Biology Edexcel B content questions
Topic 1: Biological Molecules
1.1 Carbohydrates
1. Use a labelled diagram to show how a triglyceride is formed. (3)
• Glycerol plus three fatty acids as reactants
• Ester bond labelled
• Water shown
2. Name the type of chemical reaction that joins monosaccharides together to form an amylose
molecule. (1)
• Condensation / polymerisation
3. Name the chemical bond that is formed between the monosaccharides in an amylose
molecule. (1)
• glycosidic / 1,4 glycosidic
4. Describe one structural difference between amylose and glycogen.
• Amylose is {coiled / unbranched / eq } / amylose has only 1,4 (glycosidic) bonds
5. Explain two ways in which the structures of amylose and glycogen make them suitable for
energy storage. (2)
• contain glucose / eq ;
• idea that they are compact so large {numbers of glucose / amylose / glycogen } molecules can
fit into a small volume ;
• insoluble therefore {does not affect osmosis / eq } ;
• large molecules therefore { remains in cells / too big to diffuse / eq} ;
6. Explain how the dipolar nature of water is essential for living organisms. (2)
• Idea that water can form {hydrogen bonds / eq} ;
• and any one from
• Water is a solvent / {ions / polar molecules / eq } can {dissolve / be transported / eq } in water
• Reference to cohesion/adhesion
• Idea of hydrogen bonds holding water together as a liquid, so that it can move in mass flow
systems
• Suitable ref. to specific heat capacity
• Idea of distribution of thermal energy around body
• Reference to high latent heat of vaporisation
7. Enzymes act as biological catalysts. Amylase is an enzyme present in saliva that catalyses the
hydrolysis of starch into maltose. *(a) Describe the structure of starch. (5)
• (α) glucose
• glycosidic {bonds/links}
• amylose and amylopectin
• amylose has 1- 4 (glycosidic) {bonds / links} AND amylopectin has 1- 4 and 1- 6 (glycosidic)
bonds / eq
• amylose is {spiralled / coiled}
• amylopectin is branched / eq
• compact molecule / eq
8. Explain the meaning of the following terms. (i) Catalyst (2)
• Speeds up the rate of reaction / eq
• Without being {changed/used up / eq}
• Lowers activation energy / provides an alternative reaction pathway / eq
• Does not change {products / position of equilibrium / eq } / eq
9. Explain the meaning of hydrolysis:
• Breaks the (glycosidic) bonds / eq ;
• Reference to use of water ;
10. Bread contains a high proportion of starch. If bread is chewed for a long period of time it
begins to taste sweet. Suggest why bread tastes sweet after chewing for a long period of
time. (1)
1
, • Idea that { maltose / disaccharide / glucose / monosaccharide} {is produced / tastes sweet}
11. State two differences between the structure of cells of organisms belonging to the Eukaryota
domain and those belonging to the Bacteria domain. (2)
• Eukaryote cells have { membrane bound organelles / examples of membrane bound
organelle } and prokaryotes do not
• DNA within a nucleus in Eukaryota but not in Bacteria/linear chromosomes in Eukaryota
circular in Bacteria
• Larger ribosomes in Eukaryota / 80S ribosomes in Eukaryota and 70S in Bacteria / eq
• Bacteria contain { plasmids / pili / peptidoglycan cell wall /eq } and Eukaryota do not
12. Name an organelle found in the cells of both eukaryotic and prokaryotic organisms. (1)
• Ribosomes
13. Explain the roles of ribosomes, golgi apparatus and rER in the synthesis and secretion of
digestive enzymes. (4)
• reference to involvement of ribosomes on the { rER / rough endoplasmic reticulum } ;
• amino acids {being joined by peptide bonds /
• forming polypeptide chains / forming primary structure of protein } ;
• OR
• {folded into 3-D shape / secondary or tertiary structure} in rER ;
• packaged into vesicles at the end of the rER / vesicles {move to / transported to / fuse with /
eq} the Golgi apparatus ;
• idea that { protein/ enzyme } modified in Golgi apparatus ;
• (modified protein / enzyme / eq) packaged into (secretory) vesicles (by Golgi apparatus) / eq
• exocytosis by secretory vesicles / fusion of vesicles with cell (surface) membrane / eq ;
14. Fungi produce different enzymes that can digest starch or cellulose. Using your knowledge of
the structure of starch and cellulose, suggest why it is necessary for fungi to produce different
enzymes to digest these two substances.
• Different shape molecule requires different enzymes / reference to active site having to have
different shape ;
• Cellulose is made of β glucose and starch is made of α glucose / eq ;
• 1,6 glycosidic bonds only in starch ;
• Starch made of amylose and amylopectin ;
• Cellulose is linear / starch is {branched / helical / eq} / eq ;
15. Distinguish between the structures of each of the following pairs of carbohydrate molecules.
16. (i) Monosaccharides and disaccharides (2)
• idea that a monosaccharide consists of one {sugar / named sugar / eq} (unit) whereas a
disaccharide consists of two (sugar units) ;
• idea that disaccharide has a glycosidic bond (whereas monosaccharide does not) ;
• general formula for a monosaccharide is CnH2nOn whereas formula for disaccharide is
CnH2n-2On-1
17. (ii) Amylose and amylopectin (2)
• amylose is {straight chained / unbranched / eq} whereas amylopectin is branched ;
• amylose {coiled / eq} (whereas amylopectin is not) / eq ;
• amylose has 1-4 (glycosidic) bonds whereas amylopectin has 1-4 and 1-6 (glycosidic) bonds ;
18. (b) Explain why a diet consisting of a high proportion of carbohydrates could lead to obesity
• Idea of carbohydrates providing a source of energy ;
• If the {energy / carbohydrate / eq} input is greater than the {energy output / carbohydrate use /
eq} (weight will be gained) / eq ;
• Idea of excess carbohydrate converted to fat
19. Describe the structure of glycogen and explain why it is a suitable molecule for storing energy
(4)
• Any 3 of the following:
• Consists of (α) glucose ;
• (Joined by 1,,6) glycosidic bonds ; 3. branched structure / eq ;
• Idea of compact structure ;
• Any 3 of the following:
• Idea that it is {easily / rapidly / eq} hydrolysed ;
• (Leading to) more {glucose / eq} in a smaller space (in a cell)/ eq ;
• Idea of low solubility ;
• It does not diffuse out of cells /eq ;
• It has no osmotic effect / eq ;
2
,20. The stem of a plant contains xylem vessels and sclerenchyma fibres. Compare the functions
of xylem vessels with the functions of sclerenchyma fibres. (3)
• Both are used for (structural) support / eq ;
• Only xylem (vessels) transport water / eq ;
• Only xylem (vessels) transport mineral ions / eq ;
21. Name the chemical reaction that joins the galactose and glucose molecules together. (1)
• Condensation/polymerisation
22. Name the bond that joins the galactose and glucose molecules together.
• 1-4 glycosidic (bond/link)
23. In this investigation, all the seedlings were grown from seeds from the same wheat plant.
Suggest why this would improve the validity of the results. (1)
• {Less/reduced}genetic variation/reduced effect of genotype
• Seeds are the {same age/produced under the same conditions} ;
24. Suggest why organs are considered more complex than tissues (2)
• (organs) made up of tissues;
• (organs) made up of many different cell types/eq ;
• (organs) can have more than 1 function/eq;
25. Compare the structure of a cellulose molecule with the structure of starch. (4)
• Both made up of glucose
• Both have 1-4 glycosidic bonds made by condensation reactions}
• Starch is composed of alpha glucose, cellulose is composed of Beta glucose
• Starch composed of {more than one type of molecule / amylose and amylopectin ;
• Correct reference to {branching/ 1-6bonds / helix} in starch / straight chain in cellulose ;
• All monomers same orientation in starch/every other one inverted in cellulose ;
26. Cellulose molecules form cellulose microfibrils. Explain how the arrangement of cellulose
microfibrils contributes to the physical properties of plant fibres.
