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Biochemistry > Nucleotide Biosynthesis L4 > Flashcards

Nucleotide Biosynthesis L4 Flashcards

1
Q

what are the nucleotide biosynthesis function

A 
Precursors of RNA and DNA
Currency of energy
Activators of biosynthesis 
Signal transduction pathways
components of co-enzymes
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2
Q

what are the universal currencies of energies

A

ATP
GTP
NAD

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3
Q

what are the components of major coenzymes

A

NAD
FAD
CoA

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4
Q

what are the activated intermediates in biosynthesis

A

UDP-glucose

CDP-diacylglyverol

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5
Q

what are the essential components of signal-transduction pathway

A

cAMP
cGMP second messengers within and between cells
ATP = donor of phosphoryl groups by kinases

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6
Q

which are the purines

A

PUGA – purines are guanine and adenine

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7
Q

what are purines

A

double ring

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8
Q

which are the pyrimidines

A

Cytosine
Uracyl
Thymine

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9
Q

what are pyrimidines

A

single ring

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10
Q

which are the nitrogenous bases

A 
Adenine
Guanine
Cytosine
Uracil
Thymine
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11
Q

how does the name of a base change when a sugar is attached to it

A 
becomes a nucleoside
Adenosine
Guanosine
Uridine
Cytidine
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12
Q

how does the name of base change when a sugar and phosphate ester attached

A

Adenylate (ATP)
Guanylate (GTP)
Urydylate (UTP)
Cytidylate (CTP)

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13
Q

what is chemical energy for

A

For synthesis of complex biological molecules

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14
Q

what is transport energy

A

Cells often live in dilute environments

need to expend energy to transport that nutrient into the cell

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15
Q

what is mechanical energy for

A

cells may be able to change their physical location

all cells need to move structures (DNA replication, wound repair etc…) within them

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16
Q

What happens in electron transport in aerobic conditions

A

NADH donates two electrons to electron transport chain, NADH becomes NAD+
In the membrane electron passed through a series of different proteins
Electrons combine with oxygen and protons to form water, an additional proton is pumped across
Causes an imbalance in the cell – high proton concentration out of the cell – used to fuel ATP production

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17
Q

what is the redox couple reaction

A

NAD+ NADH

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18
Q

how is water formed in electron transport

A

NADH donates electron to oxygen to form water

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19
Q

Why is aerobic respiration the most efficient

A

Oxygen is at the bottom of the tower – further down tower, more energy released

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20
Q

What is an alternative electron acceptor

A

Nitrate

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21
Q

What is nitrate reduced to

A

NO2-, N2O, N2

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22
Q

what are some of the largest monomers

A

nucleotides

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23
Q

what does the nucleotide synthesis involve

A

many steps and large amounts of energy

24
Q

what is the control of biosynthesis of nucleotides

A

once have enough, will stop producing as don’t waste energy
need to make right amount of each base
too much is made, energy wasted, too little, DNA replication and cellular metabolism come to a halt
cell sensitive to presence of pre-made nucleotides in environment, down regulate de novo synthesis pathways use what is already present in surroundings

25
Q

what are bacteria capable of

A

interconverting purines (adenine and guanine) and interconverting pyrimidines (thymidine, cytidine and uracil)

26
Q

what is de novo

A

making from new

27
Q

what is salvage

A

have got something already, saving it, taking something that was going to be destroyed

28
Q

What does the synthesis of purine start with

A

PRPP

29
Q

How is PRPP made in synthesis of purine

A

Ribose 5-phosphate + ATP

Two phosphates from ATP transferred to ribose 5-phosphate

30
Q

What is PRPP also used in biosynthesis of

A 
Purines
Pyrimidines
NAD
histidine 
tryptophan
31
Q

what does Purine synthesis start with

A

addition of an ammonia from glutamine to PRPP

32
Q

what happens in the six steps of purine synthesis

A

five membered ring of purines in synthesised with a net cost of five ATP

33
Q

what is the final product of de novo synthesis of purines

A

CAIR

34
Q

What is CAIR converted to

A

IMP

35
Q

How is CAIR converted to IMP

A

4 steps including use of ATP

36
Q

How is GMP made from IMP

A

2 steps using one ATP

37
Q

How does IMP and GMP differ

A

GMP adds an amino group (nothing removed off IMP)

38
Q

Which are the central donors of amino groups in synthesis of everything

A

Glutamine and asparagine

39
Q

What happens in the synthesis of purines

A

Add ATP
C=O gains phosphate group
Form first activated group
React with anything as reactive due to phosphate
Donor group e.g. HH3 reacts with it will form an intermediate group
Lose phosphate
C=O replaced with NH2

40
Q

what happens in the salvage reaction of purines

A

Salvage system already have purine in diet

Take phosphate groups out and reattach to PRPP

41
Q

How does purine and pyrimidine synthesis differ

A

Ring synthesized first in pyrimidines

42
Q

how is glutamate, 2 ADP and carbamoylphosphate formed in synthesis of pyrimidines

A

combining glutamine, 2 ATP and bicarbonate

43
Q

how is carbamoylaspartate made in synthesis of pyrimidines

A

Aspartate reacts with carbamoyl phosphate

44
Q

what happens to carbamoyl asparate in synthesis of pyrimidines

A

carbamoyl asparate is cyclised to form the recognisable 6 membered ring of pyrimidines

45
Q

what happens to PRPP in synthesis of pyrimidines

A

combined with the six membered ring

46
Q

what happens when an amino group is added to UTP

A

formation of CTP

47
Q

what is used in UTP synthesis

A

4 ATP (not counting PRPP formation)

48
Q

What happens if too much CTP

A

CTP feeds back to step before which is causes inhibition

Carbamoyl phosphate to carbamoyl aspartate inhibited by CTP

49
Q

What are the blocking steps in pyrimidine synthesis

A

Only thymidylate synthetase can synthesis dUMP to dTMP if mutated will cause problem

50
Q

What inhibits Dihydrofolate reductase

A

Aminopterin

Amethopterin

51
Q

What happens if excess of pyrimidine

A

Degraded by TCA cycle

52
Q

What happens to excess purines

A

Degraded, released in urea of some species

53
Q

What is the effect of allopurinol

A

Prevent excess uric acid

If too much will cause problems

54
Q

What happens if uric acid is in excess

A

Will precipitate out

55
Q

what is the benefit of uric acid

A

may contribute to longer life span and lowering incidence of cancer

56
Q

examples of clinical applications

A

Pellagra, Gout, anti-Cancer drugs, Leisch Nyhan syndrome

Biochemistry (13 decks)

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