5-5: Biosynthesis

Question 1

Is N2 metabolically useful for most organisms? Why or why not?

Answer 1

No, it is too stable (triple bond)

Question 2

What is nitrogenase?

Answer 2

An enzyme that converts N2 to NH3

Question 3

Bacteria and archaea that can convert N2 to NH3 are called what? Give an example.

Answer 3

Diazotrophs
e.g. cyanobacteria, rhizobia, archaeal methanotrophs

Question 4

Why do organisms convert N2 to NH3?

Answer 4

NH3 more metabolically useful form of nitrogen, can be used to build nucleic acids and proteins

Question 5

What two proteins is nitrogenase made of? What cofactors do they use?

Answer 5

dinitrogenase and dinitrogenase reductase that use Fe/Mo cofactors

Question 6

Explain electron flow in nitrogenase.

Answer 6

Electrons come from pyruvate, passed to flavodoxin, to dinitrogen reductase, to dinitrogenase to N2, producing NH3.

Question 7

How much ATP does dinitrogenase require? Why?

Answer 7

16 ATP per 2 NH3 produced.
Reduction of triple bond of N2 very energetically demanding

Question 8

What are two key enzymes needed for nitrogen assimilation?

Answer 8

Glutamate dehydrogenase and Glutamine synthase, which act as nitrogen donors

Question 9

How is Glu and Gln made?

Answer 9

Adding NH3 and alpha-ketogluarate to make gluatamate. A second amine is added to make glutamine.

Question 10

What is gluconeogenesis

Answer 10

Producing glucose for carbon/energy storage or as biosynthesis precursor

Question 11

Gluconeogenesis is basically what?

Answer 11

reversal of glycolysis

Question 12

How is glucose-6-phosphate activated

Answer 12

Addition of nucleotide diphosphate such as ADP-glucose, UDP-glucose which us ATP or UTP.

Question 13

Activated form of glucose-6-phosphate can be used to produce what?

Answer 13

LPS (gram (-) OM)
NAM/NAG (peptidoglycan)
Storage molecules (glycogen/starch)

Question 14

Where do the carbon skeletons of AA come from?

Answer 14

Intermediates of CAC or glycolysis

Question 15

What is a parent amino acid?

Answer 15

Precursors to producing amino acids (eg. Asp)

Question 16

What are ACP

Answer 16

Acyl carrier proteins, “holder” of substrate for f.a. synthesis

Question 17

How are fatty acids built?

Answer 17

2 carbons at a time by adding malonyl-CoA (3C) to growing chain, releasing CO2 as byproduct

Question 18

How is malonyl-ACP made?

Answer 18

Acetyl-CoA is used to maky malonyl-CoA, which is used to make malonyl-ACP>

Question 19

What are the basic building blocks for nucleotides

Answer 19

Pentoses (5C sugar, ribose)
Nucleobases

Question 20

What does pentose phosphate pathway do

Answer 20

Generates NADPH, carbon skeletons and ribose-5-P from glucose-6-phosphate, which can then be used to make nucleotides and other key metabolites.

Question 21

What is ribose-5-P used for

Answer 21

Make ribonucleotides

Question 22

Are purines and pyrimidines built using the same pathway?

Answer 22

No, seperate pathways

Question 23

What are the key intermediates of purine and pyrimidine synthesis?

Answer 23

Purines = IMP
Pyrimidines = orotate

Question 24

What does ribonucleotide reductase do

Answer 24

Converts ribonucleotides into deoxyribonucleotides for DNA synthesis