• Idea of(tensile)strength/flexible/inelastic / eq ;
• {Parallel arrangement/eq}/ reference to hydrogen bonding / several layers of fibres / reference
to {criss cross / net like} arrangement (of microfibrils) ;
27. Give two functions of xylem vessels.
• support/stability
• transport of water
• transport of minerals/ions
28. Describe the chemical nature of cellulose. (3)
• polysaccharide;
• unbranched/straight chain;
• beta / β} glucose ;
• (1-4) glycosidic bonds (between glucose molecules) ;
• reference to intermolecular hydrogen bonds / eq ;
29. Name a plant tissue that could be the main source of the lignin found in marshland peat.
• Xylem
30. Describe the role of microorganisms in the recycling of the carbon from organic compounds.
• Reference to {decomposition/decay/putrefaction } (by microorganisms) ;
• Reference to respiration;
• Releases carbon dioxide for photosynthesis / eq ;
• Methane released in anaerobic (conditions);
• (methane) available as fuel/eq;
31. Suggest why the continued draining and clearance of peatlands may contribute towards
global warming even though they may be used to produce biofuels. (5)
• Reference to(combustion of)biofuels releases carbon dioxide {recently / eq} removed from
atmosphere / eq ;
• (Therefore)there is no(net)increase in carbon dioxide (in atmosphere) / eq ;
• Carbon dioxide is a greenhouse gas/eq;
• That {absorbs / traps / eq} {infra-red / heat / long-wave} (radiation reflected from Earth’s surface)
• Reference to prevents {infra-red/heat/ long-wave} {escaping / eq} into space ;
• Reference to(therefore) mean temperature of Earth’s surface increases ;
• Idea that carbon in peat(land) was {trapped / eq} {a long time ago / eq} ;
• Idea of peatland clearance releases carbon dioxide ;
• Idea that there is a(net)gain of carbon dioxide (in the atmosphere) ;
• Idea that removal of plants (during clearance) reduces photosynthesis ;
3
, • Reference to carbon dioxide released from (clearance) machinery ;
32. Starch is a polymer of one monosaccharide. Name this monosaccharide.
• alpha glucose
33. Describe two ways in which the structure of starch is related to its function. (4)
• 1. made up of {many / eq} glucose (monomers)
• 2. reference to{energy/eq}storage/glucose
• is the respiratory substrate / synthesis of organic molecules / eq
• 3. idea that it is{large/eq}
• 4. so is un-reactive/insoluble/no osmotic effect
• 5. molecule coiling/compact/reference to amylose /eq
• 6. more can be stored (in available space)/eq
• 7. reference to branches/reference to (glycosidic) 1-6 bonds / amylopectin
• 8. {rapid/increased/eq}mobilisation of glucose units / eq
34. Name two types of plant fibre that may be present in the material eaten by cattle. (2)
• Sclerenchyma (fibres)
• Xylem (vessels)
• Cellulose (fibre) ;
35. The first stage in the decomposition of a cow pat is known as putrefaction. Explain how
carbon dioxide and ammonia are formed during this stage of decomposition. (4)
• Ref to{microorganisms/microbes/bacteria/ fungi / eq} ;
• Ref to respiration of(microorganisms/bacteria/ fungi / eq) ;
• Ref to aerobic/anaerobic(respiration);
• Converts{organic compounds/eq}to carbon dioxide / eq ;
• Converts{nitrogen compounds/proteins/amino acids/ urea} to ammonia / eq ;
1.4 DNA and protein synthesis
1. State three differences between the structure of DNA and the structure of RNA. (3)
• DNA is {double stranded/ has a double helix} and RNA is {single stranded / does not have a
double helix} ;
• DNA has{thymine/T}whileRNAhas{uracil/U};
• DNA has deoxyribose while RNA has ribose ;
• DNA is{larger/longer}thanRNA/eq;
