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Y1 AQA Biology - Burnley College (2024-25) > Biological Molecules 3.1 > Flashcards

Biological Molecules 3.1 Flashcards

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1
Q

Carbohydrates AO1

Test for starch

A

1. Add (two drops of) iodine solution to the sample solution.

2. A blue/black/purple colour indicates the presence of starch.

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2
Q

Monomers & Polymers AO1

Define a monomer (1 mark)

A

Small repeating units from which larger molecules called polymers are made

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3
Q

Monomers & Polymers AO1

Define a polymer (1 mark)

A

Molecules made from a large number of monomers (3 or more) joined together

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4
Q

Monomers & Polymers AO1

Give 3 examples of monomers

A

Glucose / Galactose / Fructose
Nucleotides
Amino acids

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5
Q

Monomers & Polymers AO1

Give 3 examples of polymers

A

Starch
Glycogen
Cellulose
DNA
RNA
Proteins / Polypeptides

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6
Q

Monomers & Polymers AO1

Which of the below molecules is NOT a polymer?

Glycogen
Triglyceride
Cellulose
Starch
DNA
Polypeptides/proteins

A

Triglyceride

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7
Q

Monomers & Polymers AO1

Molecules with carbon-carbon and carbon-hydrogen bonds are referred to as ……………………

A

Organic molecules

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8
Q

Monomers & Polymers AO1

What type of reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water (H2O)?

A

Condensation

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9
Q

Monomers & Polymers AO1

Hydrolysis reaction

A

Breaks a chemical bond between two molecules & involves the use of a water molecule (H2O).

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10
Q

Monomers & Polymers AO1

If 2 monomers are joined together via condensation reaction, how many molecules of water form?

A

1 molecule of water

For every bond formed, a condensation reaction produces one molecule of water.

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11
Q

Monomers & Polymers AO1

If 3 monomers are joined together via condensation reactions, how many molecules of water form?

A

2 molecules of water

For every bond formed, a condensation reaction produces one molecule of water.

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12
Q

Monomers & Polymers AO1

TRUE or FALSE:
Enzymes are required to catalyse the formation of bonds via condensation reactions

A

TRUE

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13
Q

Monomers & Polymers AO1

TRUE or FALSE:
Enzymes are required to catalyse the breaking of bonds via hydrolysis reactions

A

TRUE

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14
Q

Carbohydrates AO1

Monomers which form polysaccharides

A

Monosaccharides

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15
Q

Carbohydrates AO1

Common monosaccharides

A

(alpha & beta) glucose,
galactose,
fructose

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16
Q

Carbohydrates AO1

Which isomer of glucose?

A

Alpha glucose

Remember: Alpha Below Beta Above (ABBA) on C1

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17
Q

Carbohydrates AO1

Which isomer of glucose?

A

Beta glucose

Remember: Alpha Below Beta Above (ABBA) on C1

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18
Q

Carbohydrates AO1

Draw out the full chemical structure of alpha glucose

A

Remember: Alpha Below Beta Above (ABBA) on C1

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19
Q

Carbohydrates AO1

What bond is formed as result of a condensation reaction between two monosaccharides?

A

Glycosidic bond

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20
Q

Carbohydrates AO1

What disaccharide is formed by condensation reaction with two glucose molecules?

A

Maltose

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21
Q

Carbohydrates AO1

What monosaccharides are joined by a condensation reaction to form lactose?

A

Glucose

Galactose

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22
Q

Carbohydrates AO1

What disaccharide is formed by condensation reaction with glucose and fructose?

A

Sucrose

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23
Q

Carbohydrates AO1

TRUE or FALSE:

Many glycosidic bonds are found in a disaccharide?

A

FALSE

There is only 1 glycosidic bond in a disaccharide

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24
Q

Carbohydrates AO1

Draw out the formation of a glycosidic bond between two alpha glucose molecules

A
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25
Q

Carbohydrates AO1

Write out a chemical equation for the formation of a disaccharide (1 mark)

A

For every bond formed, a condensation reaction produces one molecule of water.

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26
Q

Carbohydrates AO2

A

Carbon = 18

Hydrogen = 32

Oxygen = 16

Two glycosidic bonds formed, so two molecules of water produced

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27
Q

Carbohydrates AO1

Polymer formed by the condensation of many glucose units

A

Polysaccharides

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28
Q

Carbohydrates AO1

Polysaccharides formed by condensation of α-glucose

A

Glycogen

Starch

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29
Q

Carbohydrates AO1

Polysaccharide formed by condensation of many β-glucose units

A

Cellulose

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30
Q

Carbohydrates AO1

Location of glycogen in animals

A

Liver

Muscle

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31
Q

Carbohydrates AO1

Explain how starch is related to its function (3 marks)

A

Any three from:

  1. Insoluble (in water), so doesn’t affect water potential/osmosis;
  2. Coiled / (α-)helix / helical structure, so makes molecule compact;
  3. Polymer of (α-)glucose so provides glucose for respiration;
  4. Branched / more ends for fast breakdown / enzyme action;
  5. Large (molecule), so can’t cross the cell membrane
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32
Q

Carbohydrates AO1

Bonds contained in cellulose

A

Beta (1,4) glycosidic

(many weak) Hydrogen

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33
Q

Carbohydrates AO1

Explain how the structure of cellulose is related to its function in plant cell walls (3-4 marks)

A
  1. Long / straight / unbranched chains of beta glucose
  2. (joined by weak) hydrogen bonds;
  3. Forms microfibrils;
  4. Provide rigidity / strength;
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34
Q

Carbohydrates AO1

Compare the structure of starch and cellulose

A

1.Both polysaccharides;
OR Both are glucose polymers
OR Both are made of glucose monomers;

  1. Both contain glycosidic bonds (between monomers);
  2. Both contain carbon, hydrogen and oxygen/C, H and O;
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35
Q

Carbohydrates AO1

Contrast the structure of starch and cellulose

A
  1. Starch made of α-glucose whereas cellulose made of β-glucose;
  2. Starch (molecule) is helical/coiled whereas cellulose (molecule) is straight;
  3. Starch (molecule) is branched whereas cellulose is not/unbranched;
  4. Cellulose has microfibrils whereas starch does not;
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36
Q

Carbohydrates AO1

Bonds contained by starch AND glycogen

A

alpha (1,4) glycosidic

alpha (1,6) glycosidic

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37
Q

Carbohydrates AO1

Explain how glycogen is related to its function (4 marks)

A
  1. Helix/coiled/branched so compact;
  2. Polymer of (alpha) glucose so easily hydrolysed;
  3. (Highly) branched so more ends for faster hydrolysis;
  4. (alpha) Glucose (polymer) so provides respiratory substrate for energy (release);
  5. Insoluble so does not affect osmosis / water potential;
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38
Q

Carbohydrates AO1

What term is used to describe the different structures of α-glucose and β-glucose

A

Isomer

Isomers have same molecular formula but different arrangement of atoms

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39
Q

Carbohydrates AO2

Galacto-oligosaccharides (GOS) are polymers of galactose.

Explain why GOS are described as polysaccharides (2 marks).

A

1. Galactose is a monosaccharide/monomer;

2. Polysaccharide is a carbohydrate polymer;

3. Several monosaccharides / monomers / galactose joined by condensation reactions

OR monosaccharides / monomers / galactose joined by glycosidic bonds;

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40
Q

Carbohydrates AO2

Galacto-oligosaccharides (GOS) are polymers of galactose.

Give two differences between the structures of GOS and lactose.

A

1. Lactose contains (alpha) glucose and GOS does not

OR Lactose contains (alpha) glucose + galactose and GOS contains only galactose;

2. Lactose is a disaccharide and GOS is a polysaccharide;

3. Lactose has one glycosidic bond and GOS has many glycosidic bonds;

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41
Q

Carbohydrates AO1

Describe the biochemical test for a reducing sugar (3 marks).

A

1. Add equal volumes of Benedict’s solution and sample to a test tube

2. Heat to 95⁰C.

3. Formation of a brick red precipitate if a reducing sugar is present.

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42
Q

Carbohydrates AO1

List all the reducing sugars

A

Glucose
Fructose
Galactose
Maltose
Lactose

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43
Q

Carbohydrates AO1

Rank the below colours of precipitate by concentration - lowest to highest - of reducing sugar following the Benedict’s test.

Brick red
Green/yellow
Orange

A

Lowest: green/low
Medium: orange
Highest concentration: brick red

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44
Q

Carbohydrates AO1

Following the Benedict’s test for a reducing sugar, what would a negative result look like?

A

Solution remains blue

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45
Q

Carbohydrates AO1

TRUE or FALSE:

The Benedict’s test is quantitative

A

FALSE

The different coloured precipitates are semi-quantitative

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46
Q

Carbohydrates AO1

TRUE or FALSE:

A sample containing sucrose will produce a coloured precipiate following the Benedict’s test

A

FALSE

Sucrose is a non-reducing sugar

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47
Q

Carbohydrates AO1

Describe a biochemical test to show that a solution contains a non-reducing sugar (3 marks)

A

1. Boil with acid AND neutralise;

Accept named examples, eg hydrochloric acid (HCl), sodium hydrogen carbonate (NaHCO3)

2. Heat (to 95oC) with Benedict’s (solution);

3. Red precipitate
(indicates non-reducing sugar is present);

Accept other colours eg. green/orange

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48
Q

Carbohydrates AO1

Describe how scientists produce a calibration curve to obtain estimates maltose concentration for an unknown sample (4 marks)

Do not include details of how to perform a Benedict’s test in your answer.

A

1 Make/use maltose solutions of known/different concentrations

2. Carry out Benedict’s test on each solution;

3. (Use colorimeter to) measure colour/colorimeter value (e.g. absorbance) of each solution and plot calibration curve;

4. Details of curve:
concentration on x-axis,
colorimeter value on y-axis,
draw a line of best fine.

5. Estimate concentration of sample by using calibration curve i.e. read off Y axis value to estimate concentration using the x axis

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49
Q

Carbohydrates AO1

A student carried out the Benedict’s test. Suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution (2 marks).

A

1. Filter AND dry (the precipitate);

Accept: correct reference to evaporation after filtration

2. Find mass/weight;

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50
Q

Carbohydrates AO1

Explain how you would use the below graph to determine the maltose concentration with a light absorbance of 0.45 arbitary units.

A

Line of best fit drawn;

Read off Y axis value at 0.45 (to estimate concentration using the x axis)

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51
Q

Carbohydrates AO1

Arbitary unit (AU)

A

A relative unit of measurement to show the ratio of amount of substance;

This allows comparisons.

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52
Q

Carbohydrates AO1

Using a colorimeter rather than relying on the Benedict’s test results alone improves the repeatability of the student’s results.

Give one reason why.

A

1. Quantitative OR
(Colour change is) subjective;

Accept: accurate/precise

2. Standardises (the) method;

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53
Q

Lipids AO1

Two groups of lipids

A

Triglycerides
Phospholipids

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54
Q

Lipids AO1

Triglyceride components

A

One glycerol molecule
&
three molecules of fatty acid

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55
Q

Lipids AO1

Tryglyceride bond

A

Ester

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56
Q

Lipids AO1

Number of ester bonds in a triglyceride

A

3

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57
Q

Lipids AO1

Identify the carboxyl group and hydrocarbon chain in the fatty acid

A
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58
Q

Lipids AO1

A

Everything other than the COOH inside drawn box;

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59
Q

Lipids AO1

Complete the diagram to produce a triglyceride

A
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60
Q

Lipids AO1

Saturated OR unsaturated fatty acid

A

Saturated fatty acid

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61
Q

Lipids AO1

Saturated or unsaturated fatty acid?

A

Unsaturated fatty acid

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62
Q

Lipids AO1

Unsaturated fatty acid

A

Fatty acids with double bonds between the carbon atoms in the hydrocarbon chain.

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63
Q

Lipids AO1

Saturated fatty acid

A

Fatty acids have no double bonds between carbons in the hydrocarbon chain.

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64
Q

Lipids AO1

Describe the emulsion test for a lipid
(3 marks)

A

1. Add ethanol to sample and mix
(to dissolve the lipid)

2. Then add water and mix

3. A white emulsion will be visible if fat is present

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65
Q

Lipids AO1

If the sample is a seed - which contains oils - what must you first do before starting the emulsion test?

A

Crush seeds before adding ethanol.

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66
Q

Lipids AO1

Describe how a triglyceride molecule is formed (3 marks)

A

1. One glycerol and three fatty acids;

2. Condensation (reactions) and removal of three molecules of water;

3. Ester bond(s) (formed);

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67
Q

Lipids AO1

What molecules are represented by P and Q?

A

P = Glycerol

Q = Fatty acids (chains)

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68
Q

Lipids AO1

Compare the structure of triglycerides and phospholipids.

A

Both contain ester bonds (between glycerol and fatty acid);

Both contain glycerol;

Fatty acids on both may be saturated or unsaturated;

Both contain C, H and O whereas phospholipids also contain P; Must relate to element.

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69
Q

Lipids AO1

Compare the properties of triglycerides and phospholipids.

A

Both are insoluble in water;

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70
Q

Lipids AO1

Contrast the structure of triglycerides and phospholipids.

A

Triglyceride has three fatty acids whereas phospholipid has two fatty acids;

Triglyceride has no phosphate group whereas phospholipids has 1 phosphate group;

Triglycerides have 3 ester bonds whereas phospholipids have 2;

Both contain C, H and O whereas phospholipids also contain P; Must relate to element.

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71
Q

Lipids AO1

Contrast the properties of triglycerides and phospholipids.

A

Triglycerides are hydrophobic/non-polar whereas phospholipids have hydrophilic/polar and hydrophobic region;

Phospholipids form bilayer whereas triglycerides don’t;

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72
Q

Lipids AO1

Triglycerides are hydrophobic or hydrophilic

A

Hydrophobic

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73
Q

Lipids AO1

Explain the arrangement of phospholipids in a cell-surface membrane (2 marks)

A
  1. (As a) Bilayer
  2. Hydrophobic (fatty acid) tails point away/are repelled from water

OR

Hydrophilic (phosphate) heads point to/are in/are attracted to water;

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74
Q

Lipids AO1

TRUE or FALSE
Phospholipids are hydrophobic AND hydrophilic

A

TRUE

Hydrophobic fatty acids tails and hydrophilic phosphate head

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75
Q

Lipids AO1

Explain the arrangement of phospholipids in a cell-surface membrane (3 marks)

A

1. Phospholipid both hydrophobic and hydrophilic
OR
Phospholipid polar
OR
Phosphate group is charged;

2. Triglycerides only hydrophobic
OR Fatty acid/triglyceride is non-polar;

3. Hydrophilic/phosphate group attracts water (to either side of bilayer)

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76
Q

Lipids AO1

Draw and label a simple diagram of the phospholipid bilayer

A
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77
Q

Lipids AO1

Draw and label a simple diagram of a single phospholipid molecule

A
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78
Q

Lipids AO1

The general structure of a fatty acid is RCOOH.

Name the group represented by COOH.

A

Carboxyl

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79
Q

Lipids AO1

Explain why phospholipids can form a bilayer but triglycerides cannot (3 marks)

A

1. Phospholipid both hydrophobic and hydrophilic

OR Phospholipid polar

OR Phosphate group is charged;

2. Triglycerides only hydrophobic

OR Fatty acid/triglyceride is non-polar;

3. Hydrophilic/phosphate group attracts water (to either side of bilayer);

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80
Q

Lipids AO1

A

1. 3 fatty acids rather than 2;

2. 3 ester bonds rather than 2;

3. No phosphate group;

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81
Q

Lipids AO1

Describe the hydrolysis reactions involved in the digestion of triglycerides.

Do not write about the activity of lipase.

A

1. Breaking of ester bonds;

2. By addition of water;

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82
Q

Lipids AO1

How many molecules are produced following the complete hydrolysis of a triglyceride

A

4

1 glycerol + 3 fatty acids

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83
Q

Lipids AO1

A

Type of R group = Unsaturated (fatty acid);

Explanation = Double bond (between carbons);

Accept for ‘double bond’, C=C

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84
Q

Water AO1

Explain the importance of water as a metabolite

A

Involved in metabolic reactions such as condensation and hydrolysis.

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85
Q

Water AO1

Explain the importance of water as a solvent

A

This allows metabolic reactions to occur

AND

also allows the transport of substances.

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86
Q

Water AO1

Explain the importance of the high specific heat capacity of water

A

This ‘buffers’ changes in temperature.

It requires lots of energy to break the hydrogen bonds in water

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87
Q

Water AO1

Explain the importance of the large latent heat of vaporisation of water

A

This provides a cooling effect
(through evaporation)

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88
Q

Water AO1

Explain the importance of cohesion between water molecules

A

This supports the formation of continuous columns of water (which is needed to move water up the xylem).

OR

Produces surface tension which supports small organisms on the surface of water e.g., pond skaters.

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89
Q

Carbohydrates AO1

The student controlled variables in the test using Benedict’s solution.

Give two variables the student controlled.

A
  1. Benedict’s (solution) volume;
  2. Benedict’s (solution) concentration;
  3. (Fruit) juice volume;
  4. (Water bath/water/solution) temperature;
  5. Duration of heating (in water bath);
90
Q

Proteins AO1

Draw out and label an amino acid

A
91
Q

Proteins AO1

Monomers of proteins
(aka polypeptides)?

A

Amino acids

92
Q

Proteins AO1

Describe how a peptide bond is formed between two amino acids to form a dipeptide (2 marks).

A
  1. Condensation (reaction) / loss of water.
  2. Between amine/NH2 and carboxyl/COOH groups.
93
Q

Proteins AO1

List the levels of organisation of protein structure

A

The PRIMARY structure

The SECONDARY structure

The TERTIARY structure

The QUATERNARY structure

94
Q

Proteins AO1

Describe the primary structure of all proteins

A

1. number AND sequence/order of amino acids (in a polypeptide chain);

2. Joined by peptide bonds;

95
Q

Proteins AO1

Describe how monomers join to form the primary structure of a protein (3 marks).

A
  1. Condensation reaction between amino acids
  2. Forming peptide bond
  3. Creating a specific number AND sequence of amino acids
96
Q

Proteins AO1

Bond in secondary structure of protein

A

(Many weak) hydrogen bonds

97
Q

Proteins AO1

The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how (2 marks).

A
  1. Hydrogen bonds
  2. Between NH (amine) and C=O (carboxyl groups) groups of amino acids
  3. This forms alpha helix / beta pleated sheets
98
Q

Proteins AO1

Which level of protein structure?

A

Secondary

99
Q

Proteins AO1

The tertiary structure is held together by bonds between the ____________ of different amino acids.

A

R groups

100
Q

Proteins AO1

Tertiary structure bonds

A

Hydrogen
Ionic
Disulphide bridges

101
Q

Proteins AO1

TRUE or FALSE:

The R group is the same in all amino acids

A

FALSE

102
Q

Proteins AO1

Properties of amino acid
R groups

A

Positively charged

Negatively charged

Polar and non-polar

Hydrophophic and hydrophilic

103
Q

Proteins AO1

Level of protein structure?

A

Tertiary

104
Q

Proteins AO1

Fill in the blank:

Quatenary proteins contain ………………….. polypeptide chains

A

two or more

OR

more than one

105
Q

Proteins AO1

The quaternary structure is held together by which bonds between the polypeptide chains.

A

Hydrogen
Ionic
Disulphide bridges

106
Q

Proteins AO1

Two proteins have the same number and type of amino acids but different tertiary structures. Explain why (2 marks).

A
  1. Different primary structure / different sequence of amino acids
  2. Forms ionic / hydrogen / disulphide bonds in different places
107
Q

Proteins AO1

Describe the structure of a protein (5 marks).

A

1. Polymer of amino acids

2. Amino acids joined by peptide bonds

3. Formed by a condensation reaction

4. Primary structure is number AND order/sequence of amino acids

5. Secondary structure is folding of polypeptide chain due to hydrogen bonding

6. Tertiary structure is 3D folding formed by interactions between R groups e.g. due to hydrogen / ionic / disulphide bonds

7. Quaternary structure more than one OR two or more polypeptide chains

108
Q

Proteins AO1

Biochemical test for proteins

A

Add Biuret reagent

Positive result = purple/lilac (solution)

109
Q

Proteins AO1

A dipeptide consists of two amino acids joined by a peptide bond.

Describe two other ways in which all dipeptides are similar.

A

1.  Amine/NH2 (group at end);

2.  Carboxyl/COOH (group at end);

3.  Two R groups;

4.  All contain C and H and N and O;

110
Q

Proteins AO1

A dipeptide consists of two amino acids joined by a peptide bond.

Describe one way in which they might differ.

A

Variable/different R group(s);

111
Q

Proteins AO2

A solution contained a mixture of three different amino acids. A scientist passed an electric current through the solution to separate the amino acids.

Explain what the positions of the spots in the below diagram show about these amino acids.

A
  1. Moved to negative (electrode) because positive(ly charged);
  2. (Spots move) different distances/rates because (amino acids) different charge/mass;
  3. Two spots (not three) because (amino acids) same charge/mass
112
Q

Proteins AO1

TRUE OR FALSE:

All proteins have a specific tertiary structure which gives them a specific shape which is necessary for them to carry out their function.

A

True

113
Q

Proteins AO1

Rank the bonds found in the tertiary structure of protein by strength

A

Disulphide = strongest

Ionic (broken by changes in pH)

Hydrogen = weakest (broken by changes in temperature)

114
Q

Proteins AO1

What is denaturation of proteins?

A

A permanent change in its tertiary structure

115
Q

Proteins AO1

If you added the Biuret reagent to a solution containing enzymes, what would the result be?

A

Purple/lilac = positive result

because enzymes are proteins.

116
Q

Enzymes AO1

Enzymes lower the ______________________ of the reaction they catalyse

A

activation energy

117
Q

Enzymes AO1

Enzymes are proteins which have a specific ___________ structure

A

tertiary

118
Q

Enzymes AO1

Enzyme active sites have a unique shape which is _______________ to only one substrate

A

complementary

119
Q

Enzymes AO1

When an enzyme active site binds to a substrate it forms an _______________

A

enzyme substrate complex

120
Q

Enzymes AO1

In humans, the enzyme maltase breaks down maltose to glucose. Explain why maltase only breaks down maltose (2 marks).

A
  1. Maltase has a specific tertiary structure that contains an active site;
  2. Active site complementary to only maltose / substrate
121
Q

Enzymes AO1

Describe the induced fit model of enzyme action (3 marks)

A
  1. Active site is initially NOT complementary to the substrate
  2. The substrate enters the enzyme’s active site and induces the change in the shape of the active site so now complementary
  3. Enzyme substrate complex forms which stresses the bonds in the substrate and lowers the activation energy
  4. When the product leaves the active site, active site returns to its previous shape
122
Q

Enzymes AO1

Describe one similarity between the induced-fit model of enzyme action and the lock and key model of enzyme action

A

Substrate binds to active site

OR

Enzyme-substrate complex (formed);

123
Q

Enzymes AO1

Describe one difference between the induced-fit model of enzyme action and the lock and key model of enzyme action

A

Active site changes shape with induced-fit, whereas does not change in lock and key

OR

(Initially) active site not complementary to substrate with induced-fit, whereas is complementary in lock and key

124
Q

Enzymes AO1

In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature. Explain why (3 marks).

A

1. Description of induced fit - binding of substrate causes active site to change shape (now complementary to substrate);

2. This forms an enzyme-substrate complex which stresses bonds in the substrate (so more easily broken);

3. Which lowers activation energy required for reaction;

125
Q

Enzymes AO1

Explain how the active site of an enzyme causes a high rate of reaction (3 marks)

A

1. Description of induced fit - **binding of substrate causes active site to change shape **(now complementary to substrate);

2. This forms an enzyme-substrate complex which stresses bonds in the substrate (so more easily broken);

3. Which lowers activation energy required for reaction;

126
Q

Enzymes AO1

How can you measure the rate of enzyme-controlled reactions?

A

formation of products OR

disappearance or breakdown of the substrate

(in a defined period of time)

KEY POINT: Calculating the rate of any process ALWAYS requires time

127
Q

Enzymes AO1

How to calculate the rate of an enzyme controlled reaction

A

DY (substrate or product) /
DX (always time)

(Change in Y over change in X)

128
Q

Enzymes Maths

Calculate the rate of reaction using the below triangle

Clue: DY / DX

A
DY (change in Y) / DX (change in X)
129
Q

Enzymes AO1

Explain how two enzymes with different amino acid sequences can catalyse the same reaction (2 marks)

A

1. Both active sites have similar/identical tertiary structures
OR
Both have active sites that are complementary to different parts of the substrate;

2. Form enzyme-substrate complexes (with the same substrate);

130
Q

Enzymes AO1

Factors affecting enzyme controlled reactions

A

Temperature
pH
Substrate concentration
Enzyme concentration

131
Q

Enzymes AO1

Fill in the gaps:

As the temperature increases the enzymes and substrates have more [1].

Therefore they move around more and are more likely to successfully collide and form [2].

A
  1. knetic energy
  2. enzyme-substrate complexes
132
Q

Enzymes AO1

Enzyme denaturation

A

A permanent change to the tertiary structure;

Active site no longer complementary to substrate;

fewer enzyme substrate complexes form.

133
Q

Enzymes AO1

Bonds broken in enzyme tertiary structure by increasing temperature

A

(mainly) weak hydrogen

ionic

134
Q

Enzymes AO1

pH is a measure of________________.

A

hydrogen ion concentration

Increase H+ ions (low pH) , decrease H+ ions (high pH)

135
Q

Enzymes AO1

TRUE or FALSE:

Both increases and decreases in pH can denature an enzyme

A

TRUE

136
Q

Enzymes AO1

Describe and explain the effect of increasing substrate concentration on the rate of an enzyme controlled reaction (2 marks).

A

(Describe)
Increases then plateaus;

(Explain)
Because all enzyme active sites are occupied

Plateaus because all the substrate has been used up

137
Q

Enzymes AO1

Limiting factor at the red arrow

A

Substrate concentration

138
Q

Enzymes AO1

Limiting factor at the red arrow

A

Enzyme concentration

139
Q

Enzymes AO1

Why is the initial rate of reaction faster?

A

because there’s lots of substrate and therefore more enzyme substrate complexes form.

140
Q

Enzymes AO1

Why does the rate of reaction plateau?

A

because all enzyme active sites have been occupied by the substrate;

the concentration of enzyme is a limiting factor;

141
Q

Enzymes AO1

Inhibitors __________ the rate of reaction

A

decrease

142
Q

Enzymes AO1

Competitive inhibitors have a __________________________ shape to the substrate

A

similar

143
Q

Enzymes AO1

Fill in the blanks:

Because they have a similar shape to the substrate, competitive inhibitors can bind to the enzyme’s [1].
.
Competitive inhibitors reduce [2] complexes forming.

This decreases the [3] of reaction.

A
  1. active site
  2. enzyme substrate
  3. rate
144
Q

Enzymes AO1

___________________ substrate concentration can overcome competitive inhibition

A

Increasing

145
Q

Enzymes AO2

A
  1. (Allopurinol) is a similar shape to xanthine;
  2. (Allopurinol) enters active site / is a competitive inhibitor;
  3. Less xanthine binds so fewer enzyme substrate complexes and therefore fewer uric acid crystals formed;
146
Q

Enzymes AO1

Which type of inhibitor binds to the allosteric site (away from the active site).

A

non-competitive

147
Q

Enzymes AO1

What happens after a non-competitive inhibitor binds to the allosteric site?

A

1. Change the shape of the active site so that it is no longer complementary to the substrate.

2. Fewer enzyme substrate complexes form and the rate of reaction is decreased.

148
Q

Enzymes AO1

TRUE OR FALSE:

Increasing substrate concentration can overcome non-competitive inhibition.

A

FALSE

This is because the active site has changed shape

149
Q

Enzymes AO2

Explain the results in the below graph
(2 marks).

A

1. (Rate of) increase in concentration of maltose slows as substrate/starch is used up

OR

High initial rate as plenty of starch/substrate/more enzyme-substrate complexes;

2. No increase after 25 minutes/at end/levels off because no substrate/starch left;

150
Q

Enzymes AO1

What does the addition of a buffer do in an enzyme controlled reaction?

A

Maintains a constant pH

This prevents the enzyme from denaturing

151
Q

Enzymes AO1

A competitive inhibitor decreases the rate of an enzyme-controlled reaction.

Explain how (3 marks).

A
  1. Inhibitor similar shape to substrate;
  2. Binds to active site;
  3. Reduces enzyme-substrate complex forming;
152
Q

Enzymes AO1

Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction (3 marks).

A
  1. Attaches to the enzyme at the allosteric site (other than the active site);
  2. Changes shape of the active site

OR Changes tertiary structure (of enzyme);

  1. (So active site and substrate) no longer complementary so less/no substrate can fit/bind;
153
Q

Enzymes AO2

A

High substrate concentration does not overcome inhibition

OR

(With inhibitor) increase substrate/lipid concentration does not increase rate of reaction

OR

(With inhibitor) increase substrate/lipid concentration does not increase lipase activity

154
Q

Enzymes AO3

When investigating factors that affect enzyme-controlled reactions, enzymes are often ‘isolated’ from a cell (e.g. a bacterial cell).

Explain why this is a limitation?
.

A

The process of isolation may change the enzyme’s activity

Outside the optimum conditions of the host cell, the enzyme’s activity may also change.

155
Q

Enzymes AO3

What is a common control condition that proves a specific enzyme is needed for a reaction?

A
  1. Boiled enzyme
  2. At same concentration & volume
  3. This denatures the enzyme and the reaction will not take place in this condition
156
Q

Structure of DNA AO1

DNA holds ____________ information

A

genetic

157
Q

Structure of DNA and RNA AO1

RNA transfers genetic information from ____________ to the ribosomes

A

DNA

158
Q

Structure of DNA and RNA AO1

Both DNA and RNA are polymers of ______________.

A

nucleotides

159
Q

Structure of DNA AO1

Draw out and label a DNA nucleotide

A
160
Q

Structure of RNA AO1

Pentose sugar in a RNA nucleotide

A

Ribose

161
Q

Structure of DNA AO1

Pentose sugar in a DNA nucleotide

A

Deoxyribose

162
Q

Structure of RNA AO1

Draw out and label a RNA nucleotide

A
163
Q

Structure of RNA AO1

Nitrogenous base specific to RNA

A

Uracil

164
Q

Structure of DNA AO1

Nitrogenous base specific to DNA

A

Thymine

165
Q

Structure of DNA and RNA AO1

Bond that joins together nucelotides

A

Phosphodiester

166
Q

Structure of DNA AO1

Enzyme that catalyses the formation of a phosphodiester bond via a condestation reaction of DNA nucleotides.

A

DNA polymerase

167
Q

Structure of DNA AO1

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule
(2 marks).

A
  1. Condensation reaction;
  2. Between phosphate and deoxyribose;
  3. (Catalysed by) DNA polymerase;
168
Q

Structure of RNA AO1

Enzyme that catalyses the formation of a phosphodiester bond via a condestation reaction of RNA nucleotides.

A

RNA polymerase

169
Q

Structure of DNA AO1

Fill in the blanks

A DNA molecule is a double helix with two [1] chains held together by [2] bonds between specific [3] base pairs.

A

1 - polynucleotide

2 - hydrogen

3 - complementary

170
Q

Structure of DNA AO1

The double helix structure for DNA and its replication was proposed by which scientists?

A

James Watson &
Francis Crick

171
Q

Structure of DNA AO1

In the DNA double helix, adenine forms a complementary base pair with?

A

thymine

172
Q

Structure of DNA AO1

In the DNA double helix, guanine forms a complementary base pair with?

A

cytosine

173
Q

Structure of DNA AO1

Describe the structure of DNA
(5 marks)

A

1. Polymer of nucleotides;

2. Each nucleotide formed from deoxyribose, a phosphate group and a nitrogenous base;

3. Phosphodiester bonds (between nucleotides);

4. Double helix / 2 strands held by hydrogen bonds;

5. Complementary pairing between adenine, thymine AND cytosine, guanine;

174
Q

Structure of DNA AO1

Functions of the sugar-phosphate backbone and double helix structure

A
  1. Provides strength and stability;
  2. Protects information coded in the bases and hydrogen bonding between bases;
175
Q

Structure of DNA AO1

Function of DNA being a long molecule

A

Can store a lot of information

176
Q

Structure of DNA AO1

Function of helix structure in DNA

A

Makes it compact

(more nucleotides can fit into a smaller space)

177
Q

Structure of DNA AO1

Function of the base sequence of DNA

A

Codes for the sequence of amino acids in the primary structure of proteins

178
Q

Structure of DNA AO1

Function of the DNA helix
being double stranded

A

Allows semi-conservative replication because both strands can act as a template;

179
Q

Structure of DNA AO1

Complementary base pairing between – adenine and thymine & cytosine and guanine allows ____________ .

A

accurate replication

180
Q

Structure of DNA AO1

Function of the weak hydrogen bonds between complementary bases in DNA

A

Easily broken by DNA helicase and allows separation of strands during semi-conservative replication;

181
Q

Structure of DNA Maths

A

Thymine = 18%

Guanine = 32%

182
Q

Structure of DNA Maths

A
183
Q

Structure of DNA Maths

A
184
Q

Structure of DNA and RNA AO1

Structural differences between a DNA molecule and a mRNA molecule (4 marks).

A

1. DNA has deoxyribose whereas mRNA has ribose;
2. DNA has thymine whereas mRNA has uracil;
3. DNA long whereas mRNA short;
4. DNA is double stranded / double helix whereas mRNA is single stranded
5. DNA has hydrogen bonds whereas mRNA has no hydrogen bonds
OR
DNA has (complementary) base pairing whereas mRNA does not;

185
Q

Structure of DNA and RNA AO1

Structural similarities between a DNA molecule and a mRNA molecule (4 marks).

A

1. Both polymers of nucleotides;

2. Nucleotides have pentose, (nitrogen-containing organic) base and a phosphate (group);

3. Both Cytosine, guanine and adenine (as bases);

4. Both have phosphodiester bonds;

186
Q

Structure of DNA AO1

A
  1. Hydrogen bonds;
  2. Phosphodiester bonds;
187
Q

Biological Molecules AO1

A
188
Q

Structure of DNA AO1

A

8

189
Q

Structure of DNA AO1

A

deoxyribose

190
Q

DNA replication (AO1)

The semi-conservative replication of DNA ensures ___________________ .

A

genetic continuity between generations of cells

OR

genetically identical cells following mitosis

191
Q

DNA replication AO1

Role of DNA helicase during semi-conservative DNA replication

A

Breaks hydrogen bonds;

between complementary base pairs;

To unwind DNA / separate strands;

192
Q

DNA replication AO1

Following semi-conservative replication, a new molecule of DNA will consist of _______________.

A

half “original” strand
AND
half “new” strand

193
Q

DNA replication AO1

In the process of semi-conservative DNA replication, the two strands within a DNA molecule are separated. Each then acts as a template for the formation of a new complementary strand.

Describe how the separation of strands occurs (2 marks).

A
  1. DNA helicase;
  2. Breaks hydrogen bonds between complementary base pairs
194
Q

DNA replication AO1

Role of the single-stranded DNA fragments (2 marks)

A

1.   Act as template;

2.   Determines order of nucleotides / bases;

195
Q

DNA replication AO1

Role of DNA nucleotides

A

Forms complementary pairs
e.g. Adenine to Thymine, Guanine to Cytosine

196
Q

DNA replication AO1

Bond catalysed by DNA polymerase

A

phosphodiester

197
Q

DNA replication AO1

Describe the role of DNA polymerase in the semi-conservative replication of DNA (2 marks).

A

Joins adjacent DNA nucleotides between deoxyribose and phosphate;

Via condensation reactions to form phosphodiester bonds;

198
Q

DNA replication AO1

Describe the process of semi-conservative replication of DNA
(5 marks).

A

1. DNA helicase unwinds DNA/double helix OR DNA helicase breaks hydrogen bonds;

2. Both strands act as templates;

3. (Free DNA) nucleotides line up in complementary base pairs / Adenine to Thymine and Guanine to Cytosine;

4. DNA polymerase joins adjacent nucleotides (of new strand);

5. Forming phosphodiester bonds;

6. Each new DNA molecule consists of one
old/original/template strand and one new strand;

199
Q

DNA replication AO1

Name of scientisis who provided the evidence for the semi-conservative model of replication

A

Meselson & Stahl

200
Q

DNA replication AO1

What organism did Meselson and Stahl use for their experiment?

A

Bacteria (E.coli)

201
Q

DNA replication AO1

Meselson & Stahl experiment

In generation ‘0’, all the bacteria (e.coli) were grown with which isotope of nitrogen?

A

N15

202
Q

DNA replication AO1

Meselson & Stahl experiment

In generation ‘1’, all the bacteria (e.coli) were grown with which isotope of nitrogen?

A

N14

203
Q

DNA replication AO1

Meselson & Stahl experiment

Which nitrogen isotope is heavier?

A

N15

204
Q

DNA replication AO1

Meselson & Stahl experiment

Put ticks for which generation the different DNA molecules will be found.

A
205
Q

Structure of DNA AO1

DNA is a polymer of nucleotides. Each nucleotide contains an organic base.

Explain how the organic bases help to stabilise the structure of DNA (2 marks).

A
  1. Hydrogen bonds between the complementary base pairs holds two strands together
  2. Many hydrogen bonds provides strength
206
Q

ATP AO1

ATP stands for

A

Adenosine triphosphate

207
Q

ATP AO1

Draw out and label the structure of adenosine triphosphate (ATP)

A
208
Q

ATP AO1

Products of ATP hydrolysis

A

adenosine diphosphate (ADP)
AND
an inorganic phosphate group (Pi)

209
Q

ATP AO1

Enzyme that catalyses ATP hydrolysis

A

ATP hydrolase

210
Q

ATP AO1

ATP is mostly produced in the mitochondria via which process?

A

Aerobic respiration

Smaller amounts of ATP are produced by anaerobic respiration

211
Q

ATP AO1

Describe how an ATP molecule is formed from its component molecules (4 marks).

A

1. and 2. Accept for 2 marks correct names of three components: adenine, ribose, three phosphates;

OR accept suitably labelled diagram

3. Condensation reaction (releases 1 water molecule);

4. ATP synthase;

212
Q

ATP AO1

Adding an inorganic phosphate to a biological molecules is known as phosphorylation. This makes the molecule ______________ .

A

more reactive

213
Q

ATP AO1

ATP is useful in many biological processes. Explain why (4 marks).

A

1. Releases energy in small amounts;

2. One bond broken down in a single step so immediate energy compound / makes energy available rapidly;

3. Phosphorylates / adds phosphate makes molecules more reactive / lowers activation energy;

4. Reformed / made again / resynthesised;

214
Q

ATP AO1

TRUE or FALSE

Adding a phosphate group to an enzyme can help lower the activation energy.

A

TRUE

215
Q

ATP AO1

Give two ways in which the properties of ATP make it a suitable source of energy in biological processes (2 marks).

A

1. Energy released in small amounts;

2. One bond broken down in a single step so immediate energy compound / makes energy available rapidly;

3. Soluble;

216
Q

ATP AO1

Humans synthesise more than their body mass of ATP each day. Explain why it is necessary for them to synthesise such a large amount of ATP (2 marks).

A

1. ATP cannot be stored / is an immediate source of energy;

2. ATP only releases a small amount of energy at a time;

217
Q

ATP AO1

Adenosine triphosphate (ATP) is a nucleotide derivative.

Contrast the structures of ATP and a nucleotide found in DNA to give two differences.

A

1. ATP has ribose whereas DNA nucleotide has deoxyribose;

2. ATP has 3 phosphate (groups) whereas DNA nucleotide has 1 phosphate (group);

3. ATP – base always adenine whereas in DNA nucleotide nitrogenous base can be different / varies;

218
Q

ATP AO1

A

Quaternary

Condensation/phosphorylation

Release/loss/formation

(Aerobic) respiration

219
Q

Biological Molecules AO1

A

B - is a monomer in an enzyme’s active site

D - is a monomer in cellulose

C - is produced during photosynthesis and respiration

B - forms a polymer that gives a positive result with a biuret test

220
Q

Inorganic ions (AO1)

Describe the role(s) of phosphate ions in cells

A

1. Joins nucleotides/in phosphodiester bond/in backbone of DNA/RNA/in nucleotides;

2. Used in/to produce ATP;

3. Phosphorylates other compounds (usually) making them more reactive;

4. Hydrophilic/water soluble part of phospholipid bilayer/membrane;

5. Affects osmosis/water potential;

Y1 AQA Biology - Burnley College (2024-25) (2 decks)

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