AQA A level Biology Exam
Describe how you would use a biochemical test to show that a solution contained
a non-reducing sugar, such as sucrose. [3]
-first reducing sugars test;
-boil with dilute HCl acid then Neutralize with NaHCǑ,
-add benedict and heat to 95 degrees C brick red ppt forms if reducing sugar is
present
Describe a chemical test you could carry out to show that a piece of coconut
contains lipids.
(Crush in) ethanol / alcohol; Add (to) water (Order of adding is critical for this point);
Emulsion / white color
Explain what is meant by a polymer.
Molecule) made up of many identical/similar molecules/monomers/ subunits;
Name the reaction which occurs when starch is broken down into maltose.
Hydrolysis
,What is the formula for lactose?
C12 ; H22Ō1
Describe how β-glucose molecule differs from a molecule of α-glucose.
H at top right end (instead of OH) / OH at bottom (carbon 1)
Show two ways in which the structure of cellulose is different from the structure
of starch.
Starch 1,4 and 1,6 bonds / branching Cellulose 1,4 bonds / no 1,6 bonds / straight;
starch All glucoses /monomers same way up cellulose Alternate glucoses upside
down; starch Helix / coiled/compact cellulose Straight; Starch monomer Alpha
glucose Cellulose monomer Beta glucose
Describe the structure of starch and explain how its structure is related to its
function.
Formed from α glucose; Joined by condensation/ by the removal of a water molecule/
glycosidic bonds; Between (carbons) 1 and 4 (and 1 and 6); Coiled chain; compact;
(Allows) storage of large amount in a small space; Insoluble so has no effect on
osmosis/water potential; Branches; (Allows) rapid breakdown/release of glucose /
hydrolysis;
,The structure of a phospholipid molecule is different from that of a triglyceride.
Describe how.
triglyceride has three fatty acids and phospholipid has two; no phosphate group
present in triglyceride but present in phospholipid.
What is an unsaturated fatty acid?
Some / two carbons with only one hydrogen / (double bonds) between carbon atoms
/ not saturated with hydrogen;
Describe the structure of cellulose and explain how its structure is related to its
function.
Alternate β-glucose rotated 180o, long straight chains, Many hydrogen bonds join
(polysaccharide) chains/molecules to each other / makes microfibrils / gives tensile
strength;
Which elements are found in proteins?
Carbon, hydrogen, oxygen, nitrogen (sometimes sulphur)
Describe how you would use a biochemical test to show that a solution contained
protein.
Biuret / alkali + copper sulphate; Lilac/purple/mauve/violet;
, Which bonds are found in a)Primary structure b)Secondary structure c)Tertiary
structure
a) Peptide
b) Hydrogen (and peptide)
c)Ionic, disulphide bridges, hydrophobic interactions (hydrogen and peptide)
Explain how a change in the primary structure of a globular protein may result in a
different three-dimensional structure.
Sequence of amino acids changes; tertiary structure changes/folds in a different
way; bonds form in different places (not peptide);
Describe how two-way chromatography is carried out.
Run chromatogram then turn through 90/right angle; With a different solvent;
Explain the advantage of using two-way chromatography to separate short
polypeptides.
Spreads spots/polypeptides out more/ make sure spot only contains one substance;
Describe how you would use a biochemical test to show that a solution contained
a non-reducing sugar, such as sucrose. [3]
-first reducing sugars test;
-boil with dilute HCl acid then Neutralize with NaHCǑ,
-add benedict and heat to 95 degrees C brick red ppt forms if reducing sugar is
present
Describe a chemical test you could carry out to show that a piece of coconut
contains lipids.
(Crush in) ethanol / alcohol; Add (to) water (Order of adding is critical for this point);
Emulsion / white color
Explain what is meant by a polymer.
Molecule) made up of many identical/similar molecules/monomers/ subunits;
Name the reaction which occurs when starch is broken down into maltose.
Hydrolysis
,What is the formula for lactose?
C12 ; H22Ō1
Describe how β-glucose molecule differs from a molecule of α-glucose.
H at top right end (instead of OH) / OH at bottom (carbon 1)
Show two ways in which the structure of cellulose is different from the structure
of starch.
Starch 1,4 and 1,6 bonds / branching Cellulose 1,4 bonds / no 1,6 bonds / straight;
starch All glucoses /monomers same way up cellulose Alternate glucoses upside
down; starch Helix / coiled/compact cellulose Straight; Starch monomer Alpha
glucose Cellulose monomer Beta glucose
Describe the structure of starch and explain how its structure is related to its
function.
Formed from α glucose; Joined by condensation/ by the removal of a water molecule/
glycosidic bonds; Between (carbons) 1 and 4 (and 1 and 6); Coiled chain; compact;
(Allows) storage of large amount in a small space; Insoluble so has no effect on
osmosis/water potential; Branches; (Allows) rapid breakdown/release of glucose /
hydrolysis;
,The structure of a phospholipid molecule is different from that of a triglyceride.
Describe how.
triglyceride has three fatty acids and phospholipid has two; no phosphate group
present in triglyceride but present in phospholipid.
What is an unsaturated fatty acid?
Some / two carbons with only one hydrogen / (double bonds) between carbon atoms
/ not saturated with hydrogen;
Describe the structure of cellulose and explain how its structure is related to its
function.
Alternate β-glucose rotated 180o, long straight chains, Many hydrogen bonds join
(polysaccharide) chains/molecules to each other / makes microfibrils / gives tensile
strength;
Which elements are found in proteins?
Carbon, hydrogen, oxygen, nitrogen (sometimes sulphur)
Describe how you would use a biochemical test to show that a solution contained
protein.
Biuret / alkali + copper sulphate; Lilac/purple/mauve/violet;
, Which bonds are found in a)Primary structure b)Secondary structure c)Tertiary
structure
a) Peptide
b) Hydrogen (and peptide)
c)Ionic, disulphide bridges, hydrophobic interactions (hydrogen and peptide)
Explain how a change in the primary structure of a globular protein may result in a
different three-dimensional structure.
Sequence of amino acids changes; tertiary structure changes/folds in a different
way; bonds form in different places (not peptide);
Describe how two-way chromatography is carried out.
Run chromatogram then turn through 90/right angle; With a different solvent;
Explain the advantage of using two-way chromatography to separate short
polypeptides.
Spreads spots/polypeptides out more/ make sure spot only contains one substance;
