A-Level (7402)
Biology
Paper 1
Updated Version 2024
QNS & ANS
1. Question: Define osmosis and explain its significance in
cell function.
Answer: Osmosis is the passive movement of water
molecules across a selectively permeable membrane from an
area of low solute concentration to an area of high solute
concentration. It is significant for maintaining cell turgor
pressure, which is essential for structural integrity, nutrient
absorption, and overall homeostasis in cells.
2. Question: What role does the sodium-potassium pump
play in maintaining membrane potential?
Answer: The sodium-potassium pump is an active
transport mechanism that moves sodium ions out of the cell and
potassium ions into the cell, helping to maintain the resting
membrane potential. This is crucial for processes such as nerve
impulse transmission and muscle contraction.
3. Question: Describe the difference between prokaryotic and
eukaryotic cells in terms of genetic organization.
Answer: Prokaryotic cells have a single circular DNA
molecule located in the nucleoid region, while eukaryotic cells
possess multiple linear DNA molecules contained within a
membrane-bound nucleus, often associated with histone
proteins.
,4. Question: Explain the significance of meiosis in genetic
variation.
Answer: Meiosis introduces genetic variation through
independent assortment of chromosomes during metaphase I
and crossing over during prophase I. This results in gametes
with unique combinations of alleles, contributing to genetic
diversity in offspring.
5. Question: What is the function of ribosomes in protein
synthesis?
Answer: Ribosomes are the cellular machinery that
translates mRNA into polypeptides (proteins). They facilitate the
binding of tRNAs carrying specific amino acids to the mRNA,
allowing the sequential addition of amino acids to form a
protein.
6. Question: Identify two ways in which cells exchange
substances with their environment and briefly describe each.
Answer: Cells exchange substances via diffusion, a
passive process where molecules move from an area of higher
concentration to lower concentration; and via active transport,
which requires energy to move substances against their
concentration gradient.
7. Question: Describe one mechanism by which genetic
information can be transferred between bacteria.
Answer: Conjugation is a mechanism where genetic
information is transferred between bacteria through direct
contact, often via a pilus that connects two bacteria, allowing
the transfer of plasmids which can carry antibiotic resistance
genes.
8. Question: What is the significance of the mitochondrial
structure for its function?
Answer: Mitochondria have a double membrane structure
with inner folds called cristae, which increase the surface area
for electron transport and ATP synthesis. This unique structure
allows efficient energy production through oxidative
phosphorylation.
9. Question: Explain the role of the endoplasmic reticulum in
a cell.
, Answer: The endoplasmic reticulum (ER) acts as a
network for the synthesis and transport of proteins (rough ER)
and lipids (smooth ER). It plays a critical role in maintaining
cellular functions and preparing products for secretion or further
processing.
10. Question: What is a plasmid and why is it important in
biotechnology?
Answer: A plasmid is a small, circular DNA molecule
independent of chromosomal DNA in bacteria. It is important in
biotechnology for cloning and genetic engineering, as it can
carry foreign DNA into a host cell, facilitating gene expression
and manipulation.
### Long Answer Questions
11. Question: Compare and contrast cellular respiration and
photosynthesis, emphasizing their relevance in energy transfer
within biological systems.
Answer: Cellular respiration is a catabolic process in
which glucose is broken down to produce ATP, releasing
carbon dioxide and water (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
+ ATP). It occurs in the mitochondria of both plants and
animals. Photosynthesis, on the other hand, is an anabolic
process that occurs in chloroplasts, where light energy is used
to convert carbon dioxide and water into glucose and oxygen (6
CO2 + 6 H2O + light energy → C6H12O6 + 6 O2). Together,
these processes create a cycle of energy transfer;
photosynthesis captures energy, which is then used in cellular
respiration to fuel cellular activities, supporting life on Earth.
12. Question: Discuss the implications of genetic drift on
small populations and how this concept relates to the evolution
of species.
Answer: Genetic drift refers to random fluctuations in
allele frequencies, particularly impactful in small populations
where chance events can significantly alter genetic diversity.
These changes can lead to the fixation or loss of alleles,
reducing genetic variability and potentially increasing
susceptibility to environmental changes or diseases. Over time,
genetic drift can contribute to speciation if populations become
isolated and diverge genetically, impacting evolutionary
Biology
Paper 1
Updated Version 2024
QNS & ANS
1. Question: Define osmosis and explain its significance in
cell function.
