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A2 BIOLOGY > MODULE 1.2 EXCRETION > Flashcards

MODULE 1.2 EXCRETION Flashcards

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1
Q

Define excretion

A

the removal of metabolic waste substances from the body

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2
Q

What are the two main substances to be excreted from the body

A

co2 from respiration and urea from the liver made by deamination of amino acids

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3
Q

Why is excess co2 bad

A
  • hydrogen carbonate ions form hydrogen ions which competes with 02 for haeomglobin = lack of 02 transport
  • carbaminohaemoglobin = lower affinity for o2 than normal haem
  • respiratory acidosis
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4
Q

what enzyme forms hydrogen ions from hydrogencarbonate ions

A

under the influence of the enzyme carbonic anhydrase

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5
Q

what is respiratory acidosis

A
  • co2 dissolves in blood plasma
  • combines with h2o to produce carbonic acid
  • h2co3 dissolves to release h+ and hco3- ions
  • h+ ions change ph of blood and proteins in blood act as buffers to stop this
  • little h+ ions detected by medulla oblongata and breathing increases to expel it but + h+ ions causes blood ph to drop below 7.35 and breathing slow/diff, headaches and drowsiness
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6
Q

What is the hepatic portal vein

A

has two capillaries one at either end and takes blood from digestive system to liver

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7
Q

where does the liver get oxygenated blood and what is it used for

A

from the aorta via the hepatic artery- used for aerobic respiration as the liver carries out many metabolic processes that need energy in the form of ATP

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8
Q

where does the liver get deoxygenated blood

A

the digestive system via the hepatic portal vein and this blood is rich in digestion products

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9
Q

how does blood leave the liver

A

hepatic vein where it returns to normal circulation via the vena cava

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10
Q

what does the bile duct do

A

takes bile from the liver to the gall bladder where it is stored until it is needed in the digestion of fats in the small intestine

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11
Q

describe the arrangement of cells inside the liver

A
  • split into lobes and then further into cylindrical lobules
  • hepatic portal vein + artery enter liver and split into smaller vessels and run between lobules= inter lobular vessels
  • blood mixes at intervals in a sinusoid which is lined by liver cells so exchange can take place between molecules
  • blood empties from sinusoid into a branch of the hepatic vein
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12
Q

how is the bile duct formed

A

bile released into bile canaliculli which join together to form bile duct

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13
Q

what are kupffer cells

A

specialised macrophages involved in breakdown and recycling of old red blood cells - produces bilirubin which is removed in bile and faeces

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14
Q

function and shape of liver cells

A

cuboidal shape with many microvilli

-protein synthesis, synthesis of cholesterol and bile salts, trans and storage of carbs

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15
Q

what are the by products of de amination in the liver

A

ammonia and keto acid which goes straight into respirationto release its energy

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16
Q

what are the functions of the liver

A
  • make rbc for fetus, bile,
  • destroy rbc
  • breakdown hormones
  • detoxification of alcohol
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17
Q

describe the ornithine cycle

A

converting ammonia into a less toxic form called urea bu combining the ammonia with co2
water is also produced

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18
Q

how does urea get to the bladder

A

passed back into the blood from the liver where it passes into the kidneys where urea is filtered out of the blood and concentrated in the urine
urine is stored in the bladder until it is expelled

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19
Q

define detoxification

A

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

20
Q

how is alcohol` broken down

A
  • taken to the liver where it is broken down using ethanol dehydrogenase into ethanal
  • ethanal further dehydrogenated into ethanoate by ethanal dehydrogenase
  • ethanoate combines with co enzyme a to form acetyl co enzyme a which enters respiration
21
Q

what happens to the hydrogen ions during the breakdown of alchohol

A

combine with another co enzyme called NAD to form reduced NAD

22
Q

What is NAD used for and what is a problem with insuffiecient NAD

A

used to break down fatty acids in the liver to be used in respiration
too many fatty acids = not enough NAD which means they build up in the liver as lipids and are stored in liver cells
this can cause alcohol hepatitis or cirrhosis

23
Q

what are the 4 main parts of the nephron

A

collecting duct
distal convoluted tubule
proximal convoluted tubule
loop of henle

24
Q

where does the kidney get its blood supply and how is it drained

A

renal artery

renal vein

25
Q

what are the three regions of the kidney and where are they located

A

outer region is called the cortex
inner region is the medulla
centre is the pelvis

