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alevel biology ocr > water, carbs and general-biological molecules > Flashcards

water, carbs and general-biological molecules Flashcards

1
Q

explain the charges in a water molecule

A

the oxygen atom is slightly negative and the hydrogens are slightly positive so they are attracted

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2
Q

how is water made very stable

A

hydrogen bonds are weak but collectively strong so water is made very stable as adjacent water molecules are attracted. this is vital in living organisms

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3
Q

what type of bonds do water molecules have

A

covalent

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4
Q

how is water used in reproduction (2 things)

A

used to bring male and female gametes together in fertilisation, in mammals the foetus develops in a water filled sac providing physical and thermal stability

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5
Q

how does water provide support in animals

A

water filled tissues provide skeletal support , eg annelids hydrostatic skeleton allows muscles to contract, provides buoyancy for aquatic organisms

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6
Q

how does water provide support in plants

A

in plant cells it provides turgidity to maintain ariel parts of the plant to prevent wilting. maintain max leaf surface area for light absorption for photosynthesis

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7
Q

what is an ionic bond

A

a chemical bond formed by the attraction between 2 oppositely charged ions

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8
Q

what is a covalent bond

A

a strong chemical bond where 2 atoms share a pair of electrons

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9
Q

in a glucose molecule which carbon atom is carbon 1?

A

the carbon on the right to the oxygen

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10
Q

what is a glycosidic bond

A

a covalent bond between a carbohydrate and a hydroxyl group on another molecule resulting from a condensation reaction

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11
Q

how is sucrose formed and what bond

A

condensation of glucose and sucrose forming a 1, 4 glycosidic bond (alpha)

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12
Q

how is lactose formed and what bond

A

condensation of glucose and galactose forming a 1,4 glycosidic bond (beta)

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13
Q

how is maltose formed and what bond

A

between the condensation of 2 (alpha)glucose molecules forming a 1,4 glycosidic bond (alpha)

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14
Q

what are the chemical elements that make up carbohydrates

A

carbon, hydrogen and oxygen

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15
Q

what is the chemical compostion of carbohydrates (2 elements and a ratio)

A

hydrogen and oxygen in a ratio of 2:1

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16
Q

describe the structure of starch

A

a polysaccharide made up of many alpha glucose molecules joined by glycosidic bonds

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17
Q

what are the 2 polysaccharide molecules known collectively as starch

A

amylose and amylopectin

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18
Q

describe the structure of amylose

A

alpha glucose molecules linked by only 1,4 glycosidic bonds the angle of which allows the long chain to twist forming a helix stablised by H bonds from within = more compact and less soluble than just glucose

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19
Q

describe the strucutre of amylopectin

A

alpha glucose molecules with long chains linked by 1,4 glycosidic bonds and branches linked by 1,6 glycosidic bonds that occur every 25 glucose subunits

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20
Q

what is the general formula for carbohydrates

A

Cx(H2O)y

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21
Q

examples of disaccharides

A

lactose
sucrose

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22
Q

examples of polysaccharides

A

glycogen, cellulose and starch

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23
Q

glucose contains …. carbon atoms making it ….. sugar

A

6 carbon atoms
hexose sugar

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24
Q

general formula of glucose

A

C6H12O6

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25
Q

is glucose soluble or insoluble

A

soluble

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26
Q

what is the main form carbohydrates are transported around the body of animals

A

glucose

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27
Q

what are 2 structural isomers of glucose

A

alpha glucose and beta glucose w

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28
Q

what is the difference between alpha and beta glucose

A

the OH group on carbon 1 is below on alpha and above on beta

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29
Q

what enzyme will digest maltose and what into

A

maltase into 2 glucose molecules

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30
Q

what are the 2 pentose sugars you need to know

A

ribose and deoxyribose
(will not be asked to draw them)

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31
Q

what is the difference between ribose and deoxyribose

A

on carbon 2 ribose has 1 H atom and 1-OH group whereas deoxyribose and 2H and no OH group

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32
Q

what is the difference between an alpha and beta glycosidic bond

A

alpha the bonds point down to O
beta the bond goes up O then down vv

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33
Q

in polymers, monomers are joined up by

A

glycosidic bonds

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34
Q

polysaccharides are mainly used for (2)`

A

energy store
structural components of cells (cellulose plant cell wall)

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35
Q

how is starch usually stored

A

stored as intracellular starch grains in plastids

36
Q

what are plastids

A

organelles including chloroplasts and amyloplasts eg in potatoes

37
Q

describe the structure of glycogen

A

a branched polysaccharide made up of many glucose molecules with long chains linked by 1,4 glycosidic bonds and branches formed by 1,6 glycosidic bonds

38
Q

is cellulose branched or unbranched

A

unbranched

39
Q

is glycogen branched or unbranched

A

branched

40
Q

is amylose branched or unbranched

A

unbranched

41
Q

is amylopectin branched or unbranched

A

branched

42
Q

what is the benefit of glycogen having a branched structure

A

more efficient storage and release of glucose than amylopectin etc as it increases the amount of free ends so that glucose can be stored (added) or released quicker

43
Q

glycogen is less….. and more….. than starch and what is the benefit of this

A

less dense
more soluble
it can be broken down more rapidly/quicker to digest as animals need to mobolise reserves quicker

44
Q

starch and glycogen are …… in water, why does this make them good storage molecules

A

insoluble , it means they dont affect the water potential of the cell

45
Q

starch and glycogen are …… why does this make them good storage molecules (think space)

A

coiled, it means they are compact

46
Q

starch and glycogen are…… why does this make them good storage molecules (think structure)

A

branched, it means there are more ends for fast breakdown.

