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Biology A level > 1.2 Carbohydrates > Flashcards

1.2 Carbohydrates Flashcards

1
Q

What is a monomer?

A

A smaller repeating unit from which larger polymers are made

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2
Q

What is a polymer?

A

a chain of repeating units

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3
Q

What is a condensation reaction?

A

the joining of two monomers and the removal of 1 water molecule

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4
Q

What is a hydrolysis reaction?

A

water molecules are added to the process of breaking bonds between monomers

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5
Q

What elements are carbs made from?

A

carbon
hydrogen
oxygen

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6
Q

What are the three types of carbohydrates?

A

monosaccharide
disaccharide
polysaccharide

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7
Q

What is a monosaccharide?

A

the basic monomer unit

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8
Q

What is a disaccharide?

A

2 monosaccharides

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9
Q

What are polysaccharides?

A

large no. of monosaccharides

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10
Q

What are the 3 examples of monosaccharides?

A

glucose
galactose
fructose

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11
Q

What are the 3 examples of disaccharides?

A

maltose
sucrose
lactose

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12
Q

What are the 3 examples of polysaccharides?

A

starch
glycogen
cellulose

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13
Q

What makes maltose?

A

glucose and glucose

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14
Q

What makes sucrose?

A

glucose and fructose

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15
Q

What makes lactose?

A

glucose and galactose

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16
Q

What is a reducing sugar?

A

a sugar that can donate electrons to another chemical

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17
Q

How do you test for reducing sugars?

A

Benedict’s Test:
1. 2cm3 of food sample to a test tube - if sample not liquid, grind it up in water
2. add an equal vol of benedict’s reagent
3. heat the mixture gently for 5 mins
4. solution will turn yellow-brick red if reducing sugar is present

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18
Q

How do you test for non-reducing sugars?

A

Benedicts test then..:
5. 2cm3 of food sample in equal vol HCl and gently heat for 5 mins
the dilute HCl will hydrolyse disaccs to monosaccs
6. slowly add sodium hydrogencarbonate solution to neutralise HCl, test with pH paper - alkaline
7. re-do benedicts test
8. yellow to brick-red if non-reducing sugar is present

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19
Q

What is the function of starch?

A

energy storage

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20
Q

what monosacc type is starch made from and bond type?

A

alpha glucose - arranged in a helix
glycosidic bonds

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21
Q

What is the overall structure of starch?

A

branched - has many ends
large - doesnt diffuse out of cells
compact - a lot can be stored in a small space
insoluble - doesnt affect water potential

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22
Q

What is the chemical test for starch?

A

potassium iodide solution:
1. 2cm3 of food sample in test tube
2. add two drops of iodine solution then shake/stir
3. presence of starch indicated by yellow —> blue-black colouration

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23
Q

What is the function of cellulose?

A

provides rigidity to plant cell and prevents cell from bursting as water enters by osmosis

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24
Q

Which two types of carbs are sugars?

A

monosacc and disaccs

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25
Q

What are the properties of sugars?

A

sweet
soluble
crystalline

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26
Q

What is the general formula of monosaccs?

A

CnH2nOn

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27
Q

Which two monosaccs are pentose molecules ( 5 carbons )?

A

deoxyribose and ribose

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28
Q

What monosaccs are hexose (6 carbons) molecules?

A

glucose
fructose
galactose

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29
Q

Which hexose molecules is arranged in a pentagon?

A

fructose

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30
Q

What is the function of glucose?

A

main resp substrate

31
Q

What are the properties of glucose?

A

highly soluble
sweet
crystalline
transporter of carbs in animals
abundant

32
Q

How do you label the carbon’s numbers when drawing glucose or other isomers?

A

label the carbon numbers clockwise starting from the oxygen

33
Q

What is the structure of alpha glucose?

A

hydroxyl group below carbon-1

34
Q

What function do polymers of alpha glucose have?

A

glucose storage

35
Q

What is the structure of beta glucose?

A

hydroxyl group above carbon-1

36
Q

What is the function of a polymer of beta glucose?

