Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A-Level Biology > Excretion, homeostasis and the liver > Flashcards

Excretion, homeostasis and the liver Flashcards

(132 cards)

Start Studying
1
Q

Excretion

A

Removal of waste products of metabolism from the body

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

Main metabolic waste products in mammals

A

Carbon dioxide
Bile pigments
Nitrogenous waste products

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

Carbon dioxide waste products

A

Cellular respiration excreted from the lungs

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

Bile pigments - excretion

A

Formed from the breakdown of haemoglobin from old red blood cells in the liver - excreted in the bile from the liver into the small intestine via the gall bladder and bile duct ; colours the faeces

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

Nitrogenous waste products (urea)

A

Formed from the breakdown of excess amino acids by the liver ; all mammals produce UREA as their nitrogenous waste

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

Fish nitrogenous waste

A

Ammonia

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

Birds and insects nitrogenous waste product

A

Uric acid

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

Liver

A

Largest internal organ of the body - lies below the diaphragm and is very fast growing, regenerates quickly (made up of several lobes)

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

Blood to liver

A

Oxygenated blood is supplied by the Hepatic Artery to the liver and removed from the liver
Returns to the heart in the hepatic vein
Also supplied with blood by the hepatic portal vein which carries blood loaded with the products of digestion straight from the intestines to the liver and starting point for many metabolic activities of the liver - 75% of blood flowing through liver comes via hepatic portal vein

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

Hepatocytes

A

Large nuclei, prominent Golgi apparatus and lots of mitochondria - very metabolically active which divide and replicate allowing regeneration

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

Sinusoids

A

Blood from the hepatic artery and hepatic portal vein is mixed - increases oxygen content of the blood from the hepatic portal vein, supplying hepatocytes with enough oxygen for their needs

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

Kupffer cells

A

Act as the resident macrophages of the liver - ingesting foreign particles and helping to protect against disease

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

Canaliculi

A

Hepatocytes secrete bile from breakdown of blood into spaces called canaliculi and from these bile drains into bile duct uses which take it to the gall bladder

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

Functions of the liver

A

Carbohydrate metabolism
Deamination of excess amino acids
Detoxification

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

Carbohydrate metabolism

A

Hepatocytes are closely involved in the homeostatic control of glucose levels in the blood by their interaction with insulin and glucagon - when blood glucose levels rise, insulin levels rise and stimulate Hepatocytes to convert glucose to the storage carbohydrate glycogen
Similarly when blood sugar levels fall, Hepatocytes convert the glycogen back to glucose under the influence of the hormone glucagon

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

Deamination of excess amino acids

A

Hepatocytes synthesise most of plasma proteins - Hepatocytes also carry out trans animation, conversion of one amino acid into another - overcomes the problem of the diet not always containing the required balance of amino acids

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

Deamination

A

Removal of an amine group from a molecule because body cannot store proteins or amino acids - any excess ingested proteins would be excreted if not for Hepatocytes
They delaminate amino acids and converting it first into ammonia which is very toxic and then to urea - toxic in high concentrations but not in the concentrations normally found in the blood ; urea is excreted by the kidneys and the remainder of the amino acid can then be fed into cellular respiration or converted into lipids for storage

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

Ornithine cycle

A

Ammonia produced in deamination of proteins is converted into urea in a set of enzyme-controlled reactions ; removing the amino group from amino acids and converting the highly toxic ammonia to the less toxic and more manageable urea

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

Ornithine cycle

A

Deamination of excess amino acids - NH3 produced + CO2 and Ornithine produces citruline
Citruline + NH3 produces arginine (and H2O)
Arginine + H2O -> Ornithine (produces urea)

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

Detoxification - liver

A

Liver is the site where most of these substances are detoxified and made harmless (drugs/alcohol but also urea etc)
Breakdown of hydrogen peroxide ; Hepatocytes contain catalyse that splits H2O2 into oxygen and water, liver detoxifies ethanol using alcohol dehydrogenase which breaks it down into ethanal ; which is then converted to ethanoate which may be used to build up fatty acids or used in cellular respiration

