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BIOLOGICAL MOLECULES A LEVEL
BIOLOGY EXAM WITH QUESTIONS AND
CORRECT ANSWERS
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g
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When broken
down they release twice as much energy as carbohydrates
~ They are insoluble in water so do not effect water potential - which causes
water to enter by osmosis - As triglycerides bundle into insoluble droplets
as the tails are hydrophobic

Draw a insoluble triglyceride droplet? - Correct Answers -

Relate the structure of a phospholipid to its function? - Correct Answers -~
Make up a bilayer of cell membranes controlling what enters and leaves cell
- As the tails are hydrophobic so point inwards and the heads a hydrophilic
so point into water
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They are
soluble and often used in metabolic processes
~ Antibodies - made up of 2 light and 2 heavy polypeptide chains
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Describe the structure of Collagen? - Correct Answers -~ Has 3 polypeptide
chains coiled around each other in a triple helix with cross-link which are
covalent bonds makes it strong
~ Every 3rd amino acid is glycine
~ Used in supportive tissue

Describe the biurets test? - Correct Answers -~ Solution must be alkaline so
add few drops of sodium hydroxide
~ Add some Copper(II) sulphate
~ If the solution turns purple then a protein is present, no proteins it will
stay blue

What do enzymes do? - Correct Answers -~ Lower the activation energy of a
reaction in metabolic reactions

Describe the induced-fit model? - Correct Answers -~ Substrate collides
with active site
~ The tertiary structure of the active site is able to combine with
complementary substrates
~ The active site changes to fit more closely around the substrate - held in
position by oppositely charged R-groups
~ Enzyme-substrate complex forms
~ Change in shape puts strain on the bonds, weakening them, so lowers the
activation energy
~ Enzyme-product complex forms and the substrate no longer fits so is
released

How come the enzyme binds to the substrate? - Correct Answers -~
Because the tertiary shape of the active site is complementary to the shape
of the substrate
~ So can form a enzyme substrate-complex

Why does a enzyme-substrate complex lower activation energy? - Correct
Answers -~ Being close together reduces any repulsion between the
molecules allowing them to bond more easily
~ Active site puts strain on the bond

Explain why enzymes are so specific? - Correct Answers -~ Because only
one complementary substrate will fit into the active site
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Each polypeptide chain has a Fe+
ion in the centre that binds the oxygen to the haemoglobin
~ Becomes Fe3+ when oxygen is boun

Explain the role of sodium ions? - Correct Answers -~ Helps glucose and
amino acids cross the membrane
~ Glucose & Amino acids can be transported across a cell-surface
membrane with a sodium ion through co-transporters
Define a monomer? - Correct Answers -~ one of many small molecules that
combine to form a larger one known as a polymer

Define a polymer? - Correct Answers -~ large molecule made up of
repeating smaller molecules(monomer)

4 examples of monomers? - Correct Answers -~ Monosaccharides- Glucose,
galactose
~ Nucleotides
~ amino acid
~ fatty acid or glycerol

Define a hydroylsis reaction? - Correct Answers -~ the breaking down of
large molecules into smaller ones by the addition of water molecules

Define a condensation reaction? - Correct Answers -~ chemical process in
which 2 molecules are combine to form to form more complex one with the
elimination of a simple substance usually water
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Define monosaccharides? - Correct Answers -~ A monomer of
carbohydrates

Define dissacharides? - Correct Answers -~ A molecule that is made up of
two monosaccharides

Define polysaccharides? - Correct Answers -~ A molecule formed from
more than two monosaccharides

Draw a Beta glucose? - Correct Answers -

Draw alpha glucose? - Correct Answers -

What type of sugar is a glucose? - Correct Answers -~ Hexose sugar

What is a Sucrose made up of? - Correct Answers -~ Fructose & Glucose

What is Maltose made up of? - Correct Answers -~ Glucose & Glucose

What is Lactose made up of? - Correct Answers -~ Glucose & Galactose

Draw a condensation reaction between 2 alpha glucoses? - Correct Answers
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Describe the structure of amylose? - Correct Answers -~ Long, unbranched
chains of α-glucose
~ Angles of glyosidic bonds makes it a coiled structure - this makes it
compact and good for storage
~ Amylose is insoluble so does not effect water potential
~ Contain 1-4 glyosidic bonds

Describe the structure of amylopectin - Correct Answers -~ Long,
unbranched chains of α-glucose
~ Has side branches which allows enzyme to hydrolyse bonds more easily glucose is released quickly
~ Amylopectin is insoluble so does not effect water potential inside a cell
~ Contain 1-4 glyosidic bonds
~ Branches with 1-6 glyosidic bonds

Function of amylopectin & amylase? - Correct Answers -~ Cells get energy
from glucose
~ Plants store excess glucose as starch - when glucose is needed the starch
is broken down

Draw amylopectin & amylase? - Correct Answers -

Structure and function of Glycogen? - Correct Answers -~ shorter ,
unbranched chains of α-glucose
~ highly unbrached chains amylopectin
~ Very compact molecule so good for storage
~ Glycogen is insoluble so does not effect water potential inside a cell
~ Smaller chains of 1-4 glyosidic bonds
functions:
Loads of side branches means that glucose can be released quickly to
provide energy
~ Way excess glucose is stored in animals
storage for excess sugar in liver

Function of Glycogen? - Correct Answers -storage for excess sugar in liver

Describe the structure of cellulose? - Correct Answers -~ Long, unbranched
chains of β-glucose
~ Glyosidic bonds makes a straight chained molecule

~ Cellulose chains are linked together by hydrogen bonds - forming
microfibrils
~ Microfibrils are further bunched together to form macrofibrils

Function of cellulose? - Correct Answers -~ The strong macrofibrils means
cellulose provides structural support for cells - cell walls for cells are turgid

Biochemical test for a reducing sugar? - Correct Answers -~ Add benedicts
reagent and heat it in a water bath
~ Positive result will form a brick red precipitate

Biochemical test for a non-reducing sugar? - Correct Answers -If test for
reducing is negative then do this:
~ Add dilute hydrochloric acid to the sample and heat it in a water bath - to
break non-reducing sugars down into monosaccharides
~ Neutralise with sodium hydrocarbonate
~ Carry out Benedict's test

What is a reducing sugar? - Correct Answers -~ All monosaccharides
~ Some disaccharides - Maltose & Lactose
Explain the role of phosphate ions? - Correct Answers -~ Known as a
phosphate group
~ The chemical energy in ATP is stored in bonds between phosphate groups
~ Allow the nucleotides to join up to form polynucleotides



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