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*as biology (exam style questions by topic | cognito) > carbohydrates (biological molecules) > Flashcards

carbohydrates (biological molecules) Flashcards

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1
Q

raffinose is an example of a trisaccharide made up of glucose, fructose, and galactose:
Glucose = C6H12O6
Fructose = C6H12O6
Galactose = C6H12O6
Determine the number of carbon, hydrogen, and oxygen atoms in a single molecule of raffinose (1)

A
  • 18 carbon atoms, 32 hydrogen atoms, 16 oxygen atoms
  • two molecules of H2O are lost when forming the glycosidic bonds between the three monosaccharides in a molecule of raffinose
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2
Q

name the type of reaction that would break down raffinose into its monomers

A

hydrolysis

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3
Q

the monomers of raffinose are known as reducing sugars, describe how you could show that reducing sugars are present in a solution (3)

A
  • add Benedict’s solution
  • heat (in a water bath)
  • red/orange/yellow/green precipitate will form
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4
Q

give two similarities and two differences between the structure of raffinose and the structure of lactose (4)

A
  • both contain galactose
  • both contain glucose
  • both contain glycosidic bonds
  • raffinose contains fructose, lactose does not
  • raffinose is a trisaccharide, whereas lactose is a disaccharide
  • raffinose contains 2 glycosidic bonds, whereas lactose contains 1
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5
Q

describe a biochemical test you would carry out to test for the presence of starch in a solution (2)

A
  • add iodine or potassium iodide (to the sample)
  • solution turns blue-black (if starch is present)
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6
Q

explain how the structure of starch allows it to function as an energy storage molecule in plants (3)

A
  • insoluble so it doesn’t affect water potential, or does not affect osmosis
  • coiled so it is compact
  • large molecule so it cannot diffuse out of cells, or cannot cross the cell membrane
  • branched so glucose is released quickly, or so it has more ends for fast break down (by enzymes)
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7
Q

describe two similarities between the structure of starch and cellulose (2)

A
  • both are polymers/polysaccharides, or both are made up of monosaccharides
  • both contain glucose
  • both contain glycosidic bonds, or both contain 1-4 (glycosidic) bonds/links
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8
Q

name the monomer labelled A in the diagram

A

beta-glucose

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9
Q

name the bond labelled B in the diagram

A
  • glycosidic bond, or 1-4 glycosidic bond
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10
Q

explain how cellulose is adapted for its function in plant cells (3)

A
  • long and straight/unbranched chains
  • chains linked together via hydrogen bonds
  • form microfibrils
  • provide rigidity/strength (to the cell wall)
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11
Q

describe two differences between between the structure of cellulose and starch (2)

A

differences in overall structure:
- cellulose is straight/unbranched, whereas starch is branched
- cellulose contains microfibrils/macrofibrils, whereas starch does not
differences in structure of monomers:
- cellulose is made up of beta glucose, whereas starch is made up of alpha glucose
- cellulose contains alternating inverted glucose molecules, whereas in starch all glucose molecules are in the same orientation
- cellulose contains only 1-4 glycosidic bonds, whereas starch contains 1-4 and 1-6 glycosidic bonds

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12
Q

name the type of chemical reaction that joins glucose monomers together to form glycogen

A

condensation

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13
Q

describe how glycogen acts as a source of energy for cells (2)

A
  • hydrolysis releases glucose molecules
  • glucose can be used in respiration
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14
Q

describe one structural difference between glycogen and starch (1)

A

glycogen is more highly branched than starch

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15
Q

explain how glycogens structure enables it to function as an energy storage molecule (4)

A
  • coiled so it is compact
  • branched so glucose is released quickly or so more ends for faster hydrolysis
  • insoluble so it does not affect water potential, or insoluble, so it is not easily lost from cell
  • made up of glucose so glucose can be used in respiration, or made up of glucose, so provides respiratory substrate for energy (release)
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16
Q

name the 2 monomers that make up lactose

A
  • glucose
  • galactose
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17
Q
  • a student wanted to identify two solutions, A and B, she knew one of the solutions was lactose and the other was galactose, in the first test, she added Benedict’s solution and heated the mixture in a water bath, in the second test, she added the enzyme lactase before adding Benedict’s solution and heating in a water bath, lactase hydrolyses lactose into its monomers
  • identify solutions A and B, explain your answer (2)
A
  • A = galactose AND B = lactose
  • lactase hydrolysed lactose to give more reducing sugars
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18
Q

describe how the reducing sugars investigation could be changed to give quantitative results, explain why this would improve the experiment (2)

A
  • use a colorimeter
  • filter and dry the precipitate, then weigh it
    _
  • standardises the method
  • colour change is subjective
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19
Q

a non-reducing sugar would give a negative result in test 1, describe a third test she could have carried out to identify if a solution is a non-reducing sugar (3)

A
  • heat with acid and then neutralise with an alkali
  • or heat with acid and then neutralise with sodium hydrogencarbonate
  • heat with Benedict’s solution
  • red/orange/green precipitate will form
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20
Q

on the diagram, draw a circle around the chemical groups used to form a glycosidic bond

