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A Level Biology OCR A > 2.2 Biological Molecules > Flashcards

2.2 Biological Molecules Flashcards

1
Q

what is a covalent bond?

A

when electrons are shared by atoms

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2
Q

what is a condensation reaction?

A

when two molecules are joined together with the removal of water

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3
Q

what is a hydrolysis reaction?

A

when two molecules are split apart with the addition of water

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4
Q

what elements make up carbohydrates?

A

c, h, o

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5
Q

what elements make up proteins?

A

c, h, o, n, s

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6
Q

what elements make up nucleic acids?

A

c, h, o, n, p

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7
Q

what are carbohydrate monomers called?

A

monosaccharides

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8
Q

what are carbohydrates polymers called?

A

polysaccharides

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9
Q

what are protein monomers called?

A

amino acids

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10
Q

what are protein polymers called?

A

polypeptides / proteins

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11
Q

what are nucleic acid monomers called?

A

nucleotides

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12
Q

what are nucleic acid polymers called?

A

DNA / RNA

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13
Q

what is a hydrogen bond?

A

weak interaction occurring between a slightly negatively charged molecule bonds with a slightly positively charged molecule bonds

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14
Q

why are water molecules described as polar?

A

2h (slightly positively charged) + o (slightly negatively charged)

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15
Q

what are the advantageous properties of water?

A

liquid at room temperature, density, solvent, adhesion, surface tension, high specific heat capacity, high latent heat of vaporisation, reactant

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16
Q

how is water being a liquid a useful property?

A

provides a habitat for aquatic organisms, effective transport medium, reaction medium

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17
Q

why is water a liquid at room temperature?

A

as water molecules move, they continuously make and break hydrogen bonds. hydrogen bonds make it more difficult for water molecules to escape and become a gas.

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18
Q

is ice more or less dense than water?

A

less (it floats on top)

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19
Q

why is ice less dense than water?

A

because of its polar nature, water molecules align themselves in a structure less dense than liquid water at freezing point

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20
Q

how is ice being less dense than water a useful property?

A

aquatic organisms have a stable environment to live in through winter, layer of ice insulates rest of water against heat loss,

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21
Q

why is water a good solvent?

A

water is polar so the positive and negative parts of the water molecules are attracted to and cluster around the positive and negative parts of the solute. this separates them, therefore keeping them apart. at this point they dissolve and a solution is formed.

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22
Q

why is water being a good solvent a useful property?

A

makes water a good transport medium, makes water a good reaction medium

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23
Q

why are water molecules adhesive to each other?

A

hydrogen bonding between water molecules pulls them together

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24
Q

why does water have surface tension?

A

water molecules are more attracted to the molecules below them rather than the air above them so water contracts when force is applied

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25
Q

how are adhesion, cohesion and surface tension useful properties of water?

A

columns of water can be pulled up plant vascular tissues like the xylem, insects such as pondskaters can walk on water

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26
Q

what is specific heat capacity?

A

the amount of energy need to change the temperature of 1kg of a substance by 1 degree C.

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27
Q

why does water have a high specific heat capacity?

A

water molecules are held together tightly by many hydrogen bonds therefore lots of energy is needed to increase kinetic energy and break them

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28
Q

why is the high specific heat capacity of water useful?

A

water doesn’t heat up or cool down easily, provides a stable environment for aquatic organisms to live in and for enzyme-controlled reaction to happen

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29
Q

what is the latent heat of vaporisation?

A

the amount of energy needed to evaporate water

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30
Q

why does water have a high latent heat of vaporisation?

A

water molecules are held together tightly by many hydrogen bonds therefore lots of energy is needed to increase kinetic energy and break them

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31
Q

why is the high latent heat of vaporisation of water useful?

A

mammals are cooled when sweat evaporates

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32
Q

why is water so important as a reactant?

A

it plays a key role in digestion and the synthesis of large biological molecules

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33
Q

what does it mean when it’s said that carbohydrates are ‘hydrated carbons’?

A

for every carbon atom, there are 2 hydrogen atoms and 1 oxygen atom

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34
Q

what is the common ending for monosaccharides and polysaccharides?

A

-ose

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35
Q

what are isomers?

