AQA A-Level Biology
Section 1:
What are biological molecules? molecules made and used by living organisms e.g. Carbohydrates,
Proteins, Lipids, DNA, ATP, Water, Inorganic Ions
What are the functions of carbohydrates?
energy source (glucose in respiration)
energy store (starch in plants, glycogen in animals)
structure (cellulose in cell wall of plants)
What are the building blocks for carbohydrates called? monosaccharides
Example of monosaccharides? glucose (alpha and beta), galactose, fructose
Formula for monosaccharides? C6H12O6 (isomers = same formula but different arrangement)
Difference between alpha and beta glucose? on Carbon 1, alpha glucose has a OH group on the
bottom and beta glucose has a OH group on the top
How are monosaccharides joined together? condensation reaction (removing water) – between 2
OH groups
Bond in carbohydrate? glycosidic bond
Example of disaccharides? glucose + glucose = maltose, glucose + galactose = lactose,
glucose + fructose = sucrose
Formula for disaccharides? C12H22O11
How are polymers separated? hydrolysis (add water)
What is a polysaccharide? many monosacharrides joined by condensation reaction/glycosidic
bonds
Example of polysaccharides?
Amylose (long chain of alpha glucose) which makes starch/glycogen
Cellulose (long chain of beta glucose) which makes cell wall in plants
What are Polysaccharides?
carbohydrates
made of a long chain of monosaccharides joined by condensation reaction/glycosidic
bonds
3 examples: Starch, Glycogen, Cellulose
Starch & Glycogen used as Energy Stores (starch in plants, glycogen in animals), they
are made out of many alpha glucose which are used for respiration
, Cellulose used to form Cell Wall in Plants, made out of many beta glucose
Properties of Starch and Glycogen as energy stores?
Insoluble = do not affect water potential of the cell, do not diffuse out of the cell
Coiled/Branched = compact, more can fit into a cell
Branched/Chained = glucose removed from the end
Structure of Cellulose?
β-glucose arranged in a straight chain (each alternative β-glucose is rotated 180 degrees)
= cellulose straight chain
many cellulose chains are cross linked by hydrogen bonds to form microfibrils
many microfibrils are cross linked to form marcrofibrils
forms structure of cell wall
strong material (prevents plant cell from bursting or shrinking)
Test for starch? add iodine, turns blue/black
Test for reducing sugar? heat with benedicts, turns brick red
Test for non-reducing sugar?
heat with benedicts – no change
therefore, add dilute hydrochloric acid (hydrolyses glycosidic bond)
then add sodium hydrogencarbonate (neutralises solution)
heat with benedict - turns brick red
What are 2 types of proteins? Globular and Fibrous
What are globular proteins? soluble proteins with a specific 3D shape e.g. enzymes, hormones,
antibodies, haemoglobin
What are fibrous proteins? strong/insoluble/inflexible material e.g. collagen and keratin
What are the building blocks for proteins? amino acids
Structure of amino acid? central carbon, carboxyl group to the right (COOH), amine group to
the left (NH2), hydrogen above and R group below
How do amino acids differ? have different R groups e.g. glycine has a hydrogen in its R group –
simplest amino acid
How are amino acids joined together? by condensation reaction between the carboxyl group of
one and amine group of another, leaves a bond between
carbon & nitrogen (called a peptide bond) forming a
dipeptide
,Define primary, secondary, tertiary, quaternary structure?
Primary = sequence of AA, polypeptide chain (held by peptide bonds)
Secondary = the primary structure (polypeptide chain) coils to form a helix, held by
hydrogen bonds
Tertiary = secondary structure folds again to form final 3d shape, held together by
hydrogen/ionic/disulfide bonds
Quaternary = made of more then one polypeptide chain
Examples of quaternary structure proteins? collagen (3 chains), antibodies (3 chains),
haemoglobin (4 chains)
Structure of collagen?
strong material, used to build tendons/ligaments/connective tissues
primary structure mainly made up of glycine (simplest amino acid)
secondary structure forms a tight coil (not much branching due to glycine)
tertiary structure coils again
quaternary structure made from 3 tertiary structures wrapped around each other like rope
= a collagen molecule
many of these collagen molecules make the tendons/ligaments/connective tissues
Test for protein? add biuret, turns purple
What is an enzyme? a biological catalyst (substance that speeds up the rate of reaction without
being used up – lowers activation energy)
What makes an enzyme specific? has a specific active site shape, only complementary substrates
can bind to the active site to form enzyme-substrate complexes
Lock and Key Model vs Induced Fit Model?
