Edexcel A-level biology exam
questions with complete
answers
Suggest why reducing inflammation could help reduce a patient's
immune response - Answer -There will not be such an increase in blood
flow to the wound.
-Will not be such an increase in macrophages to the area
-Fewer macrophages to present antigen to T-helper cells
-Without T-helper cell activation B cells cannot be activated etc
Explain how changes in the fibrinogen concentration might be a risk
factor for CVD - Answer -Increased concentrations of fibrinogen leads
to increased fibrin
,-Increases the risk of blood clotting
-Which blocks the lumen of arteries
Describe the structure of collagen - Answer - Primary structure is a
repeating amino acid sequence
-3 Polypeptide chains
-Chains coiled around each other
-Cross-links between chains
State what is meant by the term sex-linkage - Answer -The allele
responsible for a trait is located on a sex chromosome
-The expression of the trait is linked to gender
Explain how studying pollen grains in peat bogs can provide evidence of
climate change - Answer -Pollen is preserved in peat bogs
-A plant species can be identified by its pollen
-Climate affects the type of plant growing
-Depth of peat correlates with period of time since pollen was
produced
-Changes in pollen over time indicate changes in climate
Describe the role of mRNA in protein synthesis - Answer -mRNA is a
copy of the DNA
,-To take information out of the nucleus for translation
-Post transcriptional modification to enable more than 1 gene to code
for a peptide
Explain why it is important that a tRNA molecule can only attach to one
amino acid - Answer -tRNA is specific for an amino acid
-To ensure that the primary structure of the peptide is correct
-Otherwise folding will be incorrect
Explain why some amino acids can attach to more than 1 type of tRNA
molecule - Answer -Genetic code is degenerative
-Some amino acids have more than one code
-There will be a different tRNA for each codon on the mRNA
Explain why there are fewer possible anticodons than codons - Answer
There are stop codons that tRNA do not bind to
State the meaning of the term bacterial infection - Answer When
bacteria are inside cells
Describe an investigation, that could be carried out in a laboratory, to
determine a suitable combination of antibiotics to use against
Mycobacterium tuberculosis - Answer -Culture bacteria with agar using
aseptic techniques
, -Different antibiotics used in a number of different combinations
-Apply antibiotics using filter paper soaked in antibiotic
-Incubate bacteria with antibiotic for a period of time (greater than 12
hours)
-Most suitable combination will have the largest zone of inhibition
State the meaning of the term species - Answer Groups of organisms
that can breed together to produce fertile offspring
Explain how gel electrophoresis can be used to determine the father of
a cub - Answer -Collect DNA samples, from blood, skin, etc., from
mother, cub and all possible fathers.
-Use restriction endonucleases, load onto gel and apply a current.
-Visualise through southern blotting, adding fluorescent probes
-Match DNA bands
Describe the structure of a cell wall in a xylem vessel - Answer -
cellulose molecules as microfibrils held together by hydrogen bonds
-mesh of microfibrils
-lignified
-Lignin distributed in spirals
-Presence of pits
-Presence of pectin and hemicelluse in cell wall
questions with complete
answers
Suggest why reducing inflammation could help reduce a patient's
immune response - Answer -There will not be such an increase in blood
flow to the wound.
-Will not be such an increase in macrophages to the area
-Fewer macrophages to present antigen to T-helper cells
-Without T-helper cell activation B cells cannot be activated etc
Explain how changes in the fibrinogen concentration might be a risk
factor for CVD - Answer -Increased concentrations of fibrinogen leads
to increased fibrin
,-Increases the risk of blood clotting
-Which blocks the lumen of arteries
Describe the structure of collagen - Answer - Primary structure is a
repeating amino acid sequence
-3 Polypeptide chains
-Chains coiled around each other
-Cross-links between chains
State what is meant by the term sex-linkage - Answer -The allele
responsible for a trait is located on a sex chromosome
-The expression of the trait is linked to gender
Explain how studying pollen grains in peat bogs can provide evidence of
climate change - Answer -Pollen is preserved in peat bogs
-A plant species can be identified by its pollen
-Climate affects the type of plant growing
-Depth of peat correlates with period of time since pollen was
produced
-Changes in pollen over time indicate changes in climate
Describe the role of mRNA in protein synthesis - Answer -mRNA is a
copy of the DNA
,-To take information out of the nucleus for translation
-Post transcriptional modification to enable more than 1 gene to code
for a peptide
Explain why it is important that a tRNA molecule can only attach to one
amino acid - Answer -tRNA is specific for an amino acid
-To ensure that the primary structure of the peptide is correct
-Otherwise folding will be incorrect
Explain why some amino acids can attach to more than 1 type of tRNA
molecule - Answer -Genetic code is degenerative
-Some amino acids have more than one code
-There will be a different tRNA for each codon on the mRNA
Explain why there are fewer possible anticodons than codons - Answer
There are stop codons that tRNA do not bind to
State the meaning of the term bacterial infection - Answer When
bacteria are inside cells
Describe an investigation, that could be carried out in a laboratory, to
determine a suitable combination of antibiotics to use against
Mycobacterium tuberculosis - Answer -Culture bacteria with agar using
aseptic techniques
, -Different antibiotics used in a number of different combinations
-Apply antibiotics using filter paper soaked in antibiotic
-Incubate bacteria with antibiotic for a period of time (greater than 12
hours)
-Most suitable combination will have the largest zone of inhibition
State the meaning of the term species - Answer Groups of organisms
that can breed together to produce fertile offspring
Explain how gel electrophoresis can be used to determine the father of
a cub - Answer -Collect DNA samples, from blood, skin, etc., from
mother, cub and all possible fathers.
-Use restriction endonucleases, load onto gel and apply a current.
-Visualise through southern blotting, adding fluorescent probes
-Match DNA bands
Describe the structure of a cell wall in a xylem vessel - Answer -
cellulose molecules as microfibrils held together by hydrogen bonds
-mesh of microfibrils
-lignified
-Lignin distributed in spirals
-Presence of pits
-Presence of pectin and hemicelluse in cell wall