A

molecules with the same formula, but whose atoms are arranged differently

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36
Q

what are the 2 monosaccharide isomers?

A

a- glucose and b-glucose

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37
Q

what are the properties of monosaccharides?

A

sweet, soluble in water

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38
Q

what are the properties of disaccharides?

A

sweet, soluble in water

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39
Q

what are the most common disaccharides?

A

maltose, lactose, sucrose

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40
Q

what kind of sugar is maltose?

A

reducing sugar

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41
Q

what kind of sugar is lactose?

A

reducing sugar

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42
Q

kind of sugar is sucrose?

A

non-reducing sugar

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43
Q

a-glucose + a-glucose = ?

A

maltose

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44
Q

a-glucose + fructose = ?

A

sucrose

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45
Q

b-galactose + a-glucose = ?

A

lactose

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46
Q

how can cellobiose be obtained?

A

via the hydrolysis of the polysaccharide cellulose

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47
Q

what’s the difference between a-glucose and b-glucose?

A

alpha glucose has the OH group below the H, whilst beta glucose has the OH above the H (ABBA)

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48
Q

what type of bonds hold carbohydrates together?

A

glycosidic bonds

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49
Q

in which reaction is glucose a reactant?

A

aerobic respiration

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50
Q

how do plants store energy?

A

as starch

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51
Q

where do plants keep their energy stores?

A

chloroplasts, membrane bound starch grains

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52
Q

how do animals store energy?

A

as glycogen

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53
Q

where do animals keep their energy stores?

A

muscle cells and liver cells

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53
Q

what are the forms of starch?

A

amylose and amylopectin

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54
Q

why are starch and glycogen good energy stores?

A

compact

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55
Q

what is the advantage of energy stores having branched chains?

A

allow many glucose molecules to be broken down by hydrolysis at the same time when lots of energy is required for respiration

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56
Q

why are polysaccharides less soluble in water than monosaccharides?

A

bigger size, regions which might bond with water are hidden away inside the molecule

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57
Q

what are the properties of amylose?

A

a-glucose, straight chains coiled into a spiral, insoluble

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58
Q

what are the properties of amylopectin?

A

a-glucose, branched chains coiled into a spiral, soluble

59
Q

what are the properties of glycogen?

A

a-glucose, smaller chains than starch, doesn’t tend to coil, very branched, insoluble

60
Q

where is cellulose found in plants?

A

plant cell walls

61
Q

what is the structure of cellulose?

A

b-glucose, straight chains that do not coil but lie side by side,

62
Q

what is the structure of the cellulose cell wall?

A

microfibrils run in all directions and criss-cross for extra strength

63
Q

why is cellulose difficult to digest?

A

because glycosidic bonds between glucose molecules are hard to break

64
Q

why is the structure of the cellulose cell wall advantageous?

A

plants have no rigid skeleton so individual cells need support, space between microfibrils allow water and mineral ions to pass through making the wall permeable, high tensile strength to stop turgid cells bursting

65
Q

what are bacterial cell walls made of?

A

peptidoglycan

66
Q

what are exoskeletons made of?

A

chitin

67
Q

why are lipids insoluble in water?

A

they are not polar

68
Q

in what substance are lipids soluble in?

A

alcohol

69
Q

what are the three types of lipid macromolecules?

A

triglycerides, phospholipids, steroids

70
Q

what is the structure of a triglyceride?

A

one glycerol + 3 fatty acids

71
Q

what does it mean for a fatty acid to be saturated?

A

no C=C bond present

72
Q

what does it mean for a fatty acid to be unsaturated?

A

a C=C bond is present

73
Q

which type of fatty acid is liquid?

A

unsaturated

74
Q

why are unsaturated fatty acids liquid at room temperature?

A

the C=C changes the shape of the hydrocarbon chain and gives a kink where the double bond is. this kink pushes the molecules apart and therefore makes them more fluid

75
Q

what is an example of an unsaturated fat?

A

oil

76
Q

what is an example of a saturated fat?

A

butter

77
Q

what type of bond is present in a triglyceride?

A

an ester bond

78
Q

what are the functions of triglycerides?