2. One function of DNA is to act as a template for the synthesis of messenger RNA.
State what is meant by the term template for the synthesis of messenger RNA. (1)
• Idea that the (RNA) nucleotides attach to this strand
• OR
• idea of {nucleotide / base } sequence that directs the synthesis of {complementary sequence /
mRNA / eq} ;
3. Describe three differences between the processes of replication and transcription of DNA. (3)
• Replication uses DNA nucleotides whereas transcription uses RNA nucleotides
• Replication uses DNA polymerase whereas transcription uses RNA polymerase
• DNA replication is semi-conservative transcription is not semi-conservative
• DNA replication copies both DNA strands whereas transcription (copies) only {one strand /
template / gene / eq}
• DNA makes DNA double helix makes single strand mRNA
4. Describe the structure of a mononucleotide found in RNA. (2)
• Contains{Ribose/5Csugar/pentose}AND phosphate ;
• Reference to (nitrogenous) base / adenine / guanine / cytosine / uracil / eq ;
5. Describe the process of protein synthesis that occurs in the cytoplasm. (5)
• Reference to ribosome (attaches to mRNA);
• Idea that tRNA carries an amino acid;
• Idea of {anticodon codon interaction/complementary base pairing } between tRNA and mRNA
• Formation of hydrogen bonds (between the tRNA and mRNA) ;
• Reference to peptide bond(between amino acids);
• (Peptide bond)formed by a condensation reaction;
• Idea that tRNA released from {mRNA / ribosome} ;
• Idea that ribosome {attaches to / detaches from / eq} {sequence / eq} on mRNA ;
6. Name the process by which mRNA is formed in the nucleus. (1)
4
Topic 1: Biological Molecules
1.1 Carbohydrates
1. Use a labelled diagram to show how a triglyceride is formed. (3)
• Glycerol plus three fatty acids as reactants
• Ester bond labelled
• Water shown
2. Name the type of chemical reaction that joins monosaccharides together to form an amylose
molecule. (1)
• Condensation / polymerisation
3. Name the chemical bond that is formed between the monosaccharides in an amylose
molecule. (1)
• glycosidic / 1,4 glycosidic
4. Describe one structural difference between amylose and glycogen.
• Amylose is {coiled / unbranched / eq } / amylose has only 1,4 (glycosidic) bonds
5. Explain two ways in which the structures of amylose and glycogen make them suitable for
energy storage. (2)
• contain glucose / eq ;
• idea that they are compact so large {numbers of glucose / amylose / glycogen } molecules can
fit into a small volume ;
• insoluble therefore {does not affect osmosis / eq } ;
• large molecules therefore { remains in cells / too big to diffuse / eq} ;
6. Explain how the dipolar nature of water is essential for living organisms. (2)
• Idea that water can form {hydrogen bonds / eq} ;
• and any one from
• Water is a solvent / {ions / polar molecules / eq } can {dissolve / be transported / eq } in water
• Reference to cohesion/adhesion
• Idea of hydrogen bonds holding water together as a liquid, so that it can move in mass flow
systems
• Suitable ref. to specific heat capacity
• Idea of distribution of thermal energy around body
