Answers
Activity
1. a) Monosaccharides
i) fructose
ii) galactose
b) Dissacharides
i) maltose
ii) Glucose + fructose
iii) lactose, glucose
c) Polysaccharides
i) starch
ii) glycogen
iii) cellulose
2. a) straight
b) Secondary structure
c) folded
d) Quartenary structure
3.
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Objectives
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1.C
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3. D
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5. C
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7. A
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9. B
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2.B
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4. D
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6. A
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8. D
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10.C
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Structured questions
1.
a) maltose and
sucrose
b) maltose
is formed by the condensation of two glucose molecules sucrose is
formed by the condensation of a glucose
molecule and a fructose molecule
c) Glucose
is a reducing sugar because it can reduce copper (II) ions which are
blue in colour to a brick-red precipitate
of copper (I) oxide
d)
Glycerol and fatty acids
e)
Condensation
2. a) Amino acids
b) Essential amino acids are amino acids
that cannot be synthesised by the body
Non-essential amino acids are amino
acids that can be synthesized by the body
a)
i) The secondary
structure of proteins is formed when the polypeptide chain is coiled to form an
alpha-helix chain or folded into beta-pleated sheets. Both
the alpha-helix chain and the beta-pleated sheet structure
are held together
by
hydrogen bonds.
ii) The tertiary structure is formed
when the helix chains or beta sheets are
folded into three -dimensional
shape of a polypeptide. The tertiary structure
is held in place by ionic
bonds, disulphide bonds and hydrogen bonds that
are formed between the amino
acids of the polypeptide chains sheets.
iii)
The quarternary structure is formed when two or more tertiary structure
of
polypeptide chains are combine
into one large and complex protein
molecule.
3.
a) P – Glycerol Q – Fatty acid
b) i)
Condensation
ii) Water
c) i) A
phospholipid molecule has two fatty acids and phosphate group
attached to a molecule
of glycerol while the lipid molecule in the figure has
three fatty acids
joined to a molecule of glycerol.
ii) One end of the phospholipid molecule,
containing the phosphate group is
soluble in water, while the other end, containing the
fatty acids is insoluble
in water. When
phospholipid are in water, they form a bilayered structure
comprising of two ‘back-to-back’ layers of phospholipid
molecules. The
water soluble
(hydrophilic) ends point outwards while the water insoluble
(hydrophobic) ends
point inwards.
iii) The phospholipid bilayers
provide the structural basis for all cell
membrane.
Essay
a) i)Nucleic
acids contain carbon, hydrogen, oxygen, nitrogen and phosphorus.
(2
marks)
ii)The structural units of nucleic
acids are nucleotides which consist of a sugar, a
phosphate
and a nitrogen base. (2 marks)
iii)There
are two types of nucleic acid: DNA (deoxyribonucleic acid) and RNA
(ribonucleic acid).
(2
marks)
iv)DNA is a large complex molecule
consisting of two chains of
polynucleotide
twisted into a double helix.
(2 marks)
v) RNA is a
shorter, single-stranded molecule of polynucleotide.
(2 marks)
a)
i)DNA carries genetic information in the form
of a code to direct the cell to
synthesise
protein. (3 marks)
ii)DNA is
not involved directly in the assembly of amino acids to form protein.
(2 marks)
iii)The information in the DNA is
transcribed into RNA which direct the assembling
of amino acids into specific
protein.
(2 marks)
iv)The
types of protein in the organism determine the structure of the organism and
control the biochemical reactions in the
cell.
(3 marks)
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