AQA AS BIOLOGY FINAL PAPER 2025/2026 QUESTIONS
AND ANSWERS GRADED A+
✔✔Why is the genetic code described as being universal? - ✔✔(In all organisms /
DNA,) the same triplet codes for the same amino acid
✔✔The total number of bases in the DNA of the a-polypeptide gene is more than 423.
Give two reasons why there are more than 423 bases. - ✔✔Stop/Start sequences;
Non coding DNA/introns
Two chains/a non-coding strand/complementary base pairs
Addition of base by mutation
✔✔Advantage of Hb saturation curve shifted to the right - ✔✔lower affinity for oxygen,
oxygen can readily be unloaded so more oxygen available to tissues for a greater/faster
rate of respiration
✔✔Advantage of Hb saturation curve shifting to the left - ✔✔Higher affinity for oxygen,
can be saturated at lower partial pressures, can load more oxygen more easily. Can
carry and supply sufficient amounts of O2 to tissues for respiration
✔✔Mutagenic agents - ✔✔high energy radiation; X-rays; UV light; carcinogen; mustard
gas
✔✔Describe how a deletion mutation alters the structure of a gene. - ✔✔removal of one
or more bases/nucleotide;
frameshift/(from point of mutation) base sequence change;
✔✔Explain the importance of meiosis in the life cycle of organisms which reproduce
sexually. - ✔✔meiosis halves the chromosome number
so when gametes fuse, the diploid number is restored
introduces genetic variation
✔✔Suggest two reasons why populations might show very low levels of genetic
diversity. - ✔✔Population might have been very small
population might have started with small number of individuals
Inbreeding
✔✔Explain how SD helps in the interpretation of data. - ✔✔shows the spread of the
data
overlap= no significant difference
✔✔Explain how an asthma attack caused the drop in the mean expiration volume. -
✔✔1. Muscle walls of bronchi contract;
2. Walls of bronchi secrete more mucus;
, 3. Diameter of airways reduced;
4. (Therefore) flow of air reduced.
✔✔Volume of water passing over the gills increases if the temperature of water
increases. Why? - ✔✔Increased metabolism/ respiration;
Less oxygen dissolved in water
✔✔Suggest why water uptake might not be the same as rate of transpiration. -
✔✔Water used for support/turgidity
Water used in hydrolysis
Water used in photosynthesis
Water produced during respiration
✔✔Healthy people have amylase in their blood. This does not cause any harmful effects
in the body. Explain why. - ✔✔Amylase is specific to starch
There's no starch in human blood/cells/starch only in plants
✔✔Pancreatitis can lead to the release of protein-digesting enzymes into the blood.
This is harmful to the body. Suggest one reason why. - ✔✔They could hydrolyse/digest
own proteins such as membrane proteins/antibodies
✔✔Explain why it is necessary for humans to synthesise a large amount of ATP. - ✔✔1.
ATP is unstable;
2. ATP cannot be stored / is an immediate source
of energy;
3. Named process uses ATP ;
4. ATP only releases a small amount of energy at
a time;
✔✔Adaptations of a leaf - ✔✔Large SA:V ratio: absorb as much sunlight as possible
Leaves are thin: short diffusion distance for gases entering
Many air spaces in spongy mesophyll: diffusion of CO2/O2
Many stomata: for gaseous exchange
Transparent cuticle and upper epidermis: let light through to the photosynthetic
mesophyll cells
Long narrow upper palisade (many cells packed in): so number of chloroplasts to
absorb the light increases
✔✔Explain why converting pyruvate to lactate allows the continued production of ATP
during anaerobic respiration. - ✔✔NAD regenerated/NADH oxidised to NAD. Used in
glycolysis.
✔✔Explain the difference in the mean rate of respiration in soil under trees and soil
NOT under trees. - ✔✔Respiration higher in soil undre tree
AND ANSWERS GRADED A+
✔✔Why is the genetic code described as being universal? - ✔✔(In all organisms /
DNA,) the same triplet codes for the same amino acid
✔✔The total number of bases in the DNA of the a-polypeptide gene is more than 423.
Give two reasons why there are more than 423 bases. - ✔✔Stop/Start sequences;
Non coding DNA/introns
Two chains/a non-coding strand/complementary base pairs
Addition of base by mutation
✔✔Advantage of Hb saturation curve shifted to the right - ✔✔lower affinity for oxygen,
oxygen can readily be unloaded so more oxygen available to tissues for a greater/faster
rate of respiration
✔✔Advantage of Hb saturation curve shifting to the left - ✔✔Higher affinity for oxygen,
can be saturated at lower partial pressures, can load more oxygen more easily. Can
carry and supply sufficient amounts of O2 to tissues for respiration
✔✔Mutagenic agents - ✔✔high energy radiation; X-rays; UV light; carcinogen; mustard
gas
✔✔Describe how a deletion mutation alters the structure of a gene. - ✔✔removal of one
or more bases/nucleotide;
frameshift/(from point of mutation) base sequence change;
✔✔Explain the importance of meiosis in the life cycle of organisms which reproduce
sexually. - ✔✔meiosis halves the chromosome number
so when gametes fuse, the diploid number is restored
introduces genetic variation
✔✔Suggest two reasons why populations might show very low levels of genetic
diversity. - ✔✔Population might have been very small
population might have started with small number of individuals
Inbreeding
✔✔Explain how SD helps in the interpretation of data. - ✔✔shows the spread of the
data
overlap= no significant difference
✔✔Explain how an asthma attack caused the drop in the mean expiration volume. -
✔✔1. Muscle walls of bronchi contract;
2. Walls of bronchi secrete more mucus;
, 3. Diameter of airways reduced;
4. (Therefore) flow of air reduced.
✔✔Volume of water passing over the gills increases if the temperature of water
increases. Why? - ✔✔Increased metabolism/ respiration;
Less oxygen dissolved in water
✔✔Suggest why water uptake might not be the same as rate of transpiration. -
✔✔Water used for support/turgidity
Water used in hydrolysis
Water used in photosynthesis
Water produced during respiration
✔✔Healthy people have amylase in their blood. This does not cause any harmful effects
in the body. Explain why. - ✔✔Amylase is specific to starch
There's no starch in human blood/cells/starch only in plants
✔✔Pancreatitis can lead to the release of protein-digesting enzymes into the blood.
This is harmful to the body. Suggest one reason why. - ✔✔They could hydrolyse/digest
own proteins such as membrane proteins/antibodies
✔✔Explain why it is necessary for humans to synthesise a large amount of ATP. - ✔✔1.
ATP is unstable;
2. ATP cannot be stored / is an immediate source
of energy;
3. Named process uses ATP ;
4. ATP only releases a small amount of energy at
a time;
✔✔Adaptations of a leaf - ✔✔Large SA:V ratio: absorb as much sunlight as possible
Leaves are thin: short diffusion distance for gases entering
Many air spaces in spongy mesophyll: diffusion of CO2/O2
Many stomata: for gaseous exchange
Transparent cuticle and upper epidermis: let light through to the photosynthetic
mesophyll cells
Long narrow upper palisade (many cells packed in): so number of chloroplasts to
absorb the light increases
✔✔Explain why converting pyruvate to lactate allows the continued production of ATP
during anaerobic respiration. - ✔✔NAD regenerated/NADH oxidised to NAD. Used in
glycolysis.
✔✔Explain the difference in the mean rate of respiration in soil under trees and soil
NOT under trees. - ✔✔Respiration higher in soil undre tree