• Reference to high latent heat of vaporisation
7. Enzymes act as biological catalysts. Amylase is an enzyme present in saliva that catalyses the
hydrolysis of starch into maltose. *(a) Describe the structure of starch. (5)
• (α) glucose
• glycosidic {bonds/links}
• amylose and amylopectin
• amylose has 1- 4 (glycosidic) {bonds / links} AND amylopectin has 1- 4 and 1- 6 (glycosidic)
bonds / eq
• amylose is {spiralled / coiled}
• amylopectin is branched / eq
• compact molecule / eq
8. Explain the meaning of the following terms. (i) Catalyst (2)
• Speeds up the rate of reaction / eq
• Without being {changed/used up / eq}
• Lowers activation energy / provides an alternative reaction pathway / eq
• Does not change {products / position of equilibrium / eq } / eq
9. Explain the meaning of hydrolysis:
• Breaks the (glycosidic) bonds / eq ;
• Reference to use of water ;
10. Bread contains a high proportion of starch. If bread is chewed for a long period of time it
begins to taste sweet. Suggest why bread tastes sweet after chewing for a long period of
time. (1)
1
, • Idea that { maltose / disaccharide / glucose / monosaccharide} {is produced / tastes sweet}
11. State two differences between the structure of cells of organisms belonging to the Eukaryota
domain and those belonging to the Bacteria domain. (2)
• Eukaryote cells have { membrane bound organelles / examples of membrane bound
organelle } and prokaryotes do not
• DNA within a nucleus in Eukaryota but not in Bacteria/linear chromosomes in Eukaryota
circular in Bacteria
• Larger ribosomes in Eukaryota / 80S ribosomes in Eukaryota and 70S in Bacteria / eq
• Bacteria contain { plasmids / pili / peptidoglycan cell wall /eq } and Eukaryota do not
12. Name an organelle found in the cells of both eukaryotic and prokaryotic organisms. (1)
• Ribosomes
13. Explain the roles of ribosomes, golgi apparatus and rER in the synthesis and secretion of
digestive enzymes. (4)
• reference to involvement of ribosomes on the { rER / rough endoplasmic reticulum } ;
• amino acids {being joined by peptide bonds /
• forming polypeptide chains / forming primary structure of protein } ;
• OR
• {folded into 3-D shape / secondary or tertiary structure} in rER ;
• packaged into vesicles at the end of the rER / vesicles {move to / transported to / fuse with /
eq} the Golgi apparatus ;
• idea that { protein/ enzyme } modified in Golgi apparatus ;
• (modified protein / enzyme / eq) packaged into (secretory) vesicles (by Golgi apparatus) / eq
• exocytosis by secretory vesicles / fusion of vesicles with cell (surface) membrane / eq ;
14. Fungi produce different enzymes that can digest starch or cellulose. Using your knowledge of
the structure of starch and cellulose, suggest why it is necessary for fungi to produce different
enzymes to digest these two substances.
• Different shape molecule requires different enzymes / reference to active site having to have
different shape ;
• Cellulose is made of β glucose and starch is made of α glucose / eq ;
• 1,6 glycosidic bonds only in starch ;
• Starch made of amylose and amylopectin ;
• Cellulose is linear / starch is {branched / helical / eq} / eq ;