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

Histology of liver

A

Central vein and lobule

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

Cirrhosis

A

Normal liver tissue replaced by fibrous scar tissue ; hepatitis C and genetic conditions
Fatty liver - fat-filled vesicles displace nuclei
Alcoholic hepatitis - fatty liver and hepatic veins become narrowed
Alcoholic cirrhosis - liver tissue is irreversible damaged ; Hepatocytes can no longer divide and replace themselves so the liver shrinks and its ability to deal with toxins in the body decreases

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

Gross structure of kidneys

A

Back of the abdominal cavity - surrounded by a thick protective layer of fat and a layer of fibrous connective tissue

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

Main two roles of kidneys

A

Excretion and Osmoregulation - maintain water balance and pH of the blood and hence tissue fluid that surrounds all cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Blood supply to kidneys
Supplied with blood by renal arteries that branch off from the aorta (at arterial pressure) ; blood circulated through the kidneys is removed by the renal vein that drains into the inferior vena cava
26
Kidneys are made up of...
Nephrons that act as filtering units ; urine passes out of the kidneys down tubes called ureters and is collected in the bladder - sphincter at exit of bladder then opens and urine passes down the urethra
27
3 main areas of the kidney
Cortex, Medulla and Pelvis
28
Cortex
Dark outer layer - where the filtering of blood takes place and it has a very dense capillary network carrying the blood from the renal artery to the nephrons
29
Medulla
Lighter in colour - contains tubules of the nephrons that form the pyramids of the kidney and collecting ducts
30
Pelvis
Central chamber where the urine collects before passing out down the ureter
31
Bowman's capsule
Cup shaped structure that contains the glomerulus, a tangle of capillaries - more blood goes into glomerulus than leaves it due to the ultrafiltration
32
Proximal Convoluted Tubule
First coiled region of the tubule after Bowman's capsule which is found in the cortex - where many of the substances needed by the body are reabsorbed
33
Loop of Henle
Creates a region of high solute concentration in the tissue fluid deep in the kidney medulla - the descending loop runs down from the cortex through the medulla to a hairpin bend at the bottom of the loop ; ascending limb travels back up through the medulla to the cortex
34
Distal Convoluted Tubule
A second twisted tubule where the fine-tuning of the water balance takes place ; permeability of the walls to water varies in response to the levels of ADH ; ion balance and pH balance also takes place then
35
Collecting Duct
Urine passes down the collecting duct through the medulla to the pelvis ; more fine-tuning of water balance and walls here are sensitive to ADH
36
Is selective reabsorption active or passive?
Active - glucose is required
37
Composition of the blood that leaves the kidney
Greatly reduced levels of urea but the levels of glucose and other substances like amino acids are almost the same as when the blood entered the kidneys (glucose may be used in selective reabsoprtion)
38
Mineral ion concentration - coming out of the blood
Restored to ideal levels
39
Ultrafiltration
Specialised form of the process that results in the formation of tissue fluid in the capillary beds of the body and it is the result of the glomerulus and the cells lining the bowman's capsule
40
Glomerulus blood supply
Supplied by a relatively wide afferent arteriole and the blood leaves via a much narrower efferent arteriole ; considerable pressure in capillaries of glomerulus - forces blood out through fenestrations (sieve)
41
Basement membrane
Network of collagen fibres and other proteins that make up a second sieve - most of the plasma contents can pass through the basement membrane but the blood cells and many proteins are retained in the capillary because of their size
42
Wall of Bowman's capsule
Has podocytes which act as an additional filter - they have extensions called pedicels that wrap around the capillaries, forming slits that make sure any cells, platelets or large plasma proteins that have managed to get through the epithelial cells and basement membrane do not get through into the tubule itself
43
Composition of plasma vs filtrate
Water, glucose, amino acids, urea and inorganic ions are all the same concentrations Protein concentration decreases rapidly
44
Glomerular filtration rate
Volume of blood filtered through the kidneys in a given time
45
Reabsorption
Function is to return most of the filtered substances back to the blood
46
Proximal Convoluted Tubule
Glucose, amino acids, vitamins and hormones are moved from the filtrate back into the blood by active transport 85% of sodium chloride and water is reabsorbed as well - sodium ions are moved by active transport while the chloride ions and water follow passively down concentration gradients
