Nitrogen

Question 1

Diazotrophs eg.Cyanobacteria

Answer 1

Nitrogen fixing bacteria
Use Nitrogenase which is inactivated by O2
N2 from atmosphere becomes NH3 in biosphere which in water exists as NH4+

Question 2

Glutamate

Answer 2

Is the only amino acid that can obtain its nitrogen directly from NH4 and give its Nitrogen directly

Question 3

Assimilation

Degradation

Answer 3

NH4+ TO Proteins through glutamate

Amino Acids TO N2 through glutamate

Question 4

Transamination

Usuall Substrate pairs?

Answer 4

Process of transfering amino groups bw different molecules in order to conserve N2.
Readily Reversible - Equilibrium Constant is nearly 1
Usuall Substrate pairs are Glutamate + a-Ketoglutarate

Question 5

Amino Acid

Keto Acid

Answer 5

NH3

C=O

Question 6

All Aminotransferases rely on?

Answer 6

Pyridoxal Phospate Cofactor (PLP-dependent aminotransferase)
Made from Vit B6
Carries NH3 from Glutamate to a-Ketoglutamate

Question 7

When does Amino Acid Oxidation take place

Answer 7

Leftover amino acids from normal protein turnover are degrated (misfolded, foreign, unwanted proteins)
Dietary amino acids
Proteins in the body are broken down when carbohydrates are in short supply

Question 8

Pepsin
Trypsin/Chemotrypsin
Aminopeptidases/Carboxypeptidases - Proteolysis

Answer 8

Proteins into peptides in stomach
Proteins into peptides in small intestine
Degrade Peptides into amino acids in small intestine

Question 9

Ammonia is Transported in the Bloodstream as?

Excess glutamine is processed in?

Answer 9

Glutamine (plasma) /Alanine (skeletal muscle) which have no charge and can pass through the cell membranes easily
Intestines, Kidneys and Liver

Question 10

How is Pyruvate transported in liver?

Answer 10

Converted to Alanine

Question 11

How is Nitrogen Excreted?

Answer 11

Converted to Urea by the Urea Cycle

Using Aspartate and Carbomoyl phospate synthetase acquiring reactions

Question 12

Excess Glutamate?

Answer 12

Metabolised in Mitochondria of Hepatocytes

Question 13

Glutamate Dehydrogenase Rxn

Answer 13

2 electron oxidation of glutamate followed by hydrolysis
Net process is oxidative deamination of glutamate
Occurs in mitochondrial matrix
NAD+ NADP+ used as electron acceptors

Question 14

Exclusively Ketogenic Amino Acids

Answer 14

Leucine and Lysine

Question 15

Most abundant protein in body?

Answer 15

Collagen

Question 16

Glucogenic aa

Ketogenic aa

Answer 16

Glucogenic “feed in” to gluconeogenesis and so produce glucose / glycogen, in liver. So amino acids entrering Citric Acid Cycle Before Oxaloacetate are glucogenic.
Ketogenic “feed in” to Acetoacetyl CoA / acetyl CoA After Oxaloacetate in Citric Acid Cycle
Acetyl CoA forms Acetoacetate

Question 17

ketone Bodies

Answer 17

Small water soluble
Produced by liver
Used by brain in absence of glucose

Question 18

Phenylketonuria

Answer 18

From a genetic defect in the enzyme responsible for hydroxylating phenylalanine.

Question 19

Clinical Features of inherited metabolic disorders presenting in child?

Answer 19

Acidosis
Failure to thrive
Vomiting
CNS Dysfunction
Hypoglyceamia 
Unusual Odor

Question 20

Protein turnover?

Answer 20

Is the balance between protein synthesis and protein degradation

Question 21

Ornithine Transcarbomoylase deficiency

Answer 21

X-linked Inheritance
Hyperammonaemia
Urea Cycle Disorter

Question 22

Ornithine Transcarbomoylase deficiency

Answer 22

X-linked Inheritance
Hyperammonaemia - Elevated Glutamine
Urea Cycle Disorter

Question 23

Phenolketonuria

Answer 23

Autosomal recessive disorder
Increased phenylalanine (Phe) levels (toxic)
Amino Acid Disorter Phe - Tyrosine not possible
Absence/deficiency of Phenylalanine hydroxylase (PAH)

Impaired brain development signs when toxicity -> BBB
Treatment -> Reduced Protein, Supplement Tyrosine
Neonatal screening programme (day 5)