OCR A Level Biology (2025-2026) – Exam Paper + Mark Scheme Revision
Essential
Abiotic components - ✔✔✔-Components of an ecosystem that are non living
Abiotic factors - ✔✔✔-Non living components of an ecosystem that effect other living
organisms
Abscisic acid - ✔✔✔-Causes stomatal clouse when plant is streed by low water availabliity
Inhbits seed germination and growth
Stimulates cold protective responses I.e production of antifreeze
Acetycholine - ✔✔✔-Chemical that acts as a transmitter that diffuses across synaptic cleft
Acetycholinesterase - ✔✔✔-Enzyme in synaptic cleft that breaks down acetycholine. After it has
triggered an action potential in the post synaptic neurone, acetycholine must be broken down
otherwise it would remain in the synaptic cleft and continue to open sodium ion channels in the
post synaptic membrane causing action potentials
Acinus (plural acini) - ✔✔✔-Small group of exocrine cells in a sac like structure. in the pancreas
these surround a tubule and secrete into the tubule
Actin and myosin - ✔✔✔-Proteins involved in muscular contraction
Action potential - ✔✔✔-A brief reversal of teh potential across the membrane of a neurone
causing a peak of +40mV compared to the resting potential of -60mV
Adenyl cyclase - ✔✔✔-An intracellular enzyme that converts ATP to cyclic AMP (CAMP)
ADH (antidiuretic hormone) - ✔✔✔-Hormone made in hypothalamus, stored and released from
pituitary gland, that controls permeability of collecting duct in walls of kidneys
,OCR A Level Biology (2025-2026) – Exam Paper + Mark Scheme Revision
Essential
ADP - ✔✔✔-Adenosine diphosphate
Adrenal cortex - ✔✔✔-Outer layer of the adrenal gland
Adrenal gland - ✔✔✔-One of the pair of glands lying above kidneys, which release adrenaline
and a number of hormones known as corticoids (or corticosteroids) such as aldosterone
Adrenal medulla - ✔✔✔-Inner layer of adrenal gland
Adrenaline - ✔✔✔-Hormone released from medulla of adrenal glands which stimulates body to
prepare for fight or flight
Adrenocorticotropic hormone (ACTH) - ✔✔✔-Hormone released by pituitary gland which
stimulates adrenal cortex to produce corticosteroid hormones
Aerobic respiration -carbon cycle - ✔✔✔-Carried out by almost all organisms- gives off carbon
dioxide as a waste product
Agar - ✔✔✔-Polysacharide of galactose obtained from seaweed which is used to thicken a
medium into a gel.
Agarose - ✔✔✔-Type of sugar that can incorporated into a type of agar gel
Alkaloids - ✔✔✔-Organic nitrogen containing bases that have important physiological effects on
animals, includes nicotine, quinine, strychnine and morphine
,OCR A Level Biology (2025-2026) – Exam Paper + Mark Scheme Revision
Essential
Allele - ✔✔✔-Version of a gene
Allele frequency - ✔✔✔-Propotion of a particular allele within the gene pool
Allopatric speciation - ✔✔✔-Formation of 2 different species from one original one due to
geographic isolation
Alpha cells - ✔✔✔-Cells found in islets of langerhans that secrete glucagon
Ammonification - ✔✔✔-Decomposes like bacteria and fungi decompose dead animal and plant
matter into ammonium
Ammonification - ✔✔✔-Production of ammonia by bacterial action in the decay of nitrgenous
organic matter
AMP - ✔✔✔-Adeonside monophosphate
Aneuploidy - ✔✔✔-Abnormal chromosome number
Antagonist - ✔✔✔-Something that works against the other in opposite pairs, such as in the
muscles that are arranged in opposing pairs, so one contracts and the other elongates
Apical dominance - ✔✔✔-Inhibition of lateral buds fruther down shoot by chemicals produced
by apicial bud at tip of plant shoot.
Apoptosis - ✔✔✔-Programmed cell death
, OCR A Level Biology (2025-2026) – Exam Paper + Mark Scheme Revision
Essential
Artificial selection - ✔✔✔-Selective breeding of organisms to produce desired phenotypes
Ascending limb - ✔✔✔-Part of loop of Henle that carries fluid back into distal tubule in cortex
ATP - ✔✔✔-Adenosine triphosphate
Autoimmune response - ✔✔✔-Response in which body's immune system attacks and destroys
some of its own cells.
Autonomic nervous stsrem - ✔✔✔-Part of nervous system responsible for controlling
involuntary motor activities of body
Autoradiograms - ✔✔✔-Photographs made when photographic film is exposed to molecules
labelled with radioactivity
Autosomal linkage - ✔✔✔-Gene loci present on the same autosome (non sex chromosome) are
often inherited together
Autosome - ✔✔✔-Chromosome not concerned with sex determination
Autotrophic nutrition - ✔✔✔-Nutrition where organic molecules are synthesised from inorganic
molecules, i.e carbon dioxide and water. I.e photosynthesis where sunlight energy converted to
chemical energy to synthesise large organic molecules from smaller inorganic ones.
