CIE paper 4

Question 1

Describe the differences between eukaryotic and prokaryotic cells with respect to their
DNA

Answer 1

eukaryotic 1. linear / strands 2. in nucleus associated with, proteins or
histones 4. in chromosomes
prokaryotic circular ;free) in cytoplasm ; nakednot in chromosomes ;

Question 2

ATP is described as having a universal role as the energy currency in all living organisms.
Explain why it is described in this way

Answer 2

energy is released when it is hydrolysed ; A equation A joules for
energy
easily hydrolysed ;
(energy) used in, processes / reactions ; A named process
rapid turnover ;
links catabolic and anabolic reactions / AW ;
found in, most cells / all organisms ;
soluble so easily moved (within cell) ;
ATP produced from variety of reactions ; A named reactions

Question 3

State precisely two places where ATP is synthesised in cells

Answer 3

2
3
4
ETC / inner mitochondrial membrane / crista / stalked particles ;
grana / thylakoids / inner chloroplast membrane ;
cytoplasm / cytosol ;
mitochondrial matrix ;

Question 4

Describe the structure and synthesis of ATP and its universal role as the energy currency
in all living organisms.

Answer 4

nucleotide ;
adenine + ribose / pentose + three phosphates ;
loss of phosphate leads to energy release / hydrolysis releases
30.5 kJ ;
ADP + Pi ↔ ATP (reversible reaction) ;
synthesised during, glycolysis / Krebs cycle / substrate level
phosphorylation ;
synthesised, using electron carriers / oxidative phosphorylation /
photophosphorylation ;
in, mitochondria / chloroplasts ;
ATP synthase / ATP synthetase ;
chemiosmosis / description;
used by cells as immediate energy donor ;
link between energy yielding and energy requiring reactions / AW ;
active transport / muscle contraction / Calvin cycle / protein synthesis ;

Question 5

Outline the behaviour of chromosomes during meiosis.

Answer 5

do not credit marking points out of sequence 
prophase 1 
1 idea of condensation of chromosomes ; 
2 homologous chromosomes pair up / bivalent formed ; 
metaphase 1 
3 homologous chromosomes / bivalents, line up on equator ; 
4 of spindle ; 
5 by centromeres ; 
6 independent assortment / described ; 
7 chiasmata / described ; 
8 crossing over / described ; 
anaphase 1 
9 chromosomes move to poles ; 
10 homologous chromosomes / bivalents, separate ; 
11 pulled by microtubules ; 
12 reduction division ; 
metaphase 2 
13 chromosomes line up on equator ; 
14 of spindle ; 
anaphase 2 
15 centromeres divide ; 
16 chromatids move to poles ; 
17 pulled by microtubules ; 
9 (a) 
18 ref. haploid number ;

Question 6

Describe the ways by which gene mutations can occur

Answer 6

change in, base / nucleotide, sequence (in DNA) ; 
20 during DNA replication ; 
21 detail of change ; e.g. base, substitution / addition / deletion 
22 frame shifts / AW ; 
23 different / new, allele ; 
24 random / spontaneous ; 
25 mutagens ; 
26 ionising radiation ; 
 (b) 
27 UV radiation / mustard gas ;

Question 7

Outline the need for energy in living organisms using named examples

Answer 7

1 ATP as universal energy currency ;
2 light energy needed for photosynthesis ;
3 ATP used conversion of GP to TP ;
4 ATP used to regenerate RuBP ;
5 (energy needed for) anabolic reactions ;
6 protein synthesis / starch formation / triglyceride formation ;
7 activation energy ;
8 (activate) glucose in glycolysis ;
9 active transport ;
10 example ; e.g. sodium / potassium pump
11 movement / locomotion ;
12 example ; e.g. muscle contraction / cilia beating
13 endocytosis / exocytosis / pinocytosis / bulk transport ;
10 (a)
14 temperature regulation ; Describe the consequences for the cell of the following statements.

