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CH112 > natural products 1 > Flashcards

natural products 1 Flashcards

1
Q

what is a lipid ?

A

this is the term given to a water insoluble natural product isolated from plants and animal cells

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2
Q

what can lipids be divided up into and how ?

A

into polyketides and polyisoprenens , they are divided due to the way they are biosynthesised

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3
Q

how are polyketides synthesised ?

A

these are assembled of multiple units of 2 carbons

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4
Q

what are polyketides the basis for ?

A

the formation of fats , oils , waxes , prostaglandins , membrane lipids and a variety of bioactive cyclic compounds.

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5
Q

how are isporenes synthesised ?

A

they are assembled from multiple units of 5 carbons

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6
Q

what to isoprenes give rise to ?

A

fragrant plant perfumes , flavourings and steroid hormones

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7
Q

how are fats and oils formed ?

A

they are formed when long chain aliphatic carboxylic acids are esterified with glycerol

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8
Q

what is glycerol also known as ?

A

1-2-3-trihydroxylpropane

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9
Q

what are fats and oils also known as ?

A

triglycerides

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10
Q

what occurs when a triglyceride is hydrolysed with a acid or alkali ?

A

you get a glycerol molecule and 3 fatty acid molecules

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11
Q

are the R groups of the fatty acid the same ?

A

no they can be the same or different

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12
Q

Fatty acids can be saturated or unsaturated , whats the difference ?

A

saturated contains no double bond and only has single bonds , while unsaturated has double bonds and sometimes triple bonds.

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13
Q

why are the carboxylic acids in fats and oils called fatty acids ?

A

due to them being originally obtained from fats

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14
Q

what will the number of carbon atoms in a fatty acid usually be and why ?

A

normally be even as they will have been biosynthesised from several 2 units of carbons

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15
Q

what is the MP and BP of saturated chains and why ?

A

they have high MP and BP as they can pack together well as a result of numerous van der Waals so they form a stable crystal like lattice.

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16
Q

whats the MP and BP of unsaturated chains and why ?

A

they have a low MP and BP as they cannot pack together so tightly and neatly due to the cis double bonds.

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17
Q

if the chains had trans double bonds what would occur ?

A

there would be far less distribution

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18
Q

why do short chains have low MP and BP ?

A

due to the irregular gaps forming when the chain is packing

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19
Q

whats the composition of animal fats and why ?

A

they will have a mixture of triglycerides that contain a high proportion of saturated chains due derived from stearic acid and plamitic acid. having a high MP and BP they will be solid at room temp

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20
Q

whats the several biological functions of fats ?

A

they provide long term energy storage

provide thermal insulation

provide mechanical insulation to prevent injury

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21
Q

whats the composition of vegetable oils ?

A

they contain more unsaturated chains and as a result have a lower MP and are liquid at room temp

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22
Q

why is margarine more easier to spread than butter ?

A

butter contains more saturated fats compared to margarine. Therefore margarine has more double bonds and hence has a lower MP

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23
Q

if fats are hydrolysed in an alkali then what is obtained and how are they useful ?

A

you obtain a salt of the fatty acid that can be used as soaps

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24
Q

what occurs when these soaps are dispersed in water?

A

the hydrocarbon chains cluster together to form a sphere like structure called a micelle

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25
Q

what is the arrangment within the micelle

A

the hydrohpobic chains cluster together away from the solvent in the centre while the hydrophyllic heads are on the surface.

26
Q

why do micelles repel each other ?

A

due to the like charges they carry on the surface

27
Q

how come they are good cleaning agents ?

A

because any dirt insoluble in water is soluble in the hydrocarbon phase that makes up the centre . therefore a stable emulsion is created of the water insoluble dirt partciles

28
Q

what salts mainly make up domestic soaps ?

A

sodium salts

29
Q

what salts mainly used in shaving creams and liquid soaps ?

A

potassium salts

30
Q

what occurs if calcium and magnesium is present in the water ?

A

these ions exchange with the potassium and sodium ions and the resulting soaps are insoluble in water and therefore the new salts precipitate out as a grey scum

31
Q

why is the calcium sterate insoluble ?

A

because it has a greater hydrophobic character so that a stable micelle cannot form

32
Q

what is a detergent ?

A

this is a synthetic molecule that is similar to soaps but they don’t form insoluble salts.

33
Q

what are waxes ?

A

they are isolated from plants and animal material and are simple monoesters of long chain fatty acids and alcohols

34
Q

what is the natural function of a wax ?

A

to form a waterproof coating for plants and insects

35
Q

although waxes are solid why can they not form a crystalline ?

A

becuase the waxes are a mixture of different chain lengths.

36
Q

whats the MP of waxes and what occurs as the chain length increases ?

A

they have a high MP , they become more brittle

37
Q

what are membrane lipids very similar too and how do they differ?

A

triglycerides but one of the fatty acids is replaced with a different group , usually a phosphoric group.

38
Q

what is the most common type of membrane lipid and where is it found ?

A

lecithin ( PC) , found in egg yolks

39
Q

what is R1 typically ?

A

stearic acid , this is saturated ( single bond)

40
Q

what is R2 typically ?

A

oleic acid , unsaturated ( double bonds)

41
Q

what is lecithin also called ?

A

phosphatidylcholine ( PC)

42
Q

what are cephalins or phosphatidylethanolamines ( PE) very similar too?

A

lecithins or PC

43
Q

how are membrane lipids similar to fatty acid derived soaps and how is this useful?

A

they have a non polar tail and polar head which gives them excellent emulsifying properties

44
Q

what is the major biological function of membrane lipids ?

A

to form a membrane bilayer

45
Q

whats the function of the selectively permeable bilayer membrane?

A

It compartmentalises various materials

it supports and provides a suitable environment for the action of enzymes etc

provide sited for attachment of the cytoskeleton elements

46
Q

how is the bilayer formed?

A

due to the packing of the non polar chains away from the aqueous phase

47
Q

do cytoskeleton proteins attach to the inside or outside of the cell ?

A

inside

48
Q

describe structure of glycerophospolipids and where found ?

A

the head has N present , whether its a N or NH3+ found in plasma memnbrane of many animal cells

49
Q

where are glyceroclycolipids found ?

A

chloroplasts ,bacteria and blue green bacteria

50
Q

describe structure of glyceroglycolipids ?

A

they have a ring as their polar head and phosphate ion

51
Q

where are phosphingolipids found and describe structure?

A

found in plasma membrane of animal cells , has phosphate ion and N polar head

52
Q

describe structure and where glycosphingolipids are found ?

A

it has ring structure as head and dominant in myelin , carry blood in erthyrocytes

53
Q

describe the structure of cholestrol ?

A

it is a sterol , with 4 fused hydrocarbon rings and it has a hydrocarbon tail linked to one end and a hydroxyl group on the other end.

54
Q

is cholesterol a fatty acid derivative?

A

nope it is a terpene

55
Q

if cholesterol is present what occurs to the rigidity of the membrane ?

A

it becomes more rigid

56
Q

whats the common features of all these molecules ?

A

their overall dimensions and twin hydrocarbon tails

57
Q

is it just 2 lipid tails that can occur ?

A

nope you can get 4 tails

58
Q

what allows the bilayer hydrophobic phase to be fluid rather than gelled ?

A

due to the hydrocarbon chain distortion that occurs due to cis double bonds , rings , branched etc

59
Q

what occurs to the MP of lipids if 4 tails rather than 2 ?

A

the MP increases as more packing occurs

60
Q

is the outside head and inside head of the bilayer need to be the same charge ?

A

no one can be positive and the other can be negative

CH112 (14 decks)

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