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A A A Level Biology > Communication and Homeostasis pt2 Kidneys and Liver > Flashcards

Communication and Homeostasis pt2 Kidneys and Liver Flashcards

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1
Q

what is excretion

A

removal of metabolic waste from cells of body.

The removal of by-products or unwanted substances from normal cellular processes to maintain homeostasis

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2
Q

what is the formula of urea

what is the amine group
what is the rest know as and what is it used for

A

CO(NH2)2

NH2 is the amine group
the rest is the keto group which is involved in respiration

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3
Q

what happens to the amine group of excess amino acids

  • what and where does it take place
  • what does it form
A

removed in excretion by deamination which takes place in the liver.
amine group joined with hydrogen to form ammonia NH3 and then into urea

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4
Q

Why must ammonia be converted to urea

A

because ammonia is a highly soluble highly toxic substance.

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5
Q

what happens to the urea

A

dissolved in water in the blood and is filtered in kidneys through ultrafiltration and expelled in urine

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6
Q

what is the ornithine cycle

A
  • cycle where amine group is metabolised in liver into ammonia
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7
Q

what are the differences between excretion and secretion

A

excretion is…..

  • metabolic waste such as CO2 urea and water
  • not packaged in vesicles
  • substance removal from body

secretion is….

  • useful products such as hormones eg insulin
  • packaged into vesicles
  • excocytosis
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8
Q

why do fish excrete ammonia but mammals must convert it to urea for excretion

A
  • fish are surrounded by water in an aquatic environment so ammonia is kept as dissolved in water so is just expelled
  • terrestrial mammals aren’t surrounded by water so ammonia is not dissolved in as much water to be safe so must be converted to urea to less toxic and less soluble
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9
Q

difference between excretion and egestion

A

excretion is removal of metabolic waste out of body from cells
whereas egestion is removal of indigestible material

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10
Q

what is deamination

A

process where urea is made from excess amino acids

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11
Q

why are excess proteins removed

A

body can’t store excess proteins but removing all amino acids would be wasteful as they contain energy
(so those that arent immediately needed are deaminated in liver)

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12
Q

how is ammonia formed

A

deamination of amino acids removing the amino group together with a hydrogen atom to form ammonia (nitrogenous product)

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13
Q

why must ammonia be converted to urea

A

soluble but highly toxic substance so must be converted to stop build up in blood+ immense damage

urea is less toxic and less soluble

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14
Q

chemical equation for formation of urea

A

2NH3 + CO2&raquo_space;»> C(NH2)20+H20

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15
Q

where are the kidneys found

A

back of abdominal cavity

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16
Q

what surround the kidneys

A

thick layer of protective fat called adipose tissue and fibrous connective tissue

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17
Q

how are kidneys involved in osmoregulation

A

as well as filtering nitrogenous waste the kidneys maintain water balance and pH of blood

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18
Q

what supplies the kidneys with blood

A

oxygenated blood from renal arteries which branch from abdominal aorta at arterial pressure

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19
Q

where is deoxygenated blood removed from kidney

A

removed from renal vein that drains into inferior vena cava

about 90-120cm^3 blood passes through kidney every minute

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20
Q

what parts make up the kidney

A

cortex
medulla
pelvis

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21
Q

what does the cortex of the kidney do

A

outer layer

-where filtering takes place, very dense capillary network carrying blood from renal artery to nephrons

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22
Q

what is the function of the medulla of the kidney

A

contains tubules of nephrons that form pyramids of kidney and also the collecting ducts

appears lighter on micrographs

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23
Q

what is the function of the pelvis

A

(basin) central chamber urine collects in before going to urteter

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24
Q

where is blood filtered in kidney and what are they removing

A

the nephrons

  • nitrogenous waste (urea)
  • excess water
  • excess ions

about 3cm long and there are 1.5 million in each of the kidneys

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25
Q

why are there so many nephrons

A

-provides body with several km of tubules for reabsorbtion of water glucose +salts ect. (large SA:V)

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26
Q

STRUCTURE OF NEPHRON
what is the bowmans capsule
-what does it look like and contain?

