AS LEVEL BIOLOGY A HD20|02 DEPTH IN
BIOLOGY MONDAY 4 JUNE2018 –
AFTERNOON EXAM 2024-2025 WITH
CORRECT ANSWERS AND QUESTIONS
(a) Fig. 1.1 shows the general structure of an amino acid
State the names of the groups labelled U and V - ANS-U- amine group
V- carboxyl group
Fig. 1.2 shows a representation of a short polypeptide chain made from three amino acids
Name bond W and state what type of reaction takes place to form this bond. - ANS-Name of bond W-
peptide bond
Type of reaction- condensation reaction
Pepsin is a protease enzyme with a polypeptide chain containing 327 amino acids.
Titin is the largest known protein. It has a polypeptide chain containing at least 92 times more amino
acids than pepsin.
(i) DNA sequences in genes code for polypeptide molecules such as pepsin and titin.
Explain why a process known as transcription is necessary for polypeptide synthesis - ANS-DNA, copied
to mRNA
DNA, is too large to leave nucleus
, Calculate the minimum length of the DNA base sequence required to code for titin. Show your working -
ANS-327 x 92 x 3= 90,252
* Titin is a fibrous protein. Pepsin is a globular protein. Compare the properties and functions of fibrous
proteins and globular proteins in the human body - ANS-Properties:
Globular-soluble, Fibrous- insoluble
Globular- tertiary structure, fibrous-no tertiary structure
Globular- Hydrophilic R groups on the outside
Fibrous- Hydrophobic R groups , strong flexible
Functions:
Globular- to transport substances in blood • haemoglobin + role described e.g. carry oxygen
to transport substances across cell membranes • carrier / channel / pump + role described
enzymes / metabolic role / to catalyse reaction(s) / to lower activation energy • named enzyme + its
specific role described
• hormones / receptors / for cell signaling • named hormone / insulin + role described
Fibrous-
for protection • keratin in, skin / hair / nails
for structure • collagen in, bone
to give, elasticity / elastic properties • elastin in, (named) blood vessels / alveoli / cartilage
Using the traces shown in Fig. 2.1, name the heart rhythm abnormality that the patient is suffering from
- ANS-tachycardia
Explain how the heart is controlling the electrical activity at Y on Fig. 2.1(b) - ANS-The impulse travels to
the AV node. Here, the impulse slows for a moment before going on to the ventricles
BIOLOGY MONDAY 4 JUNE2018 –
AFTERNOON EXAM 2024-2025 WITH
CORRECT ANSWERS AND QUESTIONS
(a) Fig. 1.1 shows the general structure of an amino acid
State the names of the groups labelled U and V - ANS-U- amine group
V- carboxyl group
Fig. 1.2 shows a representation of a short polypeptide chain made from three amino acids
Name bond W and state what type of reaction takes place to form this bond. - ANS-Name of bond W-
peptide bond
Type of reaction- condensation reaction
Pepsin is a protease enzyme with a polypeptide chain containing 327 amino acids.
Titin is the largest known protein. It has a polypeptide chain containing at least 92 times more amino
acids than pepsin.
(i) DNA sequences in genes code for polypeptide molecules such as pepsin and titin.
Explain why a process known as transcription is necessary for polypeptide synthesis - ANS-DNA, copied
to mRNA
DNA, is too large to leave nucleus
, Calculate the minimum length of the DNA base sequence required to code for titin. Show your working -
ANS-327 x 92 x 3= 90,252
* Titin is a fibrous protein. Pepsin is a globular protein. Compare the properties and functions of fibrous
proteins and globular proteins in the human body - ANS-Properties:
Globular-soluble, Fibrous- insoluble
Globular- tertiary structure, fibrous-no tertiary structure
Globular- Hydrophilic R groups on the outside
Fibrous- Hydrophobic R groups , strong flexible
Functions:
Globular- to transport substances in blood • haemoglobin + role described e.g. carry oxygen
to transport substances across cell membranes • carrier / channel / pump + role described
enzymes / metabolic role / to catalyse reaction(s) / to lower activation energy • named enzyme + its
specific role described
• hormones / receptors / for cell signaling • named hormone / insulin + role described
Fibrous-
for protection • keratin in, skin / hair / nails
for structure • collagen in, bone
to give, elasticity / elastic properties • elastin in, (named) blood vessels / alveoli / cartilage
Using the traces shown in Fig. 2.1, name the heart rhythm abnormality that the patient is suffering from
- ANS-tachycardia
Explain how the heart is controlling the electrical activity at Y on Fig. 2.1(b) - ANS-The impulse travels to
the AV node. Here, the impulse slows for a moment before going on to the ventricles