15. Distinguish between the structures of each of the following pairs of carbohydrate molecules.
16. (i) Monosaccharides and disaccharides (2)
• idea that a monosaccharide consists of one {sugar / named sugar / eq} (unit) whereas a
disaccharide consists of two (sugar units) ;
• idea that disaccharide has a glycosidic bond (whereas monosaccharide does not) ;
• general formula for a monosaccharide is CnH2nOn whereas formula for disaccharide is
CnH2n-2On-1
17. (ii) Amylose and amylopectin (2)
• amylose is {straight chained / unbranched / eq} whereas amylopectin is branched ;
• amylose {coiled / eq} (whereas amylopectin is not) / eq ;
• amylose has 1-4 (glycosidic) bonds whereas amylopectin has 1-4 and 1-6 (glycosidic) bonds ;
18. (b) Explain why a diet consisting of a high proportion of carbohydrates could lead to obesity
• Idea of carbohydrates providing a source of energy ;
• If the {energy / carbohydrate / eq} input is greater than the {energy output / carbohydrate use /
eq} (weight will be gained) / eq ;
• Idea of excess carbohydrate converted to fat
19. Describe the structure of glycogen and explain why it is a suitable molecule for storing energy
(4)
• Any 3 of the following:
• Consists of (α) glucose ;
• (Joined by 1,,6) glycosidic bonds ; 3. branched structure / eq ;
• Idea of compact structure ;
• Any 3 of the following:
• Idea that it is {easily / rapidly / eq} hydrolysed ;
• (Leading to) more {glucose / eq} in a smaller space (in a cell)/ eq ;
• Idea of low solubility ;
• It does not diffuse out of cells /eq ;
• It has no osmotic effect / eq ;
2
,20. The stem of a plant contains xylem vessels and sclerenchyma fibres. Compare the functions
of xylem vessels with the functions of sclerenchyma fibres. (3)
• Both are used for (structural) support / eq ;
• Only xylem (vessels) transport water / eq ;
• Only xylem (vessels) transport mineral ions / eq ;
21. Name the chemical reaction that joins the galactose and glucose molecules together. (1)
• Condensation/polymerisation
22. Name the bond that joins the galactose and glucose molecules together.
• 1-4 glycosidic (bond/link)
23. In this investigation, all the seedlings were grown from seeds from the same wheat plant.
Suggest why this would improve the validity of the results. (1)
• {Less/reduced}genetic variation/reduced effect of genotype
• Seeds are the {same age/produced under the same conditions} ;
24. Suggest why organs are considered more complex than tissues (2)
• (organs) made up of tissues;
• (organs) made up of many different cell types/eq ;
• (organs) can have more than 1 function/eq;
25. Compare the structure of a cellulose molecule with the structure of starch. (4)
• Both made up of glucose
• Both have 1-4 glycosidic bonds made by condensation reactions}
• Starch is composed of alpha glucose, cellulose is composed of Beta glucose
• Starch composed of {more than one type of molecule / amylose and amylopectin ;
• Correct reference to {branching/ 1-6bonds / helix} in starch / straight chain in cellulose ;
• All monomers same orientation in starch/every other one inverted in cellulose ;
26. Cellulose molecules form cellulose microfibrils. Explain how the arrangement of cellulose
microfibrils contributes to the physical properties of plant fibres.
• Idea of(tensile)strength/flexible/inelastic / eq ;
• {Parallel arrangement/eq}/ reference to hydrogen bonding / several layers of fibres / reference
to {criss cross / net like} arrangement (of microfibrils) ;
27. Give two functions of xylem vessels.
• support/stability
• transport of water
• transport of minerals/ions
28. Describe the chemical nature of cellulose. (3)
• polysaccharide;
• unbranched/straight chain;
• beta / β} glucose ;
• (1-4) glycosidic bonds (between glucose molecules) ;
• reference to intermolecular hydrogen bonds / eq ;
29. Name a plant tissue that could be the main source of the lignin found in marshland peat.
• Xylem
30. Describe the role of microorganisms in the recycling of the carbon from organic compounds.
• Reference to {decomposition/decay/putrefaction } (by microorganisms) ;
• Reference to respiration;
• Releases carbon dioxide for photosynthesis / eq ;
• Methane released in anaerobic (conditions);
• (methane) available as fuel/eq;
31. Suggest why the continued draining and clearance of peatlands may contribute towards
global warming even though they may be used to produce biofuels. (5)
• Reference to(combustion of)biofuels releases carbon dioxide {recently / eq} removed from
atmosphere / eq ;
• (Therefore)there is no(net)increase in carbon dioxide (in atmosphere) / eq ;
• Carbon dioxide is a greenhouse gas/eq;
• That {absorbs / traps / eq} {infra-red / heat / long-wave} (radiation reflected from Earth’s surface)
• Reference to prevents {infra-red/heat/ long-wave} {escaping / eq} into space ;
• Reference to(therefore) mean temperature of Earth’s surface increases ;
• Idea that carbon in peat(land) was {trapped / eq} {a long time ago / eq} ;
• Idea of peatland clearance releases carbon dioxide ;
• Idea that there is a(net)gain of carbon dioxide (in the atmosphere) ;
• Idea that removal of plants (during clearance) reduces photosynthesis ;
3
, • Reference to carbon dioxide released from (clearance) machinery ;
