WA4 Mock BT P2 (Teacher)

Civics Group Index Number Name (use BLOCK LETTERS) ST ANDREW’S JUNIOR COLLEGE 2022 JC2 Weighted Assessment 4 H1 BIOLOGY 8876 STRUCTURED QUESTIONS & ESSAY 50 minutes READ THESE INSTRUCTIONS FIRST Write your name, civics group and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagram, graph or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. All working for numerical answers must be shown. Conceptual error (C) Data Quoting (D) Expression (E) Misreading the question (Q) For Examiner’s Use STQ 1 /9 STQ 2 /10 STQ 3 /14 Total /33 This document consists of XX printed pages. [Turn over H1

STRUCTURED QUESTIONS QUESTION 1 Fig. 1.2 shows an electron micrograph of part of an acinar cell found in the pancreas. Fig. 1.1 (a) With reference to Fig. 1.1,

(i) Identify organelle A ………………………………………………………………………………………………………. [1] 1 Secretory vesicle (ii) Explain how organelle A can become part of the cell surface membrane. ………………………………………………………………………………………………………. [1] 1 Secretory vesicle moves along microtubules and fuses with the cell surface membrane during exocytosis; (iii) Describe the differences in structure and function between organelles B and C. ………………………………………………………………………………………………………. [2] Structure B (rough endoplasmic reticulum) C (nucleolus) Membrane bound or not Single membrane bound Not membrane bound Ribosomes Ribosomes embedded on outer surface No ribosomes Function Transport and package proteins in transport vesicles to golgi apparatus/other organelles/ out of cell for secretion Reject: site of protein synthesis Site of rRNA synthesis/ assembly of rRNA and proteins to form ribosomal subunits (b) In eukaryotic cells, the degradation of mRNA is an essential part of the regulation of gene expression. It can be controlled in response to developmental, environmental, and metabolic signals. mRNA hydrolysis is catalysed by numerous types of nucleases, such as the endonuclease Ribonuclease A (RNAse A), shown in Fig. 1.2A.

Fig. 1.2 (i) Fig. 1.2B shows two important catalytic residues within the active site of RNAse A, which are His12 and His119. Explain how these two histidines, which are in position 12 and 119 of the 124 amino acid sequence, are brought together in the active site of the enzyme. ………………..…………………………………………………….……………….……… [3] 1 Primary structure + number, type and sequence of amino acid determines how the polypeptide chain folds upon itself; 2 To form the tertiary structure, which is stabilized by hydrogen, ionic, disulphide bonds and hydrophobic interactions between R groups of amino acids 3 Bringing faraway amino acids together within the active site; (ii) Fig. 1.3 shows the structure of histidine and phenylalanine.