Edexcel A-level biology 2024 Exam
Questions with 100% Correct Answers
Describe the events of fertilisation that occur after the acrosome
reaction. - Answer>>-Membrane of sperm and egg cell fuse
together
-cortical granules release contents into zona pellucida
-Zona pellucida thickens
-Haploid nuclei fuse
Explain how phospholipids form a cell surface membrane -
Answer>>-Hydrophilic parts associate with water
-Hydrophobic parts repel water
-a bilayer forms with hydrophobic parts pointing in towards the
centre of the bilayer
Describe the role of the CFTR protein in ensuring that the mucus
produced in the lungs has the right consistency - Answer>>-
Chloride ions move out of the cells through the CFTR protein
-Sodium ions then also move out of the cells
-The concentration of the solute increases in the mucus
-Water moves out of the cell by osmosis
Describe how DNA is organised in a bacterial cell - Answer>>-
Circular DNA that is not associated with histones
-Plasmids
-located in the cytoplasm
Describe the light-dependent reactions of photosynthesis -
Answer>>-Light energy excites a pair of electrons in PSII
-Electrons used in the electron transport chain
-Photolysis of water to produce H+, O2 and electrons
-Generation of ATP (phosphorylation)
-Reduction of NADP
,Suggest how useful body temperature is in determining time of
death - Answer>>-Drop in body temperature is linked to time
after death
-Factors affect it (eg. environmental temperature, body size etc)
-Time of death can be calculated if ambient temperature is known.
-However it's only useful for a short amount of time after death.
Suggest how useful state of decomposition is in determining time
of death - Answer>>-Body decomposes in a specific sequence
-Factors affect it (eg. environmental temperature, wounds)
-Not useful if body has fully decomposed
Why can human DNA polymerase not be used in PCR -
Answer>>Human enzymes will not work at high temperatures
as they will be denatured
Why species of plants cannot be identified from xylem material
using PCR and DNA profiling - Answer>>It is made from dead
material, there is no DNA present
Describe how the production and action of interferon differs from
lysozyme - Answer>>Interferon produced by infected cells to
inhibit the replication of viruses, whereas lysozyme present in
macrophages to destroy bacteria.
Suggest why the protein structure of lysozyme is important to the
way in which it acts against pathogens - Answer>>-Enzyme,
that has an active site of a specific shape
-Acts on the cell wall of bacteria
Explain why an insect bite, which breaks the surface of the skin,
may lead to inflammation - Answer>>-Histamine released from
mast cells as a result of damaged tissue
, -Arterioles dilate causing increased blood flow and capillaries
become more permeable
-Resulting in an oedema
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
Questions with 100% Correct Answers
Describe the events of fertilisation that occur after the acrosome
reaction. - Answer>>-Membrane of sperm and egg cell fuse
together
-cortical granules release contents into zona pellucida
-Zona pellucida thickens
-Haploid nuclei fuse
Explain how phospholipids form a cell surface membrane -
Answer>>-Hydrophilic parts associate with water
-Hydrophobic parts repel water
-a bilayer forms with hydrophobic parts pointing in towards the
centre of the bilayer
Describe the role of the CFTR protein in ensuring that the mucus
produced in the lungs has the right consistency - Answer>>-
Chloride ions move out of the cells through the CFTR protein
-Sodium ions then also move out of the cells
-The concentration of the solute increases in the mucus
-Water moves out of the cell by osmosis
Describe how DNA is organised in a bacterial cell - Answer>>-
Circular DNA that is not associated with histones
-Plasmids
-located in the cytoplasm
Describe the light-dependent reactions of photosynthesis -
Answer>>-Light energy excites a pair of electrons in PSII
-Electrons used in the electron transport chain
-Photolysis of water to produce H+, O2 and electrons
-Generation of ATP (phosphorylation)
-Reduction of NADP
,Suggest how useful body temperature is in determining time of
death - Answer>>-Drop in body temperature is linked to time
after death
-Factors affect it (eg. environmental temperature, body size etc)
-Time of death can be calculated if ambient temperature is known.
-However it's only useful for a short amount of time after death.
Suggest how useful state of decomposition is in determining time
of death - Answer>>-Body decomposes in a specific sequence
-Factors affect it (eg. environmental temperature, wounds)
-Not useful if body has fully decomposed
Why can human DNA polymerase not be used in PCR -
Answer>>Human enzymes will not work at high temperatures
as they will be denatured
Why species of plants cannot be identified from xylem material
using PCR and DNA profiling - Answer>>It is made from dead
material, there is no DNA present
Describe how the production and action of interferon differs from
lysozyme - Answer>>Interferon produced by infected cells to
inhibit the replication of viruses, whereas lysozyme present in
macrophages to destroy bacteria.
Suggest why the protein structure of lysozyme is important to the
way in which it acts against pathogens - Answer>>-Enzyme,
that has an active site of a specific shape
-Acts on the cell wall of bacteria
Explain why an insect bite, which breaks the surface of the skin,
may lead to inflammation - Answer>>-Histamine released from
mast cells as a result of damaged tissue
, -Arterioles dilate causing increased blood flow and capillaries
become more permeable
-Resulting in an oedema
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
