in capillaries
  • large molecules/proteins/cells remain in blood
  • high hydrostatic pressure in both processes
  • many molecules reabsorbed back into capillaries afterwards
  • blood vessels become narrower to maintain hydrostatic pressure
  • hydrostatic pressure greater than oncotic pressure in both
  • neutrophils/lymphocytes can pass through in both
  • both involve basement membranes
85
Q

differences between ultrafiltration and formation of tissue fluid

A
  • filtrate enters Bowman’s capsule then proximate convoluted tubule in kidney whereas tissue fluid enters intercellular space
  • molecules not reabsorbed by capillaries form urine in the kidney but molecules not reabsorbed from tissue fluid will enters cells/form lymph
  • blood filtered through 3 layers in ultrafiltration but only 1 layer in formation of tissue fluid
  • knot of capillaries in ultrafiltration whereas a network of capillaries in formation of tissue fluid

A-Level Biology (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions