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Biosynthesis > Biosynthesis > Flashcards

Biosynthesis Flashcards

1
Q

Primary metabolites

A

Trophophase
Metabolism products required for growth and the maintenance of cellular function
e.g. amino acids, fatty acids, nucleoside, vitamins, carbohydrates

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2
Q

Secondary metabolites

A

Idiophase
The end products of primary metabolism that are non-essential for cell growth/maintenance, but can be important in other cellular activities
e.g. steroids, alkaloids, antibiotics, toxins

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3
Q

Fatty acids

A

Long alkyl chain with carboxylic acid group

Alkyl chain is generally unbranched, even no. of carbons, can be unsaturated (only ‘cis’ alkenes)

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4
Q

C14 chain length

A

Myristic acid

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5
Q

C16 chain length

A

Palmitic acid

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6
Q

C18 chain length

A

Stearic acid

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7
Q

Reasons for thioester instead of normal ester in acetyl coenzyme A

A

S is a better nucleophile than O, so is easier to acetylate
Thioesters are more reactive to hydrolysis than esters (less significant resonance structure so resemble ketones, which are more reactive than esters)

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8
Q

Structure of acetyl coenzyme A

A

Draw

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9
Q

Synthesis of acetyl groups for acetyl coenzyme A

A

Draw
Step 1: Glucose + 2NAD+ + 2Pi + 2ADP —> 2 pyruvate + 2 NADH + 2ATP + 2H+ + 2H2O
Step 2: Pyruvate decarboxylation

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10
Q

NAD(P)+/NAD(P)H

A

The primary cofactors used for oxidation and reduction in biosynthesis
Draw

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11
Q

NAD(P)+

A

Oxidising agent

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12
Q

NAD(P)H

A

Reducing agent

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13
Q

Biotin

A

Nature’s carrier for CO2

Draw

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14
Q

BCCP

A

Biotin carboxyl carrier protein

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15
Q

Synthesis of malonyl coenzyme A

A

Acetyl coenzyme A can be carboxylated by carboxybiotin to give malonyl coenzyme A
Draw

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16
Q

Fatty acid biosynthesis

A

Draw

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17
Q

FAS

A

Fatty Acid Synthase

Reacts with acetyl coenzyme A in fatty acid biosynthesis

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18
Q

ACP

A

Acyl Carrier Protein

Reacts with malonyl coenzyme A in fatty acid biosynthesis

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19
Q

How is the growing fatty acid chain cleaved from ACP?

A

By a thioesterase

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20
Q

How does synthesis of unsaturated fatty acids occur?

A

Re-oxidation of the fatty acid chain by a “dithio-linked” enzyme
2 Enz-SH + 1/2O2 —> Enz-S-S-Enz + H2O

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21
Q

Terpenes

A

Hydrocarbons (few heteroatoms, but sometimes oxygenated)
Can contain unsaturation
Often polycyclic
Built from isoprene units

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22
Q

Isoprene

A

Draw

23
Q

C10 terpenes

A

Monoterpenes
Comprise 2 isoprene units
Alpha/beta-pinene, camphor

24
Q

C15 terpenes

A

Sesquiterpenes
Comprise 3 isoprene units
Artemisin, juvabione

25
Q

C20 terpenes

A

Diterpenes
Comprise 4 isoprene units
Gibberellin A3, taxol (= hybrid natural product with terpene core)

26
Q

C30 terpenes

A

Triterpenes
Comprise 6 isoprene units
Cholesterol, beta-amyrin

27
Q

Why does nature not use isoprene for terpene synthesis?

A

Isoprene is a gas

28
Q

What does nature use for terpene synthesis?

