2024 AS Level Biology A H020/02 Depth in biology Monday 4 June FINAL UPDATE PASS A+

2024 AS Level Biology A H020/02 Depth in biology Monday 4 June FINAL UPDATE PASS A+ (a) Fig. 1.1 shows the general structure of an amino acid State the names of the groups labelled U and V - ANSWER-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. - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-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 - ANSWER-tachycardia