Comprehensive Guide to OCR A
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
Magnigication - ansThe number of times larger an image appears compared to the size of the
object
Magnification calculation - ansObjective lens x eyepiece lens
Image size / actual size
Using stage graticule - ans1) insert eyepiece graticule into x10 eyepiece
2) place stage graticule on microscope stage and bring into focus using low power objective
(total mag=40)
3) align eyepiece graticule and stage graticule. Check value of one eyepiece division at this
mag
4) 1mm = 40 eyepiece divisions
5) each eyepiece divison 1000/40 = 25
6) use x10 objective Lens on microscope and focus on stage graticule
7) align then both
8) 100 eyepiece divisions now correspond 1mm
9) 1000/100 = 10
Nucleus - ansControl centre of cell
Stores organisms genome
Transmits genetic information
Nuclear envelope - ansSeparates contents of nucleus from the rest of the cell
Nucleolus - ansFound inside the nucleus and produces ribosomes
RER - ansRibosomes attached
Large surface area
SER - ansSynthesis cholesterol
Synthesis lipids/phospholipids
Synthesis steroids hormones
Golgi apparatus - ansStack membrane bound flattened scad
Processes and packages proteins
Mitochondria - ansSite of ATP production during aerobic respiration
Fluid filled matrix
Folded into cristae
Chloroplasts - ansSite of photo synthesis
Plant cells
Stacks flattened membranes ( thylakoids )
Vacuole - ansFilled with water and solutes
Maintain cell stabilityv
Lysosomes - ansEngulf old organelles and foreign matter then digest
Formed from Golgi apparatus
Cilia - ansBeat and move mucus
Ribosomes - ansSynthesise proteins
Small spherical
Attached to RER
Centrioles - ansCell organelle that aids in cell division in animal cells only
Formation cilia
,Comprehensive Guide to OCR A
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
Two bundles mucrotubules right angle
Cytoskeleton - ansA network of fibers that holds the cell together, helps the cell to keep its
shape, and aids in movement
Cellulose cell wall - ansThe rigid cell wall which surrounds plant cells.
How insulin is made - ans1) mRNA copy of instructions for insulin made in nucleus
2) mRNA leaves nucleus through nuclear pore
3) mRNA attached to a ribosome on RER leads to assemble protein (insulin)
4) insulin molecules pinched off in vesicles travel towards Golgi apparatus
5) vesicles fuse with Golgi apparatus
6) process and package insulin molecules ready for release
7) insulin pinched off in vesicles move towards plasma membrane
8) vesicles fuses
9) exocytosis
Similarities of Prokaryotes and Eukaryotes - ansPlasma membrane
Cytoplasm
Ribosomes
DNA
RNA
Differences of Prokaryotes and Eukaryotes - ansSmaller
Less developed cytoskeleton
No nucleus
No membrane bound organelles
Peptidoglycan
Smaller ribosomes
Naked dna
Flagella
Pili
binary fission - ansA form of asexual reproduction in which one cell divides to form two
identical cells.
covalent bond - ansA chemical bond that involves sharing a pair of electrons between atoms
in a molecule
condensation reaction - ansTwo molecules join with the removal of water
hydrolysis reaction - ansTwo molecules split by addition of water
hydrogen bond - ansWeak interaction
Slightly negative and slightly positive charge
water as a liquid - ansprovide habitats
major component of tissues in living organisms
medium for chemical reactions
effective transport medium
density of water - ansmore dense as it gets colder up until 4 degrees then due to polarity will
become less dense
stable environment
insulate bodies of water
,Comprehensive Guide to OCR A
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
water as a solvent - anspositive and negative parts of water attracted to positive and negative
parts of solute
molecules and ions move around and react
transport whilst in water
cohesion and surface tension of water - anshydrogen bonding between molecules pulls them
together (cohesion)
surface of water contracts to resist forces applied (surface tension)
xylem
pond skaters
high specific heat capacity of water - ansneed a lot of heat energy to increase KE and
temperature
amount of energy needed to raise 1KG substance by 1 degree
stable environment for enzyme controlled reactions
aquatic animals
high latent heat capacity of water - anshelps molecules break away from each other to
become a gas
