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Biology Module 5 > 5.2 Excretion > Flashcards

5.2 Excretion Flashcards

1
Q

define excretion

A

the removal of metabolic waste from the body

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2
Q

define egestion

A

the elimination of faeces from the body (undigested remains of food are not metabolic products)

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3
Q

what are the main excretory products

A

-Co2 from respiration
-nitrogen containing compounds eg. urea
-other compounds such as bile pigments found in faeces

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4
Q

define the excretory organs

A

-lungs
-liver
-kidney
-skin
-ureter
-bladder
-urethra

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5
Q

why is excretion important

A

-allowing products of metabolism to build up could be fatal
-metabolic products (co2, ammonia) are toxic. they interfere with cell processes by altering the PH so that normal metabolism is prevented
-other metabolic products may act as inhibitors and reduce the activity of essential enzymes

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6
Q

how does skin contribute to excretion

A

-sweat contain range of substances including salts, water, uric acid and ammonia (excretory products)
-loss of water and salts may be an important part of homeostasis- maintaining body temp and water potential of blood

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7
Q

what is respiratory acidosis

A

a condition which occurs when blood PH drops below 7.35 which causes a rapid heart rate, changes in blood pressure, drowsiness, headaches, restlessness, tremor and confusion.

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8
Q

what can respiratory acidosis be caused by

A

diseases/conditions that affect the lungs such has emphysema, chronic bronchitis, asthma, severe pneumonia or a blockage of an airway due to swelling, foreign object or vomit

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9
Q

how does the body try to prevent respiratory acidosis

A

hydrogen ions interact with bonds within haemoglobin, changing its shape which reduces the affinity of haemoglobin for oxygen, affecting oxygen transport. The hydrogen ions can combine with haemoglobin forming haemoglobinic acid

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10
Q

how does haemoglobin act as a buffer

A

it takes up hydrogen ions to resist changes in PH

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11
Q

what happens to excess hydrogen ions in the blood plasma

A

they reduce the PH of the plasma and amino acids act as buffers at a low PH as the amine group will accept hydrogen ions as amino acids are amphoteric

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12
Q

what happens if a change in PH is small

A

extra hydrogen ions are detected by the respiratory centre in the medulla oblongata of the brain which causes an increase in the breathing rate to help remove excess CO2

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13
Q

what happens to CO2 that is not converted to hydrogen carbonate ions

A

it combines directly with haemoglobin, producing carbaminohaemoglobin. Both haemoglobin and carbaminohaemoglobin are unable to combine with oxygen as normal which reduced oxygen transport further

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14
Q

how can carbon dioxide be transported in the blood

A

85% is transported in hydrogen carbonate ions
10% combines directly with haemoglobin to from carbaminohaemoglobin
5% directly dissolves in the plasma

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15
Q

what is the process of deamination

A

amino acid+ oxygen = keto acid + ammonia

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16
Q

what is the equation for the formation of urea

A

ammonia + carbon dioxide = urea + water

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17
Q

describe the structure of the liver (detailed)

A

the aorta splits into the hepatic artery which carries oxygen to the liver and the hepatic portal vein comes from the digestive system so it brings glucose and amino acids to the liver. These split into interlobular vessels. Bile is released into bile canaliculli then into the bile duct and then it is carried to the gall bladder. The liver is divided into lobes and subdivided into lobules. The special chambers of the lobules are called sinusoids and they are lined with hepatocytes which are liver cells with many microvilli. Inside the sinusoids, there are kupffer cells which are specialised macrophages. The lobes lead onto intralobular vessels which then from the hepatic vein which takes blood away from the liver to join the vena cava.

