Showing posts with label ornithine cycle. Show all posts
Showing posts with label ornithine cycle. Show all posts

Thursday, 6 December 2012

A2 Biology: Kidney Failure

If the kidney fails - unable to remove urea - not going through osmoregulation

3 main causes:

  • Diabetes mellitus
  • hypertension
  • infections
Use of dialysis

Dialysis removes waste, salts and excess fluids from the blood by passing over a dialysis membrane. Dialysis membrane is partially permeable and contains the perfect plasma, so it has right amount of glucose, water and other substances but not urea. Urea is passed through into the dialysis membrane by diffusion.

Methods of control:
  • Haemodialysis - blood from vein is passed through a machine which contains  artificial dialysis membrane and returns back into the blood. Heparin is added to act as an anticoagulant.
  • Peritoneal dialysis - filters the body's abdominal membrane. A permanent tube is implant into the abdomen and dialysis solution is poured in to fill up the space between abdomen wall and organs. Several hours later this solution is drained from the abdomen.
  • Kidney transplant - is a major surgery where a kidney from a healthy willing relative donor or a healthy kidney from a deceased person is implanted in and is attached to the blood supply and bladder. The old kidney remains in the body unless it is cancerous or likely to cause an infection. The patient would have to take immunosuppressants for life as the new organ would be treated as a foreign object and this would prevent it from being rejected.

Tuesday, 4 December 2012

My revision notes: A2 Biology: Urea + Ornithine cycle + detoxification of alcohol

Deamination is the process where ammonia (NH3) is produced. Ammonia is very soluble and highly toxic. It also produces an organic keto acid which is then used in respiration. Ammonia is converted into Urea which is less soluble and less toxic. Urea travels in the blood and is transported to the kidneys where it is filtered out of the blood and stored into the bladder until released from the body.

The ornithine cycle

2NH + CO2 > CO(NH2)2 + H2O
ammonia + carbon dioxide > urea + water

Detoxification of alcohol

Alcohol can be bad for us but it also contains chemical potential energy which could be used in respiration.
  • Alcohol is broken down b hepatocytes by the action of enzyme ehtanol dehydrogenase
  • In result of this ETHANAL is made
  • it is then dehydrogenated again by ethanal dehydrogenase
  • Which produces ethanoate (acetate)
  • combined with coenzyme A to form acetyl coenzyme A which enters respiration.
  • Ethanol > Ethanal > Ethanoic acid > Acetyl coenzyme A