A
  • cup shaped feature
  • contains glomerulus and a tangle of capillaries
  • more blood goes into glomerulus than leaves due to ultrafiltration
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27
Q

STRUCTURE OF NEPHRON

what is the proximal convoluted tubule

A
  • first coiled region of tubule after the bowmans capsule

- found in cortex where many substances needed by body are reabsorbed into blood

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28
Q

LOOK UP DIAGRAM OF STRUCTURE OF KIDNEY

A

I HOPE YOUVE DONE IT :)

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29
Q

STRUCTURE OF NEPHRON
what is the loop of Henle

where do descending and ascending limb go

A

long loop of tubule that creates a region w/ high, very solute concentration in tissue fluid deep in kidney medulla

  • the descending loop runs down cortex through medulla to a hairpin bend at the bottom of loop
  • ascending limb goes back up through medulla to cortex
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30
Q

STRUCTURE OF NEPHRON
what is the distal convoluted tubule
-what occurs here
-how does permeability of walls change

A

a second twisted tubule where the fine tuning of water takes place

  • permeability of walls to water varies in response to levels of ADH (antidiuretic hormone) in blood
  • further regulation of ion balance+pH of blood takes place here too
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31
Q

STRUCTURE OF NEPHRON

what is the collecting duct

A
  • urine passes down collecting duct through medulla to pelvis.
  • More of the fine tuning of water balance takes place here
  • walls of tubule are sensitive to ADH
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32
Q

what do the network of capillaries around nephron lead to

A

venule»»> vein

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33
Q

characteristics of blood leaving the nephron

A
  • no urea
  • levels of glucose and other substances such as amino acids needed by body stay pretty much same! some glucose is used in selective reabsorption tho
  • mineral ion concentrations restored to ideal level.
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34
Q

why does the efferent arteriole have a narrower lumen than the afferent arteriole

A

it creates a higher pressure to push substances out of capillaries into surrounding area for ultrafiltration.

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35
Q

what is the purpose microvilli in the nephron

A

increase SA for selective reabsorption

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36
Q

why are the convoluted tubules wiggly

A

to increase SA

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37
Q

where does the capillary bed of the nephron drain back to?

A

the renal venule

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38
Q

what is the glomerular filtrate

A
  • around lumen surrounding glomerulus
  • The fluid in the lumen of the Bowman’s capsule of the nephron that has been filtered from the capillaries of the glomerulus
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39
Q

what is the first stage of the removal of nitrogenous waste and osmoregulation of blood called?

A

Ultrafiltration

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40
Q

where does ultrafiltration occur

what does it form

A

in the kidney tubules in the bowmans capsule
-results in formation of tissue fluid in the capillary bed of body

its resulted of the structure of glomerulus and cells lining the bowmans capsule

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41
Q

where does glomelulus gets blood from

A

a relatively wide arteriole from renal artery (afferent arteriole)

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42
Q

where does blood leave the glomerulus

A

by narrower efferent arteriole due to pressure in capillaries of glomerulus
this forces blood out of capillary wall through the basement membrane

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43
Q

what is the basement membrane and what is it made of

A

important in filtration process

-made of network of collegen fibres and proteins making a 2nd sieve

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44
Q

what can’t go through the basement membrane

A

blood cells and many proteins left in capillary as too big to leave

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45
Q

what is the name of the specialised cells in the bowmans capsule

A

podocytes- they act as an additional filter

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46
Q

what adaptations do podocytes have

A

extensions called pedicels that wrap around capillaries which forms slits
these make sure any cells, large plasma proteins or platelets that have managed to get through epithelial cells and basement membrane dont get through the tubule itself

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47
Q

what does the filtrate entering the bowmans capsule contain

A

glucose salt urea blood plasma

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48
Q

what is the glomerular rate

A

volume of blood filtered through kidneys at given time

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49
Q

why do some substances need to be reabsorbed in nephron and give examples

A

needed by body

|&raquo_space;> eg glucose for respiration so isnt excreted (unless diabetic)

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50
Q

ultrafiltrate is _____ to the blood plasma concentration

A

hypotonic (less concentrated)

