AQA Biology Biological molecules Grasp IT A level Write on worksheet PDF

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GraspIT – AQA A level Biology - Biological molecules A. Biological molecules part 1 – Carbohydrates. 1. Describe the difference between α- glucose and β-glucose. (2) .............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. 2. The monosaccharides glucose and fructose can join to form a disaccharide. Complete the diagram to show how this happens. Name the disaccharide which is formed. Name the bond which is formed. Explain what kind of reaction this is. (5)

3. What are the two components of the polysaccharide, starch? How does the structure of these components contribute to the properties of starch? (5). .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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GraspIT – AQA A level Biology - Biological molecules 4. Cellulose is a polysaccharide of β-glucose molecules. Describe how two β-glucose molecules are able to join together and name the bond formed. (4). .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

5. Extended response question: Describe the structure of glycogen and explain how its structure makes it suitable for its function. (6). .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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GraspIT – AQA A level Biology - Biological molecules

B. Biological molecules part 2 – Lipids.

1. Describe the structure of a triglyceride. What type of bond links the components of a triglyceride? (3). .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

2. Explain the difference between a saturated and unsaturated fatty acid. (1) .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

3. Describe the difference between a triglyceride and a phospholipid. Why do phospholipids form bilayers in biological systems? (4). .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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GraspIT – AQA A level Biology - Biological molecules

4. Extended response question: Name of fatty acid lauric acid palmitic acid stearic acid oleic acid linoleic acid linolenic acid

Formula CH3(CH2)10CO2H CH3(CH2)14CO2H CH3(CH2)16CO2H CH3(CH2)7CH=CH(CH2)7 CO2H CH3(CH2)4CH=CHCH2CH=CH(CH2)7CO2H CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7CO2H

Saturated / unsaturated saturated saturated saturated unsaturated unsaturated unsaturated

Melting Point / oC 45 63 69 13 -5 -11

The table displays information about a number of fatty acids.

Describe and explain the pattern shown by the melting points of the fatty acids. (6) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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GraspIT – AQA A level Biology - Biological molecules C. Biological molecules part 3 – Proteins. 1. Draw the generalised structure of an amino acid and label the main groups of the molecule (3).

2. Using a diagram, describe how two amino acids join together. Label and name the bond which is formed (3).

3. The diagram shows the structure of a protein.

The black strips represent disulfide bonds which help stabalise the tertiary structure. (a) Name two other types of bond that stabalise tertiary structure of proteins (2). ………………………………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………………. (b) Region A is a secondary structure. Describe the nature of region A (2). ………………………………………………………………………………………………………………………………………………. © Copyright The PiXL Club Ltd, 2017

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GraspIT – AQA A level Biology - Biological molecules ……………………………………………………………………………………………………………………………………………….

4. Extended response question: Milk powder was made up to standard solutions of 1%, 2%, 3%, 4% and 5% protein. 5cm3 of 1% trypsin enzyme solution was added to 10cm3 samples of each standard solution. The time it took the milk solution to become clear at room temperature was recorded. The average of 10 trials is shown in the table below: Standard solutions Average time for milk solution to clear (s)

1% 44

2% 56

3% 65

4% 82

5% 102

A 45

B 81

Plot a calibration curve using the results for the standard solutions and use the curve to estimate the concentration of the unknown solutions A and B.

Solution A .........................%

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Solution B .........................%

(6)

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GraspIT – AQA A level Biology - Biological molecules

D. Biological molecules part 4 – Enzymes. 1. Why are enzymes sometimes referred to as ‘biological catalysts’? (2) .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

2. How do enzymes reduce the activation energy of a reaction? (2) .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

3. Why do different enzymes have a different optimum pH? (2) .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

4. Explain the importance of tertiary structure to the functioning of an enzyme. (4) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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GraspIT – AQA A level Biology - Biological molecules

5. The diagram shows an enzyme, the substrate and a non-competitive inhibitor. substrate enzyme inhibitor

Label the active site and explain how the inhibitor has its effect. (4) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

6. Extended response question: State two factors that can cause an enzyme to denature and explain how this denaturation occurs in each case (6). .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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GraspIT – AQA A level Biology - Biological molecules ..............................................................................................................................................

E. Biological molecules part 5 – Enzyme kinetics. 1. The graph shows the effect of substrate concentration on an enzyme-catalysed reaction.

C B

A

Explain the shape of the graph at points A, B and C. (3) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

2. A reduction in enzyme activity above the optimum temperature for a particular enzyme can be explained by the idea of denaturation. Explain what causes a reduction in enzyme activity below the optimum temperature. (3) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

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GraspIT – AQA A level Biology - Biological molecules 3. Extended response question: The enzyme amylase catalyses the hydrolysis of starch to malto...