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OCR A-level Biology > Excretion > Flashcards

Excretion Flashcards

(75 cards)

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1
Q

Why do we need excretion?

A

To remove harmful metabolic waste products

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2
Q

What are the 3 main waste products that need excreting?

A

CO2 from respiration

Nitrogenous waste (e.g urea)

Other compounds like bile pigments (found in faeces)

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3
Q

What are the 4 main excretory organs?

A

Lungs
Liver
Kidneys
Skin

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4
Q

What may occur if CO2 isn’t excreted properly?

A

Build up of CO2

Dissolves into blood plasma forming H2CO2 (carbonic acid)

Dissociates to form H+ which changes the pH of blood

This can change the shape of haemoglobin reducing the affinity of erythrocytes to O2

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5
Q

How does the body ensure that CO2 doesn’t build up

A

High CO2 concentrations detected by the medulla oblongata

Increases breathing rate to remove the CO2

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6
Q

What is the pH threshold of the blood and what does it cause if the pH drops below this value?

A

pH 7.35

Respiratory Acidosis

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7
Q

Why does the body not excrete excess amino acids?

A

They contain lots of energy that can be used in respiration

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8
Q

What is the name of the process where the harmful amino group is removed?

A

Deamination

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9
Q

Where does deamination occur?

A

Liver

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10
Q

What is the equation for deamination?

A

amino acid + oxygen = keto acid + ammonia

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11
Q

What is ammonia converted to after deamination?

A

Urea

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12
Q

What is the equation for the formation of Urea?

A

ammonia + carbon dioxide = urea + water

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13
Q

What is the name of liver cells?

A

Hepatocyes

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14
Q

Why must the liver have a good blood supply?

A

it is involved in many metabolic processes so requires O2 for respiration

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15
Q

What are the 2 sources of blood supply TO the liver?

A

Hepatic artery

Hepatic portal vein

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16
Q

What blood is found in the Hepatic Artery?

A

Oxygenated blood from the heart

provides oxygen for aerobic respiration of the hepatocytes

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17
Q

What blood is found in the Hepatic Portal Vein?

A

Deoxygenated blood from the digestive system

Rich in the products of digestion

any toxic compounds that have been absorbed must be removed

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18
Q

What blood vessel does blood leave the Liver by?

A

Hepatic Vein

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19
Q

What is the fourth vessel that is connected to the liver?

A

Bile duct

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20
Q

What is the function of Bile in the liver?

A

aid digestion of fats

Contains pigments (bilirubin) that must be excreted

Created by liver cells as a result of haemoglobin breakdown.

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21
Q

Describe the histology of the liver

A

Divided into lobes and then further into lobules

Inter lobular vessels (branches of the hepatic artery and hepatic portal vein) deliver their fluids into a sinusoid

It then reaches the intra lobular vessel in the centre where it leaves the liver via the Hepatic vein

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22
Q

What is a sinusoid?

A

A cavity surrounded by hepatocytes where blood flows through as toxins are removed

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23
Q

What is a bile canaliculus?

A

A cavity where bile flows into as it is produced by the hepatocytes

Flows into bile duct were bile is transported to gall bladder

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24
Q

What is the function of Kupffer cells?