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51
Q

what is the main function of the nephron

A

to return most filtered substances back to the blood

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52
Q

what is reabsorbed back into the blood

A

all amino acids, vitamins, glucose and hormones and 85% of salts and water

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53
Q

how do sodium ions move out of proximal convoluted tubule

A

active transport

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54
Q

how do Cl- ions and water leave proximal convoluted tubule

A

passively down a concentration gradient by osmosis/ diffusion

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55
Q

describe the characteristics of the cells in the proximal convoluted tubule

A
  • covered with microvilli- greatly increases surface area so substance can’t be reabsorbed
  • many mitochondria- to provide ATP needed for active transport systems
  • basement membrane which goes to lumen of blood capillary which is one endothelial cell thick
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56
Q

when substances have been removed from nephron where do they go?
how is the gradient maintained

A

they diffuse into capillary network surrounding the tubules down a concentration gradient which is maintained by constant flow of blood through capillaries

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57
Q

filtrate reaching loop of henle at the Promixmal convolued tubule end of the capillary is ______ to the tissue fluid surrounding the tubule and the blood

A

isotonic

at this point 80% of glomerular filtrate reabsorbed into blood

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58
Q

what is the function of the loop of henle

A

enables the mammals to produce urine more concentrated than their own blood

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59
Q

how does permeability change in the loop of henle

A

different areas are more permeable to water (lower part)

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60
Q

loop of henle acts as a C_____ M______ which means that it:

A

Countercurrent Multiplier
uses energy to produce a concentration gradient which results in the movement of water and other substances from one area to another

Uses ATP to transport ions by active transport and produces a concentration gradient in the medulla in the ascending limb

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61
Q

describe the permeability of the upper part of the descending limb of the loop of henle

A

-upper part impermeable to water

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62
Q

describe the permeability of the lower part of the descending limb of the loop of henle

A

permeable to water (this section is in the medulla not cortex of kidney)

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63
Q

how does the concentration of sodium ion concentration in tissue fluid of medulla change as they move through from cortex to the pyramids

what is the due to?

A

increases

due to activity of ascending limb of loop of henle

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64
Q

filtrate entering the the descending limb of the loop of henle is ______ to the blood

A

isotonic

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65
Q

how does water leave descending limb of loop of henle and where does it go

A
  • passes out into tissue fluid by osmosis
  • down a concentration into the surrouding capillaries
    (the vasa recta)
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66
Q

the descending limb of the loop of henle is _____ to sodium and chloride ions

A

not permeable

no active transport takes place

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67
Q

describe the water potential at the bottom of the loop of henle

therefore describe the fluid at the hairpin bend of the loop

A

very low
highest at top of ascending loop and also high at descending loop

fluid is very concentrated and will be hypertonic to blood in capillaries

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68
Q

which section of the loop of henle is very permeable to sodium and chloride ions

how does the differ in the second part of that section

what does this result in, in the medulla

A

the first section of the ascending limb of the loop (near bottom) the ions move out down a concentration gradient

in second section (upper) ascending limb of loop Na+ and Cl- pumped out AGAINST the concentration gradient via active transport into the medulla

high concentration of Na+ and Cl- in the medulla

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69
Q

is the ascending limb of the loop of henle permeable to water

A

no (so they dont follow the Cl- and Na+ ions

70
Q

describe the fluid in the ascending limb- how the concentrations change
what about conc. in tissue fluid of medulla

A

fluid left in the acsending limb becomes increasingly dilute
and tissue fluid in medulla developes high concentration of ions

71
Q

why is it essential there is a high concentration of ions in tissue fluid of medulla

A

means kidney can produce urine more concentrated than the blood which is a key part of the countrcurrent multiplier system of blood

72
Q

by the time dilute fluid reaches the top of the ascending limb it is ____ to blood again

this fluid then enters the____ ______ ______ and ____ ____

A

hypotonic

distal convoluted tubule and collecting duct

73
Q

what is the function of the distal convoluted tubule

A

to balance the water needs of the body which also happens in the collecting duct!!

also play role of balancing the pH of blood

74
Q

what means that the walls of of the tubules vary in permeability

A

varying levels of ADH

these cells in the tubule like the promixal ones also have many mitochondria for active transport

75
Q

what does your distal convoluted tubule do if your body lacks salt

A

sodium ions are actively transported back out of distal convoluted tubule with chloride ions down an electrochemical gradient

