Nitrogen 1

Question 1

Nitrogen-fixing bacteria live in what conditions?

Answer 1

Anaerobic

Question 2

How do some cyanobacteria maintain this condition?

Answer 2

Forming heterocysts - a cell wall that prevents the entry of oxygen

Question 3

Some plants use nitrogenase to fix nitrogen - how do legumious plants keep things anaerobic?

Answer 3

Leghaemoglobin keeps oxygen in low enough concentrations for the nitrogenase enzyme to be active

Question 4

What four amino aids are found in much higher concentrations in humans than the other 16?

Answer 4

Alanine, glutamine, glutamate, aspartate

Question 5

Most organisms can’t fix their own nitrogen (humans included) - how then do we preserve the nitrogen we do have?

Answer 5

Transamination - transferring amino groups between different molecules

Question 6

Transaminase reactions are reversible - therefore what amino acid reactions do they participate in?

Answer 6

Both synthesis and degradation

Question 7

What do all aminotransferases rely on?

Answer 7

The pyridoxal phosphate cofactor

Question 8

What molecule typically accepts amino acid groups?

Answer 8

alpha-ketoglutamate

Question 9

What is the pyridoxal phosphate cofactor?

Answer 9

PLP - cofactor made from vitamin B6

Question 10

Presence of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in plasma indicates what pathology?

Answer 10

Liver disease - normally found in liver, presence elsewhere (i.e plasma) indicates damage

Question 11

What use do we humans have for oxidation of amino acids?

Answer 11

High energy yield

Question 12

List some enzymes that cleave proteins into smaller molecules

Answer 12

1. Pepsin (stomach)
2. Trypsin and chymotrypsin (small intestine)
3. Amino and carboxypeptidase

Question 13

What is the process of ubiquititation?

Answer 13

Binding ubiquitin to cellular proteins to target them for degradation by the proteasome