A
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21
Q

draw a diagram to show the structure of one sucrose molecule

A
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22
Q

name the monosaccharides found in a maltose molecule

A
  • glucose
  • glucose
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23
Q

a student adds Benedict’s solution to a beaker containing sucrose and heats the mixture in a water bath, no colour change, explain why (2)

A
  • sucrose is a non-reducing sugar
  • no acid was used to hydrolyse sucrose into its monomers
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24
Q

what is the chemical formula for glucose

A

C6H12O6

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25
Q

use the diagram above to draw the structure of an alpha-glucose molecule

A
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26
Q

state and explain two features of glucose that make it well suited to its role (2)

A
  • soluble so it can be transported around organisms
  • small molecule so it can diffuse across membranes or can be transported
  • broken down easily to release energy or to produce ATP
  • molecules can join to produce named disaccharides (e.g. maltose) or polysaccharides (e.g. starch, glycogen, cellulose)
27
Q

two alpha-glucose molecules can join together to form a disaccharide, name the type of covalent bond formed between the molecules and the name of the resulting disaccharide

A
  • (1-4) glycosidic bond
  • maltose
28
Q

describe how the structures of starch and cellulose are related to their function (5)

A

starch:
- spiral shape so it is compact
- large molecule so cannot leave cells
- insoluble so does not affect osmosis or so does not affect water potential
- branched so glucose is released easily for respiration
cellulose:
- long/straight/unbranched chains of beta-glucose
- joined by hydrogen bonding
- forms microfibrils
- provides strength/rigidity

29
Q

how is a molecule of N-acetylglucosamine different from monosaccharides such as glucose and fructose (1)

A

N-acetylglucosamine contains nitrogen, monosaccharides do not

30
Q

using the diagram above and your knowledge of polysaccharides, give two similarities and two differences between the structures of chitin and starch (4)

A

similarities:
- both are polysaccharides/polymers
- both contain 1-4 glycosidic bonds
- both made up of monomers with a CH2OH side group
differences:
- chitin contains nitrogen, starch does not
- chitin contains no 1-6 glycosidic bonds, starch does
- chitin is not branched, starch is branched
- chitin consists of N-acetylglucosamine monomers, starch consists of alpha-glucose monomers

31
Q

using your knowledge of polysaccharides, describe how a chitin molecule is formed from its monomers and predict its structure (4)

A
  • formed by condensation reactions
  • reaction releases water
  • alternate monomers are inverted
  • due to position of the OH on carbon 1
  • forms a straight, unbranched chain
  • similar structure to cellulose
32
Q

condensation of fatty acids and monoglycerides produces

A

lipids

33
Q

hydrolysis of lipids produces fatty acids and

A

monoglycerides

34
Q

which monosaccharide is found in milk

A

galactose

35
Q

what is the name for molecules that have the same molecular formula but a different arrangement of atoms in space

A

isomers

36
Q

what are isomers

A

molecules that have the same molecular formula but a different arrangement of atoms in space

37
Q

name one non-reducing sugar

A

Sucrose, Trehalose, Raffinose, Stachyose, Verbascose

38
Q

give three polysaccharides

A

glycogen, starch and cellulose

39
Q

give three disaccharides

A

maltose, sucrose and lactose

40
Q

give three monosaccharides

A

glucose, galactose and fructose

41
Q

what type of carbohydrates can be either reducing or non reducing sugars

A

disaccharides

42
Q

when blood glucose levels decrease, glycogen is broken down to release glucose, what is this process called

A

glycogenolysis

43
Q

cellulose chains are held together by what bonds to form what

A

hydrogen bonds to form strong fibres called microfibrils

44
Q

where is starch primarily stored in plants

A

seeds

45
Q

starch is a polysaccharide formed by condensation reactions of

A

alpha-glucose

46
Q

which part of a plant cell is mostly made of cellulose

A

cell wall

47
Q
A
  • protein
  • starch
  • dna
48
Q

why must polymers in food be hydrolysed in the body

A

monomers are easier to transport than polymers

49
Q

the main energy storage material in animals is

A

glycogen

50
Q

glycogen has a branched structure and forms

A

coils

51
Q

cellulose is a (structure)

A

straight chain

52
Q

glycogen has both 1,4 and what
whereas glucose has just what

A
  • 1,6 glycosidic bonds
  • glucose just has 1,4
53
Q

cellulose is made from what monomers

A

beta glucose

54
Q

glycogen is made up of what monomers

A

alpha glucose

55
Q

glycogen can be hydrolysed to

A

glucose

56
Q

name the monomer maltose is made from

A

gucose

57
Q

starch is what in shape, making it compact for storage

A

helical

58
Q

is starch or glycogen more branched

A

glycogen

59
Q

what is the major difference between chitin and other types of polysaccharides

A

chitin is nitrogenous

60
Q
A
61
Q

what enzyme is required to breakdown cellulose

A

cellulase

62
Q

what molecule

A

beta glucose

63
Q

what molecule

A

alpha glucose

*as biology (exam style questions by topic | cognito) (4 decks)

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