LK = active site shape is rigid, only exactly complementary substrates can bind to form
ES complexes
IF = active site changes shape, the substrate binds to the active site – the active site
changes shape so the substrate fits exactly forming an ES complex
Affect of substrate concentration on enzyme activity?
increase substrate concentration, increases chance of successful collisions, increase
chance of forming an ES complex, increase rate of reaction
this continues until all the enzyme's active sites are full/saturated = maximum rate of
reaction
Affect of enzyme concentration on enzyme activity?
, increase enzyme concentration, increases chance of successful collisions, increase chance
of forming an ES complex, increase rate of reaction
this continues until all the substrates are used up = maximum rate of reaction
Affect of temperature on enzyme activity?
as temperature increases
the kinetic energy increases
the molecules move faster
increase chance of successful collisions
increase chance of forming ES complex
increase rate of reaction
carries on till optimum
after optimum
bonds in tertiary structure break (hydrogen and ionic bonds)
lose active site shape
substrate no longer complementary
cant form ES complexes
enzyme denatured
Affect of pH on enzyme activity? if change pH away from optimum, bonds in tertiary structure
break, lose active site shape, no longer form ES complex,
enzyme denatured
Competitive vs Non-Competitive Inhibitors?
Competitive = a substance with a similar shape to the substrate and a complementary shape
to the enzyme's active site, binds to the active site, blocking it, preventing ES complexes
from forming
Non-Competitive = a substance that binds to another site on the enzyme other then the
active site, causes the active site to change shape, so less ES complexes can form
What are the 3 types of Lipids?
Triglycerides (fat for energy store, insulation, protection of organs)
Phopholipids (to make membranes)
Cholesterol (for membrane stability and make hormones)
Structure of triglyceride?
made of 1 glycerol and 3 fatty acids
joined by condensation reaction, ester bonds
bond is COOC
there are 2 types of triglycerides: saturated fat and unsaturated fat
Saturated vs Unsaturated Fat?
Saturated = has no carbon double bonds in the R group of the fatty acid
Unsaturated = has carbon double bonds in the R group of the fatty acid
Section 1:
What are biological molecules? molecules made and used by living organisms e.g. Carbohydrates,
Proteins, Lipids, DNA, ATP, Water, Inorganic Ions
What are the functions of carbohydrates?
energy source (glucose in respiration)
energy store (starch in plants, glycogen in animals)
structure (cellulose in cell wall of plants)
What are the building blocks for carbohydrates called? monosaccharides
Example of monosaccharides? glucose (alpha and beta), galactose, fructose
Formula for monosaccharides? C6H12O6 (isomers = same formula but different arrangement)
Difference between alpha and beta glucose? on Carbon 1, alpha glucose has a OH group on the
bottom and beta glucose has a OH group on the top
How are monosaccharides joined together? condensation reaction (removing water) – between 2
OH groups
Bond in carbohydrate? glycosidic bond
Example of disaccharides? glucose + glucose = maltose, glucose + galactose = lactose,
glucose + fructose = sucrose
Formula for disaccharides? C12H22O11
How are polymers separated? hydrolysis (add water)
What is a polysaccharide? many monosacharrides joined by condensation reaction/glycosidic
bonds
Example of polysaccharides?
Amylose (long chain of alpha glucose) which makes starch/glycogen
Cellulose (long chain of beta glucose) which makes cell wall in plants
What are Polysaccharides?
carbohydrates
made of a long chain of monosaccharides joined by condensation reaction/glycosidic
bonds
3 examples: Starch, Glycogen, Cellulose
Starch & Glycogen used as Energy Stores (starch in plants, glycogen in animals), they
are made out of many alpha glucose which are used for respiration
, Cellulose used to form Cell Wall in Plants, made out of many beta glucose
Properties of Starch and Glycogen as energy stores?
Insoluble = do not affect water potential of the cell, do not diffuse out of the cell
Coiled/Branched = compact, more can fit into a cell
Branched/Chained = glucose removed from the end
Structure of Cellulose?
