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2.2 Biological Molecules Flashcards

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1
Q

What are examples of molecules needed for sustaining life?

A

Water, proteins, nucleic acids, lipids, vitamins and minerals, carbohydrates.

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2
Q

What is a condensation reaction?

A

A reaction that occurs when two molecules are joined together with the removal of water.

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3
Q

What is a hydrolysis reaction?

A

A reaction that occurs when a molecule is split into two smaller molecules with the addition of water.

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4
Q

What is a hydrogen bond?

A

A weak interaction that can occur wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom.

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5
Q

What is a monomer?

A

A small molecule which binds to many other identical molecules to form a polymer.

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6
Q

What is a polymer?

A

A large molecule made from many smaller molecules called monomers.

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7
Q

What is one of the most important organic molecules?

A

The carbon-hydrogen bond.

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8
Q

What are condensation and polymerisation reactions responsible for?

A

Linking and splitting apart biological molecules in living things.

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9
Q

What is the monomer and polymer of carbohydrates?

A

Monosaccharide (e.g. glucose); polysaccharide (e.g. starch).

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10
Q

What is the monomer and polymer of proteins?

A

Amino acids; polypeptides and proteins.

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11
Q

What is the monomer and polymer of nucleic acids?

A

Nucleotides; DNA and RNA.

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12
Q

What does water consist of?

A

Two hydrogen atoms, each covalently bonded to one oxygen atom.

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13
Q

What is a polar molecule?

A

One end of the molecule is slightly positive and the other end is slightly negative.

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14
Q

What are hydrogen bonds weaker than?

A

Covalent bonds.

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15
Q

What does having lots of hydrogen between chains of monomers in a polymer do to a biological molecule?

A

Helps to stabilise its structure.

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16
Q

What do the hydrogen bonds between water molecules do?

A

Make it difficult for them to escape to become a gas.

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17
Q

Why can water flow easily.

A

It has a high viscosity despite its hydrogen bonds.

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18
Q

What can water do because it’s a liquid at room temperature?

A

Provide habitats, form major component of tissues in living organisms, provide reaction medium for chemical reactions, provide effective transport medium.

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19
Q

What happens to water density as temperature decreases?

A

It becomes more dense until 4 degrees Celsius where it gets less dense until 0 degrees Celsius, due to it’s polar nature.

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20
Q

Why is it important that ice is less dense than water?

A

Aquatic organisms have a stable environment to live in through the winter, bodies of water are insulated against extreme cold.

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21
Q

What is water good at?

A

Being a solvent for many substances found in living things.

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22
Q

Why is water a good solvent?

A

It’s polar so the positive and negative parts of the water molecules cluster around the negative and positive parts of the solute. This helps to separate them causing them to dissolve.

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23
Q

Why is it important that water is a good solvent?

A

Molecules and ions can move and react together in water (e.g. in cytoplasm), molecules and ions can be transported around living things.

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24
Q

What is surface tension of water?

A

Water molecules at the surface are more attracted to the water molecules beneath them than the air molecules above them, so the surface of the water contracts.

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25
Q

What is cohesion of water.

A

Hydrogen bonds pull water molecules together so they don’t spread out.

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26
Q
A
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27
Q

Why is water surface tension and cohesion important?

A

Columns of water in plant vascular tissue are pulled up the xylem tissue from the roots, insects like pond-skaters can walk on water.

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28
Q

What do hydrogen bonds holding water molecules together mean?

A

A lot of heat energy needs to be put in to increase their kinetic energy and temperature (specific heat capacity).

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29
Q

What does water’s high specific heat capacity mean?

A

Water doesn’t heat up or cool down quickly.

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30
Q

Why is it important that water has a high specific heat capacity?

A

Living things need a stable temperature for enzyme-controlled reactions to happen properly, aquatic organisms need a stable environment to live in.

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31
Q

What does latent heat of vaporisation help with?

A

Molecules breaking away from each other to become a gas, this is high in water due to lots of hydrogen bonds holding molecules together.

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32
Q

Why is it important for water to have a high latent heat of vaporisation?

A

Water can help to cool living things and keep their temperature stable, e.g. sweat evaporating.

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33
Q

What is a carbohydrate?

A

A group of molecules containing C, H and O.

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34
Q

What are the functions of carbohydrates?

A

A source of energy (e.g. glucose), a store of energy (e.g. starch and glycogen), structural units (cellulose and chitin).

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35
Q

What are the three main groups of carbohydrates?

A

Monosaccharides, disaccharides and polysaccharides.

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36
Q

Why are monosaccharides well-suited to being a source of energy?

A

They have a large number of carbon-hydrogen bonds.

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37
Q

What are features of sugars?

A

Taste sweet, soluble in water, insoluble in non-polar solvents.

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38
Q

How are monosaccharides structured?

A

Straight chains or in ring or cyclic forms, have a single-bonded carbon atom backbone, one carbonyl group (carbon double bonded to oxygen).

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39
Q

What are the most common disaccharides?

A

Maltose (reducing), sucrose (non-reducing) and lactose (reducing).

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40
Q

What forms maltose?

A

α-glucose + α-glucose

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41
Q

What forms sucrose?

A

α-glucose + fructose

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42
Q

What forms lactose?

A

β-glucose + α-glucose

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43
Q

What forms cellobiose?

A

β-glucose + β-glucose

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44
Q

How is a glycosidic bond formed?

A

Two hydroxyl groups line up next to each other, a water molecule is removed, an oxygen atom is left to link the two monosaccharide units together, a condensation reaction.

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45
Q

How are disaccharides broken down?

A

Hydrolysis reaction, addition of water molecule provides hydroxyl group and hydrogen which break glycosidic bond.

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46
Q

What is the role of α-glucose in the body?

A

Energy source, component of starch and glycogen which act as energy stores.

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47
Q

What is the role of β-glucose?

A

Energy source, component of cellulose which provides structural support in plant cell walls.

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48
Q

What is the role of ribose in the body?

A

Component of ribonucleic acid (RNA), ATP and NAD.

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49
Q

What is the role of deoxyribose in the body?

A

Component of deoxyribonucleic acid (DNA).

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50
Q

What percentage of atoms in the human body are carbon?

A

60%

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51
Q

What percentage of atoms in the human body are hydrogen?

A

11%

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52
Q

What are macro-nutrients?

A

Main elements, ions required in large amounts in humans and plants.

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53
Q

What are micro-nutrients?

A

Trace elements, ions required in small amounts in humans and plants.

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54
Q

When do humans and plants have deficiency symptoms?

A

When not enough of a particular ion is consumed.

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55
Q

What does a deficiency in copper cause?

A

Young plants to die back.

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56
Q

What is the bond that forms between glycerol and a fatty acid?

A

An ester bond.

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57
Q

What is the molecule formed when an ester bond is made?

A

A water molecule.

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58
Q

What are the two variations of glycosidic bond?

A

1-4 and 1-6.

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59
Q

What are three molecules that are insoluble in water?

A

Triglyceride, phospholipid, and cholesterol.

60
Q

What are functions of lipids?

A

Energy storage in adipose cells, insoluble so are transported in the blood by lipoproteins.

61
Q

What is an unsaturated fatty acid?

A

A fatty acid that contains at least one double bond between two carbon atoms, so contains fewer hydrogen atoms.

62
Q

What is the function of glucose?

A

To release energy to make ATP via aerobic respiration.

63
Q

What is the structure of glucose?

A

Small so can be transported, soluble in water, can be broken down into smaller molecules to produce ATP, lots of H atoms so can produce lots of ATP.

64
Q

How are polysaccharides formed?

A

monomers of a molecule are joined by glycosidic bonds.

65
Q

Why are polysaccharides arranged in chains?

