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Summary Knowledge revision sheets for AQA A Level biology topic 1 - biological molecules

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Knowledge revision sheets for AQA A Level biology topic 1 - biological molecules. Contains key information with visual diagrams. Includes notes on: Carbohydrates Lipids Proteins Enzymes DNA ATP Water Ions

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Monosaccharides Disaccharides
Monomers from which larger carbohydrates are made • 2 monosaccharides joined by a glycosidic bond in a condensation reactions, releasing a water
e.g. fructose, galactose and glucose (include 2 isomers). molecule.

Condensation

+ + HO 2

Hydrolysis


Disaccharides Monosaccharides
Polysaccharides
Carbohydrates Maltose Glucose Glucose
Many monosaccharides joined together by glycosidic bonds Lactose Glucose Galactose
Sucrose Glucose Fructose
Starch Glycogen Cellulose
• Energy store in plants • Energy store in animal cells • Strengthens cell wall
• Polysaccharide of α-glucose • Polysaccharide of α-glucose • Polysaccharide of β-glucose
Types
• 1,4- glycosidic bonds Tests
• Every other β-glucose is
inverted in straight Reducing Sugars Non- Reducing Sugars
Amylose Amylopectin Monosaccharides, Sucrose Starch
unbranched chains.
maltose, lactose
Unbranched 1-4 glycosidic bonds • Add Benedict's • Negative result with
1-4 glycosidic solution to sample • Add iodine
And branched due to Benedict's test
bonds 1-6 glycosidic bonds Structure to Function • Heat in a boiling solution
• Heat with acid (to
water bath • Turns Blue/black
Structure to Function
hydrolyse reducing
• More branched (more 1-
• Positive result = sugar)
6 glycosidic bonds) so Positive
• Coiled so compact Structure to Function
green/yellow/orang • Neutralise with
more ends for faster
• Large so can’t leave cells e/red precipitate sodium bicarbonate
hydrolysis – release of
• Insoluble so doesn’t • Straight unbranched (alkali)
glucose for respiration to
affect water potential chains linked by many • Repeat benedict's test
produce ATP
hydrogen bonds to form • Gives positive result
• Large so can’t leave cell Negative
• Insoluble so doesn’t microfibrils making it
strong. None
affect water potential Increasing quantity of sugar

• Branched - compact

, Lipid contain the elements carbon, oxygen and hydrogen Lipids
Triglycerides Fatty Acids
• Formed from 1 glycerol molecule and 3 Glycerol • Have a hydrocarbon chain with a carboxyl group
fatty acids in a condensation reaction Ester bond
Saturated




Fatty Acid

Fatty Acid

Fatty Acid
which forms 3 water molecules and forms
3 ester bonds. • No C=C double bond in the hydrocarbon chain



Unsaturated

• One or more double bonds in the hydrocarbon
chain. Causes a bend in chain
• More liquid at room temperature as can’t pack as
Structure to Function closely together – fewer intermolecular forces
• High ratio of C-H bonds to carbon atoms in hydrocarbon chain → used in
respiration to release more energy than same mass of carbohydrate
• Hydrophobic/ non-polar fatty acids so insoluble in water → doesn’t affect
water potential of cell.


Phospholipids
Tests
• 1 phosphate group and 2 fatty acids attached to a glycerol. Phosphate • Add ethanol, shake then add water
group
• Positive result is a cloudy white emulsion
• Have hydrophilic head (attracted to water) and hydrophobic
Glycerol
tails (repelled by water) so form a phospholipid bilayer in
membranes.
Fatty Acid
Fatty Acid




Hydrophilic head
Hydrophobic tails Phospholipid
bilayer

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