large amount of energy needed for evaporation
cool things and keep temperature stable
water as a reactant - ansphotosynthesis
hydrolysis
digestion
synthesis large molecules
carbohydrates - anscarbon, oxygen, hydrogen
1:1:2
use of carbohydrates - ansenergy source
energy store
structural units
monosaccharides - anssimplest form carbohydrates
source of energy
soluble in water
insoluble in solutes
straight chains or ring
Monosaccharide examples - ansglucose, fructose, galactose
disaccharide - anstwo monosaccharides joined by a glycosidic bond
soluble
sweet
can hydrolyse
Disaccharide examples - ansalpha glucose + alpha glucose = maltose
alpha glucose + fructose = sucrose
beta glucose + alpha glucose = lactose
beta glucose + beta glucose = cellobiose
polysaccharides - anspolymers of monosaccharides
homopolysaccharide or heteropolysaccharide
, Comprehensive Guide to OCR A
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
Polysaccharide examples - ansamylose, amylopectin, glycogen
Amylose - anscoils into spiral
alpha glucose molecules
1-4 glycosidic bonds
less soluble
unbranched
Amylopectin - anscoils into spiral shape
alpha glucose molecules
1-4 and 1-6 glycosidic bonds
branched
glycogen - ansin mammals
smaller chains, less tendency to coil
1-4 and 1-6 glycosidic bonds
branched
more compacted (easier to snip off)
Cellulose - ansplant cell walls
long chains 15,000 beta glucose molecules
condensation reaction
glycosidic bonds
second molecule turned 180 degrees
microfibrils - ans60-70 cellulose cell walls joined
10-30 nm in diameter
bundle in to macrofribrils
embedded in pectins
plant cell wall structure and function - anscellulose
macrofibrils run in all directions
glycosidic and hydrogen bonds provide high tensile strength
hard to digest
fully permeable
can be reinforced with other substances
bacteria cell wall - anspeptidoglycan
exoskeleton cell walls - anschitin
lipids - ansgroup of substances soluble in alcohol rather than water
examples of lipids - anstriglycerides, phospholipids, steroids
Trigylcerides - ansglycerol + 3 fatty acids
condensation reaction
ester bonds
Saturated triglycerides - ansNo double bonds
Tend to be solid at room temp
unsaturated triglycerides - ansdouble bonds
liquid at room temp
Phosopholipids - ansphosphate + two fatty acids
condensation reaction
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
Magnigication - ansThe number of times larger an image appears compared to the size of the
object
Magnification calculation - ansObjective lens x eyepiece lens
Image size / actual size
Using stage graticule - ans1) insert eyepiece graticule into x10 eyepiece
2) place stage graticule on microscope stage and bring into focus using low power objective
(total mag=40)
3) align eyepiece graticule and stage graticule. Check value of one eyepiece division at this
mag
4) 1mm = 40 eyepiece divisions
5) each eyepiece divison 1000/40 = 25
6) use x10 objective Lens on microscope and focus on stage graticule
7) align then both
8) 100 eyepiece divisions now correspond 1mm
9) 1000/100 = 10
Nucleus - ansControl centre of cell
Stores organisms genome
Transmits genetic information
Nuclear envelope - ansSeparates contents of nucleus from the rest of the cell
Nucleolus - ansFound inside the nucleus and produces ribosomes
RER - ansRibosomes attached
Large surface area
SER - ansSynthesis cholesterol
Synthesis lipids/phospholipids
Synthesis steroids hormones
Golgi apparatus - ansStack membrane bound flattened scad
Processes and packages proteins
Mitochondria - ansSite of ATP production during aerobic respiration
Fluid filled matrix
Folded into cristae
Chloroplasts - ansSite of photo synthesis
Plant cells
Stacks flattened membranes ( thylakoids )
Vacuole - ansFilled with water and solutes
Maintain cell stabilityv
Lysosomes - ansEngulf old organelles and foreign matter then digest
Formed from Golgi apparatus
Cilia - ansBeat and move mucus
Ribosomes - ansSynthesise proteins
Small spherical
Attached to RER
Centrioles - ansCell organelle that aids in cell division in animal cells only
Formation cilia
,Comprehensive Guide to OCR A
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
Two bundles mucrotubules right angle
Cytoskeleton - ansA network of fibers that holds the cell together, helps the cell to keep its
shape, and aids in movement
Cellulose cell wall - ansThe rigid cell wall which surrounds plant cells.