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18
Q

describe the general structure of the liver

A

hepatic artery + hepatic portal vein -> interlobular vessels -> lobule -> interlobular vessels -> hepatic vein

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19
Q

what does the haemoglobin breakdown form

A

bilirubin which is part of bile and it is stored at the gall bladder

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20
Q

describe the functions of the liver

A

-controls blood glucose levels, amino acid levels, lipid levels
-synthesis of bile, plasma proteins, cholesterol
-synthesis of red blood cells in the fetus
-storage of vitamins A, D and B12, iron, glycogen
-detoxification of alcohol,drugs
-breakdown of hormones
-destruction of red blood cells

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21
Q

how does the liver detoxify hydrogen peroxide and drugs such as cocaine

A

it can render toxins harmless by oxidation, reduction and methylation. Liver cells also contain enzymes which render toxins harmless. The liver contains many ribosomes to make all the enzymes and many mitochondria for any active processes including ATP

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22
Q

what does catalase do

A

converts hydrogen peroxide to oxygen and water

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23
Q

what does cytochrome P450 do

A

breaks down drugs including cocaine and medicinal drugs. It is also used in metabolic reactions such as electron transport during respiration

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24
Q

describe detoxification of alcohol

A

Ethanol is dehydrogenated by ethanol dehydrogenase which gives off 2H and turns NAD into NADH and this gives Ethanal. Ethanal is dehydrogenated by ethanal dehydrogenase which gives ethanoate which can combine with Acetyl Coenzyme A and can enter the Krebs cycle for respiration

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25
Q

where does detoxification of alcohol occur

A

in the hepatocytes

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26
Q

what is the problem with the liver detoxifying alcohol

A

NAD is also required to oxidise and breakdown fatty acids for use in respiration. If the liver detoxifies too much, it uses up its or NAD and doesn’t have enough left to deal with the fatty acids so they end up being converted back to lipids and stored as fat in the hepatocytes causing the liver to become enlarged. This can lead to alcohol related hepatitis or to cirrhosis

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27
Q

why is the formation of urea necessary

A

excess amino acids can’t be stored as the amino groups make them toxic. They contain a lot of energy so it would be wasteful to excrete the whole molecule so they undergo treatment in the liver to remove and excrete the amino component. This consists of deamination and the ornithine cycle

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28
Q

describe the equation for the formation of urea

A

amino acid + oxygen —->ammonia + keto acid —-> Urea
deamination ornithine cycle

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29
Q

what is deamination

A

When an amino group is removed and makes ammonia. Ammonia is very soluble and toxic so it may interfere with osmosis. This also produces a keto acid which enters respiration directly

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30
Q

describe the ornithine cycle

A

Ammonia and CO2 combine with ornithine to produce citrulline which gives off water.
More ammonia is added and citrulline is converted into arginine which also gives off water.
Arginine is converted back into ornithine by the addition of water and removal of urea

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31
Q

why is urea better than ammonia and what happens to it

A

It is less soluble and less toxic. It gets passed back into the blood and transported around the body to the kidneys then in the kidneys, it is filtered out of the blood and concentrated in urine where it can be safely stored in the bladder until it is released from the body

32
Q

describe the structure of the kidney

A

the nephron tubule is located at the top of the kidney. The medulla is the inner part then it is surrounded by the cortex then is surrounded by the capsule. In the inner part of the kidney (pelvis) you will find a branch of the renal vein and branch of the renal artery. The ureter extends from the pelvis

33
Q

why is the structure of the afferent arteriole different to the efferent arteriole

A

It is wider and has a wider diameter. This ensures that the blood in the capillaries of the glomerulus maintains a higher pressure than the pressure in the bowmans capsule. The pressure difference tends to push fluid from the blood into the bowmans capsule that surrounds the glomerulus.

