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CH112 > carbs 1 > Flashcards

carbs 1 Flashcards

1
Q

what is energy from the sun stored as in chemical energy ?

A

carbohydrates

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2
Q

what are carbohydrates metabolic precursors for ?

A

most biomolecules

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3
Q

what does the breakdown of carbohydrates result in ?

A

it provides the energy that sustains animal life

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4
Q

how come carbohydrates have a structural function ?

A

ribose and deoxyribose are vital components of RNA and DNA.

Also the polysaccarides ( carbohydrates) are the major structural protein of cell walls for plants and bacteria.

Cellulose is also found in plant cell walls and gives stability as we cannot digest it.

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5
Q

what is chitin a main structural component of ?

A

the exoskeletons found on crustaceans , insects and spiders

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6
Q

what are hyaluronates important for ?

A

important for the vitreous humour of eyes ( transparent lining ) , as well as synovial fluid and cartilage

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7
Q

where are chondroitans and collagen found ?

A

in tendons , cartlidge and connective tissue

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8
Q

what is dermatan sulfate a component of ?

A

the extracellular skin matrix

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9
Q

what are glycoproteins ?

A

these are proteins that have a carbohydrate covalently attached.

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10
Q

why are glycoproteins important ?

A

they are used in cell recognition and cel adhesion.

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11
Q

how come the carbohydrate part of a glycoprotein is vital for infection of a cell ?

A

the virus uses it to bind to the cell

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12
Q

what is a carbohydrate made up of and what is it formula ?

A

glucose C6H1206

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13
Q

How many carbons must the simplest carbohydrate have ?

A

3

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14
Q

what 2 molecules can be descried as being a carbohydrate ?

A

polyhyroxyl ketone

polyhydroxyl aldehyde

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15
Q

what is an aldehyde and what is produced if it is oxidised ?

A

this is a hydrocarbon that has a carbonyl at the end ,the carbonyl group is bonded to at least one hydrogen. it is oxidised to produce an acid

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16
Q

what is a ketone ?

A

this is a hydrocarbon that has a carbonyl group in the middle which is bonded to 2 carbon atoms

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17
Q

what are simple carbohydrates and give examples ?

A

this is when the monomers cannot be hydrolysed to produced smaller carbohydrates as they are sugars , i.e ribose , glucose , fructose.

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18
Q

what are these simple carbohydrates called ?

A

monosaccarides

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19
Q

how do you name these simple monosaccharides ?

A

they are given the suffix -ose
the prefic aldo or keto is used
the prefix describes the number of carbons

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20
Q

what are complex carbohydrates ?

A

these consist of 2 or more monosaccarides that are joined by a covalent bond ( glycosidic linkage)

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21
Q

disaccarides hydrolyse to produce ?

A

2 monosachharodes

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22
Q

trisaccardies hydrolyse to produce ?

A

3 monosachharides

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23
Q

how many monosaccharides do oligosaccharides contain ?

A

between 2-10

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24
Q

how many monosaccharides do polysaccharides contain ?

A

a large number , thousands

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25
Q

what is a stereocentre and do carbohydrates contain them ?

A

yes all carbs contain them , this is a carbon atom that has 4 different groups attached so there is no plane of symmetry

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26
Q

what are stereoisomer ?

A

this is when molecules have the same molecular formula and bond conifuragation but they differ in the position of atoms.

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27
Q

if you are converting between 2 configurations then what does this require ?

A

covalent bonds to be broken and reformed

can also be achieved by rotation

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28
Q

what are stereoisomer either ?

A

an enantiomer or diastereoisomer

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29
Q

what are enantiomers ?

A

pairs of molecules that are non super imposable mirror images. they have identical physical and chemical properties but differ in biological properties

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30
Q

how do enantiomers interact with plane polarised light?

A

they rotate it in opposite directions in equal amounts

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31
Q

what is thalidomide a good example of ?

A

how enantiomers have different biological properties. The R form of thalidomide helps reduce morning sickness however the S form causes birth defects. The R and S describe stereocentres.

32
Q

if a molecule is chiral can it be superimposed ?

A

nope

33
Q

what does optically active mean ?

A

if a molecule rotates plane polarised light in opposite directions. Therefore enantiomers are optically active.

34
Q

what is the specific rotation [a]D a quantitive measure of ?

A

optical activity

35
Q

from this what can the molecules be grouped as ?

A

dextroroatory ( +)

levorotatory ( -)

36
Q

what are diastereoisomers ?

A

theses are pair of molecules that are not mirror images , they have different physical properties and different but similar chemical properties

37
Q

what method is the standard to show the stereocentres in 2D?