47
Q

starch and glycogen are polymers of ….., why does this make them good storage molecules

A

glucose, it means they can provide glucose for respiration

48
Q

what is the starch that is found in animals and fungi

A

glycogen

49
Q

starch and glucose are …. molecules, why does this make them good storage molecules (think size)

A

large, it means they cant cross the cell surface membrane

50
Q

why is glycogen insoluble

A

because it doesn’t have enough free polar groups to participate in hydrogen bonding with water. This is because most of the polar OH groups in glycogen hydrogen bond with other groups within the molecule leaving few groups available to participate in bonding with water.

51
Q

what is the most abundant organic polymer

A

cellulose

52
Q

cellulose prevents cells from

A

bursting when they take in excess water

53
Q

describe the structure of cellulose

A

long chains of beta glucose molecules joined by [beta]1,4 gbonds, the glucose chains form rope like microfibrils which are layered to form a network

54
Q

is cellulose a branched or straight chain molecule and why

A

straight because beta 1-4 gbonds cant form branches as one glucose has to flip so that the OH groups are close enough to react but that means that it cannot coil or form branches and so it is straight

55
Q

is cellulose easy or hard to digest

A

hard because we lack the neccessary enzymes to breakdown the beta gbonds

56
Q

cellulose molecules form … bonds with each other meaning

A

H bonds forming microfibrils which join together to form macrofibrils which combine to produce fibres that provide tensile strength for the plant cell wall

57
Q

in starch the polysaccharide that makes up the coiled shape is

A

amylose

58
Q

in starch the polysaccharide that makes up the branched part is

A

amylopectin

59
Q

what is a hydrogen bond

A

a weak chemical bond between the positive charge on a hydrogen atom and the negative charge on the adjacent molecule

60
Q

what is a polysaccharide

A

a polymer molecule formed of one or more monosaccharides joined by glycosidic bonds

61
Q

define cohesion

A

the force of attraction between water molecules which makes them stick to each other

62
Q

explain how the polar properties of water molecules cause cohesion

A

a positively charged H atom of one water molecule is attracted to the negatively charged O atom of another water molecule forming a H bond between the two molecules

63
Q

describe the process of adhesion in plants

A

water molecules are attracted to the impermeable wall of xylem tissue

64
Q

what is a monomer

A

the smaller unit from which larger molecules are made

65
Q

what is a polymer

A

a molecule made from a large number of monomers joined together

66
Q

what is a condensation reaction

A

a reaction that forms a chemical bond between 2 molecules and eliminates a water molecule

67
Q

what is a hydrolysis reaction

A

a reaction that breaks a chemical bond between two molecules and uses a water molecule

68
Q

What chemical test is used to detect the presence of reducing and non-reducing sugars and what colour change would be seen with a positive result?

A

is detected using the Benedict’s test
+ result: change from blue to green, yellow, orange or brick red depending on the conc of the sugar

69
Q

is glycogen quicker or slower to digest than starch and why is this beneficial

A

it is quicker to digest which is necessary because animals are mobile and plants arent

70
Q

compare the density and the solubility of glycogen and starch

A

glycogen is less dense and more soluble than starch

71
Q

how is glycogen stored

A

as small granules in the muscles and liver

72
Q

animals do not store starch but

A

as glycogen

73
Q

what do hydrolysis reactions do

A

break poly/disaccharides into monosaccharides

74
Q

break poly/disaccharides into monosaccharides

A

starch and cellulose in plants and glycogen in animals

75
Q

what are polysaccharides mainly used fo

A

as an energy store and as structural components of cells

76
Q

what are polysaccharides

A

long chain carbohydrates formed from many monosaccharides joined by glycosidic bonds . they are formed by condensation reactions

77
Q

what effect does the structural differences of alpha and beta glucose have

A

major effect on the biological role

78
Q

glucose is the main form in which…..

A

carbohydrates are transported around the body

79
Q

what are examples of disaccharides

A

glycogen, cellulose and starch

80
Q

what are disaccharides

A

large sugars, double sugars formed from 2 monosaccharides

81
Q

what are examples of monosaccharides

A

glucose, fructose, ribose

82
Q

what is a monosaccharide

A

a small simple sugar

83
Q

what is the general formula of monosaccharides

A

(CH20)n where n can be 3-7

84
Q
A
85
Q
A

alevel biology ocr (19 decks)

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