34
Q

What happens as a result of the pressure difference pushing fluid from the blood into the bowmans capsule

A

It creates a high hydrostatic pressure. Each glomerulus is surrounded by a bowmans capsule. Fluid from the blood is pushed into the bowmans capsule by the process of ultrafiltration which is filtration of the blood at a molecular level under pressure. The glomerulus is a network of capillaries

35
Q

what are the 3 layers that make up the barrier between the blood in the capillary and the lumen of the bowmans capsule

A
  1. the endothelium of the capillary
  2. the basement membrane
    3.epithelial cells of the bowmans capsule (podocytes)
36
Q

describe the endothelium of the capillary

A

there are narrow gaps between cells of the endothelium wall. The cells of the endothelium also contain pores (fenestrations) which allow blood plasma and substances dissolved in it to pass out the capillary

37
Q

describe the basement membrane

A

Consists of fine mesh of collagen fibres and glycoproteins which act as a filter to prevent passage of molecules with a relative molecular mass greater than 69000-most proteins are held in the capillaries of the glomerulus

38
Q

describe the epithelial cells of the bowmans capsule (podocytes)

A

they have a specialised shape as they have many major processes. On each major process, there are minor processes or foot processes that hold cells away from the endothelium of the capillary. The projections ensure there are gaps between the cells. Fluid from the blood in the glomerulus can pass between these cells into the lumen of the bowmans capsule.

39
Q

what are the parts of the blood that become glomerular filtrate

A

water
amino acids
glucose
urea
inorganic mineral ions (sodium, chloride,potassium)bc they are small

40
Q

why does some water move back into the blood at the glomerulus

A

the presence of proteins means that the blood has a very low water water potential. This ensures that some of the fluid is retained in the blood and this contains some of the water and the dissolved substances

41
Q

describe selective reabsorption

A

sodium ions are moved out the proximal convoluted tubule through sodium potassium ion pumps (active transport). This creates a concentration gradient. The sodium ions move along their concentration gradient through facilitated diffusion and the amino acids/glucose go with them through cotransport. As the amino acids/glucose are moving against their concentration gradient, this is secondary active transport. The movement of these molecules causes the water potential in the cells to lower therefore water follows through osmosis. The amino acids/glucose move from the cells to the tissue fluid and blood by facilitated diffusion. Ions pass through protein channels and amino acids and glucose move through carrier proteins. Small proteins which pass through ultrafiltration are reabsorbed through endocytosis.

42
Q

what happens if an equilibrium is reached during selective reabsorption

A

The sodium potassium ion pumps will start working again and sodium ions will move out through active transport.

43
Q

how are the cells which line the proximal convoluted tubule adapted for selective reabsorption

A

-plasma membrane next to tubule fluid is folded to form microvilli- increases SA for reabsorption
-Plasma membrane contains special cotransporter proteins which transport glucose/amino acids with sodium into the cell
-the plasma membrane next to the tissue fluid is also folded to increase the SA. Also contains sodium potassium ion pumps
-cell cytoplasm has many mitochondria-produce lots of ATP

44
Q

describe what happens at the loop of henle

A

sodium and chloride ions are actively transported out the ascending limb into the tissue fluid. This lowers the water potential in the tissue fluid and as a result water diffuses into the tissue fluid from the descending limb through osmosis. The sodium and chloride ions in the tissue fluid diffuse through facilitated diffusion into the descending limb and more water diffuses Into the tissue fluid from the descending limb through osmosis. The tissue fluid has a high concentration of ions so more sodium and chloride ions diffuse into the descending limb from the tissue fluid. The tubule fluid at the bottom of the loop of henle has a very high ion concentration. sodium and chloride ions diffuse out the bottom of the ascending limb to reach an equilibrium. Sodium and chloride ions are actively transported out the ascending limb again and the process repeats.

45
Q

what is the purpose of the loop of henle

A

to allow mineral ions to be transferred from the ascending limb to the descending limb. The overall effect is to increase the concentration of mineral ions in the tubule fluid which has a similar effect upon the concentration of mineral ions in the tissue fluid. This gives the tissue fluid in the medulla a very low water potential. The deeper into the medulla tissue fluid you go, the lower the water potential. The arrangement of the loop of henle is known as a hairpin countercurrent multiplier system.