A

fisher projections

38
Q

how do you differentiate between L and D fischer projections ?

A

if OH on highest numbered stereocentre is on left then L but if oH on right then D

39
Q

whats the most abundant monnosacharide ?

A

D-

40
Q

how do you work out the possible number of stereoisomers ?

A

2*(N-2)

where N is the number of carbons

41
Q

what is the most common aldose ?

A

hexose

42
Q

what is an epimer ?

A

this is when a pair of sugars differ in configuration at only one carbon

43
Q

whats most common aldoses or ketoses ?

A

aldoses

44
Q

what does cyclisation of glucose result in ?

A

this creates a cyclic hemiacetal. there is 2 forms as a new stereocentre is created at C1 . Theres a a-D-glucopyranose ( OH below) and a B-D-glucopyranose (OH above)

45
Q

what are the 2 cyclic forms called and are they diastereoisomers or enantomers ?

A

they are both anomers and are diastereoisomer ( not mirror images)

46
Q

Why does glucose have unexpected properties ?

A

the formation of cyclic hemiacetal resulted in there being no free aldehyde group

47
Q

what does glucose normally exist as ?

A

a six membered cyclic hemiacetal

48
Q

what are the 6 membered sugar rings called ?

A

pyranoses

49
Q

pyranose rings can adopt a boat or chair form. These forms are not flat ( planar) , so how are they described ?

A

they are puckered

50
Q

between the boat and the chair form , what has the lowest energy arrangement ?

A

The chair form

51
Q

what determines the stability of each confirmation ?

A

the hydrogen atoms

52
Q

how are cyclic hemiacetals often drawn ?

A

as haworth projections

53
Q

what is the ether oxygen ?

A

the oxygen in the upper right

54
Q

what is the anomeric carbon ?

A

the carbon on the right vertex

55
Q

on converting a fisher projection to a haworth , how are the OH on the right drawn ?

A

OH are down in haworth

56
Q

OH on left in fischer , how in haworth ?

A

OH face up in haworth

57
Q

what is the CH2OH group in haworth for D monosaccharides?

A

they face up

58
Q

what are furanoses ?

A

theses are 5 membered sugar rings

59
Q

what mainly gives pyranose forms ?

A

aldohexoses and aldopentoses

60
Q

what does ketohexoses mainly form ?

A

a mixture of pyransoes and furanoses

61
Q

what rings are the most stable and why ?

A

5 and 6 membered rings as they have the strongest bonding.

62
Q

what is mutarotation and why does it occur ?

A

this is when there is a change in the optical rotation because there is a change in the equilibrium between the 2 anomers. Caused by a reversible ring opening of cyclic hemiacetal to an open chain which then recloses.

63
Q

what is mutaroation accelerated by ?

A

acids and bases

64
Q

why does the boat form have the highest energy ?

A

it is a result of the hydrogen - hydrogen repulsions

65
Q

are cyclohexane rings rigid and what does this lead to ?

A

no they can flip between 2 chair forms which is called ring flipping

66
Q

what occurs during ring flipping ?

A

the equatorial positions become axial and the axial positions become equatorial

67
Q

during ring flipping is there a lot of bonds breaking and reforming ?

A

no just a lot of rotating of atoms

68
Q

the 2 chair forms exist in equilibrium however , what will exist in the greatest amount ?

A

the form with the lowest energy

69
Q

what repulsions are most significant ?

A

repulsions between axial substituents

70
Q

what chair form is said to be most stable ?

A

the chair form with the fewest bulky axial substituents

71
Q

what conformation of b-D- glucopyranose is said to be most stable ?

A

the conformation with the all equatorial

72
Q

between a-D-glucopyranose and B-D-glucopyranoses what one is most abundant and why ?

A

B -D-glucopyranose as it is most stable

73
Q

what is the anomeric effect ?

A

this is the preference for the A anomer. It is a stabilizing electronic effect as the oxygen lone pair is trans coplanar to a C-X bond.

74
Q

what can the anomeric effect often result in ?

A

electronegative substituents forming axial e.g a halogen

75
Q

what is the arrangment of the furanose ring ?

A

it is also puckered as it isnt flat. It takes an evelope conformation as the four atoms are coplanar while the fifth atom is out of the ring plane.

76
Q

the ribose rings in nucleic acids are puckered , why is this ?

A

it relieves the ring strain caused by the 5 atoms being in the same plane . By having C3 . out the plan it reduces the strain

77
Q

are the ribose rings furanoses or pyransoes

A

furanoses

CH112 (14 decks)

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