A

So glucose can be easily ‘snipped off’ when it’s needed via hydrolysis reaction.

66
Q

How are polysaccharides stored in plants?

A

As starch (amylose and amylopectin).

67
Q

How are polysaccharides stored in humans?

A

Glycogen.

68
Q

What is the structure of amylose?

A

A store of energy in plants, made of alpha glucose monomers, forms an unbranched chain that coils into a spiral with H bonds holding its structure.

69
Q

What are the pros of the structure of amylose?

A

Coiled shape means more can fit in a small space so it’s compact, OH groups are within the coil so it’s less soluble and doesn’t affect the water potential of the cell.

70
Q

What is the structure of amylopectin?

A

Store of energy in plants, monomers of glucose bonded together with 1-4 glycosidic bond, branches formed by 1-6 glycosidic bonds.

71
Q

What are the pros of the structure of amylopectin?

A

Coiled and branched shape means more can fit in a small space so it’s compact, OH groups are within the coil so it’s less soluble, easy to remove glucose through hydrolysis.

72
Q

What is the structure of cellulose?

A

Found in all plants, made of beta glucose monomers with 1-4 glycosidic bonds, every second glucose molecule is rotated 180 degrees, long straight unbranched chains, form cross-links, many hydrogen bonds.

73
Q

What are the pros of the structure of cellulose?

A

Cross-links stop it spiraling, hydrogen between chains give strength and rigidity.

74
Q

What is the structure of glycogen?

A

Store of energy in humans, 1-4 and 1-6 glycosidic bonds, branches formed between glucose monomers, less coils because of smaller chain length.

75
Q

What are the pros of the structure of glycogen?

A

OH groups make it less soluble, more branches than amylopectin so more compact and easier to hydrolyse.

76
Q

What are features of micro and macro-fibrils?

A

Have immense strength due to glycosidic bonds and H bonds making them good for cell walls, beta 1-4 glucose bonds make it hard to digest.

77
Q

What are the two types of lipids?

A

Fatty acids and glycerol.

78
Q

What are sources of lipids in the diet?

A

Any fat/oil and any fatty/oily food.

79
Q

What are the functions of lipids?

A

Provide source of energy, store energy, insulate, metabolic source of water, protects organs, insoluble in water.

79
Q

What are features of lipids?

A

Usually contain fatty acids and glycerol, broken down by lipase, contains the element carbon, large complex molecules but not polymers.

80
Q

How are triglycerides formed?

A

One glycerol and three fatty acids, also produces water, called esterification.

81
Q

What are fatty acids made from?

A

A carboxylic group and a hydrocarbon tail.

82
Q

What are the three types of fatty acids?

A

Saturated (no double bonds), mono-unsaturated (one double bond), poly-unsaturated (many double bonds).

83
Q

What does more double bonds in a fatty acid mean?

A

More kinks so it’s more likely to be fluid.

84
Q

What are the properties of triglycerides?

A

Release twice as much energy as the same amount of a carbohydrate, very compact, stored in adipose tissue which insulates, far less dense than water,protects organs by surrounding them, lots of hydrogen to release lots of energy.

85
Q

What are the properties of phospholipids?

A

Same structure as triglycerides but one fatty acid replaced by a phosphate group with a negative charge when in water (polar), fatty acid tails are hydrophobic (non-polar), less energy than triglycerides as they have one less fatty acid.

86
Q

What are the properties of cholesterol?

A

Made from 4 carbon-based rings, comprises testosterone, oestrogen and vitamin-D, small hydrophobic molecule which sits in the middle of the phospholipid area, found in liver of animals, insoluble so good for energy storage.

87
Q

What are the three groups in an amino acid?

A

Carboxylic group, R group, amine group.

88
Q

What does the R group do?

A

Determines the different properties of an amino acid and represents the side chain.

89
Q

What is the bond created when a dipeptide is formed?

A

A peptide bond (covalent) which can only be broken down by an enzyme (protease).

90
Q

What are three examples of protease activity?