Question 8

• Each cell has only a very small quantity of ATP in it at any one time. • The molecules, ATP, ADP (adenosine diphosphate) or AMP (adenosine monophosphate) rarely pass through the cell surface membrane

Answer 8

1. (cell uses) ATP as source of energy ;
2. ATP broken down ;
3. (so) cell must regenerate ATP ;
4. from ADP and Pi ;
5. ref. ADP / AMP, must be synthesised in the cell

Question 9

Describe the structure of a mitochondrion and outline its function in a plant cell

Answer 9

1. 0.5–1.0 µm, diameter / width ;
2. double membrane ;
3. inner membrane folded / cristae ;
4. hold, stalked particles / ATP synthase / ATP synthetase ;
5. site of ETC ;
6. ref. H + and intermembrane space ;
7. ATP production ;
8. oxidative phosphorylation / chemiosmosis ;
9. matrix is site of, link reaction / Krebs cycle ;
10. enzymes in matrix ;
11. 70S ribosomes ;
12. (mitochondrial) DNA ;

Question 10

State two ways in which the structure of ATP differs from the structure of an adenine nucleotide in a DNA molecule.

Answer 10

contains ribose (not deoxyribose) ;

has three phosphate groups (not one) ;

Question 11

Name the molecule that is required to react with ATP in order to convert ATP into ADP and an inorganic phosphate.

Answer 11

water

Question 12

Describe the first division of meiosis (meiosis I) in animal cells

Answer 12

reduction division / (to) halve number of chromosomes / diploid to haploid / AW ; 2. homologous chromosomes pair up / bivalents form ; 3. ref. chiasmata / ref. crossing over ; 4. homologous chromosome pairs / bivalents, line up on equator ; 5. independent assortment ; 6. spindle / microtubules, attached to centromeres ; 7. chromosomes of each pair pulled to opposite poles ; 8. by shortening of, spindle / microtubules ; 9. nuclear envelopes re-form ; 10. cytokinesis / AW

Question 13

State why rubisco is said to have quaternary structure.

Answer 13

made up of more than one polypeptide

Question 14

Describe how the structure of ATP is related to its role as energy currency

Answer 14

1 small ;

2 water soluble ;

3 easily transported around the cell ;

4 easily hydrolysed (to release energy) ;

5 (so) relatively large quantity of energy released

/

30.5

kJ

mol–1 ;

6 idea of, rapid turnover

/

small cellular ATP content is sufficient for cell’s requirements ;

Question 15

role of mineral ions

Answer 15

Fe2+ oxygen transport

/

haemoglobin structure ; red blood cell
Na+ co-transport in the kidney proximal convoluted tubule

/

epithelial ;
Ca+ synaptic transmission

/

described ; neurone

Question 16

(a) Explain how meiosis and fertilisation may result in genetic variation in offspring

Answer 16

chiasma / crossing over ;

between non-sister chromatids ;

of, homologous chromosomes / bivalent ;

in prophase 1 ;

exchange of genetic material / AW ; R genes unqualified

linkage groups broken ;

new combination of alleles ;

independent assortment (of homologous chromosomes) ;  
 R random assortment 

at equator ;

(during) metaphase 1 ;

possible mutation ;

random mating ;

random fusion / fertilisation of gametes

Question 17

) Explain how changes in the nucleotide sequence of DNA may affect the amino acid sequence in a protein.

Answer 17

1. (amino acid) code is three, bases / nucleotides ; A triplet code
2. (gene) mutation ; R chromosome mutation
3. base / nucleotide, substitution / addition / deletion
4. addition / deletion, has large effect (on amino acid sequence) ;
5. frame shift ;
6. completely new code after mutation / alters every 3 base sequence which follows ;
7. substitution may have little or no effect / silent mutation ;
8. different triplet but same amino acid / new amino acid in non-functional part of protein ;
9. substitution may have big effect (on amino acid sequence) ;
10. could produce ‘stop’ codon ;
11. sickle cell anaemia / PKU / cystic fibrosis ;
12. reference to transcription or translation in correct context ; A description

Question 18

Suggest an explanation for each of the following Foods containing starch made up mostly of amylose have lower GIs than foods containing starch made up mostly of amylopectin

Answer 18

1 amylose has 1–4 bonds / amylopectin has 1–4 bonds plus 1–6 bonds ; 2 amylose, digested / broken down to glucose / acted on by amylase, more slowly ; 3 because fewer sites for enzyme to work on / AW ; accept ora

Question 19

(a) Describe how crossing over and independent assortment can lead to genetic variation