A

energy source, energy store, insulation, buoyancy, protection

79
Q

how are triglycerides good energy sources?

A

they can be broken down in respiration to release energy and generate ATP

80
Q

how are triglycerides good energy stores?

A

they are insoluble in water and therefore do not affect the water potential of the cell, 1g of fat releases twice as much energy as 1g of glucose

81
Q

where do mammals store fat?

A

adipose cells under the skin

82
Q

why do fats contain more energy than carbohydrates?

A

have a higher proportion of hydrogen atoms and almost no oxygen atoms

83
Q

how are triglycerides good insulators?

A

blubber in whales, nerve cells, animals preparing for hibernation store extra fat

84
Q

how do triglycerides provide buoyancy?

A

fat is less dense than water

85
Q

how do triglycerides provide protection?

A

humans have fat around delicate organs like the kidneys to act as a shock absorber

86
Q

what is the structure of a phospholipid?

A

1 hydrophilic phosphate head + 2 hydrophobic fatty acid tails (commonly one tail is saturated and one unsaturated)

87
Q

why are phospholipids described as amphipathic?

A

hydrophilic head and hydrophobic tails

88
Q

what are the properties of phospholipids in water?

A

may form a layer on the surface of the water with hydrophobic tails sticking out of the water, or micelles

89
Q

is the phospholipid bilayer permeable?

A

only selectively. only small and non-polar molecules can move through the tails in the bilayer

90
Q

what kind of molecule is cholesterol?

A

a steroid alcohol

91
Q

is cholesterol hydrophobic or hydrophilic?

A

hydrophobic

92
Q

what is the purpose of cholesterol in the phospholipid bilayer?

A

regulates fluidity of the membrane and acts as a buffer against ph and temperature changes

93
Q

where in animals is cholesterol mainly made?

A

the liver

94
Q

what is the cholesterol derivative in plants called?

A

stigmasterol

95
Q

what is the difference between stigmasterol and cholesterol?

A

it has a double bond

96
Q

which steroid hormones are made from cholesterol?

A

testosterone, oestrogen and vitamin d

97
Q

can steroid hormones pass through the phospholipid bilayer?

A

yes, as they are small, hydrophobic, and made from cholesterol

98
Q

can animals make all the amino acids they require?

A

they can make some, but must ingest others (called essential amino acids)

99
Q

can plants make all the amino acids they require?

A

yes, as long as they have access to fixed nitrogen (such as nitrate)

100
Q

which amino acid has only 1 H as the R group?

A

glycine

101
Q

what is the common ending for amino acids?

A

-ine, with the exception of acidic R groups such as aspartic acid

102
Q

what bond joins together amino acids?

A

peptide bonds

103
Q

how are proteins digested?

A

protease enzymes in the intestines break peptide bonds during digestion

104
Q

what is the primary structure of a protein?

A

the sequence of amino acids, held together by peptide bonds

105
Q

what is the secondary structure of a protein?

A

a-helix or b-pleated sheet, held together by hydrogen bonds

106
Q

what is the tertiary structure of a protein?

A

when the a-helix or b-pleated sheet itself starts to fold into either a supercoiled fibrous protein or a spherical globular protein, held together by ionic bonds or disulphide links

107
Q

what is the quaternary structure of a protein?

A

how multiple polypeptide chains are arranged to make the complete protein molecule

108
Q

what type of bond are peptide bonds?

A

covalent

109
Q

what are the properties of fibrous proteins?

A

insoluble in water, regular and repetitive amino acids, strong

110
Q

what are three examples of fibrous proteins?

A

collagen, elastin, keratin

111
Q

what are the properties of globular proteins?

A

spherical (hydrophobic R groups on inside and hydrophilic R groups on outside), water soluble, often have specific shapes

112
Q

what are three examples of globular proteins?

A

haemoglobin, insulin, pepsin

113
Q

what is the function of collagen?

A

provide mechanical strength in tendons that connect muscle to bone, artery walls to prevent arteries from bursting due to high blood pressure, bones, cartilage

114
Q

what is the function of keratin?

A

provides mechanical protection, impermeable barrier to infection, waterproof so prevents entry of water-borne pollutants and makes body parts hard such as fingernails, hooves, claws, horns, scales, fur, feathers, hair

115
Q

why is keratin so strong?