26
Q

what is the nephron

A

microscopic tubule that recieves fluid from the blood capillaries in the cortex and turns in into urine which drains into the ureter

27
Q

what is the glomerulus

A

a fine network of capillaries that increases the local bp to squeeze fluid out of the blood, the bowman capsule collects the fluid and leads it to the nephron

28
Q

what is the difference between an afferent vessel and an efferent vessel

A

afferent carries blood into the organ and efferent carries it away

29
Q

what are podocytes

A

specialised cells that make up the lining of the bowmans capsule

30
Q

what is ultrafiltration

A

the filtration of substances on a molecular level

31
Q

what are the 3 sections in the barrier between the blood in the capillary and the fluid in the lumen of the bowmans capsule and how are they adapted

A
  • endothelium; small pores that allow blood plasma and substances in it to dissolve through
  • basement membrane; mesh network of collagen fibres and glycoproteins- main part of ultrafiltration (most proteins and all blood cells remain in glomerelus)
  • podocytes which have major processes that ensure there are gaps between the cells so fluid can pass through into the bowmans capsule
32
Q

what is filtered out of the blood

A

urea, water, small inorganic ions, glucose, amino acids and a small amount of protein

33
Q

what is left in the capillary during ultrafiltration and why

A

almost all proteins and blood cells

proteins keep very negative water potential to allow for necessary water re absorption

34
Q

define osmoregulation

A

the regulation and control of water potential in the bloody and bodily fluids

35
Q

how does the levels of ADH make the collecting duct wall more permeable

A
  • cells in the wall contains membrane bound receptors for ADH
  • adh binds and sends of enzyme contolled chain reactions in cell
  • this inserts vesicles containing aquaporins in cell
  • more ADH means more aquap which means wall is more permeable to water so more water moves out collecting duct via osmosis; less pee that is more concentrated
36
Q

how are the walls of the collecting duct made less permeable

A

plasma membrane folds inwards making new vesicles that remove aquaporins from membrane which makes wall less permeable which means more pee that is more dilute

37
Q

what are osmoreceptors

A

receptors that monitor the water potential of the blood; when low they lose water by osmosis and shrink which causes stimulation of neurosecretory cells

38
Q

what are neurosecretory cells

A

cells that act like nerve cells but manufacture and release ADH
ADH made in cells body but pass down the axon and are stored in the terminal bulb; if an action potential passes down then ADH is released

39
Q

how is the level of ADH adjusted in blood

A
  • osmoreceptors in hypothalamus
  • low wp causes osmoreceptors to shrink and trigger neurosecretory cells in hp
  • these produce and release ADH from the terminal bulb in the posterior pituitary gland when stimulated
  • ADH runs through blood capillaries to the rest of the body and acts on cells of the collecting ducts
  • when wp of blood rises less adh released
40
Q

what 3 things can cause kidney failure

A

diabetes mellitus
hypertension
infection

41
Q

what is dialysis

A

the use of a partially permeable mebrane to filter the blood

42
Q

what is haemodialysis

A
  • blood from a vein passed into the dialysis machine
  • heparin added to avoid clotting
  • any substances in excess are removed through the membrane into the dialysis fluid and any substances low in conc diffuse into blood
43
Q

what is peritonal dialysis

A
  • bodies own abdominal membrane is filter
  • permanent tube inserted into abdomen
  • dialysis fluid in tube and fills space between abdominal walls and organs
  • after the used solution is drained from the abdomen
44
Q

what happens to amino acids so that they are not wasted from the body

A

go to liver where potentially dangerous amine group is removed
amino group forms ammonia
can be converted into urea + water when combined with co2
any keto acid that is made can be used in respiration

45
Q

how are the cells lining the proximal convoluted tubule specialised for re absorption

A
  • many microvilli for increased surface area of readsorption
  • special co transporter proteins that transport glucose or amino acids from the tubule into the cell aka facilitated diffusion
  • sodium pottasium pumps
  • many mitochondria to produce a lot of ATP
46
Q

how does reabsorption occur

A
  • na/k pumps na out of cell reducing conc of na ions in cell
  • na ions enter cell with glucose/amino acids from pt lumen
  • as level of glucose and amino acids rise in cell can be transported back out of the cell into the blood plasma
  • all this decreases water potential of cells and increases in PT fluid so water will enter the cells and be put back into the blood via osmosis

A2 BIOLOGY (4 decks)

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