46
Q

what is the overall effect of the hairpin countercurrent multiplier system in the loop of henle

A

to increase the efficiency of transfer of mineral ions from the ascending to limb to the descending limb in order to create the water potential gradient seen in the medulla.

47
Q

What happens at the final stage of the loop of henle

A

the tubule fluid still contains a lot of water (high water potential). The collecting duct carries the fluid back down through the medulla to the pelvis. As the tubule fluid passes down the collecting duct, water moves by osmosis from the tubule fluid into the surrounding tissue. It then enters the blood capillaries by osmosis and is carried away.

48
Q

Which limb in the loop on henle is permeable to water

A

descending limb is permeable
ascending limb is impermeable

49
Q

what is osmoregulation

A

the control of the water potential in the body. It controls levels of both water and salt in the water.

50
Q

why is controlling the correct water balance between cells and surrounding fluids important

A

Because it is necessary to prevent water entering cells and causing lysis or leaving cells and causing crenation

51
Q

OSMOREGULATION- what happens when it is a very hot day and someone has done a lot of exercise so the water potential is low (in hypothalamus)

A

The hypothalamus in the brain contains osmoreceptors. When water potential of the blood is low, the osmoreceptors lose water by osmosis and shrink which stimulates neurosecretory cells in the hypothalamus. They are specialised neurones which produce and release ADH. The ADH is manufactured in the cell body which lies in the hypothalamus and it moves down the axon to the terminal bulb in the posterior pituitary gland, where it is stored in vesicles. The neurosecretory cells are stimulated by the osmoreceptors and they carry action potentials down their axons and cause the release of more ADH by exocytosis. It enters the blood capillaries and is transported to the collecting duct.

52
Q

what do osmoreceptors do

A

detect changes in water potential

53
Q

OSMOREGULATION- what happens when it is a very hot day and someone has done a lot of exercise so the water potential is low (in collecting duct)

A

The cells in the walls of the collecting duct respond to the level of ADH in the blood as they contain specific membrane bound receptors for ADH. ADH binds to these receptors and causes a chain of enzyme controlled reactions inside the cell. As a result, vesicles containing aquaporins fuse with the cell surface membrane which makes the walls more permeable to water. When levels of ADH in the blood rise, more aquaporins are inserted-allows more water to be reabsorbed by osmosis into the blood. Less urine is produced, it is highly concentrated and has a low water potential

54
Q

OSMOREGULATION- what happens when it is a cold day and someone hasn’t done much exercise and water potential is high

A

The osmoreceptors in the hypothalamus swell and stimulate the neurosecretory cells. The neurosecretory cells carry action potentials down their axon and cause the release of less ADH by exocytosis. The ADH binds to some of the ADH specific receptors on the collecting duct and cause a chain of enzyme controlled reactions. The cell surface membrane folds inwards to create new vesicles that remove the aquaporins from the membrane. This makes the walls less permeable and less water is reabsorbed by osmosis into the blood. More water passes down the collecting duct to form a greater volume of urine which is more dilute.

55
Q

what is ADH control an example of

A

negative feedback

56
Q

What happens to the ADH in the blood eventually

A

It is slowly broken down and the collecting ducts receive less stimulation because the body no longer needs to reabsorb more water

57
Q

how does alcohol effect the release of ADH

A

it inhibits the release of ADH. It reduces absorption from the collecting ducts and causes greater volumes of urine with a high water potential, causing the individual to become dehydrated.

