5.2- Excretion as an example of homeostatic control

  • Created by: McTighe
  • Created on: 09-08-18 13:57
What is the definition of excretion?
Removal of metabolic waste from the body (Unwanted products of cell metabolism)
1 of 109
Why do many substances need to be excreted?
Because the chemicals can build up and inhibit enzyme activity or become toxic
2 of 109
Name the three main excretory products
Carbon Dioxide; Nitrogen-containing compounds (e.g. Urea); Bile Pigements
3 of 109
Name the four main excretory organs
Lungs, liver, kidney, skin
4 of 109
Describe the role of lungs in the excretory system
Every living cell produces carbon dioxide from respiration. It passes from tissues to blood and transported to lungs. The lungs excrete carbon dioxide
5 of 109
Describe the role of liver in the excretory system
Many metabolic roles e.g. break down amino acids into urea (deamination). Some of the substances produced will pass into bile for excretion with faeces
6 of 109
Describe the role of Kidney in the excretory system
Urea passes into bloodstream to be transported by kidney. Urea is transported in solution. ey remove urea from blood to become part of urine. Urine is stored in bladder and excreted from body via urethra
7 of 109
Describe the role of skin in the excretory system
Sweat can be produced which contains a range of substances including salts, urea, water, uric acid and ammonia. The loss of water and salts may be important part of homeostasis, maintaining body temperature and the water potential of the blood
8 of 109
Why are carbon dioxide and ammonia toxic?
They interfere with cell processes by altering the pH, so normal metabolism is prevented
9 of 109
How does carbon dioxide change into hydrogencarbonate ions?
Carbon dioxide binds to water to form carbonic acid. Carbonic acid breaks into hydrogen ions and hydrogencarbonate ions
10 of 109
What enzyme encourages the formation of hydrogencarbonate ions?
Carbonic anhydrase
11 of 109
How is haemoglobinic acid formed?
Hydrogen ions interact with bonds within haemoglobin reducing affinity for oxygen. The hydrogen ions then bind with the haemoglobin to form haemoglobinic acid
12 of 109
How is carbaminohaemglobin formed
Carbon dioxide that is not converted to hydrogencarbonate ions can combine directly with haemoglobin
13 of 109
Why would it be wasteful to excrete excess amino acids?
Because they contain almost as much energy as carbonhydrates
14 of 109
What happens to amino acids?
They are transported to the liver and the amino group is removed (deamination) to form ammonia. Ammonia is then converted to a urea which is transported to the kidneys.
15 of 109
What is the equation of deamination?
Amino Acid + Oxygen --> Keto Acid + Ammonia
16 of 109
What is the equation of formation of urea?
Ammonia + Carbon Dioxide --> Urea + Water
17 of 109
What are liver cells called?
18 of 109
What does the internal structure of the liver ensure?
As much of the blood as possible flows past as many liver cells as possible
19 of 109
What is the hepatic artery?
A artery which carries oxygenated blood from the heart to the liver. This supplies oxygen essential for aerobic respiration as liver cells are very metabolically active.
20 of 109
What is the hepatic portal vein?
Deoxygenated blood from digestive system enters liver via hepatic portal vein. It is rich in products of digestion. Concentrations of various substances will be uncontrollable.
21 of 109
What is the hepatic vein?
Blood leaves liver via a hepatic vein, and rejoins the vena cava in blood's circulation
22 of 109
What is the bile duct?
Site of bile synthesis. Secreted from liver and has the function of digestion and excretion. The duct carries bile from liver to gall bladder, where stored until required. Can contains bile pigements
23 of 109
Name one type of bile pigment
24 of 109
What is the liver divided into?
25 of 109
What are the lobes divided into?
26 of 109
What are the vessels called which run parallel to the lobules?
Intralobular vessels
27 of 109
What are the chambers called which link hepatic artery or hepatic portal vein to the central vein?
28 of 109
What are the specialised macrophages found in sinusoids called?
Kupffer Cells
29 of 109
What is the role of Kupffer cells?
Breakdown and recycle old red blood cells. Breakdown haemoglobin into bilirubin
30 of 109
What is bile released into?
Bile Canaliculi
31 of 109
What do bile canaliculi link to form?
A bile duct
32 of 109
What is the 'central vein'?
Found at the centre of each lobule, and is a branch of the hepatic vein (intralobular vessel). Branches of hepatic vein from different lobules join to form hepatic vein.
33 of 109
What are the functions of the kidney?
-Control blood glucose, amino acids and lipid levels -Synthesis of bile, plasma proteins, chloesterol -Sythesis of red blood cells in fetus -Storage of vitamins A, D, B12, Iron, Glycogen -Detoxification of alcohol, drugs -Breakdown of hormones
34 of 109
Name four ways toxins can be rendered harmless in the liver?
Oxidation, Reduction, Methylation, Combination with another molecule
35 of 109
What is Catalase used for in the liver?
Converts hydrogen peroxide into oxygen and water
36 of 109
What is Cytochrome P450 used for in the liver?
Group of enzyme used to breakdown drugs, and can also be used in other metabolic reactions (e.g. Electron transport during respiration)