β-glucose arranged in a straight chain (each alternative β-glucose is rotated 180 degrees)
= cellulose straight chain
many cellulose chains are cross linked by hydrogen bonds to form microfibrils
many microfibrils are cross linked to form marcrofibrils
forms structure of cell wall
strong material (prevents plant cell from bursting or shrinking)
Test for starch? add iodine, turns blue/black
Test for reducing sugar? heat with benedicts, turns brick red
Test for non-reducing sugar?
heat with benedicts – no change
therefore, add dilute hydrochloric acid (hydrolyses glycosidic bond)
then add sodium hydrogencarbonate (neutralises solution)
heat with benedict - turns brick red
What are 2 types of proteins? Globular and Fibrous
What are globular proteins? soluble proteins with a specific 3D shape e.g. enzymes, hormones,
antibodies, haemoglobin
What are fibrous proteins? strong/insoluble/inflexible material e.g. collagen and keratin
What are the building blocks for proteins? amino acids
Structure of amino acid? central carbon, carboxyl group to the right (COOH), amine group to
the left (NH2), hydrogen above and R group below
How do amino acids differ? have different R groups e.g. glycine has a hydrogen in its R group –
simplest amino acid
How are amino acids joined together? by condensation reaction between the carboxyl group of
one and amine group of another, leaves a bond between
carbon & nitrogen (called a peptide bond) forming a
dipeptide
,Define primary, secondary, tertiary, quaternary structure?
Primary = sequence of AA, polypeptide chain (held by peptide bonds)
Secondary = the primary structure (polypeptide chain) coils to form a helix, held by
hydrogen bonds
Tertiary = secondary structure folds again to form final 3d shape, held together by
hydrogen/ionic/disulfide bonds
Quaternary = made of more then one polypeptide chain
Examples of quaternary structure proteins? collagen (3 chains), antibodies (3 chains),
haemoglobin (4 chains)
Structure of collagen?
strong material, used to build tendons/ligaments/connective tissues
primary structure mainly made up of glycine (simplest amino acid)
secondary structure forms a tight coil (not much branching due to glycine)
tertiary structure coils again
quaternary structure made from 3 tertiary structures wrapped around each other like rope
= a collagen molecule
many of these collagen molecules make the tendons/ligaments/connective tissues
Test for protein? add biuret, turns purple
What is an enzyme? a biological catalyst (substance that speeds up the rate of reaction without
being used up – lowers activation energy)
What makes an enzyme specific? has a specific active site shape, only complementary substrates
can bind to the active site to form enzyme-substrate complexes
Lock and Key Model vs Induced Fit Model?
LK = active site shape is rigid, only exactly complementary substrates can bind to form
ES complexes
IF = active site changes shape, the substrate binds to the active site – the active site
changes shape so the substrate fits exactly forming an ES complex
Affect of substrate concentration on enzyme activity?
increase substrate concentration, increases chance of successful collisions, increase
chance of forming an ES complex, increase rate of reaction
this continues until all the enzyme's active sites are full/saturated = maximum rate of
reaction
Affect of enzyme concentration on enzyme activity?
, increase enzyme concentration, increases chance of successful collisions, increase chance
of forming an ES complex, increase rate of reaction
this continues until all the substrates are used up = maximum rate of reaction
Affect of temperature on enzyme activity?
as temperature increases
the kinetic energy increases
the molecules move faster
increase chance of successful collisions
increase chance of forming ES complex
increase rate of reaction
carries on till optimum
after optimum
bonds in tertiary structure break (hydrogen and ionic bonds)
lose active site shape
substrate no longer complementary
cant form ES complexes
enzyme denatured
Affect of pH on enzyme activity? if change pH away from optimum, bonds in tertiary structure
break, lose active site shape, no longer form ES complex,
enzyme denatured
Competitive vs Non-Competitive Inhibitors?
Competitive = a substance with a similar shape to the substrate and a complementary shape
to the enzyme's active site, binds to the active site, blocking it, preventing ES complexes
from forming
Non-Competitive = a substance that binds to another site on the enzyme other then the
active site, causes the active site to change shape, so less ES complexes can form
What are the 3 types of Lipids?
Triglycerides (fat for energy store, insulation, protection of organs)
Phopholipids (to make membranes)
Cholesterol (for membrane stability and make hormones)
Structure of triglyceride?
made of 1 glycerol and 3 fatty acids
joined by condensation reaction, ester bonds
bond is COOC
there are 2 types of triglycerides: saturated fat and unsaturated fat
Saturated vs Unsaturated Fat?
Saturated = has no carbon double bonds in the R group of the fatty acid
Unsaturated = has carbon double bonds in the R group of the fatty acid
