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OCR A level Biology > 2.1.2 - Biological Molecules > Flashcards

2.1.2 - Biological Molecules Flashcards

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1
Q

Definition of carbohydrate

A

Group of substances used as both an energy source and structural material

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2
Q

General formula of carbohydrates

A

Cx(H2)y

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3
Q

3 main groups of simple carbohydrates

A

Monosaccharide
Disaccharide
Polysaccharide

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4
Q

Key facts about glucose

A

Abundant and very important
Major energy source
Highly soluble and main form of carbohydrates transported in animals

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5
Q

Why is glucose a hexose sugar

A

It has 6 carbon atoms

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6
Q

What does glucose exist as

A

Structural isomers

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7
Q

Common isomers of glucose

A

Alpha glucose

Beta glucose

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8
Q

What is the difference between the isomers of glucose

A

The OH is below the first carbon in the structure of alpha glucose whereas it is above the first carbon in the structure of beta glucose

Minor structural difference has a major effect on roles of alpha and beta glucose

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9
Q

Key points about fructose

A

Fructose is very soluble and the main sugar in fruits

It is much sweeter than glucose

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10
Q

Key points about galactose

A

It is not as soluble as glucose and fructose

It is important in making glycolipids and glycoproteins

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11
Q

Important pentoses

A

Ribose

Deoxyribose

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12
Q

What is the difference in the structures of ribose and deoxyribose

A

Ribose has a H above the second carbon and an OH below

Deoxyribose has only a H above and below the second carbon

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13
Q

What does the prefix ‘glyco’ tell us

A

It has something to do with carbohydrates

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14
Q

Condensation reaction

A

Attaching two monosaccharides by the formation of a glycosidic bond to produce a disaccharide and water

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15
Q

Hydrolysis reaction

A

Breaking the glycosidic bond in a disaccharide with the addition of water

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16
Q

Maltose

A

Glucose and Glucose

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17
Q

How is maltose joined

A

By an alpha 1-4 glycosidic bond

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18
Q

Sucrose

A

Fructose and Glucose

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19
Q

How is sucrose joined

A

By an alpha 1-4 glycosidic bond

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20
Q

Lactose

A

Galactose and Glucose

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21
Q

How is lactose joined

A

By an beta 1-4 glycosidic bond

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22
Q

Are monosaccharides reducing or not

A

Reducing

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23
Q

Heterogeneous

A

Composed of different types

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24
Q

Macromolecules

A

Molecules consisting of large numbers of atoms

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25
Q

Metabolism

A

All the chemical reactions that occur in cells

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26
Q

Monosaccharide

A

A sweet-tasting molecule consisting of a single unit

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27
Q

Nucleic acid

A

A kind of acid abundant in the nuclei of cells, includes DNA and RNA

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28
Q

What makes up organic compounds

A

Carbon and hydrogen

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29
Q

What are the four categories of macromolecules

A

Lipids
Proteins
Nucleic acids
Carbohydrates

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30
Q

What is a monomer

A

Small building blocks that make up biological molecules

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31
Q

Why are lipids important

A

Make up all of the cell membranes
Great source of energy
They don’t have a single type of monomer

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32
Q

Are lipids polar or unpolar

A

Polar

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33
Q

What are nucleic acid monomers

A

RNA

DNA

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34
Q

What are nucleic acid monomers made of

A

Nucleotides

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35
Q

What are the functions of nucleic acids

A

Carry genetic material

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36
Q

What differentiates amino acids

A

Their ‘R’ group

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37
Q

What are carbohydrate monomers

A

Sugars

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38
Q

Dehydration synthesis

A

The process of putting monomers together where water is lost and peptide bonds are formed between amino acids

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39
Q

Hydrolysis

A

Splitting apart polymers using water

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40
Q

What are the three parts of a nucleotide

A

Phosphate
5-carbon sugar (pentose)
Base

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41
Q

Differences between DNA and RNA

A

They have different bases and DNA has a double helix

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42
Q

4 nucleotides in DNA

A

Cytosine
Guanine
Adenine
Thymine

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43
Q

4 nucleotides in RNA

A

Cytosine
Guanine
Adenine
Uracil

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44
Q

What makes DNA anti parallel

A

The helixes run in different directions

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45
Q

How many amino acids are there

A

20

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46
Q

What determines the directionality of a protein

A

Carboxyl side

Amino side

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47
Q

Different types of lipids

A

Cholesterol
Free fatty acid
Triglyceride
Phospholid

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48
Q

What is the similar structure between all the lipids

A

Hydrocarbon tails

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49
Q

What is significant about hydrocarbons found in lipids

A

They’re non polar

A huge amount of energy can be released

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50
Q

What is unique about phospholids

A

It has a non polar and polar portion

Can form bilayers or micelles

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51
Q

What does amphipathic mean

A

It has a charged polar portion

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52
Q

What is the difference between saturated and unsaturated fatty acids

A

Unsaturated fats bend because they have a double bond

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53
Q

What determines the directionality in carbohydrates

A

Where the bond comes off

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54
Q

Amylose

A 
Form of starch
Found as granules in cells
Alpha 1-4 glycosidic bond only 
Compact helical structure 
Unbranched chains
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55
Q

