Biology 2020 Paper 1 Past Paper Questions and Answers, Exams of Advanced Education

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Biology 2020 Paper 1 past paper

questions

Q1 1.1 function of ATP hydrolase (2 marks) - - hydrolyse ATP into ADP and Pi -> releasing energy

• the energy allows ions to move ions against their concentration gradient across the membrane. Q1 1.2 The movement of NA ions out allows the absorption of glucose into the lining of the ileum. Explain how (2 marks) - - causes a conc. gradient of NA from the ileum to the cell (lower conc. inside of cell compared with the outside)
• causes NA ions to move into cell lining via facilitated diffusion using sodium glucose cotransporter proteins which brings glucose with it Q1 1.3 two features you may find in a cell specialized for absorption (2 marks) - - microvilli (finger like projections) increases SA for absorption
• larger number of protein carriers/ cotransporter protein carriers to increase the rate of absorption Q1 1.4 structure of a phospholipid - 2 fatty tails (hydrophobic) 1 phosphate head (hydrophilic) Q1 1.5 Describe how amino acids join to form a polypeptide so always NH2 and COOH are at the end ( marks) - - the amine group (NH2) joints to the carboxyl group (COOH) and forms a peptide bond in a condensation reaction.
• a polypeptide chain is formed =, there is always a free amine group and carboxyl group at each end Q3 3.1 Figure 3 shows that the pressure in the left ventricle is increasing. At the same time as this, the rate of blood flow has not yet started to increase in the aorta. Explain why ( 2 marks) - Because the pressure in the aorta is higher than the pressure in the ventricle. This means that the semi lunar valves are closed shut and therefore blood flow cannot increase yet. Q3 3.2 At Q on Figure 3 there is a small increase in pressure and in rate of blood flow in the aorta. Explain how this happens and its importance. (2 marks) - The small increase in blow flow and pressure is due to the aortas elastic tissue stretching as blood is forced out of the ventricle into the vessel. It is

important because it helps maintain blood pressure so that the oxygenated blood leaving the aorta can reach the different parts of the body. Q3 3.3 A student correctly plotted the right ventricle pressure on the same grid as the left ventricle pressure in Figure 3. Describe one way in which the student's curve would be similar to and one way it would be different from the curve shown in Figure 3. (2 marks) - similarity = similar shape of the curve. this is because the ventricles contract simultaneously and so will be drawn at the same time. difference = right ventricle will be drawn at a lower pressure. This is because the left ventricle needs to be pumped at a higher pressure as the blood has further to travel Q3 3.4 Use information from Figure 3 to calculate the heart rate of this dog (1 mark) - cardiac output = heart rate x stroke volume 60/ 0.8-0.44 = 166. Name two other variables the student should have kept constant during this investigation (2 marks) - 1 - temperature 2 - type of blueberries used/ concentration of ethanol After 1 hour, the student filtered the samples. She placed the filtrate in a colorimeter and measured the light absorbance. Her results are shown in Figure 4. Use your knowledge of membrane structure to explain the results in Figure 4 (4 marks) - - figure 4 shows that there must be more anthocyanin as it shows an increase in absorption in the graph. the pigment absorbs light due to...

• increased damage to the cell membrane makes it more permeable
• means more anthocyanin released once crushed
• describe E,F,G E= acid breaks down membrane by denaturing the proteins, phospholipid bilayer in cell membrane is broken down by ethanol G= water however still absorb because pigment is released when blueberries are crushed Q6 6.1 Explain why death of alveolar epithelium cells reduces gas exchange in human lungs ( 3 marks ) - - death of alveolar epithelium decreases surface area for gas exchange to occur. tidal volume also decreases.
• rate of gas exchange decreases as diffusion pathway becomes longer

Q7 7.1 Alpha-gal is a disaccharide found in red meat. Alpha-gal is made of two galactose molecules. Galactose has the chemical formula C6H12O6 Give the chemical formula for the disaccharide, alpha-gal, and describe how it is formed from two galactose molecules. (2 marks) - formula = C12H22O11 c= 6x h= 24-2=22 (condensation reaction h20) o=12- formed in a condensation reaction where a glyosidic bond is formed Q7 7.2 draw and label an antibody and label specific alpha gel binding site (3 marks) - antigen binding site = alpha gel binding site Q7 7.3 suggest how one antibody can be specific to tick protein and to an alpha gel ( 2 marks) - The tick protein and alpha gel have a similar shape or molecular structure and so the antibody is complementary to both and is able to form an antigen-antibody complex. Q7 7.4 The scientists' hypothesis was that an earlier immune response to tick protein causes the allergic reaction. Consider whether Figure 7 supports this hypothesis. ( 3 marks) - - first tick protein exposure causes an increase in the specific alpha gel antibodies

• second exposure total antibodies increase quickly due to memory cells
• the conc. of total antibodies increases more than specific alpha gel suggesting that it may be other antibodies causing the allergic reaction Q8 8.1 3 differences between DNA in the nucleus of a plant cell and prokaryotic cell (3 marks) - DNA in nucleus =
• DNA associated with histones
• DNA helical/linear
• introns DNA in prokaryotic =
• no histones
• DNA circular plasmids
• no introns

Q8 8.2 define 'non coding base sequences' and describe where the non coding multiple repeats are positioned in the genome ( 2 marks) - non-coding are sections of DNA that do not code for a polypeptide. located/ positioned between gene also known as intron Q8 8.4 use table 3 to evaluate how this information affects the validity of the phylogenetic tree ( 2 marks) - supported because it shows that it is more closely related than any other species. However, it may not be valid due to how small the sample size is (only 5 individual of sweet pots)