How to Use
The aim of this pack is simple — we wanted to condense the A-level Biology course into a few super condensed
pages. Now you have a concise summary of the entire course that focuses on the most important defi
...
How to Use
The aim of this pack is simple — we wanted to condense the A-level Biology course into a few super condensed
pages. Now you have a concise summary of the entire course that focuses on the most important definitions, key
terms, diagrams and concepts.
We’ve spent weeks working with top designers, academic writers and illustrators to ensure this is the best cheatsheet
out there. Our promise to you is you won’t find anything better. The cheatsheet pack has been built off the AQA
specification to ensure no important information is missed — below is a table which summarises how our cheatsheets
map to the AQA specification.
We hope you enjoy using it and wish you the best of luck in your A-levels.
SnapRevise
Specification Points Cheatsheet
3.1.1—3.1.4.2 Carbohydrates, Lipids & Proteins
3.1.5.1—3.1.8 Nucleic acids, ATP, Water & Inorganic ions
3.2.1.1—3.2.2 Cell structure & Replication
3.2.3—3.2.4 Cell transport & Immunity
3.3.1—3.3.4.2 Gas exchange, Digestion & Mass transport
3.4.1—3.4.7 Genetic Information, Protein Synthesis, Classification & Biodiversity
3.5.1—3.5.2 Photosynthesis & Respiration
3.5.3—3.5.4 Energy, Ecosystems & Nutrient Cycles
3.6.1.1—3.6.2.2 Responses, Receptors, Neurones & Synapses
3.6.2.2—3.6.4.3 Muscles & Homeostasis
3.7.1 Inheritance
3.7.2—3.7.4 Populations, Evolution & Ecosystems
3.8.1—3.8.3 Stem Cells, Mutations, Gene Regulation, Cancer & Genome Projects
3.8.4.1—3.8.4.3 Gene Technologies
snaprevise.co.uk
CARBOHYDRATES, LIPIDS & PROTEINS
CHEAT SHEET
Monomers & Polymers
• Monomers are individual molecules that make up a polymer.
• Polymers are long chains that are composed of many individual
monomers that have been bonded together in a repeating
pattern.
• Condensation Reactions occurs when two molecules combine to
form a more complex molecule with the removal of water.
• Hydrolysis Reactions occurs when larger molecules are broken
down into smaller molecules with the addition of water.
Carbohydrates
• Monosaccharides are the simplest carbohydrates, consisting of
only one sugar molecule (e.g. Glucose, Fructose & Galactose).
• Glucose is a hexose sugar with 2 isomers
• Disaccharides are sugars that are composed of two
monosaccharides joined together in a condensation reaction,
forming a glycosidic bond.
Disaccharide Constituent monosaccharides
Maltose 2 × α-glucose
Sucrose glucose and fructose
Lactose glucose and galactose
• Polysaccharides are formed by many monosaccharides joined
together.
◦ Starch, made of the amylose and amylopectin is the main
polysaccharide energy store in plants, is composed of
α-glucose.
◦ In animals, the polysaccharide energy store is called
glycogen, composed of α-glucose.
◦ Cellulose is a structural component of plant cell walls,
composed of long unbranched chains of β-glucose.
Lipids
• Fatty acids can be:
◦ Saturated – there are no double C=C bonds and the molecule
has as many hydrogen atoms as possible.
◦ Unsaturated – there is at least one double C=C bond,
therefore the molecule contains fewer hydrogen atoms than
is maximally possible.
• A triglyceride molecule is formed by joining one molecule
of glycerol to three fatty acids through three condensation
reactions, forming ester bonds.
• Triglycerides have key roles in
respiration and energy storage
due to its insolubility and high
carbon to hydrogen ratio.
• Phospholipids replace one of the fatty acid chains in
triglycerides with a phosphate molecule.
• The non-polar hydrophobic tails
and the polar hydrophilic heads
of phospholipids allow them to
form phospholipid bilayers.
Proteins
• Amino acids are the monomer units used to make proteins.
• The 20 naturally occurring amino acids only differ in their R groups.
• Dipeptides are formed when two
amino acids are joined together by
a condensation reaction, forming a
peptide bond.
• A polypeptide is a polymer made of
many amino acids joined together
by peptide bonds.
• A protein may contain one or more polypeptide chains.
• There are four structural levels:
Level Definition Bond type
Primary The specific sequence of amino
acids in a polypeptide chain
Peptide bonds
Secondary The curling or folding of the
polypeptide chain into α-helices
and β-pleated sheets due to the
formation of hydrogen bonds
Hydrogen bonds
Tertiary The overall specific 3-D shape of
a protein, which is determined by
interactions between R groups
and the properties of R groups
Hydrogen bonds
Ionic bonds
Disulphide
bridges
Covalent bonds
Hydrophobic/
hydrophilic
interactions
Quaternary The specific 3-D shape of a
protein that is determined by the
multiple polypeptide chains and/or
prosthetic groups bonded together
Hydrogen bonds
Ionic bonds
Disulphide
bridges
Biochemical Tests
Molecule Reagent Positive result
Reducing
sugars
Benedict’s reagent → Heat Red/orange
precipitate
Starch Iodine in potassium iodide
solution
Blue/black
Non-reducing
sugars
Hydrochloric acid → Heat
Sodium hydrogencarbonate
Benedict’s reagent → Heat
Red/orange
precipitate
Proteins Sodium hydroxide
Copper (II) sulphate
Purple
Lipids Ethanol
Water → Shake
Cloudy white
Enzymes
• Enzymes are biological catalysts that speeds up the rate of reaction
and remains unchanged and reusable at the end of the reaction.
• They lower the activation energy of the reaction.
• The lock and key model proposed that each substrate is a key
that only fits a specific lock or enzyme. The alternative induced fit
model has been proposed (below)
• The specificity of enzymes is due to the tertiary structure of its
active site, allowing complementary binding to substrates.
• Enzymes catalyse both intracellular and extracellular reactions
that determine structures and functions from cellular to whole
organism level.
• Factors affecting enzyme activity include:
pH: Temperature Enzyme
concentration
Substrate
concentration
Competitive & non
[Show More]