Amylopectin

A

Form of starch
Found as granules in cells
Glucose molecules joined by alpha 1-4 glycosidic bonds and alpha 1-6 glycosidic bonds
Branches and cannot form a helix

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56
Q

What is the percentage composition of starch

A

Amylopectin - 70-80%

Amylose - 20-30%

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57
Q

How is starch stored in plants

A

In plastids

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58
Q

Plastids

A

Intracellular starch grains in organelles

Made from green chloroplasts and colourless amyloplasts

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59
Q

What does cellulose stop

A

Cells from bursting

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60
Q

Structure of cellulose

A

Beta glucose joined by beta 1-4 glycosidic bonds
H bonds between chains
Can form micro and macofibrils

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61
Q

Microfibrils

A

Glucose in a rope like form which are then layered in a network

62
Q

What is special about formation of cellulose

A

Every other glucose molecule molecule rotates 180 so that the hydroxyl groups are adjacent

63
Q

What gives cellulose great tensile strength

A

Hydrogen bonds

They are very weak on their own but strong in large numbers

64
Q

Glycogen compared to starch

A

Less dense
More soluble
Broken down more rapidly as ends are exposed
Both insoluble

65
Q

Structure of glycogen

A

Similar structure to amylopectin but it’s more branched

66
Q

Why don’t animals store starch

A

They store glycogen instead

67
Q

What molecule is produced in the condensation of nucleotides

A

DNA

68
Q

What molecule is produced in the hydrolysis of DNA

A

Nucleotides

69
Q

What molecule is produced in the condensation of amino acids

A

Protein

70
Q

What molecule is produced in the condensation of fructose and glucose

A

Sucrose

71
Q

What molecule is produced in the condensation of glycerol and fatty acid

A

Lipids

72
Q

What molecule is produced in the hydrolysis of protein

A

Amino acids

73
Q

What molecules are produced in the hydrolysis of sucrose

A

Fructose and glucose

74
Q

What molecules are produced in the hydrolysis of lipids

A

Glycerol and fatty acids

75
Q

What are the chemical elements that make up carbohydrates

A

Carbon
Hydrogen
Oxygen

76
Q

What are the chemical elements that make up lipids

A

Carbon
Hydrogen
Oxygen

77
Q

What are the chemical elements that make up proteins

A 
Carbon 
Hydrogen
Oxygen 
Nitrogen 
Sulfur
78
Q

What are the chemical elements that make up nucleic acids

A 
Carbon 
Hydrogen 
Oxygen 
Nitrogen
Phosphorous
79
Q

What type of links are formed in the synthesis of lipids

A

Ester links are formed by condensation between the alcohol groups on a glycerol molecule and three fatty acids

80
Q

What happens as a result of water’s polarity

A

Adjacent water molecules are attracted to and become bonded to each other

81
Q

How are hydrogen bonds formed

A

The slight positive charge of a hydrogen atom of one molecule is attached to the slight negative charge of an adjacent oxygen atom

82
Q

Functions of water

A

Transport
Chemical reactions (metabolism)
Temperature control - high latent heat of evaporation (stable environment for aquatic org.)
Support
Efficient transport medium - cohesion and adhesion
Reproduction

83
Q

Transport as a function of water

A

Transpiration stream and water-based movement of sugars and amino acids, hormones etc. in phloem occurs in solution
Many essential metabolites dissolve completely

84
Q

What is the transpiration stream held together by

A

Cohesion

Adhesion

85
Q

Cohesion

A

Water molecules hydrogen bond to other molecules

86
Q

Adhesion

A

Water molecules bind to the side of xylem vessel

87
Q

Chemical reactions as a function of water

A

Combination of thermal stability and excellent solvent properties make water and ideal environment for chemical reactions

Water acts as a reactant for:

1) . Light dependent stage in photosynthesis
2) . Hydrolytic reactions

88
Q

Support as a function of water

A

In plant cells water offers turgidity
In animals, water-filled tissues also contribute to skeletal support
For aquatic organisms, water provided support through buoyancy

89
Q

Reproduction as a function of water

A

Water brings the male and female gametes together in fertilisation
Foetus develops in water filled sac

90
Q

Test for starch

A

Iodine dissolved in KI turns from brown/orange to blue/black

91
Q

Test for reducing sugars (all mono, maltose and lactose)

A

Benedict’s test
Add Bendicts reagent
Heat solution in water bath > 80 degrees for 5 mins
Solution turns from blue to green/ yellow/ orange/ brown or brick-red suspension

92
Q

Test for proteins

A

Biurets test
Add NaOH
Add copper (II) sulphate solution
Solution turns from blue to purple if protein’s present

93
Q

Test for lipids

A

Emulsion test
Add water and shake
Add ethanol to dissolve lipid
A white emulsion/ band floating near or at the top in the presence of lipids

94
Q

Properties of water influenced by its polar nature

A

Solvent properties
Thermal properties
Cohesion tension
Specific heat capacity

95
Q

Types of lipids

A

Triglycerides
Phospholipids
Saturated and unsaturated fatty acid

96
Q

What chemical elements make up lipids

A

Carbon
Hydrogen
Oxygen

97
Q

Components of a triglyceride

A

1 glycerol molecule and 3 fatty acid chains attached by Ester bonds

98
Q

What are triglycerides known as

A

True fats or neutral fats

99
Q

Characteristics of triglycerides

A

Rich in energy and used to store energy
Good insulators and provide buoyancy
Can be broken down in aerobic respiration and water is released

100
Q

Saturated fats

A 
Solid at room temp
Only single bonds 
Have a lot of hydrogen 
Found in animals 
Higher melting point
101
Q

Unsaturated fats

A 
Liquid at room temp 
Double carbon bonds 
Bent (linked) 
Found in plants 
Lower melting point
102
Q

Function of lipids in the body

A 
Energy store
Thermal insulation 
Repel water 
Shock absorbent 
Buoyant 
Waterproof
103
Q

How do phospholipids differ in their structure from triglycerides

A

Phosphate group replaces one fatty acid

104
Q

Why are lipids useful storage molecules

A

Insoluble molecules

High energy yield (2x as much as carbohydrates)

105
Q

What factors do substances need to have to be ‘transport’ carbohydrates

A

Small
Soluble
Not reactive

106
Q

What causes the colour change in the Benedict’s test

A

The copper is reduced by the reducing sugars to form ions

107
Q

Why can’t humans digest all polysaccharides

A

We do not possess the appropriate enzymes

108
Q

How to reverse condensation reactions

A

Hydrolysis reactions

Adding acid

109
Q

Functions of proteins

A 
Signalling 
Catalysis 
Structure and movement 
Defence and survival 
Transport
110
Q

How do plants make amino acids

A

From photosynthesis and nitrate/mmonium

111
Q

How many amino acids do human need

A

Twenty but we cannot make any of the 8/10 essential and 12/10 non essential amino acids

112
Q

Why is the R group important

A

The Residual group is the only thing that differs in amino acids

113
Q

Formation of peptide bond

A

Water is removed (condensation reaction)

Peptide bond is formed (covalent C-N bond)

114
Q

Dipeptide

A

2 amino acids

115
Q

Polypeptide/ protein

A

Many amino acids

116
Q

Primary structure of proteins

A

Subunits held together by peptide bonds

Order determined by base sequences in DNA

117
Q

Secondary structure of proteins

A

Folding or coiling of polypeptide chains for stabilisation

Hydrogen bonds cause polypeptide to coil into alpha helix or fold into beta sheets

118
Q

What breaks hydrogen bonds

A

High temperature

pH change

119
Q

How does a breakage of bonds affect the protein

A

It affects the shape and function

120
Q

Tertiary structure of proteins

A

The secondary structure is folded into a more complex 3D shape

121
Q

What is the tertiary structure stabilised by

A

Disulphide bonds between sulfur containing R groups
Ionic bonds between R groups
Hydrogen bonds between polar R groups
Hydrophobic/ hydrophilic interaction

122
Q

Quaternary structure of proteins

A

Made up from multi sub-unit proteins
Held together by same bonds in 3’
Most proteins only have one polypeptide chain and so no quaternary structure

123
Q

Globular proteins

A

Spherical and usually soluble
Hydrophobic R groups in centre, hydrophilic R groups point outside
Activity in metabolism relies on 3D shape
Shape and activity sensitive to high temp.

