OCR AS Level Biology A H020/02 Depth in biology

INSTRUCTIONS • The Insert will be found inside this document. • Use black ink. You may use an HB pencil for graphs and diagrams. • Complete the boxes above with your name, centre number and candidate number. • Answer ...

INSTRUCTIONS • The Insert will be found inside this document. • Use black ink. You may use an HB pencil for graphs and diagrams. • Complete the boxes above with your name, centre number and candidate number. • Answer all the questions. • Write your answer to each question in the space provided. If additional space is required, you should use the lined page(s) at the end of this booklet. The question number(s) must be clearly shown. • Do not write in the barcodes. INFORMATION • The total mark for this paper is 70. • The marks for each question are shown in brackets [ ]. • Quality of extended responses will be assessed in questions marked with an asterisk (*). • This document consists of 24 pages. © OCR 2018 [601/4261/3] DC (ST/JG) 157107/5 OCR is an exempt Charity Turn over You must have: • the Insert (inserted) You may use: • a scientific or graphical calculator • a ruler (cm/mm) * 7 0 0 1 7 3 5 1 7 3 * First name Last name Centre number Candidate number2 © OCR 2018 Answer all the questions. 1 (a) Fig. 1.1 shows the general structure of an amino acid. U R group V Fig. 1.1 (i) State the names of the groups labelled U and V. U ........................................................................................................................................ V ........................................................................................................................................ [1] C H H O O C N H H3 © OCR 2018 Turn over (ii) Fig. 1.2 shows a representation of a short polypeptide chain made from three amino acids. Bond W Valine Alanine Glycine Fig. 1.2 Name bond W and state what type of reaction takes place to form this bond. Name of bond W ............................................................................................................... Type of reaction ................................................................................................................. [1] (b) 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. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2] (ii) Calculate the minimum length of the DNA base sequence required to code for titin. Show your working.