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A Level - Biology > 1: Biological Molecules > Flashcards

1: Biological Molecules Flashcards

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1
Q

What is a polymer?

A

Long chain of monomer sub-units

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2
Q

What is the transformation of a monomer to a polymer?

A

Polymerisation

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3
Q

What does the delta symbol mean?

A

Slightly

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4
Q

What is a dipolar molecule?

A

Means a molecule which has two different charged regions

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5
Q

Why is water dipolar?

A

As electrons are slightly closer to the oxygen

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6
Q

What are the charges on a water molecule?

A

Oxygen is slightly negative

Hydrogen atoms are slightly positive

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7
Q

What is a hydrogen bond?

A

Attraction between water molecules caused by attraction

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8
Q

How strong are hydrogen bonds?

A

Very weak

Many needed to make a difference

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9
Q

What is the general formula of monosaccharides?

A

(CH20)n

n= any number from 3-7

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10
Q

What are the features of monosaccharides?

A

Sweet
Small
Soluble
Crystals

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11
Q

What does the suffix -ose mean?

A

A sugar

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12
Q

Name some examples of monosaccharides

A

Glucose, galactose, and fructose

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13
Q

What are the two isomers of glucose?

A

Alpha and Beta Glucose

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14
Q

What is a hexose?

A

Sugars with 6 carbons

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15
Q

What is a steroisomer?

A

Different forms of the same isomers

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16
Q

What is the difference between alpha and beta glucose?

A

OH (hydroxide) on carbon 1 is downwards on the alpha glucose and vice versa on the beta glucose

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17
Q

What is the use of beta glucose?

A

Used in plant cells to create cellulose

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18
Q

What is the use of alpha glucose?

A

Used in animals to create glycogen

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19
Q

What are the features of disaccharides?

A

Small
Sweet
Soluble
Crystals

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20
Q

What is a disaccharide?

A

Two monosaccharides joined together

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21
Q

What reaction forms a disaccharides?

A

Condensation reaction

Creates a water molecule and glycosidic link

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22
Q

What is a glycosidic link?

A

Bond that is formed between two monosaccharides

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23
Q

a Glucose + a Glucose

A

Maltose

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24
Q

Glucose + Fructose

A

Sucrose

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25
Q

Glucose + Galactose

A

Lactose

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26
Q

Where is sucrose found?

A

Transported in plants

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27
Q

Where is lactose found?

A

Milk (lactose intolerance)

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28
Q

What reaction would split up a disaccharide and why?

A

Hydrolysis - as water is required to form both monosaccharides

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29
Q

What are the reducing sugars?

A

All monosaccharides and some disaccharides (maltose & lactose)

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30
Q

What is reduction?

A

Chemical reaction involving the gain of electrons

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31
Q

What is a reducing sugar?

A

Sugar that can donate electrons to another chemical

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32
Q

What chemical is used for the reducing sugar test?

A

Benedict’s Reagent (copper sulphate + alkaline solution)

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33
Q

What ions are relevant in the Benedict’s Reagent?

A

Copper 2+ ions

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34
Q

What happens to the Benedict’s Reagent in the reducing sugar experiment?

A

Forms an insoluble red precipitate (Cu2O)

if reducing sugar present

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35
Q

Give the step-by-step method of the test for reducing sugars

A

Add 2 cm2 of the sample to a test tube, and if not liquid grind it up in water
Add an equal volume of Benedict’s reagent
Heat the mixture in a gently boiling water bath for 5 minutes

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36
Q

Why is the colour of the reducing sugar test semi quantitative?

A

As it can be used to give a rough idea about the amount of sugar produced

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37
Q

What colours in the reducing sugar test show the most sugar present?

A

(most to least)

red, orange, yellow, green, blue

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38
Q

Name 2 ways to make the reducing sugar quantitative?

A

Colorimeter

Weighing dry mass of the precipitate

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39
Q

What is hydrolysis?

A

Addition of water that causes breakdown

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40
Q

Name a common non-reducing sugar

A

Disaccharides (Sucrose)

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41
Q

What is the non-reducing sugar test?