Answer: Osmosis is the passive movement of water
molecules across a selectively permeable membrane from an
area of low solute concentration to an area of high solute
concentration. It is significant for maintaining cell turgor
pressure, which is essential for structural integrity, nutrient
absorption, and overall homeostasis in cells.
2. Question: What role does the sodium-potassium pump
play in maintaining membrane potential?
Answer: The sodium-potassium pump is an active
transport mechanism that moves sodium ions out of the cell and
potassium ions into the cell, helping to maintain the resting
membrane potential. This is crucial for processes such as nerve
impulse transmission and muscle contraction.
3. Question: Describe the difference between prokaryotic and
eukaryotic cells in terms of genetic organization.
Answer: Prokaryotic cells have a single circular DNA
molecule located in the nucleoid region, while eukaryotic cells
possess multiple linear DNA molecules contained within a
membrane-bound nucleus, often associated with histone
proteins.
,4. Question: Explain the significance of meiosis in genetic
variation.
Answer: Meiosis introduces genetic variation through
independent assortment of chromosomes during metaphase I
and crossing over during prophase I. This results in gametes
with unique combinations of alleles, contributing to genetic
diversity in offspring.
5. Question: What is the function of ribosomes in protein
synthesis?
Answer: Ribosomes are the cellular machinery that
translates mRNA into polypeptides (proteins). They facilitate the
binding of tRNAs carrying specific amino acids to the mRNA,
allowing the sequential addition of amino acids to form a
protein.
6. Question: Identify two ways in which cells exchange
substances with their environment and briefly describe each.
Answer: Cells exchange substances via diffusion, a
passive process where molecules move from an area of higher
concentration to lower concentration; and via active transport,
which requires energy to move substances against their
concentration gradient.
7. Question: Describe one mechanism by which genetic
information can be transferred between bacteria.
Answer: Conjugation is a mechanism where genetic
information is transferred between bacteria through direct
contact, often via a pilus that connects two bacteria, allowing
the transfer of plasmids which can carry antibiotic resistance
genes.
8. Question: What is the significance of the mitochondrial
structure for its function?
Answer: Mitochondria have a double membrane structure
with inner folds called cristae, which increase the surface area
for electron transport and ATP synthesis. This unique structure
allows efficient energy production through oxidative
phosphorylation.
9. Question: Explain the role of the endoplasmic reticulum in
a cell.
, Answer: The endoplasmic reticulum (ER) acts as a
network for the synthesis and transport of proteins (rough ER)
and lipids (smooth ER). It plays a critical role in maintaining
cellular functions and preparing products for secretion or further
processing.
10. Question: What is a plasmid and why is it important in
biotechnology?
Answer: A plasmid is a small, circular DNA molecule
independent of chromosomal DNA in bacteria. It is important in
biotechnology for cloning and genetic engineering, as it can
carry foreign DNA into a host cell, facilitating gene expression
and manipulation.
### Long Answer Questions
11. Question: Compare and contrast cellular respiration and
photosynthesis, emphasizing their relevance in energy transfer
within biological systems.
Answer: Cellular respiration is a catabolic process in
which glucose is broken down to produce ATP, releasing
carbon dioxide and water (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
+ ATP). It occurs in the mitochondria of both plants and
animals. Photosynthesis, on the other hand, is an anabolic
process that occurs in chloroplasts, where light energy is used
to convert carbon dioxide and water into glucose and oxygen (6
CO2 + 6 H2O + light energy → C6H12O6 + 6 O2). Together,
these processes create a cycle of energy transfer;
photosynthesis captures energy, which is then used in cellular
respiration to fuel cellular activities, supporting life on Earth.
12. Question: Discuss the implications of genetic drift on
small populations and how this concept relates to the evolution
of species.
Answer: Genetic drift refers to random fluctuations in
allele frequencies, particularly impactful in small populations
where chance events can significantly alter genetic diversity.
These changes can lead to the fixation or loss of alleles,
reducing genetic variability and potentially increasing
susceptibility to environmental changes or diseases. Over time,
genetic drift can contribute to speciation if populations become
isolated and diverge genetically, impacting evolutionary
