Nitrogen 1

Question 1

What is the name given to nitrogen fixing bacteria?

Answer 1

Diazotrophs

Question 2

What does the assimilation stage of the nitrogen cycle consist of?

Answer 2

Fixation (n2 to ammonium) TO
Glutamate TO
other amino acids TO
Proteins and other amino acids

Question 3

What is the degradation stage of the nitrogen cycle?

Answer 3

Proteins/nucleotides
TO
Other amino acids
TO
Glutamate
TO
NH4+

Question 4

What is the effect of lightning on nitrogen gas?

Answer 4

Breaks the triple bond and makes NO(nitric oxide) or NO2 (nitrite)

Question 5

What ways of fixing nitrogen exist?

Answer 5

Haber process, Lightning, Nitrogen fixing bacteria

Question 6

Name two nitrogen fixing bacteria

Answer 6

Cyanobacteria and rhizobia

Question 7

What do the nitrogen fixing bacteria require?

Answer 7

Lots of ATP, nitrogenase enzyme inhibited by oxygen - anaerobic conditions needed , cyanobacteria form heterocysts whose cell wall forms a wall to oxygen, leguminous plants contain legheomoglobin which binds to oxygen and provides an environment that nitrogenase can work.

Question 8

What happens to ammonium once it is fixed?

Answer 8

Nitrifiction to nitrite (NO2-) to nitrate (NO3-) this is taken up by plants and microbes - then converted to ammonia via nitrile

Question 9

What is special about glutamate?

Answer 9

It is the only amino acid that can directly obtain its nitrogen from NH4 and the only one that can give up its nitrogen directly

Question 10

What are the 4 amino acids usually found in much higher concentrations than others?

Answer 10

Alanine, glutamine, glutamate and aspartate

Question 11

How do organisms conserve N2?

Answer 11

Transamination - The transfer of amino groups from one biological molecule to another

Question 12

What type of reaction is transamination if the reaction is reversible?

Answer 12

Synthesis and degradation

Question 13

What do amino transferases rely on?

Answer 13

Pyridoxal phosphate cofactor transfers the amino acid during the reaction.

Question 14

What molecule usually accepts the amino groups?

Answer 14

alpha ketoglutarate

Question 15

Which molecule usually acts as a temporary storage of nitrogen?

Answer 15

L - Glutamine (possible of donating the amino acid when it is needed for biosynthesis)

Question 16

What is pyridoxal phosphate made from?

Answer 16

Made from vitamin B6

Question 17

What does presence of amino transferases in the plasma indicate?

Answer 17

Cell damage, as they are intracellular proteins

Question 18

How much of a herbivores energy intake is met by amino acids?

Answer 18

Small fraction

Question 19

Under which three circumstances do amino acids go under oxidative catabolism?

Answer 19

Leftover amino acids from normal protein turnover
Excess dietary amino acids
Proteins in the body are broken down (during starvation)

Question 20

How are dietary proteins enzymatically hydrolyzed?

Answer 20

Pepsin cuts proteins into peptides in the stomach
Pepsin and chymotrypsin cut proteins into smaller peptides in the small intestine
Aminopeptidase and carboxypeptidase degrade peptides in the small intestine to amino acids

Question 21

Where can the aminopeptidases be found?

Answer 21

Intestine - membrane bound proteins

Question 22

What is a carbon skeleton?

Answer 22

The leftovers of an amino acid

Question 23

What is a ubiquinated protein?

Answer 23

Covalently modified protein to fit into the proteosome which is effectively a protein destroying machine.

Question 24

What cellular proteins are degraded?

Answer 24

Misfolded proteins,
Foreign proteins
Unwanted proteins

Question 25

Eventually all proteins are …..

Answer 25

Turned over

Question 26

Why do all excess amino acids have to be catabolised?

Answer 26

There is no storage facility for protein