Natural products 2

Question 1

what are boundary lipids ?

Answer 1

these are the lipids that surround membrane penetrating proteins.

Question 2

what occurs when a membrane is cooled ?

Answer 2

it passes a fluid to gel phase which can affect the distribution of proteins in the membrane making them clump together

Question 3

what is phase seperations ?

Answer 3

this is when there could be gel patches of lipid against a fluid background

Question 4

what can some toxins cause ?

Answer 4

they can damage the phospholipids so they cannot pack together properly and the bilayer is damaged

Question 5

between the lipid head , glycerol backbone and hydrocarbon tails , describe their movements ?

Answer 5

the polar heads and glycerol backbone have little movement. Whereas the tails have freedom to move

Question 6

describe the structure of prostaglandins ?

Answer 6

they have a ring structure that has 2 fused side chains. They normally have an OH or CO group at C9 , C11.

Question 7

what are prostaglandins related to their function?

Answer 7

fatty acids that have hormone like actions in animal tissue

Question 8

what do prostaglandins have influence over ?

Answer 8

blood clotting , blood pressure , fever , pain , inflammation and induction of childbirth

Question 9

structurally what are prostaglandins derivatives of ?

Answer 9

prostanoic acid

Question 10

2 molecules PGE1 and PGH2 describe what that means ?

Answer 10

E and H is oxidation pattern of ring

1 and 2 is number of double bonds

Question 11

what are prostaglandins synthesised from ?

Answer 11

arachindionic acid which is a 20 carbon fatty acid chain that has 4 cis double bonds derived from linoeic acid

Question 12

whats the importance of PGH2 ?

Answer 12

it is the initial precursor from which all the other prostaglandins are derived from. It also acts as a precursor for thromboxanes and prostacyclins

Question 13

what are thromboxanes and prostacylins involved in ?

Answer 13

blood clotting and blood vessel diameter

Question 14

what is PGE2 ?

Answer 14

an important broncho dilator and vasodilator in the lungs. It is also a key component that leads to inflammation.

Question 15

how does aspirin work ?

Answer 15

it inhibits the prostaglandin synthesis which reduces inflammation and the clotting risk is reduced

Question 16

what do the derivatives from polyketides form ?

Answer 16

clinically effective drugs such as antibiotics , anti fungals and anti cancers

Question 17

what is formed when polyketides are cyclised ?

Answer 17

macrocyclic rings

Question 18

how is the macrocyclic ring complexity increased ?

Answer 18

by the presence of multiple chiral centres , addition of sugars , methyl and hydroxyl groups.

Question 19

what are cyclised polyketides synthesised by ?

Answer 19

a wide range of organisms such as plants , marine life , bacteria etc

Question 20

where is the most abundant source of polyketides ?

Answer 20

in a diverse order of gram positive bacteria

Question 21

are all cyclic polyketides beneficial ?

Answer 21

no some are dangerous as they look similar to DNA bases so when replication occurs there is some errors

Question 22

how is the biosynthesis of polyketides all derived from ?

Answer 22

the head to tail linking of acetate units to form longer chains

Question 23

what does the linking of 4 acetate groups form ?

Answer 23

a polyketo acid

Question 24

what can a polyketo acid be reduced to ( carbonyl groups removed) ?

Answer 24

a fatty acid ( octanoic acid) as there is 2 carbons in an acetate so 4x2=8.

Question 25

what temperature does biosynthesis occur ?

Answer 25

37

Question 26

the polyketo acid can be folded in different ways to produce what ?

Answer 26

aromatic acids , phenols

Question 27

how is fatty acid biosynthesis acheived ?

Answer 27

by linking together 2 carbon acetates to form a long chain. It occurs via reactions that are analogous to the aldol condensations. It requires a strong base to occur

Question 28

to achieve the same chain building reactions under physiological conditions ( no base) what needs to occur ?

Answer 28

the acetyl units need to be made more reactive , specifically the methyl hydrogens need to be made more acidic and the carbonyl carbon needs to be more susceptible to nucleophilic attack.

Question 29

what is the enhancement of reactivity required brought about by ?

Answer 29

esterfying the acetic acid with a thiol ( SH) group of a co enzyme or protein.

Question 30

why is a thiol ester much more reaction than a ordinary oxygen ester ?

Answer 30

because there is less electronic delocalisation , so a thiol ester is much better at forming carbanions

Question 31

how does making acetyl coA help to produce bigger molecules ?

Answer 31

the acetyl coA means that the H+ can be removed from the methyl of the acetyl group to give a carbanion which can react with other carbanions to build bigger molecules

Question 32

what does the reduction cycle to remove the carbonyl groups require and explain how and where it occurs ?

Answer 32

several enzymes . The cyclical reactions takes place within the confines of a multi enzyme complex in which the phosphopantotheine ‘arm’ of the
( acyl carrier protein ) ACP swings round like a hand and this allows the growing fatty acyl chain to visit each enzyme in turn. Each sweep of the ‘ hand’ adds and reduces another acetyl unit until the chain is the correct length

Question 33

what moves the molecule between each enzyme ?

Answer 33

the carrier protein

Question 34

what does repeated reaction with malonyl coA without the reduction steps taking place result in ?

Answer 34

A polyketoacid chain that can be folded to create phenolics