47
Adaptations of the cells lining the proximal convoluted tubule
Covered with microvilli, greatly increasing the SA over which substances are reabsorbed Many mitochondria to provide the ATP needed in active transport
48
Once substances have been removed from the nephron (down PCT)
Diffuse into extensive capillary network which surrounds the tubules down steep concentration gradients - maintained by the constant flow of blood through the capillaries
49
Filtrate reaching the loop of Henle
Isotonic with the tissue fluid surrounding the tubule and isotonic with the blood
50
Purpose of the Loop of Henle
Act as a countercurrent multiplier by using energy to produce concentration gradients that result in the movement of substances such as water from one area to another - cells use ATP to transport ions using active transport and this produces a diffusion gradient in the medulla
51
How do the two limbs interact with each other?
Changes in the descending limb of the loop of Henle depend on the high concentrations of sodium and chloride ions in the tissue fluid of the medulla that are the result of events in the ascending limb of the loop
52
What are the outermost cells called?
Endothelial cells
53
Name of the fluid in medulla
Interstitial fluid
54
Descending limb
Permeable to water
55
What is happening in the descending limb?
The filtrate has a higher water potential than the medulla (which is very salty) - thus water moves via osmosis from an area of high water potential to the interstitial fluid
56
How does the level of osmosis vary down the descending limb?
The interstitial fluid becomes saltier as you go down the medulla thus osmosis continues on due to the maintenance of a strong concentration gradient
57
By the time filtrate reaches the loop of Henle?
It is very concentrated with a very low water potential
58
Where does water move to once in interstitial fluid?
Down concentration gradient into surrounding capillaries
59
Descending limb permeability?
Impermeable to sodium and chloride ions so no active transport takes place thus the fluid that reaches hairpin is hypertonic to the blood in the capillaries
60
Ascending limb
Impermeable to water
61
First section of ascending limb
Sodium and chloride ions move out via diffusion down a concentration gradient
62
Second section of ascending limb
Actively pumped out into medulla against concentration gradient - produces high sodium/chloride concentration in the medulla
63
What does this mean for water potential of the filtrate?
Fluid left in ascending limb becomes increasingly dilute while tissue fluid develops the very high concentration of ions that is essential for the kidney to produce urine that is more concentrated than the blood
64
By the time filtrate reaches the top of the ascending limb?
Hypotonic to the blood again and it then enters the distal convoluted tubule and collecting duct
65
Distal convoluted tubule
This, alongside collecting duct, is where balancing the water needs of the body takes place - permeability of walls varies with ADH
66
Cells lining DCT
Have many mitochondria for active transport
67
If the body lacks salt
Sodium ions are actively pumped out of the distal convoluted tubule with chloride ions following down an electrochemical gradient
68
If there is an increase in ADH
Water can also leave the distal tubule, concentrating the urine and increasing water levels in the blood
69
Distal Convoluted Tubule role
Balancing pH of the blood
70
Collecting duct
Because the level of sodium ions increases through the medulla from the cortex to the pelvis- water can be removed all the way along its length, producing very hypertonic urine (when water needs to be conserved)
71
Major function of the kidneys besides excretion
Osmoregulation - osmotic balance within a narrow range (regardless of external factors)
72
Why is changing the concentration of urine crucial?
In order to maintain a dynamic equilibrium - water potential should be maintained regardless of the water and solutes taken in as you eat and drink
73
ADH
Produced by the hypothalamus and secreted into the posterior pituitary gland, where it is stored ; ADH increases the permeability of the distal convoluted tubule and the collecting duct to water
74
Water gains
Respiration in cells Food Drink
75
Water losses
Faeces Exhaled air Sweat Urine
76
What type of hormone is ADH
Protein
77
Mechanism of ADH?
Binds to receptors on the cell membrane and triggers the formation of cyclic AMP as a second messenger inside the cell - this causes a cascade of events
78
Cascade of events from cAMP
Vesicles in the cells fuse with the cell surface membranes on the side of the cell in contact with the tissue fluid of the medulla Membranes of these vesicles have aquaporins (protein based water channels) which make it permeable to water Provides a route for water to move out of the tubule cells into the tissue fluid of the medulla and blood capillaries by osmosis
