protein and amino acid metabolism

Question 1

compounds containing nitrogen

Answer 1

amino acids, proteins, purines and creatine phosphate

Question 2

what is creatinine and what is it used for

Answer 2

break down product of creatine phosphate and creatine. used to measure muscle mass as its presence is proportional to muscle present. also used to detect renal function

Question 3

explain the nitrogen balance

Answer 3

approx 2kg of protein in the body. it enters via diet and leaves via loss through hair and nails or in the faces and urine. whilst in the body it is in either a polol of amino acid or is in a nitrogen containing compound

Question 4

explain protein turnover

Answer 4

proteins enter the body through amino acid synthesis or the diet. they are then found in the body as either free amino acids or cellular protein e.g in muscle. free proteins are able to enter the liver where the amine group is excreted as urine or it is used for energy through glucogenisis or ketogenesis.

Question 5

how are glucogenis or ketogenic amino acids used for energy

Answer 5

they all will enter the TCA cycle in different ways after undergoing ketogenesis or glucogenesis. e.g alanine which is glucogenic enters as pyruvate, lysine which is ketogenic and enters as acetyl coA and therein which is both keto/glucogenic enters as succinyl coA

Question 6

how are protein reserves controlled

Answer 6

insulin and growth hormones will increase protein synthesis and decrease protein degradation and glucocorticoids especially cortisol will increase protein degradation and decrease protein synthesis

Question 7

what is the amino acid structure

Answer 7

contains r group, COOH group and NH2 group.

Question 8

how many amino acids are essential and how many of these are conditional

Answer 8

9 are essential, as in they can’t be synthesised by the body they must be taken in via the diet. conditional means amino acids that are only sometimes essential e.g as a child

Question 9

which amino acid is needed for the synthesis of the thyroid hormone

Answer 9

tyrosine. amino acids are needed for the synthesis of many other compounds

Question 10

2 ways in which amine group is removed from the amino acid and why this must happen

Answer 10

either via transamination or deamination. this must happen because NH2 cannot be metabolised and the body is unable to store it because its toxic

Question 11

explain the 2 types of transamination that take place in the liver

Answer 11

alanine aminotransferase catalyses the transfer of the amine group from alanine to form glutamate using alpha-ketogluterate and the formation of another ketoacid. aspartate aminotrasnferase catalyses glutamate to aspartate using oxaloacetate forming another ketoacid aswell.

Question 12

what do these enzyme levels tell us

Answer 12

enzyme levels measure liver function. if levels are high then could indicate hepatitis or an autoimmune liver disease.

Question 13

explain deamination

Answer 13

NH2 freed to form ammonia. ammonia enter the urea cycle which is a soluble, inter, non-toxic compound excreted via the urine.

Question 14

what is refeeding syndrome

Answer 14

enzymes are up and down regulated depending on the demand for them. this is why when someone is malnourished they must have protein reintroduced very slowly as they will not have the correct enzymes to remove the NH2 group. this can be fatal.

Question 15

what happens if you have a genetic disorder meaning there is an enzyme deficiency in the urea cycle

Answer 15

this will cause high levels of ammonia in the blood and accumulation of intermediates. NH3 toxicity requires low protein diet and Amino acids to be replaced with ketoacids. can be very severe and causes death very quickly. symptoms of this include vomiting, lethargy, seizures and coma.

Question 16

why is ammonia toxic

Answer 16

it can diffuse into the brain causing things such as disruption of cerebral flow, alteration of the blood brain barrier and pH defects

Question 17

how are amino acids transported from the tissues to the liver/kidney. explain the 2 mechanisms

Answer 17

1) NH3 + glutamate forms glutamine which travels to the kidneys or liver where it is catalysed back glutaminase to the start reactants. in liver enters urea cycle and in kidneys goes into urine
2) amin group transaminate to glutamate and then pyruvate is transmainated by glutamate to form alanine. this is transported to. liver where it is converted back to pyruvate and used to synthesise glucose and glutamate is transferred to urea cycle

Question 18

what is PKU

Answer 18

it is the build up of phenylalanine affecting tyrosine synthesis. It is caused by the disfunction of phenylalanine hydroxylase. Seen by musty smelling urine and presence of PKU in urine.

Question 19

what is a side effect of PKU and how is it treated

Answer 19

tyrosine not synthesised and therefore no melanin, thyroid hormone, adrenaline and more synthesised. To treat it hey must have low protein diet and take tyrosine. if don’t treat this it results in retardation

Question 20

what is homocystinurias

Answer 20

have problem breaking down methionine. excess homocysteine in urine and this is caused by defect in cystathionine beta synthase (requires bit B6 as cofactor). accumulation of homocysteine and methionine cause disease symptoms affecting connective tissues, muscles, CNS and CVS. treated by low protein/methionine diet. associated with cardiovascular disease.

Question 21

what are the 9 essential amino acids

Answer 21

If - isoleucine 
Learnt - Lysine 
This - Threonine
Huge - Histadine 
List - Leucine 
May - Methionine 
Prove - Phenylalanine
Truly - Tryptophan 
Valuable - Valine