37 of 109
How is alcohol converted into Acetyl coeynzyme A in the liver?
Ethanol dehydrogenated by enzyme Ethanol dehydrogenase to form Ethanal. Ethanal is converted to Ethanoic acid by enzyme ethanal dehydrogenase. Ethanoic acid combines with coenzyme A to form Acetyl Conenzyme A
38 of 109
What is Acetyl Coenzyme A used for?
39 of 109
How are the hydrogen ions which are released by dehydrogenation of ethanol used?
The H+ bind with conenzyme NAD to form reduced NAD
40 of 109
What is the role of conenzyme NAD?
It is required to oxidise and breakdown fatty acids for respiration
41 of 109
Why is liver not good for the liver?
Stores of NAD will be used to detoxify alcohol, so less is used to break down fatty acids. Fatty acids therefore are converted to lipids and stored as fat. This causes liver to become enlarged 'fatty liver'
42 of 109
Name two alcohol-related diseases of the liver?
Hepatitis and Cirrhosis
43 of 109
What is the keto acid used for, produced in deamination?
44 of 109
How many kidneys does a normal person have?
45 of 109
What are the blood vessels called linked to the kidney?
Renal Artery and Renal Vein
46 of 109
Name the three main regions of the kidney?
Cortex, Medulla, Pelvis
47 of 109
Is the cortex the inner or outer part of the kidney?
48 of 109
How many nephrons does each kidney contain?
Approx 1 million
49 of 109
Where do the nephrons start?
In cortex at the Bowman's Capsule,
50 of 109
What is the name of the arterioles which the renal artery splits into?
Afferent Arterioles
51 of 109
What do the afferent arterioles lead to?
52 of 109
Where does the blood move into after the glomerulus?
Efferent Arteriole
53 of 109
What causes high pressure in the glomerulus?
The afferent arteriole has a wider diameter than the efferent arteriole, so blood cannot move out of glomerulus as quickly. This forces small components of blood out of capillaries
54 of 109
What is the pressure called?
Hydrostatic Pressure
55 of 109
What is the structure called which surrounds the glomerulus?
Bowman's Capsule
56 of 109
What is the process called of fluid from blood being pushed into Bowman's Capsule by hydrostatic pressure?
57 of 109
What are cells called in the inner layer of Bowman's Capsule?
58 of 109
What are the cells called in the outer layer of Bowman's Capsule?
Squamous Epithelial Cells
59 of 109
What is the glomerular filtration rate?
Amount of filtrate produced by kidneys each minute
60 of 109
Name the three layers in the barrier between blood in capillary and lumen of Bowman's Capsule
Endothelium of capillary; Basement Membrane; Epithelial cells of Bowman's Capsule
61 of 109
Describe the endothelium of the capillary
Narrow gaps between cells in endothelium of capillary wall. The cells also contain pores called fenestrations. Gaps allows blood plasma and substances dissolved in it to pass out of capillary
62 of 109
Describe the basement membrane of the capillary
Membrane consists of fine mesh of collagen fibres and glycoproteins. Mesh acts as filter to prevent passage of molecules with relative molecular mass greater than 69000. This means proteins are held in capillaries.
63 of 109
Describe the epithelial cells of Bowman's Capsule
Podocytes have specialised shape, with finger-like projections (Major Processes). On each major processes, there are minor processes that hold cells away from endothelium of the capillary. These projections ensure that there are gaps between cells.
64 of 109
Describe what ultrafiltration is
Filtering of blood at a molecular level
65 of 109
Wat molecules are pushed out of blood?
Water, Amino acids, glucose, urea, inorganic ions
66 of 109
What sustances are left in the blood?
Blood cells and proteins
67 of 109
How is the fluid absorbed by bowman's capsule altered as it passes along the nephron tubule?
Selective reabsorption
68 of 109
What fluid is altered in the proximal convoluted tubule?
Reabsorptioin of sugars, mineral ions and water
69 of 109
How much fluid is reabsorbed in the proximal convoluted tubule?
approx 85%
70 of 109
Why does the proximal convoluted tubule have a large surface area?
The cells are highly folded producing a brush border
71 of 109
What is this brush border called?
72 of 109
How are the cells lining the proximal convoluted tubule specialised for reabsorption?
-Microvilli increase surface area -Contains special cotransporter proteins -Opoosite membrane is also folded -Lots of mitochondria -Contains sodium/potassium pumps
73 of 109
What is the process of reabsorption of glusoce/amino acids?
1. Na+ pumped out of cel by active transport. Concentration in cytoplasm decreases creating conc. gradient. 2. Na+ diffuses into cell by cotransporter protein, carrying glucose/AA. Reduced water potential 3.Water moves in by osmosis 4.Gluose diffuse
74 of 109
into blood, followed by water
75 of 109
What does this mean about the composition of urine?
It will contain less glucose, amino acids and water, and a higher percentage of other susbstances such as urea.
76 of 109
What are the three sections of the loop of Henle?
-Descending Limb -Thick Ascending Limb -Thin Ascending Limb
77 of 109
What does the structure of the loop of Henle allow?
Mineral ions to be transferred from ascending limb to descending limb. This increases conc. of mineral ions in the tubule fluid, giving tissue fluid in medulla very low water potential