79
Where is ADH released from?
Posterior pituitary gland
80
Where is detection of water potential?
Osmoreceptors
81
More ADH released and vice versa?
More aquaporins and thus more water lost via diffusion - concentrated urine produced and water returned to capillaries to increase WP (and tissue fluid) and vice versa
82
What type of system is needed for osmoregulation?
Negative feedback system
83
Osmoreceptors
Sensitive to the concentration of inorganic ions in the blood and are linked to the release of ADH
84
When there is an excess of water?
Blood becomes more dilute and water potential becomes less negative - change is detected by the osmoreceptors of the hypothalamus. Nerve impulses to the posterior pituitary are reduced or stopped and so the release of ADH is inhibited - thus very little reabsorption can take place because the walls remain impermeable and large amounts of dilute urine are produced
85
What can urine be used as?
A useful diagnostic tool
86
Urine composition?
Contains water, mineral salts, toxins etc - if you are affected by a disease, new substances will show up in the urine (for example glucose is a sign of Type 1/2 Diabetes) - muscle damage will result in creatinine in urine
87
Pregnancy tests?
Test for hCG in the urine, but they rely on monoclonal antibodies - a lot more sensitive
88
hCG
Site of the developing placenta then begins to produce hCG (6 days after conception) and this hormone is found both in the urine and blood of the mother
89
Monoclonal antibodies
Are antibodies from a single clone of cells that are produced to target particular cells or chemicals in the body
90
How to make monoclonal antibodies?
Mouse is injected with hCG - makes the appropriate antibody through the B cells, which are removed from the spleen and fused with a myeloma which divides very rapidly - this is called a hybridoma
91
Hybridomas?
Reproduces rapidly resulting in a clone of millions of living factories making the desired antibody
92
Main stages in pregnancy test
Wick is soaked in the first urine passed in the morning - highest level of hCG Test contains mobile monoclonal antibodies that have coloured beads attached to them - specifically bind to hCG - they bind and form a hCG/antibody complex Then - further up - there are immobilised monoclonal antibodies arranged in a line or a pattern such as a positive sign that only bind to the hCG/antibody complex - if woman is pregnant then coloured line appears in the first window There is a second window of immobilised monoclonal antibodies which bind to excess mobile antibodies regardless of them being in a complex or not - coloured line formed is simply an indication that the test is working (always forms)
93
Not pregnant
Only one coloured line appears
94
Pregnant
Two coloured lines
95
Urine and anabolic steroids
These are steroids that mimic the action of testosterone and stimulate the growth of muscles - by testing the urine using gas chromatography and mass spectrometry, scientists can show that an individual has been using these drugs
96
How do they test for steroids in urine?
Sample is vaporised with a known solvent and passed along a tube - lining of the tube absorbs the gases and is analysed to give a chromatogram that can be read to show the presence of the drugs
97
What else can urine be used to test for and why?
Drugs including alcohol - metabolites, breakdown products of drugs, are filtered through the kidneys and stored in the bladder - possible to find drug traces in the urine
98
What are the two ways the sample is divided when testing for drugs?
First sample is tested by an immunoassay, using monoclonal antibodies to bind to the drug or its breakdown product If positive then run through a gas chromatograph/mass spectrometer to confirm the presence of the drug
99
If kidneys are infected or affected by high blood pressure?
Protein in the urine - if basement membrane or podocytes of the Bowman's capsule are damaged they no longer act as filters and large plasma proteins can pass into the filtrate and are passed out in the urine Blood in the urine - sign of filtering process is not working
100
If kidneys fail completely?
Concentrations of urea and mineral ions build up in the body
101
Effects of kidney failure?
Loss of electrolyte balance - body can't excrete excess sodium, potassium and chloride ions causing osmotic imbalances in the tissues Build up of toxic urea - poisons cells High blood pressure - osmoregulation gone so may cause strokes/heart problems Weakened bones as calcium/phosphorous balance in the blood is lost Pain and stiffness in joints due to build up of abnormal proteins Anaemia - kidneys are involved in the production of erythropoietin that stimulates formation of RBCs - when kidneys fail this may cause a reduction in RBCs and thus causing tiredness and lethargy
