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Flashcards in Nitrogen 1 Deck (26)
1

What is the name given to nitrogen fixing bacteria?

Diazotrophs

2

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

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

3

What is the degradation stage of the nitrogen cycle?

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

4

What is the effect of lightning on nitrogen gas?

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

5

What ways of fixing nitrogen exist?

Haber process, Lightning, Nitrogen fixing bacteria

6

Name two nitrogen fixing bacteria

Cyanobacteria and rhizobia

7

What do the nitrogen fixing bacteria require?

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.

8

What happens to ammonium once it is fixed?

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

9

What is special about glutamate?

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

10

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

Alanine, glutamine, glutamate and aspartate

11

How do organisms conserve N2?

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

12

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

Synthesis and degradation

13

What do amino transferases rely on?

Pyridoxal phosphate cofactor transfers the amino acid during the reaction.

14

What molecule usually accepts the amino groups?

alpha ketoglutarate

15

Which molecule usually acts as a temporary storage of nitrogen?

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

16

What is pyridoxal phosphate made from?

Made from vitamin B6

17

What does presence of amino transferases in the plasma indicate?

Cell damage, as they are intracellular proteins

18

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

Small fraction

19

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

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

20

How are dietary proteins enzymatically hydrolyzed?

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

21

Where can the aminopeptidases be found?

Intestine - membrane bound proteins

22

What is a carbon skeleton?

The leftovers of an amino acid

23

What is a ubiquinated protein?

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

24

What cellular proteins are degraded?

Misfolded proteins,
Foreign proteins
Unwanted proteins

25

Eventually all proteins are .....

Turned over

26

Why do all excess amino acids have to be catabolised?

There is no storage facility for protein