76
Q

can water leave the distal convoluted tubule

A

yes- this will concentrate the urine (if you have had little to drink say)
This is because the walls of the tubule are permeable in response to higher levels of ADH

77
Q

where is the concentration and volume urine determined in the nephron

A

in the collecting duct

and also the distal CT

78
Q

where does the collecting duct pass down

A

through concentrated tissue fluid of renal medulla

79
Q

how does water move out of collecting duct and where does it pass through

A

osmosis down a conc. grad.
through renal medulla

this means the urine becomes more concentrated

water can move out of collecting duct along its whole length depending on how much water needs to be conserved

80
Q

how does the level of sodium ions in fluid surrounding collecting duct change as to medulla from cortex

A

increases

81
Q

the fluid in the collecting duct is ____ to blood when body needs to conserve water

A

hypotonic

hypotonic/ yellow urine

82
Q

what controls how permeable the collecting duct is to water

A

the level of ADH so also determines how much water is reabsorbed

83
Q

how would someone with one kidney need to change their diet

A

less protein so it doesnt need to work as hard

84
Q

how would you distinguish a glomerulus under a microscope

A
  • many nuclei in small area
  • irregular arrangement of nuclei
  • mass knot of capillaries
  • larger than surrounding tissue
  • white unstained area surrounds glomerulus
85
Q

what are vasa recta

A

straight loop shaped capillaries near loop of henle

86
Q

what does the basement membrane act as

A

a filter or second sieve between capillary wall and bowmans capsule
after the first layer of endothelium acts as a sieve too

87
Q

which cells line the bowmans capsule

A

podocytes which form fenestrations

88
Q

which substances are reabsorbed from prox. CT

A

glucose, amino acids, vitamins, 85% sodium ions and chloride ions

89
Q

how are glucose, amino acids, vitamins and hormones moved back to blood in PCT

A

active transport with help from mitochondria which the cells in the PCT have many of

90
Q

what are podocytes

A

foot like projections in epithelium on bowmans capsule and lumen of bowmans capsule

pod=foot

91
Q

where is the net pressure gradient in the glomerulus

where is the net solute conc. grad.

A

from blood plasma into lumen of renal capsule with glomerular filtrate

from lumen of renal capsule to blood plasma

these gradients go through basement membrane and endothelium

92
Q

What is the purpose of Kidney dialysis

A

Aka renal dialysis- where function of kidney is carried out artificially

93
Q

What are the two types of kidney dialysis

A

Haemodialysis and peritoneal dialysis

94
Q

What does Haemodialysis do

Where does it flow into and what does this mimic?

A

Uses a machine in the hospital and blood leaves the body through the artery in arm for eg

> and flows into a large machine with large SA
>where it goes between a partially permeable dialysis membrane which mimics the one in the basement membrane

95
Q

What is present in the machine used in haemodialysis

What is the concentration of this stuff

A

Dialysis fluid which flows in and then out carrying the waste products and urea

Dialysis fluid is isotonic to the blood concentration of sugar minerals and ions

96
Q

What prevents blood clotting in dialysis machine

A

Blood thinners

97
Q

Where does the clean blood flow through when leaving the dialysis machine

A

Clean blood flows through bubble trap to get rid of any bubbles and then returns to vein in arm

98
Q

Why must dialysis fluid be controlled carefully

A

To prevent loss of substances and must contain normal plasma levels of glucose to ensure there is no net movement out of blood

Also same with ions and minerals which restores the electrolyte balance of blood

99
Q

Describe the concentration of urea in dialysis fluid at start

A

None to create a steep concentration gradient for urea so it all diffuses out of blood

100
Q

What is the purpose of the countercurrent exchange system in dialysis machine

A

Dialysis fluid flows in different directions to maximise exchange that takes place

101
Q

Haemodialysis relies on ___1/2_____?

1) steep concentration gradients
2) active transport

A

1) steep concentration gradients

102
Q

How long and often must some one using haemodialysis treatment use the machine

What kind of lifestyle choices must someone with dialysis treatment make

A

4-8 hours a few times a week

Deduce intake if protein and watch diets

103
Q

How is peritoneal dialysis done?