A

Digestion, hormone regulation, ageing.

91
Q

What is the primary structure?

A

Sequence of amino acids in a polypeptide chain, every protein has a unique primary structure, determines the function of each protein.

92
Q

What are the four levels of protein structure?

A

Primary, secondary, tertiary, quaternary.

93
Q

What do the linked amino acids that make up a polypeptide possess?

A

Both -NH and -C=O groups on either side of every peptide bond.

94
Q

What is the secondary structure?

A

The -NH and -C=O groups form hydrogen bonds which cause the peptide chains to be twisted into a 3D shape.

95
Q

What are the two different types of secondary structures?

A

α helix (coils) and β pleated sheets (folded).

96
Q

What are features of the alpha helix structure?

A

Right hand coil, hydrogen bonds between oxygen and hydrogen atoms, stabilises the protein.

97
Q

What are features of the beta helix structure?

A

Folded up on itself forming anti-parallel chains, hydrogen bonds formed between oxygen and hydrogen atoms, stabilises the protein.

98
Q

What is the tertiary structure?

A

Secondary structure twisted and folded to give complex, often unique 3D structure of each protein.

99
Q

Which bonds maintain the tertiary structure?

A

Disulfide bonds, ionic bonds, hydrogen bonds, hydrophobic and hydrophilic interactions.

100
Q

How do disulfide bonds maintain the tertiary structure?

A

Form between cysteine residues and help to stabilise the structure.

101
Q

How do ionic bonds maintain the tertiary structure?

A

Negatively charged R groups attracted to positively charged R groups.

102
Q

How do hydrogen bonds maintain the tertiary structure?

A

Slightly positively charged H atoms in some R groups bonded to slightly negatively charged O atoms in other R groups.

103
Q

How do hydrophobic and hydrophilic interactions maintain the tertiary structure?

A

Hydrophobic R groups clump together, so hydrophilic R groups are pushed to the outside.

104
Q

What is vital to each function of a protein?

A

Its tertiary structure (e.g. enzymes shape for active sites, hormone receptors shape for binding, collagen’s shape for strength).

105
Q

What is the quaternary structure?

A

Proteins made of more than one polypeptide chain.

106
Q

What are features of the quaternary structure?

A

May have an inorganic component, can’t function without all components.

107
Q

What are features of globular proteins?

A

Ball shaped, compact, hydrophobic amino acids turn inwards and hydrophilic interactions turn outwards making them water soluble, e.g. haemoglobin, insulin, pepsin.

108
Q

What are features of fibrous proteins?

A

Form fibres which give strength due to cross-links, unreactive, regular repetitive amino acid sequences which run parallel to each other, usually insoluble due to few hydrophilic gaps, e.g. collagen, keratin, elastin.

109
Q

What is the structure, function and use of collagen?

A

Structure: three long chains, lots of glycine, minerals bind to proteins, Function: strong, flexible, rigid when minerals added, Use: bones, cartilage, connective tissue, artery walls, tendons.

110
Q

What is the structure, function and use of keratin?

A

Structure: Lots of cysteine, number of disulfide bonds dictates flexibility, Function: can be tough or flexible, Use: hair, nails, skin, feathers.

111
Q

What is the structure, function and use of elastin?

A

Structure: lots of soluble tropelastin molecules cross-linked, Function: large, strong, stable, stretch and recoil, insoluble, Use: skin, bladder, lungs.

112
Q

What is the structure, function and use of haemoglobin?

A

Structure: 2 α globulin chains, 2 β globulin chains, conjugated protein, prosthetic group (haem), Function: specific shape, haem contains iron that oxygen bonds to, Use: transport.

113
Q

What is the structure, function and use of insulin?

A

Structure: α helix chain and β pleated chain joined by disulfide bridges, Function: soluble in water, specific shape, Use: binds to glycoprotein receptor to increase rate of glucose uptake.

114
Q

What is the structure, function and use of pepsin?