A

structural polysacc

37
Q

What is the structure of fructose?

A

x1 CH2OH group below carbon 1
6 carbons but has a pentagon shape

38
Q

What is the structure of galactose?

A

alpha glucose with hydroxyl group above carbon-4

39
Q

Where is galactose found?

A

glycolipids or glycoproteins on membranes for recognition

40
Q

What is the structure of ribose?

A

5 carbons - so alpha glucose minus 1 carbon

41
Q

What is the structure of deoxyribose?

A

ribose but missing an oxygen on carbon 2
C5 H10 O4

42
Q

Where is ribose found?

43
Q

Where is deoxyribose found?

44
Q

How are disaccs prodcuced?

A

condensation reactions of monosaccs

45
Q

What bond is formed by a condensation reaction?

A

1-4 glycosidic bond

46
Q

What bond is present in maltose and sucrose?

A

alpha 1-4 glycosidic bond

47
Q

What bond is present in lactose?

A

beta 1-4 glycosidic bond

48
Q

What is the function of maltose?

A

resp substrate in germinating seeds

49
Q

What is the function of sucrose?

A

table sugar

50
Q

What is the function of lactose?

A

milk sugar

51
Q

What are the two polymers of alpha glucose?

A

glycogen and starch

52
Q

What is the advantage of alpha glucose polymers being compact?

A

can store more glucose in the cell

53
Q

How do polymers of glucose release glucose?

A

by being hydrolysed

54
Q

What is the advantage of alpha polymers of glucose being branched?

A

larger SA for hydrolysis so faster rate that glucose is released
can be condensed into very compact structure - ideal for storage

55
Q

What is the advantage that polymers of alpha glucose are insoluble in water?

A

doesnt affect water potential - osmotically inert

56
Q

What are starch and glycogen made of?

A

amylose and amylopectin

57
Q

What is the structure of amylose?

A

1-4 bonds, facing downwards = the chain starts to curl in on itself and forms a helical shape

58
Q

What is the structure of amylopectin?

A

1-4 and 1-6 bonds
due to the 1-6 bonds it has a branched structure = higher SA for hydrolysis

59
Q

Why can glycogen release glucose faster than starch?

A

glycogen has more 1-6 bonds so it more branched and has a higher SA for hydolysis

60
Q

What is the function of polymers of beta glucose?

A

structural function

61
Q

Describe cellulose structure.

A

1-4 bonds, hydroxyl group above carbon-1 - straight chain
the glycosidic bonds flip so every alternate beta glucose molecule is rotated 180’
1-4 bonds have alternate up/down positions - results in a straight chain
hydrogen bonds forming cross links between chains
To form microfibrils

62
Q

What is a microfibril?

A

multiple cellulose chains

63
Q

What is the advantage of H bonds forming cross links in cellulose?

A

provides cellulose with its high tensile strength there are a large number of H bonds

64
Q

How is a helical shape formed in starch?

A

1-4 bonds occur in downward position which puts a strain on the chain

65
Q

What enzyme hydrolyses starch?

66
Q

What enzyme breaks down glycogen?

A

glycogen phosphorylase

67
Q

What does osmotically inert mean?

A

doesnt affect water potential

68
Q

What is the advantage of cellulose molecules forming microfibrils?

A

provides high tensile strength so it is suitable for a plant cell wall

69
Q

What is cellulose function in cells?

A

It has high strength and rigidity to resist osmotic pressure as the glycosidic bonds are difficult to break
It resists digestion and the action of enzymes

70
Q

What are examples of monomer and polymer reactions?

A

amino acids to form a protein
alpha glucose to form starch or glycogen

71
Q

What is the structure of glycogen?

A

alpha glucose branched chain
coiled = more compact
1-4 and 1-6 bonds

72
Q

What are features of starch that make it a good storage molecule?

A

insoluble
branched/ coiled
polymer of alpha glucose
large molecule

73
Q

How is glycogen used as a source of energy?

A

hydrolysed to glucose - used in resp

Biology A level (34 decks)

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