AQA AS BIOLOGY PRACTICE EXAMS 2025/2026 QUESTIONS
AND ANSWERS GRADED A+
✔✔test for reducing sugars - ✔✔heat with benedicts, turns brick red
✔✔vacuole - ✔✔surrounded by membrane called tonoplast
contains cell sap
keeps cell turgid
pushes chloroplasts to surface
✔✔test for non reducing sugar? - ✔✔-heat with benedicts, no change
-add dilute hcl (hydrolyses glycosidic bond)
-add sodium hydrogen carbonate to neutralise
-heat with benedicts, will turn brick red
✔✔structure of bacteria? - ✔✔circular DNA and plasmids
no membrane bound organelles
smaller ribosomes
cell wall made of murein
some have slime capsule (protect from phagocytosis) and flagella (movement)
✔✔types of proteins? - ✔✔globular and fibrous
✔✔structure of virus? - ✔✔DNA or RNA
if RNA, contains reverse transcriptase enzyme to convert it into DNA
capsid
phospholipid membrane
attachment proteins to identify and attach to host
✔✔what are globular proteins? - ✔✔have a specific 3d shape, soluble eg. haemoglobin
✔✔how does a virus infect their host cell? - ✔✔uses attachment protein to attach
send in DNA capsid which uses cell to make virus components
producing copies and destroying host cell
✔✔what are fibrous proteins? - ✔✔insoluble, inflexible and strong eg. keratin
✔✔how do amino acids differ? - ✔✔have different r groups
✔✔what is a chromosome? - ✔✔coiled DNA
formed during interphase
made of 2 sister chromatids joined by centromere
2 copies of same DNA molecule
,✔✔what is a homologous pair of chromosomes? - ✔✔1 maternal 1 paternal
same genes but different alleles
✔✔how are amino acids joined? - ✔✔condensation reaction between carboxyl group
and amine group. leaves bond between carbon and nitrogen, DIPEPTIDE
✔✔primary structure of a protein? - ✔✔sequence of AA, polypeptide chain. change in
sequence, bonds will be formed in different places in secondary.
✔✔secondary structure? - ✔✔primary structure coils to form an alpha helix, hydrogen
bonds form between amino acids
✔✔tertiary structure? - ✔✔secondary structure folds again to form final 3d shape, held
by ionic/hydrogen/disulfide bonds
✔✔quarternary structure? - ✔✔more than one polypeptide chain, non protein can be
involved
✔✔quarternary structure examples? - ✔✔haemoglobin, antibodies, collagen
✔✔collagen structure? - ✔✔-strong
-primary structure glycine
-secondary tight coil
-tertiary coils again
-quarternary three chains wrapped like rope
✔✔protein test? - ✔✔biruet reagent, turns purple
✔✔what is an enzyme? - ✔✔biological catalyst
speeds up reaction without being used up
lowers activation energy
✔✔what makes an enzyme specific? - ✔✔specific active site, only complimentary
substrates can bind and form enzyme substrate complexes
✔✔lock and key model? - ✔✔active site is rigid, only exactly complimentary substrates
fit
✔✔induced fit model? - ✔✔shape of active site changes slightly so substrate fits exactly
forming ES complex
✔✔affect of substrate concentration on enzyme activity? - ✔✔more substrate, more
chance of successful collisions, ES complex, increase rate
increases until all enzymes are saturated
, ✔✔affect of enzyme concentration on enzyme activity? - ✔✔more enzymes, more
successful reactions, ES complexes
continues until all the substrates are used up
✔✔affect of temperature on enzyme activity? - ✔✔as temp increases, kinetic energy
increases, molecules move faster
more collisions, more ES complexes
carries on until optimum
after optimum, tertiary bonds break
lose active site shape
no longer complimentary
denatured
✔✔affect of ph on enzyme activity? - ✔✔if ph is changed away from optimum, bonds in
tertiary structure break, enzyme denatured
✔✔competitive inbibitor? - ✔✔similar shape to substrate
fits in active site
blocks ESCS from forming
✔✔non competitive inhibitor - ✔✔binds on somewhere other than active site, changes
the enzymes shape, prevents substrate from binding
✔✔3 types of lipids? - ✔✔triglycerides
phospholipids
cholesterol
✔✔triglyceride structure - ✔✔1 glycerol 3 fatty acids
joined by ester bonds in condensation reaction
COOC bond
either saturated or unsaturated
✔✔phospholipid stucture? - ✔✔1 glycerol 2 fatty acids 1 phosphate group
phosphate forms hydrophilic head
fatty acid hydrophobic tail
forms phospholipid bilayer
✔✔what are nucleic acids? - ✔✔polymers made from nucleotides
eg DNA and RNA
✔✔what is DNA? - ✔✔deoxyribonucleic acid
in all organisms
carries genes, section of DNA coding for a protein