A

Structure: single polypeptide chain, symmetrical 3D structure, lots of H bonds, 2 disulfide bridges, 327 amino acids with acidic R groups, Function: specific shape, stable in stomach, Use: enzyme.

115
Q

What do calcium ions (Ca2+) do?

A

Bone formation, involved in transmission of nerve impulses and release of insulin from pancreas, co-factor for many enzymes.

116
Q

What do potassium ions (K+) do?

A

Important in generation of nerve impulses, muscle contraction, and regulating fluid balance in the body, activates essential enzymes in photosynthesis.

117
Q

What do sodium ions (Na+) do?

A

Important in generation of nerve impulses, muscle contraction, and regulating fluid balance in the body

118
Q

What do hydrogen ions (H+) do?

A

Affects pH of substances, important in photosynthesis reactions.

119
Q

What do ammonium ions ([NH4]+) do?

A

Important source of nitrogen used to make amino and nucleic acids.

120
Q

What do chloride ions (Cl-) do?

A

Co-factor for amylase, involved in chloride shift to help maintain pH.

121
Q

What do hydroxide ions (OH-) do?

A

Affects pH of a substance.

122
Q

What do nitrate ions ([NO3]-) do?

A

Important source of nitrogen used to make amino and nucleic acids.

123
Q

What do hydrogen carbonate ions ([HCO3]-) do?

A

Acts as buffer, maintains pH of blood.

124
Q

What do phosphate ions ([PO4]3-) do?

A

Involved in photosynthesis and respiration, needed in synthesis of many biological molecules.

125
Q

What is chromatography used for?

A

To separate components in a mixture, can be qualitative or quantitative.

126
Q

What is the stationary phase of chromatography?

A

A solid or a liquid supported on a solid, either chromatography paper or a TLC plate.

127
Q

What is the mobile phase of chromatography?

A

A liquid or a gas, either water (for polar molecules), or ethanol (for non-polar molecules).

128
Q

What is a TLC plate?

A

Thin layer chromatography plate, sheet of plastic or glass coated with silica gel of aluminium hydroxide.

129
Q

What do TLC plates and chromatography paper have in common?

A

Both have exposed -OH groups pointing outwards in contact with the mobile phase to make the surface very polar and allow molecules to form H bonds with it.

130
Q

How will different components move in chromatography?

A

At different rates, depends on solubility in the solvent and polarity.

131
Q

What will a highly polar substance do in chromatography?

A

Form less or no bonds and therefore move very quickly.

132
Q

How is the RF value calculated in chromatography?

A

Distance travelled by solute / distance travelled by solvent

133
Q

What is validity?

A

Whether the data answers the question being investigated?

134
Q

What things affect validity?

A

Control variables, sample size, starting temperature, taking accuracy into account.

135
Q

What is accuracy?

A

How close measurements or calculations are to the true value.

136
Q

What does the quality of results depend on?

A

How accurately you measure particular solutions or take down your data.

137
Q

What factors improve accuracy?

A

Use more intermediate values around the closest, use more sophisticated equipment to remove human error and obtain quantitative results, take samples at more regular intervals.

138
Q

What is precision?

A

How close the points are to each other (can be a random error).

139
Q

What factors improve precision?

A

Use correct apparatus and techniques, reduce error by using more sensitive equipment.

140
Q

What is a systematic error?

A

An error that is the same throughout the investigation.

141
Q

What is the consequence of a systematic error?

A

Results may still be precise, but not accurate.

142
Q

How can a systematic error be resolved?

A

If the cause of the systematic error is identified, repeat the experiment or use a correction factor.

143
Q

What is a random error?

A

An error that occurs when the procedure is not carried out in the same way each time it is performed.

144
Q

What is the consequence of a random error?

A

Some results will be affected but not all, may cause one or more anomalous result.

145
Q

How can a random error be resolved?

A

Remove anomalies and repeat data to find an average.

Biology (5 decks)

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