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CH112 > Carbs 2 > Flashcards

Carbs 2 Flashcards

1
Q

what can the hydroxyl groups of carbohydrates be converted into ?

A

they can be converted to esters or ethers. Also can be oxidized

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2
Q

what can the carbonyl groups be converted to and what can they react with ?

A

they can be oxidised or reduced and react with nucleophiles.

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3
Q

in a cyclic sugar what carbon is the most react and why ?

A

the anomeric carbon ( C1) as it has 2 c-0 bonds whereas all the others have one c-0 bond. The 2 oxygens have a withdrawing effect on the electrons so they become slighty negative while the C become slightly positive and as a result is prone to nucleophilic attack.

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4
Q

what is the cyclic form of monosaccharides ?

A

hemiacetals

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5
Q

what can the hemiacetals react with and what does this produce ?

A

react with alcohol and acids to form an acetal at the anomeric carbon.

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6
Q

what are these monosachharide acetals called ?

A

glycosides

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7
Q

what are glucose acetals called ?

A

glycosides

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8
Q

monnose acetal ?

A

mannosides

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9
Q

fructose acetals ?

A

fuctosides

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10
Q

what is produced when D glucose reacts with methanol and hydrochloric acid ?

A

methyl alpha - D- pyranoglucoside and methyl beta - D - glucopyranoside

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11
Q

do glycosides undergo hydrolysis with water and base ?

A

nope

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12
Q

what is required for a glycoside to undergo hydrolysis and what is produced ?

A

acid , it forms a hemiacetal sugar and alcohol ( aglycone) due to the presence of the 2 oxygens at the anomeric carbon

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13
Q

what will a reducing sugar contain and what do they react with ?

A 
an OH group at the anomeric carbon react with oxidising agents such as 
hydrogen peroxide 
bromine water 
benedicts solution
tollens reagent
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14
Q

what occurs to the sugar and the reagent ?

A

the sugar is oxidised to an aldonic acid while the reagents are reduced . This is a redox reaction

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15
Q

what is tollen’s reagent ?

A

Oxidising agent. this is a solution of silver nitrate and ammonia , it is reduced to form a silver mirror

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16
Q

What is benedict’s solution ?

A

Oxidising agent. this is an aqueous solution containing copper ions. It is reduced to give a brick red percipitate as copper oxide is formed

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17
Q

what does a positive test to a benedict’s solution tell you ?

A

that the sugar is a reducing agent , this will have a hemiacetal group which is in equilibrium with the open chair form ( ketone or aldehyde)

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18
Q

what does it tell you if a sugar doest react with the chemical oxidising agents ?

A

then it is a non reducing sugar that has an acetal at the anomeric carbon ( glycoside)

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19
Q

what does the oxidation of the primary alcohol group in a aldose produce ?

A

a - uronic acid

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20
Q

what are oligosaccarides associated with ?

A

proteins (glycoproteins) and lipids ( glycolipids)

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21
Q

what’s the most common oligosachharide ?

A

disaccharide , 2 component monosaccaride

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22
Q

what forms between 2 sugars ?

A

a glycosidic link between the C1 and any hydroxyl group on the second sugar.

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23
Q

what occurs if the glycosidic link is different each time ?

A

then different proteins and DNA will be produced

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24
Q

what is starch hydrolysed to produced and what is needed for this to occur ?

A

Produces maltose and enzyme diastase is needed.

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25
Q

what does partial hydrolysis of cellulose produce ?

A

cellobiose which is an isomer of maltose

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26
Q

what is maltose and cellobiose composed of ?

A

2 glucose units linked by a 1 - 4 glycosidic link

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27
Q

what anomer of glucose is maltose ?

A

A anomer

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28
Q

what anomer of glucose is cellobiose ?

A

b anomer

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29
Q

what determines if the oligosaccaride is digestable ?

A

the position of the glycosidic link , whether its an a or b anomer

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30
Q

what is lactose composed of ?

A

two different monosaccarides , D - glucose and D - galactose

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31
Q

whats the difference between glucose and galactose ?

A

They are epimers and only differ in orientation of hydroxyl at C-4.

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32
Q

why are some people lactose intolerant ?

A

they lack the enzyme lactase ( galactosidase) to hydrolyse the glycosidic bond between the 2 monnosaccarides

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33
Q

what is sucrose ?

A

the most abundant natural type of disaccharide

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34
Q

is sucrose a reducing sugar and does it undergo mutarotation ?

A

not a reducing sugar and no

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35
Q

what does sucrose produce when hydrolysed ?

A

Mixture of glucose and fructose called invert sugars

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36
Q

what enzymes catalyses the hydrolyses of sucrose ?

A

B -D- fructofuranoside

37
Q

what can polysaccarides also be called ?

A

glycans

38
Q

what are heteropolysaccarides composed of ?

A

more than one type of monosaccaride unit

39
Q

what are homopolysaccarides composed of ?

A

one type of monosaccride unit

40
Q

what are glucose homopolysaccarides called ?

A

glucans

41
Q

what are galactose homopolysaccarides called ?

A

galactans

42
Q

describe the primary structuure of polysacarides ?

A

this is the monomer building blocks

43
Q

give an example of a primary structure , linear polysaccaride.