102
Glomerular filtration rate
Used as a measure to indicate kidney disease - blood test measures levels of creatinine in the blood
103
What is creatinine?
Breakdown products of muscles and it is used to give an estimated GFR (eGFR) - units are cm^3/min
104
If levels of creatinine go up?
Sign that kidneys are not working properly
105
What factors need to be taken into account when measuring eGFR?
GFR decreases steadily with age even if you are healthy and men usually have more muscle mass and therefore more creatinine than women
106
If GFR falls below 15?
Kidney failure - kidneys are filtering so little blood they are virtually ineffective
107
Two ways kidney failure is treated?
Dialysis (artifical function) and a transplant - one healthy kidney is enough
108
Two types of dialysis
Haemodialysis and peritoneal dialysis
109
Haemodialysis
Blood leaves through an artery and flows into the dialysis machine where it flows between partially permeable dialysis membranes which mimic the basement membrane of the Bowman's capsule
110
What is on the other side of the membranes?
Dialysis fluid
111
Purpose of dialysis
Vital that they lose urea and mineral ions that have built up in the blood - equally important they do not lose glucose/mineral ions
112
What precaution must be taken when on dialysis machine?
Blood thinners must be used to prevent clotting Bubble trap to get rid of bubbles
113
Loss of substances control during dialysis?
Dialysis fluid contains normal plasma levels of glucose to ensure there is no net movement of glucose out of the blood DF contains normal plasma levels of mineral ions so excess ions diffuse down conc gradient - restoring the electrolyte balance DF contains no urea meaning there is a very steep concentration gradient from the blood to the fluid and as a result, much of the urea leaves the blood
114
Flow of blood in dialysis
Blood and dialysis flow in opposite directions to maintain a countercurrent exchange system and maximise the exchange that takes place
115
Dialysis logistics?
Just depends on diffusion no active transport - takes about 8 hours and has to repeated regularly on a weekly basis
116
What else do patients on haemodialysis have to do?
Manage their diets carefully eating relatively little protein and salts and monitor fluid intake to maintain blood chemistry
117
When is the only time patients can eat and drink?
Beginning of dialysis
118
Peritoneal dialysis
Done inside the body - makes use of the natural dialysis membranes formed by the lining of the abdomen - the peritoneum ; usually done at home and patients can carry on with their usual lives
119
How does diffusion work during peritoneal dialysis?
Dialysis fluid is introduced via a catheter - left for several hours for dialysis to take place so that urea and excess mineral ions pass out of the blood capillaries into the tissue fluid into the DF - fluid is then drained off and discarded, leaving the blood balanced again and the urea/excess minerals removed
120
DF
Dialysis fluid
121
Transplant
If long term then a single healthy kidney is placed within the body - blood vessels are joined and ureter + bladder and kidney will function for many years
122
Main problem with transplants?
Risk of rejection - antigens on the donor organ differ from the antigens on the cells of the recipient and the immune system will reject the organ and destroy the new kidney
123
Old kidneys?
Usually left in the body
124
How to reduce risk of rejection?
Match between the antigens of the donor and the recipient is made as close as possible - people with same blood group
125
Recipient of transplant is given?
Immunosuppressant drugs for the rest of their lives - helps to prevent rejection of their new organ
126
Disadvantage of immunosuppressant drugs?
Prevent the patients from responding effectively to infectious diseases - must take great care if they become ill in any way - small price to pay for a new, functioning kidney
127
Once transplanted organ starts to fail?
Patient returns to dialysis until another suitable kidney is found
128
Dialysis advantages
Much more readily available Enables patients to live a relatively normal life
129
Dialysis disadvantages
Must monitor their diet carefully and need regular sessions on the machine Long-term dialysis is more expensive than a transplant and can eventually cause more damage to the body
130
Transplant advantage
Free from the restrictions of dietary monitoring and regular dialysis sessions
131
Transplant disadvantage
Shortage of kidneys - not many register Fewer people die in traffic accidents as cars are safer
132
Future of kidney treatment?
Grow a functioning kidney from stem cells - whole new kidneys can hopefully be grown without the antigens which trigger the immune response of rejection so immunosuppressant drugs are not needed

A-Level Biology (37 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions