answers to end of chapter qs for chapters 1 and 2

1 a diastole / atrial systole;

reason 1: aortic / pulmonary artery / semilunar valve(s) closed;

reason 2: atrioventricular / mitral / tricuspid valve(s) open; (3)

b A: prevents valve inverting;

B: adjusts tension in A/name/contracts to pull on A; (2)

(Total 5 marks)

2 Points accepted in correct context only

1 Polysaccharides are {polymers / eq} of monosaccharides / correct general formula (C6H10O5)n;

2 Linked by glycosidic bonds;

3 (monomers are) α-glucose;

4 Starch made up of amylose and amylopectin;

5 Credit reference to structure of {amylose / amylopectin};

6 Glycogen branched chains;

7 Starch is an energy store in plants;

8 Glycogen is an energy store in animals;

9 Broken down to glucose for respiration;

10 Amylopectin and glycogen broken down faster/can be used to produce energy faster than amylose because more ends for enzymes to break off glucose molecules; (max. 10 marks)

3 H2O;

(di)polar;

hydrogen / H;

solvent;

(specific) heat capacity; [not latent heat capacity]

(Total 5 marks)

4 a (i) glycerol / propan 1,2,3 triol (1)

(ii) ester (1)

b {Stearic acid / saturated fatty acids} have more hydrogen atoms;{Stearic acid / saturated fatty acids} have no double carbon–carbon bonds;{Stearic acid / saturated fatty acids} have no kinks;[allow converse statements about unsaturated fatty acids] (2)

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Edexcel AS Biology Implementation and Assessment Guide for Teachers and Technicians ©Pearson Education Limited 2008

Unit 1 Topic 1

1 of 3 Examzone: Answers to practice questions

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c 1 Energy stores;

Qualification: {More than / twice as much as) carbohydrate OR Insoluble / compact / minimise mass OR Subcutaneous / adipose / blubber;

2 Protection / mechanical insulation;

Qualification: Around {organs / named organ} OR Reference to adipose tissue OR Ear wax giving protection against infection;

3 Waterproofing;

Qualification: Of skin / fur / feathers / insect cuticle / ear wax OR Hydrophobic / insoluble / repels water;

4 Electrical insulation;

Qualification: Reference to myelin sheath / nerve cells / neurones / axons / dendrons OR Non-polar;

5 Heat insulation;

Qualification: Subcutaneous / adipose / blubber OR Prevents heat loss from body;

6 Buoyancy;

Qualification: Less dense than {water / muscle};

7 Making beeswax;

Qualification: Formation of honeycomb;

8 Membrane fluidity;

Qualification: Reference to cholesterol;

9 Cell membrane structure;

Qualification: Reference to phospholipids;

10 Reference to hormones;

Qualification: As steroids;

11 Source of metabolic water;

Qualification: Reference to respiration OR Desert adaptation (2 x 2 marks)

(Total 8 marks)

Unit 1 Topic 1 (cont.)

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5 a Coronary artery ; (1)

b (i) (Increase in cholesterol level) gives increase in risk

(ignore reference to smokers) ;

Slight / insignificant /eq increase between 5 and 6 (mmol dm–3)

(not time reference so not faster / slower) ;

Increase in risk greater above 6.0–6.5 (mmol dm–3) ;

Risk at 8 (mmol dm–3) 2× that at 5 (mmol dm–3) /

(sensible use of figures); (max. 2)

(ii) Risk in both increases as cholesterol level increases;

At low cholesterol /OR 5 mmol dm–3 little difference between smokers and non-smokers (not time references so not faster / slower);

As cholesterol level increases, risk increases more in smokers than in non-smokers / bigger difference at 8 than at 5;

Credit use of figures;

Smokers always at greater risk than non-smokers /eq; (4)

(iii) Age;

Weight / mass / BMI;

Reference to lifestyle, qualified / occupation / stress level;

Reference to exercise level / type / frequency of exercise;

Reference to genetic / family history;

Reference to other diseases / illnesses / e.g. diabetes;

Blood pressure; (max. 2)

c (i) Reference to absence of double bonds (in (hydro)carbonchains of constituent fatty acids) /eq ; (1)

(ii) Japan; (1)

(iii) As ratio / proportion of polyunsaturated to saturated fat increases,risk of heart disease seems to decrease (allow converse); (1)

(Total 12 marks)


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Unit 1 Topic 2

Any two correct boxes for one mark (Total 4 marks)

2 a large surface area;thin lining;(partially) permeable (lining);concentration gradients maintained by mass flow systems; (max. 3)

b contraction of diaphragm muscles lowers / flattens diaphragm;contraction of external intercostal muscles raises ribcage;volume of thorax / lungs increases thus intrapulmonic pressure falls / eq;reference to control by medulla / eq; (max. 3)

(Total 6 marks)

3 a (i) O (1)

C –– N H;

(ii) peptide; (1)

b An explanation to include two from: 1 chain folds into secondary structure / reference to α-helix or β pleated sheets; 2 then folds into tertiary structure; 3 {bonds / interactions} between R groups; 4 reference to named bond; [reject peptide] (2)

c (i) An explanation to include: 1 substrate concentration limiting the rate / eq or converse; 2 correct reference to not all active sites occupied by substrate / eq; (2)

(ii) An outline to include four from: 1 identify independent variable and dependent variable; 2 select suitable range of concentrations (at least 5); 3 fixed volumes of enzyme / substrate; 4 control of named variable(s); 5 description of apparatus used; 6 correct method of obtaining quantitative results;

7 reference to replication / calculation of rate / mean values; (4)

Process Takes place against a concentration gradient

Requires energy in the form of ATP

Diffusion ✗ ✗

Facilitated diffusion ✗ ✗

Osmosis ✗ ✗

Active transport ✓ ✓

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(Total 10 marks)

4 a Tryptophan - glycine - lysine - valine - glycine;

[all correct = 2 marks, 1 error = 1 mark] (2)

b (i) Substitution / point mutation; (1)

(ii) Codes for a different amino acid / could be a stop codon / changes sequence of amino acids;affects primary structure of protein;reference to different bonding in protein;this affects the tertiary structure;could change shape of protein / active site / changes activity in protein;possibly has no effect if doesn’t change protein shape; (3)

(Total 6 marks)

5 a parents do not show disorder (∴ not dominant);affects both male and female (∴ not sex-linked); (2)

b (radioactive) gene probe / marker / indicator;identify DNA sequence of gene / allele; (2)

c can be done earlier than 14th–15th week/eq;results quicker / sooner / within 24 hours;cells actively dividing so no need to culture;less risk to fetus / allow converse; (max. 2)

(Total 6 marks)



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answers to end of chapter qs for chapters 1 and 2

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