5.1.2 Liver and Excretion

Question 1

Deamination

Answer 1

Amino Acid + Oxygen ->keto acid + ammonia
Keto Acid enters respiration to release energy
Ammonia enters the ornithine cycle to be converted into urea

Question 2

Examples of Excretion

Answer 2

CO2: waste from respiration, excreted via the lungs
Nitrogenous Waste: urea, produced in the liver and excreted as urine via the kidneys
Bile Pigments: produced from the breakdown of haemoglobin in the liver and excreted as bile in the intestines (faeces)

Question 3

Hepatic Artery

Answer 3

supplies liver with oxygenated blood from the heart

Question 4

Hepatic Vein

Answer 4

Takes deoxygenated blood away from the liver

Question 5

Hepatic Portal Vein

Answer 5

brings blood from the duodenum and ileum so that toxins can be filtered out and broken down here in the liver

Question 6

Bile duct

Answer 6

takes bile produced by the liver to the gall bladder to be stored

Question 7

carbohydrate metabolism

Answer 7

Hepatocytes are involved in the homeostatic control of glucose levels in the blood. When the blood glucose levels rise, insulin levels rise and stimulate hepatocytes to convert glucose into glycogen.

Question 8

Detoxification

Answer 8

Level of toxins tend to increase. Apart from urea, many other metabolic pathways produce potentially poisonous substances. The liver is where most of these are detoxified.

Question 9

Transamination

Answer 9

The conversion of one amino acid into another. This is important because the diet does not always contain the required balance of amino acids but transamination can resolve this issue

Question 10

Excretion in kidneys

Answer 10

Blood enters kidney through renal artery and then passes through capillaries in cortex. When in capillaries, substances are filtered out of blood into tubules called ultrafiltration. Useful substances reabsorbed back into the blood called selective reabsorption. Remaining substances such as urea pass along tubules then along the ureter to the bladder to be expelled during urination. Filtered blood passed out of the kidney through the renal vein.

Question 11

Selective Reabsorption

Answer 11

Occurs throughout the nephron after the renal capsule. When filtrate is first formed, it is hypotonic to the blood.

Most of this occurs in the PCT, cells lining tubule are adapted for the reabsorption of substances from the lumen, across them, into the blood capillaries around them.

85% reabsorbed

Question 12

Causes of Kidney Failure

Answer 12

Diabetes
Hypertension
Genetics
Kidney stones

Question 13

Main Problems with Kidney Failure

Answer 13

blood in urine
proteins in urine 
selective reabsorption may stop 
urea and toxins may accumulate in the blood 
disrupted water/ion balance

Question 14

Glomerular Filtration Rate (GFR)

Answer 14

Rate that substances are filtered out of the blood in the glomerulus into the renal capsule

below normal rate = kidneys not functioning

blood test measures conc of creatinine (a breakdown product from muscle cells)

Age, Gender and Fitness need to be taken into consideration

Question 15

GFR readings

Answer 15

reading below 60 for 3+ months indicated severe chronic kidney disease

reading below 15 shows kidney failure

Question 16

Haemodialysis

Answer 16

Patients blood is passed through a dialysis machine — blood flows in one side of the partially permeable membrane and dialysis fluid flows on the other side

Waste products diffuse into fluid, removing them from the blood. Larger molecules can’t pass.

Each session takes 3-5 hours and need 2-3 sessions weekly in hospital

patients feel unwell between sessions as waste products build up

Question 17

Peritoneal Dialysis

Answer 17

Dialysis fluid is put through a tube that passed from outside the abdomen into their abdomen cavity. Waste products diffuse out into fluid across the peritoneum.

Fluid then drained out through tube

can be carried out at home either several times a day or one long overnight session

risk of infection around site of tube and patient doesn’t have dialysis free days.

Question 18

Kidney Transplant

Answer 18

new kidney implanted to replace damaged kidney

doner must have same blood and tissue type. often donated from living relatives but can receive one from an organ doner.

advantage; cheaper, more convenient, can live fairly normal life

disadvantage; major surgery with risk of infection, risk of rejection, will have to take immunosuppressants so more at risk to illness

Question 19

pregnancy tests

Answer 19

hCG molecules carried up test in urine and bind to mobile antibodies to form hCG/antibody complex

complex bunds to immobilised antibodies to form a coloured line of woman is pregnant

mobile antibodies within hCG move up to second window

excess mobile antibodies bind to immobilised antibodies to form a line whether pregnant or not

Question 20

pregnancy test

Answer 20

A coloured line only occurs at the bottom window if woman is pregnant (requires presence of hCG)

A coloured line will spread in the top window either way — this is a control window to ensure test is working

Question 21

recreational drugs

Answer 21

drugs such as cannabis, ecstasy or cocaine will be present in the urine

test strips containing antibodies that the drug will bind to

a sample of urine is applied to test strip and if present a colour change is i’ll occur indicating a positive result

if positive, urine sample is sent for further testing to confirm which drugs are used. second test uses GC/MS

Question 22

Anabolic steroids

Answer 22

Drugs that build up muscle tissue that can cause liver damage.

Tested using Gas Chromatography/ Mass Spectrometry (GC/MS)

In GC, urine sample is vaporised and passed through a column containing a polymer. Different substances move through as different speeds to separate out.

Once separated, MS converts them into ions then separated via mass and charge

Results analysed by computer by comparing results of known substances to detect what was in the urine sample

Question 23

Osmoregulation

Answer 23

controlling the amount of water and salts in the body

Question 24

Increased Water Potential

Answer 24

Red Blood Cells become hypotonic and water enters the cell and it will eventually burst.

Water enters cell via diffusion (high to low conc)

Kills cells and reduces amount of red blood cells in the body

Question 25

Decreased Water Potential

Answer 25

Red Blood Cells become hypertonic and shrink

Water leaves cells via diffusion (high to low conc) and enters the vessel

reduces oxygen carrying capacity and function

Question 26

Ways water is lost

Answer 26

urine
faeces
breathing
sweating

Question 27

ultrafiltration

Answer 27

Produces filtrate— some of this is reabsorbed (water, proteins, glucose) and some is excreted (urea, some mineral ions)