78 of 109
What is the aim of the loop of Henle?
Ensure water potential in medulla is lower than water potential in collecting duct. This means water can be reabsorbed by osmosis from the collecting duct regardless of hydration state.
79 of 109
Describe the process in the Loop of Henle
1.Na+ and Cl- are actively pumped out of thick ascending limb, lowering water potential of medulla. 2.Na+ and Cl- diffuse into ascending limb causing conc. to rise 3. Water moves out of descending limb by osmosis 4.As filtrate moves up ascending limb
80 of 109
it becomes more conc. As result, sodium and chloride ions are able to passively diffuse out of thin ascending limb.
81 of 109
What is the process called in the Loop of Henle?
hairpin countercurrent multiplier system
82 of 109
What is the tubule called from the top of the ascending limb?
Distal convoluted tubule
83 of 109
Where does the fluid go after the tubule?
Collecting Duct
84 of 109
What part of the kidney does the collecting Duct flow through?
The Medulla
85 of 109
What happens as fluid passes down the collecting duct?
Water moves by osmosis out of the tubule into the surrounding tissues (low water potential medulla)
86 of 109
What does the amount of water reabsorbed depend on?
Permability of the collecting duct walls
87 of 109
What does the urine contain when it reaches the pelvis?
Low water potential and the concentration of minerals and urea is higher than in blood
88 of 109
What is Osmoregulation?
Control of the water potential in the body. It involves controlling levels of both water and salt in the body
89 of 109
Name three sources where the body gains water from?
Food, Drink, Respiration
90 of 109
Name three ways water is lost from the body?
Urine, Sweat, Water Vapour, Faeces
91 of 109
How do kidneys alter the volume of urine produced?
Altering permability of the collecting ducts walls
92 of 109
What does ADH stand for?
Antidiuretic Hormone
93 of 109
How does ADH affect permability of the collecting Duct walls?
Cells in walls of the collecting duct respond to level of ADH in blood as they have membranes for ADH. ADH binds to receptors producing reactions inside cells. These reactions cause vesicles contain water-permable channels calle aquaporins to fuse
94 of 109
with cell membrane. Water moves into cell from collecting duct into fluid then into blood. When ADH increases, more aquaporins are inserted.
95 of 109
What happens if the level of ADH in blood falls?
Cell membrane fold inwards (Invaginates) to create new vesicles that remove aquaporins from membrane. Walls are less permable so less water is reabsorbed by osmosis.
96 of 109
What detected the water potential in blood?
Osmoreceptors in hypothalamus
97 of 109
What cells do the osmoreceptors stimulate?
Neurosecretory cells in hypothalamus
98 of 109
How does neurosecretory cells produce ADH?
ADH maunfactured in cell body, move down axon to terminal bulb and stored within vesicles in posterior pituitary gland. Action potential go down axons and release ADH by exocytosis.
99 of 109
What are some causes of kidney failure?
Diabetes Mellitus, Hypertension, Heart Disease, Infection
100 of 109
What is 'acute' disease
Fast Development, short activity, easily, recovery
101 of 109
What is 'chronic' disease
Slower development, long activity,less easily treatable, slow/no recovery
102 of 109
What is Renal Dialysis?
Most common treatment for kidney failure. Waste products are removed from blood by passing over a permable dialysis membrane that allows exchange of susbstances. Fluid contains correct conc. of minerals. Anything is excess in blood diffuses into flui
103 of 109
What are the two types of renal dialysis?
Haemodialysis and Peritoneal Dialysis
104 of 109
What are advantages of a kidney transplant?
-Freedom from time-sonsuimg renal diaysis -Feeling physically fitter -Improved quality of life -Improved self image
105 of 109
What are disadvantages of a kidney transplant?
-Need to take immunosuppressant drugs -Need for major surgery under general anaesthetic -Need for regular checks for signs of rejection -Side effects
106 of 109
What can a urine anaylsis test for?
-Glucose in the diagnosis of diabetes -Alcohol -Recreational drugs -Human Chorionic gonadotrophin -Anabolic steroids
107 of 109
What can human Chorionic Gonadotropin (hCG) test for?
When a human embryo is impated in the uterine lining, it produces hormone called hCG. This is a small glycoproteins that is found in urine 6 days after conception. Preganancy sticks use monoclonal antibodies which bind to hCG
108 of 109
How are anabolic steroids tested for?
These steroids increase protein systhesis in cells, result in build up of tissue. This gives an advantage in sportd. They have a half life of 16 hours and remain in blood for many days. They enter nephron easily. Tested using chromotograpghy
109 of 109

Other cards in this set

Card 2


Why do many substances need to be excreted?


Because the chemicals can build up and inhibit enzyme activity or become toxic

Card 3


Name the three main excretory products


Preview of the front of card 3

Card 4


Name the four main excretory organs


Preview of the front of card 4

Card 5


Describe the role of lungs in the excretory system


Preview of the front of card 5
View more cards


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Excretion resources »