A

Breaking up disaccharides into monosaccharides (hydrolysis)

Then perform reducing sugar test

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42
Q

Give the step-by-step method of the test for non-reducing sugars

A

Perform reducing sugars test
If no colour change (blue), add 2 cm2 of fresh sample to 2cm2 of HCl and place in waterbath for 5 mins
Add NaHCO3 to solution until neutralised
Perform reducing sugar test on this sample

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43
Q

What is a positive result of a the non-reducing sugar test?

A

The solution will go orange-brown

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44
Q

Why is it necessary to add hydrochloric acid in the non-reducing sugar test?

A

Hydrolyses the disaccharide into both its constituent monosaccharides

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45
Q

Why is it necessary to add sodium hydrocarbonate in the non-reducing sugar test?

A

Neutralise the solution as Benedict’s doesn’t work in acidic conditions

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46
Q

What is a polysaccharide?

A

Polymers of many monosaccharide molecules joined by glycosidic bonds

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47
Q

What reaction forms polysaccharides?

A

Condensation reactions

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48
Q

What is the solubility of polysaccharides and why?

A

Insoluble as very large molecules

Therefore suitable for storage

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49
Q

What happens when polysaccharides are hydrolysed?

A

Breaks up into monosaccharides or disaccharides

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50
Q

What is the composition of starch?

A

Between 200 and 100 000 a-glucose molecules connected by glycosidic links

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51
Q

What is starch?

A

Polysaccharide used for energy storage
Found in starch grains in cytoplasm and chloroplasts
Can be branched and unbranched

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52
Q

What are the structures of starch?

A

Unbranched tight coil - very compact

Branched - quick hydrolysis

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53
Q

Why is starch suited for its role of energy storage?

A

Insoluble - doesn’t affect water potential
Large & insoluble - cannot diffuse out of a cell
Compact - can be stored in a small space
Made of a-glucose - easily transported & used in respiration
Branched form - many ends means enzymes can simultaneously release a-glucose

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54
Q

How easy is hydrolysis of starch?

A

Branched - Easy

Unbranched coils - Not as easy

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55
Q

What are two types of starch?

A

Amylose (unbranched)

Amylopectin (branched)

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56
Q

What are the digestive enzymes of starch?

A

Amylase

Maltase

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57
Q

What is the tensile strength of starch?

A

Low

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58
Q

What is the step-by-step test for starch?

A

2 cm2 of sample and add two drops of iodine
Shake or stir
Starch shown by solution going black-blue

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59
Q

Where is glycogen found?

A

Small granules in animals and bacteria, never in plants

Mainly in muscles and liver

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60
Q

What is the structure of glycogen?

A

Linear highly branched (shorter than starch)

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61
Q

What is the use of glycogen?

A

Carbohydrate storage in animals

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62
Q

Why is the mass of carbohydrate storage in animals small?

A

Fat is the main energy storage in animals

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63
Q

Why is the structure of glycogen suited to energy storage?

A

Insoluble - doesn’t affect water potential
Large & insoluble - cannot diffuse out of a cell
Compact - can be stored in a small space
More highly branched - many ends means enzymes can break it down faster

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64
Q

Why is highly branched glycogen useful?

A

Means glucose can be released faster for respiration

Important as animals with high metabolic & respiratory rate so its needed

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65
Q

What is the monomerof cellulose?

A

B-glucose

Every other molecule is flipped which allows the glycosidic link to form

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66
Q

What is the structure of cellulose?

A

Straight unbranched chains

They run parallel and form many hydrogen bonds

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67
Q

What is the use of cellulose?

A

Main component of cell wall

Groups of them form microfibrils, and groups of these in parallel form fibres

68
Q

What is the function of the cellulose cell wall?

A

Provides rigidity
Prevents bursting from osmosis - exerts inwards pressure
Cells therefore turgid and form a semi-rigid structure

69
Q

In which plant cells are strong cell walls important?

A

Stems and leaves (max SA for photosynthesis)

70
Q

Why is cellulose suited for its role?

A

Made of “flipped”B-glucose - forms unbranched chains
Chains are parallel - hydrogen bonds can form
Fibers and microfibrils - provide more strength
Insoluble - doesn’t affect water potential

71
Q

What is the digestive enzyme of cellulose?