A

Specialised macrophages that breakdown old erythrocytes

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25
How might hepatocytes be specialised to carry out metabolic reactions?
Dense cytoplasm High numbers of specific organelles
26
What are the metabolic functions of the liver?
control of blood glucose, amino acid and lipid levels synthesis of bile, plasma and cholesterol synthesis of RBC's storage of vitamins (A, D, B12) Detoxification of drugs and alcohol breakdown of hormones breakdown of RBC's Storage of glycogen
27
In what form does the liver store glycogen?
Granules in the cytoplasm of hepatocytes
28
Describe 2 enzymes the liver uses to detoxify compounds?
Catalase - converts H2O2 to H2O Cytochrome P450 - Break down drugs such as cocaine and various medicinal drugs. Can interfere with other metabolic functions giving the side affects of drugs Ethanol dehydrogenase - turn ethanol to acetate and H+ which are used used in respiration
29
Why does alcohol lead to hepatitis or liver cirrhosis?
Too much NAD is used to remove H+ produced when alcohol is broken down Not enough NAD available for fatty acid breakdown fat builds up on liver causing hepatitis or cirrhosis
30
What is the ornithine cycle?
Conversion of ammonia (NH3) to urea (CO(NH2)2)
31
Why must ammonia be converted immediately after it is formed in deamination?
it is highly soluble and highly toxic
32
Where does urea go after it is created?
to the kidneys it is then filtered out of the blood excreted in the urine
33
What are the two main blood vessels connected to the kidneys?
Renal Vein | Renal Artery
34
What is the other vessel connected to the kidneys and what is its function?
Ureter | transport urine from kidneys to the bladder
35
What are the 3 main sections of the kidneys?
Cortex - outer region Medulla - inner region Pelvis - centre connected to the pelvis
36
What is the name of the tine tubules that make up the kidneys?
Nephrons
37
What is the name of the structure at the start of a nephron?
Bowman's capsule
38
What is the name of the knot of capillaries in the Bowman's Capsule?
Glomerulus
39
what is the name of the process where blood is pushed into the Bowman's capsule?
Ultrafiltration
40
How is the Bowman's capsule specialised to carry out ultrafiltration?
The endothelium of capillary - small gap between capillary and endothelium, also contains fenestrations which allow substances through Basement membrane - a fine mesh of collagen and glycoproteins between capillary and endothelium, keep RBC's in the capillary Epithelia of Bowman's capsule (Podocytes) - Have projections that make gaps between cells so fluid can pass into the lumen of the Bowman's capsule
41
What the the 4 parts of a nephron tubule called?
Bowman's capsule Proximal convoluted tubule loop of Henle Distal convoluted tubule
42
What is filtered out of the blood in the kidneys?
``` Water Amino acids Glucose Urea Inorganic mineral ions (Na+, Cl-, K+) ```
43
What is the function of the nephron after ultra filtration?
selective reabsorption
44
What is reabsorbed into the blood in the proximal convoluted tubule?
Sugars, Mineral ions and some water
45
What happens in the descending limb of the loop of Henle?
mineral ions added back water removed water potential decreased
46
What happens in the ascending limb of loop of Henle?
mineral ions removed by active transport | water potential increased
47
What happens in the collecting duct?
Water removed | water potential decreased
48
What is the final product left in the collecting duct?
Urine
49
How are the cells lining the proximal convoluted tubule specialised to perform selective reabsorption?
surface membrane folded to form microvilli surface membrane contains cotransporter proteins for moving glucose or amino acids into the cells has lots of mitochondria to produce lots of ATP for active transport
50
Explain the role of Na+ in selective reabsorbtion
Na+ is actively transported out of the cell It then diffuses back into the cell and acts as a cotransporter by bringing glucose or amino acids in against their concentration gradient Known as secondary active transport
51
What are the two main parts of the loop of Henle?
Descending limb | Ascending limb
52
What is the function of the loop of Henle?
To reabsorb water from the filtrate
53
How does the loop of Henle regulate ion concentrations in the filtrate?
Filtrate entering decending limb is of high water potential Water moves out down its osmotic gradient Filtrate at the highest concentration at the bottom of the loop Na+ and CL- are actively transported out of the ascending limb and water moves in Filtrate is at its most dilute at the top of the ascending limb
54
Why must osmoregulation occur?
Too much or too little water could cause cell lysis or crenation
55
What hormone controls permeability of the collecting duct?
Antidiuretic Hormone (ADH)
56
What binds to cell surface or collecting duct cells in order to increase permeability?
Vesicles containing aquaporins
57
What happens when ADH concentration is high?
More aquaporins bind to cells in collecting duct Increased permeability more reabsorption of water Urine becomes more concetrated
58
What happens when ADH concentrations fall?
Membrane invaginates to re-form vesicles membrane permeability is reduced less reabsorption of water urine is more dilute
59
Where in the brain detects changes in water potential in the blood?
Osmoreceptors in the Hypothalamus
60
Where is ADH stored and released from?
posterior pituitary gland
61
By what process of movement is ADH released?
Exocytosis
62
What is the measure of Kidney function?
Glomerular filtration rate (GFR)
63
How do you measure GFR?
Analysis of urine for certain protiens
64
What is normal GFR, and what values would indicate issues?
Healthy = 90-120 cm3/min Chronic kidney disease = <60 cm3/min Kidney failure = <15 cm3/min
65
What are common causes of Kidney faliure?
Diabetes mellitus Heart disease hypertension infection
66
What are the 2 main treatments for Kidney failure?
Renal Dialysis | Kidney transplant
67
What are the 2 types of renal dialysis?
``` Haemodialysis Peritoneal dialysis (PD) ```
68
describe the process of haemodialysis
Blood is passed into the machine containing the dialysis membrane anti-clotting agent is added Dialysis fluid flows in countercurrent direction to improve the efficiency of exchange
69
How often does haemodialysis need to be performed?
2-3 times /week at a clinic
70
Describe peritoneal dialysis?
The membrane is implanted in the bodys own abdominal membrane (peritoneum) Dialysis fluid is poured into the abdomen via a tube and then must be drained after a few hours
71
What are the advantages of a Kidney transplant?
No need for time consuming dialysis Feeling physically fitter Ability to travel Don't feel chronically ill
72
What the disadvantages of a Kidney transplant?
Requires major surgery Must take immunosuppressant drugs that can cause hypertension and make infections more common Possibility for rejection Organ waiting list is long so may take years to get a match
73
Give example of molecules that can be detected in urine analysis and where they are used in the world
Glucose in diabetes diagnosis Alcohol to determine if drivers are drunk Recreational drugs, tests done by police or employers human chronic gonadotrophin (hCG) in pregnancy tests anabolic steroids, in sporting competitions
74
What is used in pregnancy tests to test for hCG?
monoclonal antibodies
75
What process is used to test for anabolic steroids after a urine sample has been taken?
Gas Chromatography

OCR A-level Biology (24 decks)

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