How insulin is made - ans1) mRNA copy of instructions for insulin made in nucleus
2) mRNA leaves nucleus through nuclear pore
3) mRNA attached to a ribosome on RER leads to assemble protein (insulin)
4) insulin molecules pinched off in vesicles travel towards Golgi apparatus
5) vesicles fuse with Golgi apparatus
6) process and package insulin molecules ready for release
7) insulin pinched off in vesicles move towards plasma membrane
8) vesicles fuses
9) exocytosis
Similarities of Prokaryotes and Eukaryotes - ansPlasma membrane
Cytoplasm
Ribosomes
DNA
RNA
Differences of Prokaryotes and Eukaryotes - ansSmaller
Less developed cytoskeleton
No nucleus
No membrane bound organelles
Peptidoglycan
Smaller ribosomes
Naked dna
Flagella
Pili
binary fission - ansA form of asexual reproduction in which one cell divides to form two
identical cells.
covalent bond - ansA chemical bond that involves sharing a pair of electrons between atoms
in a molecule
condensation reaction - ansTwo molecules join with the removal of water
hydrolysis reaction - ansTwo molecules split by addition of water
hydrogen bond - ansWeak interaction
Slightly negative and slightly positive charge
water as a liquid - ansprovide habitats
major component of tissues in living organisms
medium for chemical reactions
effective transport medium
density of water - ansmore dense as it gets colder up until 4 degrees then due to polarity will
become less dense
stable environment
insulate bodies of water
,Comprehensive Guide to OCR A
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
water as a solvent - anspositive and negative parts of water attracted to positive and negative
parts of solute
molecules and ions move around and react
transport whilst in water
cohesion and surface tension of water - anshydrogen bonding between molecules pulls them
together (cohesion)
surface of water contracts to resist forces applied (surface tension)
xylem
pond skaters
high specific heat capacity of water - ansneed a lot of heat energy to increase KE and
temperature
amount of energy needed to raise 1KG substance by 1 degree
stable environment for enzyme controlled reactions
aquatic animals
high latent heat capacity of water - anshelps molecules break away from each other to
become a gas
large amount of energy needed for evaporation
cool things and keep temperature stable
water as a reactant - ansphotosynthesis
hydrolysis
digestion
synthesis large molecules
carbohydrates - anscarbon, oxygen, hydrogen
1:1:2
use of carbohydrates - ansenergy source
energy store
structural units
monosaccharides - anssimplest form carbohydrates
source of energy
soluble in water
insoluble in solutes
straight chains or ring
Monosaccharide examples - ansglucose, fructose, galactose
disaccharide - anstwo monosaccharides joined by a glycosidic bond
soluble
sweet
can hydrolyse
Disaccharide examples - ansalpha glucose + alpha glucose = maltose
alpha glucose + fructose = sucrose
beta glucose + alpha glucose = lactose
beta glucose + beta glucose = cellobiose
polysaccharides - anspolymers of monosaccharides
homopolysaccharide or heteropolysaccharide
, Comprehensive Guide to OCR A
Level Biology Curriculum.
An ultimate Guide to Exam Study
Guide 2025/2026.
Polysaccharide examples - ansamylose, amylopectin, glycogen
Amylose - anscoils into spiral
alpha glucose molecules
1-4 glycosidic bonds
less soluble
unbranched
Amylopectin - anscoils into spiral shape
alpha glucose molecules
1-4 and 1-6 glycosidic bonds
branched
glycogen - ansin mammals
smaller chains, less tendency to coil
1-4 and 1-6 glycosidic bonds
branched
more compacted (easier to snip off)
Cellulose - ansplant cell walls
long chains 15,000 beta glucose molecules
condensation reaction
glycosidic bonds
second molecule turned 180 degrees
microfibrils - ans60-70 cellulose cell walls joined
10-30 nm in diameter
bundle in to macrofribrils
embedded in pectins
plant cell wall structure and function - anscellulose
macrofibrils run in all directions
glycosidic and hydrogen bonds provide high tensile strength
hard to digest
fully permeable
can be reinforced with other substances
bacteria cell wall - anspeptidoglycan
exoskeleton cell walls - anschitin
lipids - ansgroup of substances soluble in alcohol rather than water
examples of lipids - anstriglycerides, phospholipids, steroids
Trigylcerides - ansglycerol + 3 fatty acids
condensation reaction
ester bonds
Saturated triglycerides - ansNo double bonds
Tend to be solid at room temp
unsaturated triglycerides - ansdouble bonds
liquid at room temp
Phosopholipids - ansphosphate + two fatty acids
condensation reaction