A

Inside body with natural dialysis membrane found in lining of abdomen called the peritoneum

104
Q

True or false peritoneal dialysis takes place at home

A

True It can be done at home so the patient carries out their normal routine

Careful with hygiene
They have a bag and catheter attached to them

105
Q

Describe the process of peritoneal dialysis

A

Tissue fluid introduced to abdomen using catheter and left for several hours for dialysis to take place across peritoneal membrane
-urea and excess ions pass out of blood capillaries into tissue fluid
»»and out across peritoneal membrane into dialysis fluid

Fluid is then drained off and discarded leaving blood balances

106
Q

Why are transplants the best option for kidney failure patients

A

Long term option and healthier as long term dialysis can have serious side effects

107
Q

What are the problems associated with kidney transplants

A
  • rejection- antigens of reciprocant May differ from antigens of donor so T cells could attack kidney so patient must be on immunosuppressants which makes them susceptible to infection
  • can sometimes only last 10 years so a need for another
  • short supply as few people die of sudden death eg safer cars
108
Q

Briefly outline how a new kidney is transplanted

A

Healthy kidney from donor and blood vessels are joined to the ureter and inserted into the bladder

If successful the kidney will function for many years

109
Q

Dialysis and Transplants

  • which is more easily accessible?
  • which one means patient can live more normal lifestyle
  • which is more expensive
A
  • Dialysis more accessible
  • kidney allows more normal life
  • long term dialysis very expensive but so is kidney transplant
110
Q

What is a proposed replacement for both dialysis and kidney transplants

A

Embryonic stem cells to grow kidney and hopefully without antigens!

111
Q

What kind of feedback system is osmoregulation

A

Negative feedback

Under the control of hormones

112
Q

Why must the water balance of blood be under tight control

A

To stop osmotic effects between tissue fluid and cells

  • cells need water for metabolic processes
  • too much can cause cell to swell/lysis
113
Q

which receptors are sensitive to water potential of blood

A

osmoreceptors in the hypothalamus

114
Q

which cells produce ADH

A

nerve cells (neurosecretory) of the hypothalamus

115
Q

where is ADH stored and how does it get there?

A

stored in posterior pituitary gland

|&raquo_space;but ADH gets there by passing along axon of nerve cells which terminate in the posterior pituitary gland

116
Q

when is ADH released

A

from Posterior pituitary gland when blood water potential too low

117
Q

what causes the ADH to be released into blood

A

action potentials, which create a wave of depolarisation, are sent down the axons from osmoreceptors in the hypothalamus
to cause ADH release into blood

118
Q

how is the ADH detected and create a response

A

1) ADH detected by hormone receptors of cell surface membrane
2) causes Enzyme controlled reaction
with 2nd messenger cAMP
3) Vesicles containing water permeable channels called aquaporins fuse to membrane
4) more water can be reabsorbed into capillary next to kidney so urine is hypotonic (more conc.) than blood and is passed through collecting duct

119
Q

why must urine have some water in it

A

urea is still toxic so must be dissolved in something

120
Q

where does mechanism of ADH take place

A

specifically lumen of collecting duct and distal convoluted tubule

121
Q

outline is there was a high level of water-how much ADH would be produced

A

secretion of ADH reduced
no binding to receptor
so no cAMP which means that no vesicles fuse

122
Q

what does ADH do to the permeability of walls

and which walls does it effect and how?

A

increases the permeability of the distal convoluted tubule and collecting duct by binding to the cell surface receptors

123
Q

how long does ADH last for

A

half life of 20 mins

|&raquo_space;» broken down in blood so effects decrease over time

124
Q

what does the binding of ADH to receptor cause

A

2nd messenger cAMP to be released

125
Q

what is the function of cAMP as a 2nd messenger to ADH

A

causes vesicles embedded w/ the aquaporins in the membrane to fuse with the membrane on the side of the cells facing the lumen of the collecting duct

126
Q

what does the aquaporin do

A

increases the permeability of the cell surface membrane to water so more water can enter by osmosis down a conc. grad. so water enters blood and less in urine

127
Q

a GFR value below 15 means what

A

kidney failure

128
Q

name some main causes of kidney failure

A

> infections - structure of podocytes and tubules damaged or destroyed
raised blood pressure damaging epithelial cells and basement membrane of bowmans cap.
genetic conditions such as polycystic kidney disease where healthy kidney tissue replaced by fluid filled cysts of damage from pressure of cysts

129
Q

symptoms of kidney infection or affected by high pressure?