58
Q

define the glomerular filtration rate and describe what It is

A

the rate at which fluid enters the nephrons each minute
It is how you assess kidney function
A normal reading is in the range 90-120cm3min-1
A figure below 60 indicates there may be some form of chronic kidney disease
A figure below 15 indicates kidney failure and a need for immediate medical attention

59
Q

define the monoclonal antibodies

A

antibodies made from one type of cell-they are specific to one complementary molecule

60
Q

define renal dialysis

A

a mechanism used to artificially regulate the concentrations of solutes in the blood

61
Q

what happens if the kidneys fail completely

A

they are unable to regulate the levels of water and electrolytes in the body or to remove waste products such as urea from the blood which will rapidly lead to death

62
Q

Apart from the glomerular filtration rate, how can you also assess kidney function

A

by analysing urine for substances such as proteins. Proteins in the urine indicate the filtration mechanism has been damaged

63
Q

describe the causes of kidney failure

A

diabetes (type 1 and 2) heart disease, hypertension and infection

64
Q

what are the treatments for kidney failure

A

renal dialysis and kidney transplant

65
Q

describe renal dialysis

A

Most common treatment for kidney failure
Waste products, excess fluid and mineral ions are removed from the blood by passing it over a partially permeable dialysis membrane that allows the exchange of substances between the blood and dialysis fluid. The dialysis fluid contains the correct concentrations of mineral ions, urea, water and other substances found in blood plasma. Any substances in excess om the blood diffuse across the membrane into the dialysis fluid. Any substances too low in concentration diffuse into the blood from the dialysis fluid

66
Q

what are the 2 types of renal dialysis

A

haemodialysis
Peritoneal dialysis

67
Q

describe haemodialysis

A

blood from an artery or vein is passed into a machine that contains an artificial dialysis membrane shaped to form many artificial capillaries, which increase SA for exchange. Heparin is added to avoid clotting. The artificial capillaries are surrounded by dialysis fluid which flows in the opposite direction to the blood. This improves the efficiency pf exchange. Bubbles are removed before the blood is returned to the body via a vein

68
Q

describe peritoneal dialysis

A

The dialysis membrane is the body own abdominal membrane. A surgeon implants a permanent tube in the abdomen. Dialysis solution is poured through a tube and fills the space between the abdominal wall and organs. After hours, the used solution is drained from the abdomen.

69
Q

where is haemodialysis carried out

A

at a clinic 2 or 3 times a week for several hours each session. Can be learned to be carried out at home

70
Q

where is peritoneal dialysis carried out

A

At home or at work. The patient can walk around while having dialysis. Must be combined with a carefully monitored diet.

71
Q

describe kidney transplants

A

-best life extending treatment
-involves major surgery
-surgeon implants new organ onto the lower abdomen and attaches it to the blood supply and the bladder
-patients are given immunosuppressant drugs to help prevent their immune system recognise the new organ as a foreign object and rejecting it

72
Q

describe the advantages of kidney transplants

A

-freedom from time consuming renal dialysis
-feeling physically fitter
-improved quality of life-able to travel
-improved self image- no longer have feeling of being chronically ill

73
Q

describe the disadvantages of kidney transplants

A

-need to take immunosuppressant drugs
-need for major surgery under general anasthetic
-need for regular checks for signs of rejection
-side effects of immunosuppressant drugs- fluid retention, high blood pressure, susceptibility to infections

74
Q

what Substances can be tested for in urine?

A

-glucose in the diagnosis for diabetes
-alcohol to determine blood alcohol levels in drivers
-many recreational drugs (tests at work)
-human chorionic gonadotrophin (hCG) in pregnancy testing
-anabolic steroids to detect improper use in sporting competitions

75
Q

describe how pregnancy testing is carried out

A

once a human embryo is implanted in the uterine lining, it produces a hormone called hCG
pregnancy testing kits use monoclonal antibodies that bind to hCG in urine
-urine is poured onto a stick
-hCG binds to mobile antibodies attached to a blue bead
-mobile antibodies move down the test stick
-if hCG is present, it binds to fixed antibodies holding the bead in place, blue line forms
-mobile antibodies with no hCG attached bind to another fixed site to show the test is working.

76
Q

how can anabolic steroids be tested for

A

anabolic steroids increases protein synthesis within cells which results in the build up of cell tissue, especially in the muscles.
provide advantage in competitive sports but have dangerous side effects
testing for them involves analysing a urine sample in a laboratory using gas chromatography

Biology Module 5 (7 decks)

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