AND ANSWERS GRADED A+
✔✔test for reducing sugars - ✔✔heat with benedicts, turns brick red
✔✔vacuole - ✔✔surrounded by membrane called tonoplast
contains cell sap
keeps cell turgid
pushes chloroplasts to surface
✔✔test for non reducing sugar? - ✔✔-heat with benedicts, no change
-add dilute hcl (hydrolyses glycosidic bond)
-add sodium hydrogen carbonate to neutralise
-heat with benedicts, will turn brick red
✔✔structure of bacteria? - ✔✔circular DNA and plasmids
no membrane bound organelles
smaller ribosomes
cell wall made of murein
some have slime capsule (protect from phagocytosis) and flagella (movement)
✔✔types of proteins? - ✔✔globular and fibrous
✔✔structure of virus? - ✔✔DNA or RNA
if RNA, contains reverse transcriptase enzyme to convert it into DNA
capsid
phospholipid membrane
attachment proteins to identify and attach to host
✔✔what are globular proteins? - ✔✔have a specific 3d shape, soluble eg. haemoglobin
✔✔how does a virus infect their host cell? - ✔✔uses attachment protein to attach
send in DNA capsid which uses cell to make virus components
producing copies and destroying host cell
✔✔what are fibrous proteins? - ✔✔insoluble, inflexible and strong eg. keratin
✔✔how do amino acids differ? - ✔✔have different r groups
✔✔what is a chromosome? - ✔✔coiled DNA
formed during interphase
made of 2 sister chromatids joined by centromere
2 copies of same DNA molecule
,✔✔what is a homologous pair of chromosomes? - ✔✔1 maternal 1 paternal
same genes but different alleles
✔✔how are amino acids joined? - ✔✔condensation reaction between carboxyl group
and amine group. leaves bond between carbon and nitrogen, DIPEPTIDE
✔✔primary structure of a protein? - ✔✔sequence of AA, polypeptide chain. change in
sequence, bonds will be formed in different places in secondary.
✔✔secondary structure? - ✔✔primary structure coils to form an alpha helix, hydrogen
bonds form between amino acids
✔✔tertiary structure? - ✔✔secondary structure folds again to form final 3d shape, held
by ionic/hydrogen/disulfide bonds
✔✔quarternary structure? - ✔✔more than one polypeptide chain, non protein can be
involved
✔✔quarternary structure examples? - ✔✔haemoglobin, antibodies, collagen
✔✔collagen structure? - ✔✔-strong
-primary structure glycine
-secondary tight coil
-tertiary coils again
-quarternary three chains wrapped like rope
✔✔protein test? - ✔✔biruet reagent, turns purple
✔✔what is an enzyme? - ✔✔biological catalyst
speeds up reaction without being used up
lowers activation energy
✔✔what makes an enzyme specific? - ✔✔specific active site, only complimentary
substrates can bind and form enzyme substrate complexes
✔✔lock and key model? - ✔✔active site is rigid, only exactly complimentary substrates
fit
✔✔induced fit model? - ✔✔shape of active site changes slightly so substrate fits exactly
forming ES complex
✔✔affect of substrate concentration on enzyme activity? - ✔✔more substrate, more
chance of successful collisions, ES complex, increase rate
increases until all enzymes are saturated
, ✔✔affect of enzyme concentration on enzyme activity? - ✔✔more enzymes, more
successful reactions, ES complexes
continues until all the substrates are used up
✔✔affect of temperature on enzyme activity? - ✔✔as temp increases, kinetic energy
increases, molecules move faster
more collisions, more ES complexes
carries on until optimum
after optimum, tertiary bonds break
lose active site shape
no longer complimentary
denatured
✔✔affect of ph on enzyme activity? - ✔✔if ph is changed away from optimum, bonds in
tertiary structure break, enzyme denatured
✔✔competitive inbibitor? - ✔✔similar shape to substrate
fits in active site
blocks ESCS from forming
✔✔non competitive inhibitor - ✔✔binds on somewhere other than active site, changes
the enzymes shape, prevents substrate from binding
✔✔3 types of lipids? - ✔✔triglycerides
phospholipids
cholesterol
✔✔triglyceride structure - ✔✔1 glycerol 3 fatty acids
joined by ester bonds in condensation reaction
COOC bond
either saturated or unsaturated
✔✔phospholipid stucture? - ✔✔1 glycerol 2 fatty acids 1 phosphate group
phosphate forms hydrophilic head
fatty acid hydrophobic tail
forms phospholipid bilayer
✔✔what are nucleic acids? - ✔✔polymers made from nucleotides
eg DNA and RNA
✔✔what is DNA? - ✔✔deoxyribonucleic acid
in all organisms
carries genes, section of DNA coding for a protein