A
  • protein in urine - basement membrane or podocytes no longer act as filters in bowmans capsule so large plasma proteins can pass through and out in urine
  • blood in urine- another symptom that filters no longer work
130
Q

symptoms and what would happen if kidney failure

A
  • high blood pressure can cause strokes ect
  • build up of toxic urea can poison cells
  • loss of electrolyte balance so can’t secrete Na+,K+ Cl- ions ect which causes osmotic inbalance in tissue and death
  • anemia - kidneys produce hormone erythroprotein which stimulates formation of red blood cells, without this we become tired
  • pain stiffness as abnormal proteins build in blood
  • weakend bones due to loss of calcium+phosphorus
131
Q

what does a GFR measure

A

glomerular filtration rate used to indicate kidney disease
-can be done with urine sample test to measure levels of creatinine in blood which is the breakdown product of muscles

however as you age it decreases naturally and men have more muscle mass so more creatinine than women

132
Q

what is GFR measured in

A

cm^3/min

133
Q

why do birds excrete urea as uric acid

A

flight demands a low body mass so removing nitrogenous waste as uric acid means large amounts of water arent required. Insects do this too as they are prone to water loss
uric acid has low toxicity but more ATP required than other methods

134
Q

how is uric acid formed

A

deamination of purines adenine and guanine

135
Q

isotonic means

A

same concentration as/in balance with

136
Q

hypotonic means

A

lower concentration than

137
Q

hypertonic means

A

higher concentration than

138
Q

why might sodium ions be actively pumped out of DST into blood

A

if body low on salt

139
Q

the ______ limb of the loop of henle is permeable to Na+ and H20

A

descending

140
Q

the _____ limb of the loop of henle is impermeable to Na+ and H20

A

ascending

141
Q

what are the survival advantages of the loop of henle

A

conserves water

very concentrated urine can be produced

142
Q

what does the hormone hCG stand for and what is it

A

human Chlorionic Gonadotrophin

results in changes in female during pregnancy and maintains uterus lining

143
Q

how are pregnancy tests made? (monoclonal antibody)

A

antigen from hCG injected into a mouse

  • clonal selection+expansion take place
  • plasma cells extracted from mouse and combined with tumor cells which rapidly divide out of control
  • this creates a hybridoma
  • this produces lots of monoclonal antibodies with a variable region specific to hCG only
144
Q

how do pregancy tests work if positive

A
  • women wees on stick
  • hCG is combined with monoclonal antibody which is linked to dye
  • monoclonal antibodies connected to wall of test region and join to hCG and other MCA and the dye will show blue in the first window
  • in the second window a different MCA (immunoglobulin variable protein) will recognise other MCAs which means test is done properly
145
Q

how do pregnancy tests work if negative

A

-no hCG present means no binding of MCA to antibody in test region so goes straight through to second region where MCA joins to immunoglobulin with variable protein and shows blue to show test fin

146
Q

characteristics of the specialised cells of the liver

A

Hepatocytes

-large nuclei, prominant Golgi, many mitochondria and metabolically very active

147
Q

where does the liver recieve oxygenated blood

A

hepatic artery

148
Q

where does the liver recieve deoxygenated blood

A

hepatic portal vein

149
Q

section of the liver is called a

A

lobule

150
Q

what are lobules lined with

A

hepatocytes

151
Q

what is in the centre of the lobule

A

hepatic venule which joins to hepatic vein

152
Q

what are sinusoids

A

passage for blood in liver (honeycomb like)

153
Q

where is the bile made in the liver

A

canaliculus (lots of canaliculi) doesnt link to venule

bile drains into bile ductules which goes to the gall bladder

154
Q

what are Kupffer cells

A

line sinusoid walls and described as fixed phagocytes (macrophage in phagocytosis)

get rid of worn out erythrocytes+leucocytes as haemoglobin has short life

155
Q

what is bilirubin

A

pigment formed in the breakdown of haemoglobin and found in bile (makes faeces brown and lack of makes faeces white)

156
Q

the hepatic artery….