Answer 19

1 occur during meiosis I ; crossing over 2 between non-sister chromatids ; 3 of, (a pair of) homologous chromosomes / a bivalent ; 4 in prophase 1 ; 5 at chiasma(ta) ; 6 exchange of genetic material / AW ; R genes unqualified 7 linkage groups broken / AW ; 8 new combination of alleles (within each chromosome) ; independent assortment 9 of homologous chromosomes pairs / bivalents ; 10 each pair lines up independently of others ; 11 line up on equator ; 12 (during) metaphase 1 ; 13 results in gametes that are genetically unique / AW

Question 20

Describe how an insecticide could irreversibly inhibit acetycholinesterase

Answer 20

1 permanently ;

2 binds with / blocks, active site ;

3 binds with, another part of enzyme / allosteric site ;

4 change (shape) of active site ;

Question 21

Explain how changes in the nucleotide sequence of DNA may affect the amino acid sequence in a protein

Answer 21

1 code is three, bases / nucleotides ; A triplet code

2 (gene) mutation ; R chromosome mutation

3 base, substitution / addition / deletion ;

4 addition / deletion, large effect (on amino acid sequence) ;

5 frame shift ;

6 completely new code after mutation / alters every 3 base sequence which follows ;

7 (substitution) often has no effect / silent mutation ;

8 different triplet but same amino acid / new amino acid in non-functional part of protein ;

9 (substitution) may have big effect (on amino acid sequence) ;

10 could produce ‘stop’ codon ;

11 sickle cell anaemia / PKU / cystic fibrosis ;

12 reference to transcription or translation in correct context ; A description

12a AVP ; e.g. protein produced, is non-functional / not produced / incomplete

Question 22

Explain the role of ATP in active transport of ions and in named anabolic reactions.

Answer 22

Active transport or anabolic reactions

1. ATP provides energy (linked to either) ; ignore ref. to energy currency alone

active transport 2. movement against concentration gradient ;

3. carrier / transport, protein (in membrane) ; ignore pump
4. binds to (specific) ion ;
5. protein changes shape ;

anabolic reactions 6. synthesis of complex substances from simpler ones ;

7. starch / cellulose / glycogen, from, monosaccharides / named monosaccharides / named sugar ;
8. glycosidic bonds ;
9. lipid / triglyceride, from fatty acids and glycerol ;
10. ester bonds ;
11. polypeptides / proteins, from amino acids ;
12. peptide bonds ;
13. other named polymer from suitable monomer ;
14. appropriate named bond ;

Question 23

Bacteria are members of the kingdom Prokaryota. Describe the main features of a bacterial cell.

Answer 23

a) 1. DNA not surrounded by nuclear membrane / no nucleus;
2. (prokaryote) DNA is circular;
3. DNA not associated with histones; A naked DNA
4. plasmids (may) be present;
5. no (double) membrane-bound organelles; A no, mitochondria / chloroplasts
6. no, ER / Golgi; A ribosomes not attached to membranes
7. ribosomes,70S / 18 nm / smaller (than eukaryotic cells);
8. cell wall made of, peptidoglycan / murein / amino sugars / AW;
9. (usually) unicellular;
10. 0.5 to 5.0 µm diameter; A any value between 0.5 and 5.0 as long as µm is used
11. AVP; (may) have, flagella / pili / capsule / slime layer [8 max

Question 24

Explain what is meant by the term water potential

Answer 24

tendency of water molecules to move from one region to another

/

potential
energy of water

/

ability of water to do work ; [1]

Question 25

Explain how meiosis and fertilisation can result in genetic variation amongst offspring

Answer 25

1 chiasma

/

crossing over ; 2 between non-sister chromatids ; 3 of, homologous chromosomes
/
bivalent ; 4 in prophase 1 ; 5 exchange of, genetic material
/
DNA ; R genes unqualified 6 linkage groups broken ; 7 new combination of alleles ; 8 random
/
independent, assortment of, homologous chromosomes
/

bivalents (at equator) ; 9 (during) metaphase 1 ; 10 random
/
independent, assortment (of, sister chromatids

/

chromosomes)
at metaphase 2 ; 11 possible chromosome mutation ; 12 random mating ; 13 random, fusion
/
fertilisation, of gametes ; [max 8]

Question 26

Some insecticides have a similar structure to acetylcholine. Suggest how these insecticides may affect the functioning of acetylcholinesterase.

Answer 26

) acts as a competitive inhibitor ; complementary (shape) to active site ; binds with
/
blocks, active site ; ACh not, broken down
/
hydrolysed ;