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. Fig. 1.3 Predict and explain how the catalytic activity of RNAse would be affected if both histidines were replaced by phenylalanines. ……….………………………………………………………………………….……… [2] 1 Histidine has an R-group that is polar whereas phenylalanine has an R-group that is non-polar;;

2 This causes the change in the interaction between the catalytic residues and the substrate at the active site; therefore; RNAase catalytic activity will be greatly reduced / lost;; [Total: 9] QUESTION 2 (a) Fig. 2.1 is a diagram showing DNA replication. Fig. 2.1 (i) Identify the bases labelled X and Y on Fig. 1.1 and state whether they are purine or pyrimidine. …..……….………………………………………………………………………….……… [1] 1 X: Cytosine (pyrimidine) 2 Y: Thymine (pyrimidine) (ii) Explain how Fig. 2.1 shows semi-conservative replication. …..……….………………………………………………………………………….……… [3] 1 The two parental DNA strands separate due to the breaking of hydrogen bonds between complementary bases; 2 Each strand acts as a template for the synthesis of new complementary DNA strands; 3 Each new DNA molecule contains one parental DNA strand and one newly synthesised daughter DNA strand;

(b) Fig. 2.2 is an electron micrograph showing the process of protein synthesis in a prokaryote. Fig. 2.2 (i) Identify structures A and C. …..……….………………………………………………………………………….…….… [1] A: Ribosomes C: DNA (ii) Label in the boxes in Fig. 2.2 to show the 5’ and 3’ ends of the structure C. [1] (c) Fig 2.3 shows the Calvin cycle that occurs during photosynthesis. 3’ 5’

Fig. 2.3 (i) State the number of carbon atoms in one molecule of compound X. ……………………………………………………………………………………..….......... [1] 3 (ii) A plant undergoing active photosynthesis, was placed in an environmen t where there was no carbon dioxide. State the label number of the solid arrow that represents the reaction in Fig 8.1 inhibited by the absence of carbon dioxide. ……………………………………………………………………………………..….......... [1] 4 (iii) Identify a compound that would start to accumulate in the above scenario and explain why it accumulates. ……………………………………………………………………………………..….......... [2] 1 RuBP 2 No carbon fixation as lack of CO2 to combine with RuBP to form PGA; 3 PGA is converted into PGAL, (some of) which is used to regenerate RuBP. [Total: 10] QUESTION 3 Fig. 1.1 is a photomicrograph of plant root cells near the growing tip. Some of the cells are undergoing mitosis.

Fig. 3.1 (a) State the letter, A to D, of the cell in Fig. 2.1 which is in (i) Prophase: ………………………… (ii) Anaphase: ……………………….. [1] Prophase: B Anaphase: C (b) Fig. 3.2A shows a DNA base sequence. It also shows the effect of two mutations on this base sequence. Fig. 3.2B shows DNA triplets that code for different amino acids. Original DNA base sequence A T T G G C G T G T C T Mutation 1 DNA base sequence A T T G G A G T G T C T Mutation 2 DNA base sequence A T T G G C C T G T C T Fig. 3.2A DNA triplets Amino acid GGT, GGC, GGA, GGG Gly GGT, GTA, GTG, GTC Val ATC, ATT, ATA Ile TCC, TCT, TCA, TCG Ser CTC, CTT, CTA, CTG Leu Fig. 3.2B Some mutations affect the amino acid sequences while others do not. Using the information in Fig. 2.2A and Fig. 2.2B, explain (i) why mutation 1 has no effect on the protein structure. ………………………………………………………………………….…………..…......... [2] 1 base substitution on the last DNA triplet from GGC to GGA encodes for the same amino acid, gly; 2 no change in amino acid sequence, no change in R group interactions, no change in protein folding

(ii) why mutation 2 could lead to the formation of a non-functional enzyme. ………………………………………………………………………….…………..…......... [2] 1 substitution mutation from GTG to CTG changes the amino acid encoded from val to leu; 2 change in R group interactions, change in protein folding, change in active site configuration (c) Some beetles h ave spines on their legs to help them capture prey. Three alleles determine the presence and type of spines a beetle will produce. The inheritance of a single LC allele produces curved spines on the legs. The L s allele is recessive to L C allele, and produces straight spines. Beetles that are homozygous recessive for the Ln allele produces no spines on its legs. When a beetle with curved spines was crossed with a beetle with straight spines, they produced the following offspring: 62 curved spines 28 straight spines 30 no spines (i) Draw a genetic diagram to show the cross between the beetle with curved spines and the beetle with straight spines described above. ………………………………………………………………………….…………..…......... [3] Parental phenotype: Curved spines x Straight spines Parental genotype: LCLn x LsLn Gametes: LC Ln Ls Ln F1 genotypes: LCLs LCLn LsLn LnLn F1 phenotypic ratio: 2 curved spines : 1 straight spines : 1 no spines Mark scheme: 1 Parental