(03) WMP/Jun13/BIOL1

Transcription

1 3 Do not write outside the box Answer all questions in the spaces provided. 1 The diagram shows the structure of the cell-surface membrane of a cell. C B A 1 (a) Name A and B. A... B... (2 marks) 1 (b) (i) C is a protein with a carbohydrate attached to it. This carbohydrate is formed by joining monosaccharides together. Name the type of reaction that joins monosaccharides together.. (1 mark) 1 (b) (ii) Some cells lining the bronchi of the lungs secrete large amounts of mucus. Mucus contains protein. Name one organelle that you would expect to find in large numbers in a mucus-secreting cell and describe its role in the production of mucus. Organelle... Description of role (2 marks) 5 Turn over (03) WMP/Jun13/BIOL1

2 Describe how you would test a piece of food for the presence of lipid. [2 marks] Figure 8 shows a phospholipid. Figure 8

3 The part of the phospholipid in Figure 8 labelled A is formed from a particular molecule. Name this molecule. [1 mark] Name the type of bond between A and fatty acid X. [1 mark] Which of the fatty acids, X or Y, in Figure 8 is unsaturated? Explain your answer. [1 mark] Question 7 continues on the next page Turn over

4 18 Scientists investigated the percentages of different types of lipid in plasma membranes from different types of cell. Table 2 shows some of their results. Table 2 Type of lipid Percentage of lipid in plasma membrane by mass Cell lining ileum of mammal Red blood cell of mammal The bacterium Escherichia coli Cholesterol Glycolipid Phospholipid Others The scientists expressed their results as Percentage of lipid in plasma membrane by mass. Explain how they would find these values. [2 marks] Cholesterol increases the stability of plasma membranes. Cholesterol does this by making membranes less flexible Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum. [1 mark]

5 E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why. [2 marks] Turn over for the next question Turn over

6 6 3 (a) The structure of cell membranes can be described as proteins floating in a sea of lipids. This membrane structure allows certain substances to pass through freely whereas other substances cannot. State the term used to describe a membrane through which some substances can pass freely but others cannot.... [1] (b) Complete the following paragraph about cell membranes, using the most appropriate terms. The model of cell membrane structure is called the model. Phospholipid bilayers with specific membrane proteins account for the ability of the membrane to allow both passive and... transport mechanisms. Ions and most polar molecules are insoluble in the phospholipid bilayer. However, the bilayer allows diffusion of most non-polar molecules such as... Protein channels, which may be gated, and... proteins enable the cell to control the movement of most polar substances. [4] (c) One function of membranes that is not mentioned in (b) is cell signalling. (i) State what is meant by cell signalling.... [1] OCR 2013

7 (ii) 7 Explain how cell surface membranes contribute to the process of cell signalling. In your answer you should use appropriate technical terms, spelled correctly.... [4] [Total: 10] OCR 2013 Turn over

8 3 The fluid mosaic model describes the structure and properties of cell membranes. (a) The diagram below shows the structure of a cell membrane based on this model. Proteins A Proteins (i) Name the molecule labelled A and describe its structure. (3) Name Structure... *N35850A0520* 5 Turn over

9 (ii) Explain how the properties of molecule A contribute to the structure of the cell membrane. (3) (b) Some proteins in the cell membrane are involved in active transport and facilitated diffusion. Describe the role of proteins in these cell transport mechanisms. (3) Active transport... Facilitated diffusion... 6 *N35850A0620*

10 (c) In an investigation into the properties of the cell membrane, the proteins in the membranes of two cells, A and B, were stained using different dyes. The proteins of one cell were stained green and the proteins of the other cell were stained red. The cells were then fused (merged together) to form a single cell. The diagram below shows the distribution of the proteins in the cell membranes before and after fusion. Red-stained proteins Green-stained proteins Cells before fusion Cell A Cell B A single cell after fusion (i) Describe the distribution of the proteins in this single cell after fusion. (2) (ii) Describe how the results of this investigation can be explained by the fluid mosaic model. (2) (Total for Question 3 = 13 marks) *N35850A0720* 7 Turn over