32. Starch is a polymer of one monosaccharide. Name this monosaccharide.
• alpha glucose
33. Describe two ways in which the structure of starch is related to its function. (4)
• 1. made up of {many / eq} glucose (monomers)
• 2. reference to{energy/eq}storage/glucose
• is the respiratory substrate / synthesis of organic molecules / eq
• 3. idea that it is{large/eq}
• 4. so is un-reactive/insoluble/no osmotic effect
• 5. molecule coiling/compact/reference to amylose /eq
• 6. more can be stored (in available space)/eq
• 7. reference to branches/reference to (glycosidic) 1-6 bonds / amylopectin
• 8. {rapid/increased/eq}mobilisation of glucose units / eq
34. Name two types of plant fibre that may be present in the material eaten by cattle. (2)
• Sclerenchyma (fibres)
• Xylem (vessels)
• Cellulose (fibre) ;
35. The first stage in the decomposition of a cow pat is known as putrefaction. Explain how
carbon dioxide and ammonia are formed during this stage of decomposition. (4)
• Ref to{microorganisms/microbes/bacteria/ fungi / eq} ;
• Ref to respiration of(microorganisms/bacteria/ fungi / eq) ;
• Ref to aerobic/anaerobic(respiration);
• Converts{organic compounds/eq}to carbon dioxide / eq ;
• Converts{nitrogen compounds/proteins/amino acids/ urea} to ammonia / eq ;
1.4 DNA and protein synthesis
1. State three differences between the structure of DNA and the structure of RNA. (3)
• DNA is {double stranded/ has a double helix} and RNA is {single stranded / does not have a
double helix} ;
• DNA has{thymine/T}whileRNAhas{uracil/U};
• DNA has deoxyribose while RNA has ribose ;
• DNA is{larger/longer}thanRNA/eq;
2. One function of DNA is to act as a template for the synthesis of messenger RNA.
State what is meant by the term template for the synthesis of messenger RNA. (1)
• Idea that the (RNA) nucleotides attach to this strand
• OR
• idea of {nucleotide / base } sequence that directs the synthesis of {complementary sequence /
mRNA / eq} ;
3. Describe three differences between the processes of replication and transcription of DNA. (3)
• Replication uses DNA nucleotides whereas transcription uses RNA nucleotides
• Replication uses DNA polymerase whereas transcription uses RNA polymerase
• DNA replication is semi-conservative transcription is not semi-conservative
• DNA replication copies both DNA strands whereas transcription (copies) only {one strand /
template / gene / eq}
• DNA makes DNA double helix makes single strand mRNA
4. Describe the structure of a mononucleotide found in RNA. (2)
• Contains{Ribose/5Csugar/pentose}AND phosphate ;
• Reference to (nitrogenous) base / adenine / guanine / cytosine / uracil / eq ;
5. Describe the process of protein synthesis that occurs in the cytoplasm. (5)
• Reference to ribosome (attaches to mRNA);
• Idea that tRNA carries an amino acid;
• Idea of {anticodon codon interaction/complementary base pairing } between tRNA and mRNA
• Formation of hydrogen bonds (between the tRNA and mRNA) ;
• Reference to peptide bond(between amino acids);
• (Peptide bond)formed by a condensation reaction;
• Idea that tRNA released from {mRNA / ribosome} ;
• Idea that ribosome {attaches to / detaches from / eq} {sequence / eq} on mRNA ;
6. Name the process by which mRNA is formed in the nucleus. (1)
4
