4.2.1 EXCRETION PT.2

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Outline the structure of liver lobules
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Outline the formation of urea
Deamination then ornithine cycle
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Describe deamination
amino acid removed to form ammonia/ produces ammonia and organic acid/ organic acid respired for ATP or converse into carbohydrates so can be stored as glycogen
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Describe the ornithine cycle - what happens once urea is made
ammonia and CO2 --> urea + water/ urea released from liver into blood kidneys then filter blood to form urine
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Outline the structure of the kidney
...
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What is the bowman capsule?
network of capillaries called glomerulus/ ultrafiltration takes place here
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what is the proximal convoluted tubule?
from capsule to loop of henle
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What is the loop of henle?
where water reabsorption occurs - dips into medulla
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What is the collecting duct?
connects nephrons together and joins to pelvis of kidneys
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Outline ultrafiltration
high pressure forces small molecules and liquids out of capillary and into renal capsule to form glomerulus filtrate
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How does the filtrate reach the renal capsule?
through pores in capillary endothelium --> basement membrane (podocytes and collagen mesh) --> epithelium of renal capsule
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What is selective reabsorption? where does it take place?
useful substances are reabsorbed/ PCT loop of Henle and DCT
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How are the PCT and DCT specialised?
contain many microvilli to maximise reabsorption as large SA
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Outline selective reabsorption
solutes like glucose/ amino A/ vitamins/ salts/some urea absorbed by active transport, facilitated diffusion/ diffusion// cotransporter proteins facilitate diffusion of glucose and amino A// water potential of cell decreases and h2o will enter
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Describe the characteristics of the Loop of Henle
dips into medulla/ descending limb impermeable to ions/ ascending limb impermeable to water
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Outline the counter current mechanism that takes place in the loop of henle
Na+ and Cl- actively transported out of ascending - created low water pot in medulla/ water moves out of descending due to water pot/ near bottom of ascending limb Na and Cl diffuse into medulla
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What is ADH?
Antidiuretic hormone
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How are water levels monitored in the body?
osmoreceptors in hypothalamus monitor water potential of blood/ if too low impulses sent to posterior pituitary gland to release ADH into the blood
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What happens when ADH is released?
binds to receptors on men of DCT and collecting duct/ causes protein channels called aquaporins to open/ allows water to pass through by osmosis so water can be absorbed
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How does alcohol affect water levels?
decreases water levels in body - affects release of ADH
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Why does the length of the Loop of Henle differ in animals?
animals that live in warmer countries typically have a longer loop of henle to maximise water reabsorption to prevent its loss
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Other cards in this set

Card 2

Front

Outline the formation of urea

Back

Deamination then ornithine cycle

Card 3

Front

Describe deamination

Back

Preview of the front of card 3

Card 4

Front

Describe the ornithine cycle - what happens once urea is made

Back

Preview of the front of card 4

Card 5

Front

Outline the structure of the kidney

Back

Preview of the front of card 5
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