124
Q

Why is haemoglobin a conjugated protein

A

It has a prosthetic group

125
Q

What is a prosthetic group in a protein

A

An attachment not made from protein e.g. Haem

126
Q

Structure of haemoglobin

A

All 4 polypeptide chains are attached to a haem group

127
Q

What ions do haem contain

A

Fe 2+ ions and they bond with O2

128
Q

Sub units of haemoglobin

A

2 alpha chains
2 beta chains
4 haem groups

129
Q

Amylase

A

Alpha helix and beta sheets
Globular shape has an complementary active site
Active site holds Cl- (co-factor - essential for correct action)

130
Q

Insulin

A

2 polypeptides held together by disulphide bridges
Globular protein w/ spp, fixed shape
Specific 3D shape complementary to glycoproteins receptor

131
Q

Fibrous proteins

A

Form long strands and usually insoluble
Have structural roles in the body
Regular sequence of amino acids
Unreactive

132
Q

Collagen

A

3 polypeptide chains wound around each other
Fibrous protein that is flexible but does not strech
Not easily stretched
Found in walls of arteries and tendons

133
Q

Keratin

A

2 coiled polypeptide chains containing sulfur
Protect delicate things e.g. nails,claws, hair, feathers, hooves
Found in outer layers of skin cells (permeability)

134
Q

Elastin

A

Linking tropelastin fibres
Coiled and can be stretched and recoiled
Used where stretching is required e.g. alveoli, walls of arteries, airways, bladder

135
Q

Test for non reducing sugars (sucrose)

A

Add HCl to sample whilst heating iin a water bath > 80 degrees (to hydrolyse sample)
Add NaOH (to neutralise sample)
Then conduct test for reducing sugars

136
Q

Where are peptide bonds formed

A

Between the hydroxide from the amine group and the H from the carboxyl group

137
Q

What happens when proteins are over heated

A 
Increased kinetic energy 
Molecule vibrates 
H bonds break 
Change in 3’ structure 
Denatures
138
Q

What is thin layer chromatography used for

A

Separation of proteins, carbs, vitamins or nucleic acids

139
Q

Starch + amylase —>

A

Maltose

140
Q

Properties of water useful to living things

A

Strong cohesive forces between water molecules at the water surface mean that it is a good medium for support
H bonds attract water molecules to each other but are weak so that water molecules can move easily in relation to one another

141
Q

Test for reducing sugars if using a solid

A

Crush the solid w/ water
Filter out the solid
Continue test as normal

142
Q

Compare conc. of reducing sugars

A

Filter sol. and weigh ppt. formed, the heaver the ppt, the more conc.
Compare colours after benedict’s test - less accurate

143
Q

Colorimetry - to find unknown glucose sol.

A

Make up several sol. of KNOWN glucose conc. (serial dilution)
Carry out Benedicts’s test - same vol. of reagent
Remove any ppt
Using colorimeter measure absorbance
Plot calibration curve , with glucose conc. on x and absorbance on y

144
Q

How to use a colorimeter

A

Set up w/ red filter - no effect w/ blue
Add distilled water to cuvette to calibrate colorimeter- light should pass through clear side
Use a pippette to transfer each solution of sol. of known glucose conc into seperate cuvettes
Measure absorbance for each

145
Q

Glucose bisensors

A

Determines conc of glucose in a solution
Glucose oxidase immobilised to electrodes, binds to and catalyses oxidation of glucose
Creates a charge which is then converted by a transducer
The electrical signal is then processed to work out the glucose conc.

146
Q

Mobile phase in chromatography

A

Where the molecules can move
Solvent (ethanol) in bother paper and TLC
The more time spent here the faster/ further up the stationary phase

147
Q

Stationary phase in chromatography

A

Where the molecules can’t move

Paper in paper chromatography or silica gel on a glass plate in TLC

148
Q

Structure of cholesterol

A

Sterol
4 carbon rings w/ hydroxyl group
Hydroxyl group is polar o rest of molecule is hydrophobic

149
Q

Biological roles of lipids due to their non polar nature

A

Membrane formation and the creation of hydrophobic barrier
Hormone production
Electrical insulation (nerves)
Waterproofing

150
Q

Separating amino acids w TLC

A

Follow normal TLC procedure but after silica gel plate has been allowed to dry, spray w/ ninhydrin spray to give a purple/brown colour

151
Q

Catalase

A

4’ protein w 4 haem groups

Fe2+ speeds up the breakdown of H2O2 - common by-product of metabolism but dangerous if accumulates

OCR A level Biology (25 decks)

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