5-5: Biosynthesis

Question 1

Is N2 metabolically useful for most organisms? Why

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? e.g.?

Answer 3

Diazotrophs
e.g. cyanobacteria

Question 4

Why convert N2 to NH3

Answer 4

NH3 more metabolically useful form of nitrogen, can be used to build nitrogen containing molecules (nucleic acids, proteins, etc)

Question 5

nitrogenase is composed of…

Answer 5

Two proteins: dinitrogenase and dinitrogenase reductase

Question 6

Explain electron flow in nitrogenase

Answer 6

Electrons come from pyruvate, passed to flavodoxin, to dinitrogen reductase, to dinitrogenase to N2, which is reduced to two 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 is gluconeogenesis

Answer 8

Producing glucose for carbon/energy storage or as biosynthesis precursor

Question 9

Gluconeogenesis is basically the…

Answer 9

reversal of glycolysis

Question 10

How is glucose-6-phosphate activated

Answer 10

Addition of nucleotide diphosphate such as ADP-glucose, UDP-glucose

Question 11

Activated form of glucose-6-phosphate used to produce:

Answer 11

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

Question 12

Why are aa needed

Answer 12

Produce proteins, peptidoglycan, etc

Question 13

Where do aa carbon skeletons come from

Answer 13

Intermediates of CAC or glycolysis

Question 14

How many pathways are there for producing a given aa

Answer 14

Some cases, multiple

Question 15

Glutamate dehydrogenase, glutamine synthase do..

Glutamine/Glutamate do…

Answer 15

are the enzymes involved in using inorganic nitrogen (NH3) to build nitrogen-containing molecules

are the nitrogen donors that produce other key nitrogen containing molecules

Question 16

What are ACP

Answer 16

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

Question 17

How are f.a. built

Answer 17

2 carbons at a time by adding malonyl-CoA (3C) to growing chain
CO2 released as biproduct

Question 18

What is malonyl CoA made from? What is malonyl ACP made from?

Answer 18

Acetyl CoA, malonyl CoA

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 ribose-5-P from glucose-6-phosphate

Question 21

What is ribose-5-P used for

Answer 21

Make ribonucleotides

Question 22

What else does pentose phosphate pathway generate

Answer 22

NADPH, carbon skeletons

Question 23

Are purines and pyrimidines built using the same pathway?

Answer 23

No, seperate pathways

Question 24

Key intermediates of purine and pyrimidine synthesis

Answer 24

Purines = IMP
Pyrimidines = orotate

Question 25

What does ribonucleotide reductase do

Answer 25

Converts ribonucleotides into deoxyribonucleotides for DNA synthesis