A

IPP (isopentenyl pyrophosphate)

DMAPP (dimethylallyl pyrophosphate)

29
Q

Pyrophosphate

A

2 phosphate groups joined together

30
Q

Lovastatin

A

Drug for the treatment of high blood cholesterol

Inhibits HMG-CoA reductase, which catalyses the RDS for the whole biosynthetic route to cholesterol

31
Q

Uses of monoterpenes

A

Monoterpenes = low molecular weight and low polarity so often volatile
Have characteristic odours so often used as perfumes/fragrances/flavourings

32
Q

Synthesis of sesquiterpenes

A

Geranyl pyrophosphate + IPP —> farnesyl pyrophosphate

33
Q

Synthesis of diterpenes

A

Farnesyl pyrophosphate + IPP —> geranylgeranyl pyrophosphate

34
Q

Synthesis of triterpenes

A

Synthesised from squalene, which is synthesised from 2 farnesyl units in a “head to head” fashion

35
Q

What is squalene used in?

A

The synthesis of steroids
Starts with the formation of 2,3-oxidosqualene, which then undergoes electrophilic cyclisation and rearrangement to access the ‘steroidal nucleus’

36
Q

Polyketides

A

Highly oxygenated - often a pattern to the oxygenation with an O on every other C
Generally involve rings (often aromatic, but not always)
Biosynthetically related to fatty acids

37
Q

Biosynthesis of polyketides

A

(Draw biosynthesis of orsellinic acid)

First part is the same as for fatty acids minus the 3 steps after the Claisen ester condensation

38
Q

Structure of orsellinic acid

A

(draw)

39
Q

O-Methylation of polyketides

A

Carried out by S-adenosylmethionine (SAM)
= methionine linked to the nucleoside adenosine
Provides a source of electrophilic Me

40
Q

Structure of S-adenosylmethionine

A

Draw

41
Q

Elucidation of polyketide synthesis

A

Using doubly-labelled acetate
Will be incorporated into doubly-labelled acetyl-CoA by the species
Collect polyketide product from organism and run {1H}-13C NMR
Will see coupling between the two 13Cs to give doublets
Each doublet will have a coupling constant that will be the same for both carbons in a coupling pair (i.e. both from the same acetate unit), so we can figure out which 2 carbons came from the same acetate unit

42
Q

Why does the quantity of doubly-labelled acetate need to be carefully controlled?

A

So the species is using a mixture of doubly-labelled and non-labelled acetyl-CoA for biosynthesis
Ideally need to be statistically most likely to end up with one doubly-labelled acetate unit per molecule of polyketide product

43
Q

Alkaloids

A

Structurally diverse
All contain a basic nitrogen (called ‘alkaloids’ because they behave like alkali)
Mostly derived from amino acids

44
Q

Useful property of the basic nitrogen in alkaloids

A

Enables their isolation from other natural products
Can carry out an acidic aqueous extraction of the plant/animal matter, followed by neutralisation then back-extraction into an organic solvent

45
Q

Pyridoxal phosphate

A 
(draw)
Can carry out a variety of functional group interconversions:
Amine --> ketone
Ketone --> amine
Racemisation of alpha-amino acids
Decarboxylation of alpha-amino acids
Amino acid --> aldehyde
46
Q

Amine –> ketone

A

i.e. amino acid —> alpha-ketocarboxylic acid
Process can also operate in the opposite direction because all steps are equilibria i.e. can transform alpha-keto acid into an alpha-amino acid

47
Q

Shikimic acid

A

(Draw)
Shikimic acid is an important biosynthetic precursor to the aromatic amino acids: Phe, Tyr, Trp
Also the precursor to the flavonoids
Starting material for the manufacture of Tamiflu
Precursor for the K vitamins and chloramphenicol

48
Q

Biosynthesis of shikimic acid

A

(Draw)
Starts with phosphoenol pyruvate
Names of some intermediates: shikimate, chorismate, prephenate

49
Q

Pathways for the conversion of prephenate into Phe and Tyr

A

Redox-neutral
Requires oxidative step
(draw)

50
Q

Biosynthesis of cocaine

A

Draw

51
Q

Alpha amino acid racemisation

A

Draw

52
Q

Decarboxylation of alpha amino acid

A

Draw

53
Q

Alpha amino acid to aldehyde

A

Draw

Biosynthesis (2 decks)

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