A

Cellulase

Not found in humans

72
Q

Are hydrogen bonds important in cellulose?

A

Yes

Although one isn’t very strong, the sheer number makes a difference

73
Q

What are the characteristics of lipids?

A

Made of Hydrogen, Carbon, Oxygen
Insoluble in water
Proportion of oxygen to carbon & hydrogen is smaller than in carbohydrates
Soluble in organic solvents (alcohols)

74
Q

What are the two types of lipids?

A

Tryglycerides and phospholipids

75
Q

Name some roles of lipids

A 
Cell membrane
Source of energy
Waterproofing
Insulation
Protection
76
Q

Why is a lipid suited to be a source of energy?

A

When oxidised it provides more than 2x the energy compared to the same mass of carbohydrates
Releases water

77
Q

Why is a lipid suited to do waterproofing?

A

Insoluble in water

Plants have waxy cuticles, mammals have oily secretion from glands in the skin

78
Q

Why is a lipid suited to insulation?

A

Slow conductor of heat

Acts as electrical insulator in myelin sheath around nerve cells

79
Q

What state are lipids?

A

Fats are solid at room temp. whereas oils are liquids

80
Q

What is the structure of triglycerides?

A

Glycerol bonded to three fatty acids

81
Q

What type of bonding is present in lipids?

A

Ester bonds - formed by 3 condensation reactions

82
Q

What causes variation in properties in triglycerides?

A

Fatty acid groups - all with carboxylic acid (COOH) group at the end
Over 70 different

83
Q

What does an unsaturated or saturated fatty acid mean?

A

Saturated - all c-c bonds are single (holding max number of hydrogen)
Mono/poly unsaturated - one/many c-c bonds are double

84
Q

What is the state of saturated and unsaturated lipids?

A

Saturated fats- straight chains so they pack closely and therefore are solids
Unsaturated oils - chains have kinks due to double bonds therefore are liquids

85
Q

Why are triglycerides suited for energy storage?

A

High ratio of c-h energy storing bonds to c atoms
Low mass to energy ratio - animal doesn’t have to waste energy on carrying heavier store
Large and non-polar - insoluble, no affect on water potential
High ratio of hydrogen to oxygen - release water when oxidesed, important for desert animals

86
Q

What is the structure of a phospholipid?

A

Glycerol
Two fatty acids
One phosphate group

87
Q

What is the solubility of phospholipids ?

A

Hydrophillic phosphate “head” - attracted to water

Hydrophobic fatty acid “tails”

88
Q

What does the polar nature of phospholipids cause?

A

Bilayers which is the basis of membranes

Hydrophobic barrier formed between inside and outside of cell

89
Q

What do phospholipids do in water?

A

Hydrophillic head tries to get as close to water

Hydrophobic tails tries to get as far away as possible

90
Q

What can an interaction between a carbohydrate and a phospholipid?

A

Glycolipid can be formed

Used for cell recognition

91
Q

What is the name of the test for lipids?

A

Emulsion test

92
Q

Give the step-by-step test for lipids

A

2 cm3 of sample in a dry and clean test tube with 5 cm3 of ethanol
Shake thoroughly to dissolve lipid
Add 5 cm3 of water and shake gently
Cloudy-white coloured emulsion indicates lipid

93
Q

Give the step-by-step test for proteins

A

Add sample to test tube with equal volume of sodium hydroxide
Add a few drops of very dilute copper (II) sulphate solution (biuret solution)
Purple indicates presence of peptide bonds

94
Q

What is the size of proteins?

A

Very large molecules

95
Q

What elements are in proteins?

A

Carbon, oxygen, hydrogen, nitrogen

96
Q

What is the monomer and polymer called of a protein?

A

Amino acids

Polypeptides

97
Q

How many amino acids have been identified?

A

100 amino acids

20 naturally occurring

98
Q

What does 20 naturally occurring amino acids suggest?

A

Indirect evidence for evolution

99
Q

What are the four parts of amino acid?

A 
Amino group (NH2)
Carboxyl group (COOH)
Hydrogen atom (H)
R group (different chemical)
100
Q

What reaction joins amino acids?

A

Condensation reaction forms peptide bond

101
Q

Where is a peptide bond?

A

Between the carboxyl group of one and a amino group is another

102
Q

How can a peptide bond be broken?

A

Hydrolysis

103
Q

What is the primary structure of proteins?

A

Polypeptide chain
Many different possible sequences
Simple protein

104
Q

What are the two secondary protein structures?

A

Alpha helix

Beta pleat

105
Q

What does protein structure determine?

A

Protein function

106
Q

Why do proteins form alpha helix?

A

H of NH group is positive and O of CO is negative

Causes hydrogen bonds which cause alpha helix

107
Q

What forms between beta pleats?

A

Hydrogen bonding

108
Q

How can tertiary protein structure be described?

A

Globular like structure

Formed by twisting and folding secondary

109
Q

What bonds are found in tertiary protein structure?

A

Disulphide bridges - quite strong, not easily broken
Ionic bonds - between carboxyl and amino acids, weak adn broken by pH change
Hydrogen bonds - numerous but easily broken

110
Q

What is the solubility of globular proteins?

A

Soluble

111
Q

What is a prosthetic group?

A

Non-protein structure

Found in Quaternary structure

112
Q

Name a prosthetic group

A

Myoglobin has a haem prosthetic

113
Q

What is the Quaternary structure?

A

Two or more interlinked globular proteins

114
Q

What type of proteins are enzymes?

A

Globular tertiary proteins

115
Q

What is a catalyst?

A

Something that alters the rate of a chemical reaction without undergoing permanent changes

116
Q

What is activation energy?

A

The minimum amount of energy required to active a reaction

117
Q

How do enzymes affect activation energy?

A

Lowers activation energy by forming an enzyme-substrate complex

118
Q

What is an intra-cellular enzyme?

A

Works inside the cell

DNA

119
Q

What is an extracellular enzyme?

A

Secreted by cells and words outside

Pepsin, amylase

120
Q

What is the suffix typically associated with enzymes?

A

-ase

121
Q

What is a catabolic reaction?

A

Larger molecules broken helped by active sites affecting bonds

122
Q

What is an anabolic reaction?

A

Enzymes bring substrate molecules together

123
Q

What does the lock-and-key hypothesis suggest?

A

The enzyme and substrate molecules fit together exactly like a lock and key

124
Q

What is the problem with the lock-and-key hypothesis?

A

It suggests the active site is rigid

However crystallographic studies indicates proteins are flexible

125
Q

What is the induced-fit hypothesis?

A

The active site only assumes catalytic confirmation (shape) after the substrate molecule binds to the site

126
Q

What happens if the incorrect molecule binds to an enzyme?

A

Will bind but causes no conformational change

No reaction occurs

127
Q

What happens to the active site after a substrate is broken down?

A

Reverts to inactive state

128
Q

What is a substrate?

A

A molecule which an enzyme acts on

129
Q

How do enzymes lower activation energy?

A

Strains the bonds in the substrate

130
Q

What two things must occur for an enzyme to work?

A

Come into physical contact with substrate

Have an active site which fits the substrate

131
Q

How do you measure the rate of reaction of enzymes?

A

Formation of products

Disappearance of substrate

132
Q

What is the turnover number?

A

Number of substrate molecules transformed / minute by one enzyme

133
Q

Describe the rate of reaction vs enzyme concentration graph?

A

As enzyme conc. increases the rate of reaction increases

Until a point when it plateaus, when the rate of reaction doesn’t change as conc. increases

134
Q

Explain the start of the rate of reaction vs enzyme concentration graph?

A

Enzyme is the limiting factor
Substrate molecules outnumber enzymes
Adding more enzymes adds more active sites

135
Q

Explain the latter part of the rate of reaction vs enzyme concentration graph?

A

Substrate is limiting factor
Adding more enzymes doesn’t affect reaction
Adding more substrate makes more ESC

136
Q

How can you calculate the change in rate of reaction?

A

Calculate gradient of a graph of product produced or substrate disappearance

137
Q

How can the rate of reaction graph vs substrate reaction be described?