Chemosynthesis uses energy derived from chemical reactions (e.g nitrifying bacteria in soil)
Auxins
E.g IAA (indole 3 acetic acid) - ✔✔✔-Promotes cell elongation
Inhibits leaf abcission
Essential
Abiotic components - ✔✔✔-Components of an ecosystem that are non living
Abiotic factors - ✔✔✔-Non living components of an ecosystem that effect other living
organisms
Abscisic acid - ✔✔✔-Causes stomatal clouse when plant is streed by low water availabliity
Inhbits seed germination and growth
Stimulates cold protective responses I.e production of antifreeze
Acetycholine - ✔✔✔-Chemical that acts as a transmitter that diffuses across synaptic cleft
Acetycholinesterase - ✔✔✔-Enzyme in synaptic cleft that breaks down acetycholine. After it has
triggered an action potential in the post synaptic neurone, acetycholine must be broken down
otherwise it would remain in the synaptic cleft and continue to open sodium ion channels in the
post synaptic membrane causing action potentials
Acinus (plural acini) - ✔✔✔-Small group of exocrine cells in a sac like structure. in the pancreas
these surround a tubule and secrete into the tubule
Actin and myosin - ✔✔✔-Proteins involved in muscular contraction
Action potential - ✔✔✔-A brief reversal of teh potential across the membrane of a neurone
causing a peak of +40mV compared to the resting potential of -60mV
Adenyl cyclase - ✔✔✔-An intracellular enzyme that converts ATP to cyclic AMP (CAMP)
ADH (antidiuretic hormone) - ✔✔✔-Hormone made in hypothalamus, stored and released from
pituitary gland, that controls permeability of collecting duct in walls of kidneys
,OCR A Level Biology (2025-2026) – Exam Paper + Mark Scheme Revision
Essential
ADP - ✔✔✔-Adenosine diphosphate
Adrenal cortex - ✔✔✔-Outer layer of the adrenal gland
Adrenal gland - ✔✔✔-One of the pair of glands lying above kidneys, which release adrenaline
and a number of hormones known as corticoids (or corticosteroids) such as aldosterone
Adrenal medulla - ✔✔✔-Inner layer of adrenal gland
Adrenaline - ✔✔✔-Hormone released from medulla of adrenal glands which stimulates body to
prepare for fight or flight
Adrenocorticotropic hormone (ACTH) - ✔✔✔-Hormone released by pituitary gland which
stimulates adrenal cortex to produce corticosteroid hormones
Aerobic respiration -carbon cycle - ✔✔✔-Carried out by almost all organisms- gives off carbon
dioxide as a waste product
Agar - ✔✔✔-Polysacharide of galactose obtained from seaweed which is used to thicken a
medium into a gel.
Agarose - ✔✔✔-Type of sugar that can incorporated into a type of agar gel
Alkaloids - ✔✔✔-Organic nitrogen containing bases that have important physiological effects on
animals, includes nicotine, quinine, strychnine and morphine
,OCR A Level Biology (2025-2026) – Exam Paper + Mark Scheme Revision
Essential
Allele - ✔✔✔-Version of a gene
Allele frequency - ✔✔✔-Propotion of a particular allele within the gene pool
Allopatric speciation - ✔✔✔-Formation of 2 different species from one original one due to
geographic isolation
Alpha cells - ✔✔✔-Cells found in islets of langerhans that secrete glucagon
Ammonification - ✔✔✔-Decomposes like bacteria and fungi decompose dead animal and plant
matter into ammonium
Ammonification - ✔✔✔-Production of ammonia by bacterial action in the decay of nitrgenous
organic matter
AMP - ✔✔✔-Adeonside monophosphate
Aneuploidy - ✔✔✔-Abnormal chromosome number
Antagonist - ✔✔✔-Something that works against the other in opposite pairs, such as in the
muscles that are arranged in opposing pairs, so one contracts and the other elongates
Apical dominance - ✔✔✔-Inhibition of lateral buds fruther down shoot by chemicals produced
by apicial bud at tip of plant shoot.
Apoptosis - ✔✔✔-Programmed cell death
, OCR A Level Biology (2025-2026) – Exam Paper + Mark Scheme Revision
Essential
Artificial selection - ✔✔✔-Selective breeding of organisms to produce desired phenotypes
Ascending limb - ✔✔✔-Part of loop of Henle that carries fluid back into distal tubule in cortex
ATP - ✔✔✔-Adenosine triphosphate
Autoimmune response - ✔✔✔-Response in which body's immune system attacks and destroys
some of its own cells.
Autonomic nervous stsrem - ✔✔✔-Part of nervous system responsible for controlling
involuntary motor activities of body
Autoradiograms - ✔✔✔-Photographs made when photographic film is exposed to molecules
labelled with radioactivity
Autosomal linkage - ✔✔✔-Gene loci present on the same autosome (non sex chromosome) are
often inherited together
Autosome - ✔✔✔-Chromosome not concerned with sex determination
Autotrophic nutrition - ✔✔✔-Nutrition where organic molecules are synthesised from inorganic
molecules, i.e carbon dioxide and water. I.e photosynthesis where sunlight energy converted to
chemical energy to synthesise large organic molecules from smaller inorganic ones.
Chemosynthesis uses energy derived from chemical reactions (e.g nitrifying bacteria in soil)
Auxins
E.g IAA (indole 3 acetic acid) - ✔✔✔-Promotes cell elongation
Inhibits leaf abcission