A

carries oxygenated blood TO the liver from heart via aorta

157
Q

the hepatic portal vein….

A

takes blood rich in products of digestion from intestines TO liver

158
Q

the hepatic vein

A

rejoins vena cava takes deoxygenated blood out of liver

159
Q

how are hepacytes involved in metabolism

A

homeostatic control of blood glucose concentration
insulin influemces them+ they convert glucose into storage carbohydrate glycogen
hepatocytes convert glycogen to glucose under influence of glucagon

160
Q

what is transamination and when is it important

A

conversion of one amino acid into another

important as diet doesnt always contain required balance of amino acids so it overcomes this

161
Q

what is deamination and why is it important

what role do hepatocytes play

A

removal of the amine group from a molecule as body can’t store proteins or amino acids (excess energy stored as fat)
any excess ingested protein would be excreted +wasted if it werent for hepatocytes

162
Q

describe the ornithine cycle

A

the deamination of amino acids to ammonia and then to urea through enzyme controlled reactions in the ornithine cycle

remaining amino acids are used in cellular respiration or converted into lipids for storage

163
Q

what is detoxification

A

-other metabollic pathways other than urea, produce potentially posionous substances and also things like alcohol and drugs by choice
»»liver detoxifies to make less harmful.

hepatocytes contain enzyme catalase

164
Q

example of detoxification with hydrogen peroxide

A

catalase breaks down into oxygen and water

165
Q

how does the liver detoxify alcohol

A

alcohol contains ethanol the active drug in drinks
-alcohol dehydrogenase breaks down ethanol to acetaldehyde and further into acetic acid and acetyl-CoA. whihc forms ethananoate (made from acetic acid) which builds up fatty acids or used in cellular respiration

166
Q

how does the liver store glycogen

A

When blood sugar rises in the blood, insulin is released by the pancreas and travels through the blood. The insulin binds to receptor cells in the liver and receptor molecules on muscle cells, causing them to take in and store the excess glucose as glycogen.

by glycogenesis

opposite is glycogenolysis caused by glucacon and adrenaline

167
Q

describe the process of ultrafiltration

A

> 1st step of removal of nitrogenous waste and osmoregulation
results in formation of tissue fluid in capillary beds of glomerulus and cells lining bowmans capsule

> glomerulus supplied with blood from wider afferent arteriole from renal artery and THEN leaves by narrower efferent arteriole which creates higher pressure in capillaries of glomerulus
This pressure forces blood through capillary wall and then this fluid passes through the BASEMENT MEMBRANE. This membrane is made up of collegen fibres

MOST PLASMA CONTENTS CAN GET THROUGH BASEMENT MEMBRANE BUT BLOOD CELLS AND PROTEINS ARE RETAINED IN CAPILLARY DUE TO THEIR SIZE

> podocytes in wall of bowmans capsule act as an additional filter as pedicel extensions wrap around capillaries forming slits that make sure any cells, platelets or large plasma proteins that have managed to get through epithelial cells+basement membrane DONT get into tubule itself.

168
Q

describe the process of selective reabsorption

A

main function of the nephron after the bowmans capsule is to return most filtered substances back into the blood.

169
Q

how does kidney failure effect glomerular filtration rate and electrolyte balance

A

> A decrease or decline in the GFR implies progression of underlying kidney disease or the occurrence of a superimposed insult to the kidneys. This is most commonly due to problems such as dehydration and volume loss. An improvement in the GFR may indicate that the kidneys are recovering some of their function.4

> When there is a malfunction of the kidneys, the balance of fluid and electrolytes can be altered, leading to an imbalance of certain electrolytes. This can, therefore, affect the transmission of impulses of the nerves and muscles throughout the body, which can have serious implications

170
Q

how does liver break down ethanol

A

alcohol dehydrogenase enzyme breaks down ethanol to ethanal which is made into ethanoate which is used to build fatty acids or used in cellular respiration

171
Q

what % of water and solutes are removed from blood plasma

A

20%

172
Q

the filtrate reaching the loop of henle at prox convoluted tubule end is _____ to the tissue fluid surrounding the tubule

A

isotonic

A A A Level Biology (22 decks)

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