A

cellulose

44
Q

can we digest cellulose and what is it composed of ?

A

nope composed of glucose molecules joines by a 1 - 4 glycosidic link

45
Q

what is cellulase required for ?

A

its an enzyme that is required to hydrolyse the glycosidic bonds between the glucose molecules in cellulose

46
Q

where are these enzymes normally found ?

A

in the digestive tract

47
Q

whats the 2 groups that starch can be divided into ?

A

amylose and amylopectin

48
Q

describe amylose

A

insoluble in cold water

49
Q

describe amylopectin

A

soluble in cold water

50
Q

when starch is eaten what is it hydrolysed by ?

A

an enzyme called glycosidase

51
Q

what glycosidic link does glycosidases hydrolyse ?

A

A not b

52
Q

why is D glucose stored as a polymer than monomer units ?

A

to avoid large osmotic pressure

53
Q

what would occur in plants if glucose was stored in monomeric units rather then polymer ?

A

the membrane would rupture due to large osmotic pressure

54
Q

describe the structure of amylopectin ?

A

it is a glucan polymer

55
Q

what is glycogen a polysaccaride of ?

A

glucose

56
Q

whats is more heavily brachned , glycogen or amylopectin ?

A

glycogen

57
Q

what has high glycogen stores and why ?

A

skeletal muscles and the liver so that this allows quick release of energy

58
Q

what is needed to convert glycogen to glucose ?

A

glycogen phosphorylase

59
Q

where does glycogen phorphorolase work and what occurs ?

A

at the non reducing end of the glycogen unit and it works one glucose molecule at a time

60
Q

whats the limit to how glycogen phosphorlayse works ?

A

it cannot cleave glycosidic linkages that are closer than 4 glucose unit from a branch

61
Q

what is 75% of the carbohydrtaes consumed by ?

A

the brain as glucose

62
Q

what is most of the carbohydrates intake in the form of ?

A

starch with some glycogen

63
Q

can the body use starch and glycogen directly ?

A

nope must be broken down to glucose

64
Q

what is the secondary structure detail ?

A

the way the backbone is folded to give 3D shape

65
Q

what does secondary structure result from ?

A

the local conformational variety , which is due to rotations around the bonds involved in glycosidic linkages

66
Q

what does the favourable bond rotation around a link produce ?

A

helix

67
Q

what does the favourable bond rotations around b link form ?

A

zig zag

68
Q

what is an arrangement associated with cellulose ?

A

ribbons

69
Q

what is tertiary structure concerned with ?

A

the way the polysaccaride backbone is arranged in 3D space.

70
Q

what is quaternanry polysaccaride structure associated with ?

A

The way the polysaccaride interacts with other chains

71
Q

what is the chain packing and folded dictated by ?

A

the non covalent , long range interactions between the functional groups present on the monosacaride units

72
Q

explain what makes up a ribbon structure ?

A

this is when the b linked glucose units ( cellulose) or units in chitin are described as b linked ribbons. In both molecules there is a uniform distribution of hyroxyl groups on the outside of each chain. , so when 2 or more cellulose or chitin chains make contact the OH groups are ideally arranged to make hydrogen bonds

73
Q

what is the roatation of each glucose unit in cellulose at ?

A

180 relative to the next glucose unit

74
Q

what is the resulting ribbon stabilised by ?

A

intramolecular hydrogen bonds between OH groups on adjacent glucose units

75
Q

where is cellulose found and is it soluble in water ?

A

Found in cells walls and it is insoluble in water

76
Q

what type of glycosidic bonds do amylose and amylopectin have and what does this result in ?

A

they have a glycosidic bonds and as a resuly the chains have a wide hollow helix that is stabilised by hydrogen bonds

77
Q

if small molecules are accomidated into the central cavities of the helix what forms ?

A

An inclusion complex

78
Q

what does the iodine starch tests result in the blue - violet colour ?

A

because the aqueous solution of the iodine and ions forms an inclusion complex with the starch. The tri iodide anions fit in the middle of the cavity

79
Q

when are buckled ribbons formed ?

A

this is when the polysaccaride chain packs but leaves a cavity

80
Q

what can these cavities be filled with and how is this beneficial ?

A

can be filled with water or metal ions to give extra stability to the polysaccharide

81
Q

give an example of an acid that forms a buckled ribbon

A

pectic acid

82
Q

what are cyclodextrins ?

A

this is when there is natural occurring macrocycles composed of sugar units

83
Q

how are cyclodextrins obtained ?

A

due to the enzymatic degradation of starch

84
Q

whats the interior and exterior of cyclodextrins?

A

the inside is hydrophobic but outside is hydrophyllic

85
Q

what is the interior ideal for ?

A

apolar guests such as drug molecules

86
Q

whats the exterior being hydrophilic mean ?

A

that any molecule that complexes with the cyclodextrin is soluble in water which means the drug can be transported to their receptors

87
Q

what is rocuronium ?

A

this is a muscle relaxant used as part of the anaesthesia during surgery

88
Q

what is used to reverse the action of rocuronium and what is it ?

A

sugammadex which is a a cyclodextrin

89
Q

how does sugammedex work ?

A

it binds the rocoronium within its hydrophobic inteiror

CH112 (14 decks)

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