natural products 3

Question 1

the biosynthesis of an unsaturated fatty acid ( double bond) takes place how ?

Answer 1

due to the direct dehydrogenation ( remove H) by a desaturase enzyme at a certain point in the saturated chain.

Question 2

what is this route known as and why ?

Answer 2

aerobic route as it requires oxygen

Question 3

how are anaerobic organsim’s introduce double bonds ?

Answer 3

by the chain elongation cycle , since no oxygen is required it is called the anaerobic route

Question 4

what are the special fatty acid derivatives found as ?

Answer 4

aromas of tea and pears , however some function as sex attractants , alarm substances and population control for some substances

Question 5

What happens to the stability of the membrane if there’s a cyclopropyl ring ?

Answer 5

the membrane stability increases

Question 6

what does the cyclisation of polyketo acids produce ?

Answer 6

phenols and phenolic acids

Question 7

what is the cyclisation of polyketo acids similar to and why ?

Answer 7

the biosynthesis of fatty acids except there is no reduction step of the carbonyl group

Question 8

whats the reactivity of polyketoacids and what occurs in vitro ?

Answer 8

free polyketones are very reactive however in vitro they do not always cyclise to form rings spontaneously

Question 9

what is the mechanism used to control the cyclisation or folding of the chain ?

Answer 9

there is a system of carrier proteins that have chains built upon them and metal ions

Question 10

whats the different reactions that can fold the chain ?

Answer 10

aldol like reaction
claisen like reaction
dehydration
enolisation

Question 11

what can the dehydration cause to form ?

Answer 11

orsellininc acid

Question 12

what is an elonisation reaction ?

Answer 12

where enols are formed

Question 13

claisen reaction ?

Answer 13

Similar to condensation reaction for aldols

Question 14

aldol reaction ?

Answer 14

abbreviation of alcohol and aldehyde , it is when the enolate of the aldehyde or ketone reacts with the carbonyl of another molecule

Question 15

what are terpenes and how are they obtained , whats their composition ?

Answer 15

this is the pleasant smelling oily liquid obtained from plant materials by steam distillation. They are composed of 10 , 15 or 20 carbon atom compounds

Question 16

how many carbon atoms do monoterpenes have ?

Answer 16

10

Question 17

how many carbon atoms do sesquiterpenes have ?

Answer 17

15

Question 18

how many carbon atoms do diterpenes have ?

Answer 18

20

Question 19

how many carbon atoms do triterpenes have ?

Answer 19

30

Question 20

what is the basic terpene unit referred to as ?

Answer 20

isoprene unit

2- methyl - 1,3 - butadiene

Question 21

give an example of the tetraterpene ?

Answer 21

lycopene ( red colour of tomatoes )

carotenes ( orange colour in carrots

Question 22

what happens as the terpene gets longer and what occurs ?

Answer 22

produces a conjugated system , alternating double and single bond and colour is produced as it absorbs light in the visible colour spectrum

Question 23

what does B cartoene a precursor for and whats it important for ?

Answer 23

vitamen A ( retinol) which plays an important role in process of vision

Question 24

what are steroids derived from ?

Answer 24

triterpenes that have been further modified.

Question 25

what do steroids function as ?

Answer 25

hormones or hormone precursors

Question 26

in animals where are most hormones made ?

Answer 26

the adrenal cortex above the kidney

Question 27

give an example of a glucocorticoids and whats their function ?

Answer 27

cortisone , have roles in metabolic control

Question 28

give an example of a mineralorticoid and function ?

Answer 28

aldosterone , cause increased reabsorption of sodium . chlorine , bicarbonate in the kidneys which increase blood pressure

Question 29

give examples of androgens and their function ?

Answer 29

estrogen and prostegins , regulate reproductive function and physical development

Question 30

how is cholesterol involved in the hardening of the arteries ( atherosclerosis) ?

Answer 30

they are a constituent of the lipid plaque found in the arterial wall as plaques

Question 31

what is cholesterol a precursor for ?

Answer 31

more than 100 types of steroid hormones and vitamin D2 by UV light

Question 32

what does the androgen testosterone promote ?

Answer 32

spermatogenesis

Question 33

what is estradiol ?

Answer 33

an estrogen secreted form ovaries that stimulates growth and cell division , development of sex organs

Question 34

what is progesterone and whats its function ?

Answer 34

its a prostegin that regulates pregnancy and suppresses ovulation

Question 35

give an example of a bile acid ?

Answer 35

cholic acid

Question 36

if bile acids are combined with sodium salts of amino acids glycine what do they make ?

Answer 36

soap like molecules that help emulsify fats in the gut as an aid to the enzymatic digestion

Question 37

what can synthetic steroids be used in and are they safe ?

Answer 37

contraceptive pills and body boosting drugs. The body boosting drugs can be dangerous as cause liver damage

Question 38

how are terpenes biosynthesised ?

Answer 38

due to the head to tail linking of the 5C isoprene units

Question 39

wharts the 4 stages of the biosynthesis of polyisoprenoids ?

Answer 39

conversion of 3 acetyl groups to mevalonate
conversion of mevalonate to 5 carbon pyrophosphate
head to tail coupling of 5 carbon units
folding and cyclisation of polyisoprene chain to give terpenes

Question 40

what does the R of mevalonate indicate ?

Answer 40

chirality

Question 41

describe the conversion of mevalonate to 5 carbon pyrophosphate

Answer 41

the primary OH of MVA is phosphorylated twice with ATP to form 5 pyrophosphate . The tertiary OH is phosphorolaed once to give 3 - phosphate. Then there is a trans elimination of co2 and phosphate to give nucleophilic IPP. The IPP is then isomerised to give a n electrophilic DMAPP

Question 42

what is IPP and DMAPP biological equivalents of ?

Answer 42

isoprene

Question 43

describe how come the head to tail coupling can occur ?

Answer 43

IPP and DMAP are complementary reactives as the IPP has a nucleophilic and the DMAPP has an elctrophile.

Question 44

what is geranyl pyrophasphate a precursor for ?

Answer 44

many types of acyclic , monocylic and biocyclic monoterponoids

Question 45

what does the cyclisation of monoterpenes begin with ?

Answer 45

The isomerisation of geranyl pyrophosphate to give 2 monoterpene pyrophosphates

Question 46

what are the 2 monoterpene pyrophosphates called ?

Answer 46

neryl and linalyl

Question 47

what does coupling of the IPP unit and geranyl pyrophosphate generate ?

Answer 47

farnesyl pyrophosphate

Question 48

how is squalene formed ?

Answer 48

by linking 2 farensyl pyrophosphates

Question 49

when is tetracyclic and pentacylic tritepenoids formed ?

Answer 49

when the squalene is cyclised by the enzyme oxidocyclase

Question 50

what happens when the epoxide is protonated ?

Answer 50

it opens to a C+ ion adjacent to the next double bond along the chain.

Question 51

what’s the conformation of lanosterol ?

Answer 51

it has the 6 membered fused rings.

Question 52

how are steroids formed ?

Answer 52

due to the further transformations of lanosterol where the methyl groups are removed so there is less distribution in the membrane packing

Question 53

what produces the majority of natural products and why ?

Answer 53

plants due to their struggle for survival

Question 54

how is a bad flavour defence achieved ?

Answer 54

chemicals such as quinene , morphine , atrophine

Question 55

why do plants have to continually search for new defences ?

Answer 55

as insects can develop immunity quickly