A

As substrate conc. increases the rate of reaction increases

Until a point when it plateaus, when the rate of reaction doesn’t change as conc. increases

138
Q

How can the rate of reaction graph vs substrate reaction be explained?

A 
Same as enzyme concentration
Except reversed (at first substrate is limiting factor, then enzyme)
139
Q

What is denaturation?

A

Permanent change whereby an enzyme can no longer function

140
Q

What is pH?

A

A measure of the number of H+ ions present in a solution

141
Q

What is the mathematical process behind working out pH?

A

-log10(H+)

E.g 0.1M = pH1

142
Q

How do enzymes perform in varying pH?

A

Only work in a narrow range of pH

Have an optimum pH which their rate is fastest

143
Q

How do H+ ions denature enzymes?

A

Charges on the active site

Disrupts hydrogen and ionic bonds

144
Q

How does changing the charge of the active site denature the enzyme?

A

H+ ions reversed the charge of the active site

Substrate can no longer bind to the AS and ESC can’t form

145
Q

How does disrupting bonds in the enzyme denature the enzyme?

A

Hydrogen and ionic bonds which keeps 3D structure is disrupted
Shape of AS is lost and no ESC can form

146
Q

Describe the temp. vs enzyme activity graph

A

Increases steadily as temp. increases

Until optimum, after which is denatured. Then as temp. increases it decreases quickly

147
Q

Explain the gradual increase in enzyme activity as temperature increases

A

Increases kinetic energy of molecules
Moves more rapidly and and collisions more often between enzyme and substrate
More ESC form

148
Q

Explain the dramatic decrease in enzyme activity as temperature increases past a point

A

High kinetic energy means atoms within enzyme vibrate
Causes weak hydrogen bonds to break
Loses tertiary structure and AS lost, no ESC can form

149
Q

What is the temperature coefficient (Q10)?

A

Rate of change of a reaction when the temp is increased by 10C
(rate doubles every 10C rise in temp.)

150
Q

What is the equation of Q10?

A

Rate of reaction at (x+10) / rate of reaction at x

151
Q

What is an inhibitor?

A

A chemical which inhibits enzyme activity

152
Q

What are the two types of inhibitors?

A

Competitive and non-competitive

153
Q

How do competitive inhibitors work?

A

Same shape as substrate
Binds to enzyme but causes no change in shape
Not broken down
Therefore enzyme not breaking down substrate so slows rate of reaction

154
Q

How can you overcome the effect of competitive inhibitors?

A

Try to remove inhibitor from solution

Increase concentration of substrate

155
Q

Explain why competitive inhibitors can be overcome

A

Increasing conc. of substrate increases the likelihood that ESC will form

156
Q

What will the graph of rate of reaction vs substrate conc. look like with competitive inhibitors?

A

Reaches same plateau but takes longer to get there

less steep curve

157
Q

How do non-competitive inhibitors work?

A

Binds to allosteric site
Changes shape of AS
No ESC can form

158
Q

Why do non-competitive inhibitors support the induced fit hypothesis?

A

Suggests that the AS is somewhat flexible

159
Q

Is an inhibitor permanent?

A

Can be reversible or irreversible

160
Q

What is the effective change to an enzyme from a irreversible non-competitive enzyme?

A

Denaturation

161
Q

Can non-competitive inhibition be overcome?

A

No

Unless make the inhibitor disassociate

162
Q

What will the graph of rate of reaction vs substrate conc. look like with non-competitive inhibitors?

A

Plateaus lower

Takes longer to get there

163
Q

What chemical process is associated with gout?

A

Xanthine -> uric acid
Uses enzyme xanthine oxidase
Uric acid causes gout

164
Q

What chemical is used to treat gout and why?

A

Allopurinol
Acts as a competitive inhibitor
Less uric acid produced

165
Q

What is a metabolic pathway?

A

Series of chemical reactions converting substrate into end products using enzymes

166
Q

What is end-product inhibition?

A

The final product of a metabolic pathway inhibits one of the enzymes
Non-competitive

A Level - Biology (22 decks)

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