A

rich in cysteine so lots of disulphide links alongside hydrogen bonding

116
Q

what is the function of elastin?

A

found where living things must stretch like skin to stretch around bones and muscle, allows lungs to inflate and deflate, allows bladder to expand to hold urine, allows blood vessels to stretch and maintain blood pressure

117
Q

why is elastin strong and stretchy?

A

lots of cross-linking and coiling

118
Q

what is the function of haemoglobin?

A

carries oxygen from lungs to tissues, oxygen binds to iron, turning haemoglobin from purple to red

119
Q

what is the structure of haemoglobin?

A

quaternary structure of 4 polypeptides (2 a-globin chains and 2 b-globin chains) and 1 Fe haem group (prosthetic group makes haemoglobin a conjugated protein)

120
Q

what is the function of insulin?

A

binds to glycoprotein receptors on fat and muscle cells to increase their uptake of glucose from the blood therefore reducing the blood glucose concentration

121
Q

what is the structure of insulin?

A

2 polypeptide chains, one a-helix and one b-pleat joined together by disulphide links, water soluble

122
Q

what is the function of pepsin?

A

digests protein in the stomach

123
Q

what is the structure of pepsin and how is it related to its function?

A

single polypeptide chain made of mostly complex amino acids which allows it to remain stable in acidic stomach environment

124
Q

what are the cations?

A

Ca2+, Na+, K+, H+, NH4+

125
Q

what are the anions?

A

NO3-, HCO3-

126
Q

what is Ca2+ used for?

A

increases bone rigidity, important in blood clotting, important in muscle contraction, regulates transmission of nerve impulses, regulates permeability of cell membranes

127
Q

what is Na+ used for?

A

involved in the regulation of osmotic pressure and pH maintenance, contributes to nervous transmission and muscle contraction, component of plant vacuoles to maintain turgidity

128
Q

what is K+ used for?

A

assists active transport across the cell membrane, involved in the synthesis of glycogen and protein, generates healthy leaves and flowers, contributes to nervous transmission and muscle contraction, component of plant vacuoles to maintain turgidity

129
Q

what is H+ used for?

A

involved in photosynthesis, respiration, regulation of blood pH, oxygen and carbon dioxide transport within blood

130
Q

what is NH4+?

A

ammonium

131
Q

what is NH4+ used for?

A

component of amino acids, vitamins, chlorophyll, nucleic acids, nitrogen cycle, maintains pH of the human body

132
Q

what is NO3-?

A

nitrate

133
Q

what is NO3- used for?

A

component of amino acids, vitamins, chlorophyll, nucleic acids, nitrogen cycles

134
Q

what is HCO3-?

A

hydrogencarbonate

135
Q

what is HCO3- used for?

A

involved in regulation of blood pH, involved in transport of carbon dioxide in and out of the blood

136
Q

what is the condition of lacking a particular ion called?

A

a deficiency

137
Q

how do you test for starch?

A

iodine in potassium iodide solution, turns from brown to blue black if starch is present

138
Q

how do you test for non-reducing sugars?

A

Benedict’s test, add Benedict’s solution then heat, blue to orange red if sugar is present (backwards rainbow intensity)

139
Q

what can this test be used for medically?

A

to detect glucose in the urine of diabetics

140
Q

how do you test for reducing sugars?

A

test a sample for reducing sugars to ensure there are none, boil another sample with hydrochloric acid to hydrolyse the sucrose intro glucose and fructose, use sodium hydrogencarbonate solution to neutralise, test for reducing sugars again, backwards rainbow if present

141
Q

how do you test for lipids?

A

emulsion test, mix sample with ethanol, cloudy white emulsion if lipids present

142
Q

how do you test for proteins?

A

biuret test, biuret reagent turns from blue to purple if polypeptides are present

143
Q

what is the qualitative test for non-reducing sugars?

A

colorimetry

144
Q

how is chromatography used?

A

to test for illegal drugs in the urine of athletes, analysis of food to ensure no contamination, analysis of drug purity

A Level Biology OCR A (17 decks)

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