Question 1
Bacteria are widely used in biotechnology and genetic modification. State two features of bacteria that make them useful.
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- rapid reproduction rate / reproduce quickly (1)
- (able to) make complex molecules (1) allow named example e.g. proteins
Question 2
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanApart from their rapid reproduction and their ability to make complex molecules, bacteria are useful in genetic modification for other reasons. Explain two of these other reasons.
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- few ethical concerns over their manipulation / growth (1)
- have plasmids (1)
- (plasmid) can have a gene inserted / can carry the gene into the bacterium (1)
- Max 2
Question 3
Ethanol can be produced by yeast for use as a biofuel. Describe the role of anaerobic respiration in yeast in this process.
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- yeast respires without oxygen / anaerobically (1) ignore 'ferments' alone
- breaks down sugar / glucose (1)
- to produce ethanol / alcohol (and carbon dioxide) (1)
- ethanol is separated and used as a fuel (1)
- Max 3
Question 4
Bakers add yeast to dough and leave it in a warm place before baking. Describe and explain what happens to the dough, and to the substances made by the yeast, during bread-making.
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- yeast respires anaerobically (1)
- producing carbon dioxide (1)
- bubbles of gas trapped in the dough make it rise (1) reject ethanol makes the dough rise
- gas bubbles expand when baked (1)
- ethanol / alcohol is also produced and evaporates during baking (1)
- Max 4
Question 5
Pectinase is added to crushed fruit when making fruit juice. What is the effect of pectinase?
- It kills bacteria in the juice
- It breaks down cell walls so more juice is released
- It makes the juice sweeter by making glucose
- It stops the fruit from rotting
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Answer: B (1)
Question 6
A student investigates how well a biological washing powder removes egg white stains from cloth at different temperatures. (a) Name the type of enzyme in the powder that breaks down the egg white stain. [1] (b) State two variables the student should keep the same. [2] (c) Suggest what the student should measure. [1] (d) The stain was not removed at 80 °C. Explain why. [2]
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- (a) protease (1) reject lipase / amylase
- (b) size / type of cloth (1)
- amount / volume of egg white stain (1)
- volume of water / solution (1)
- mass / concentration of washing powder (1)
- pH / amount of stirring (1)
- Max 2 for (b)
- (c) time taken for the stain to disappear (1) allow how much stain is left after a fixed time
- (d) enzyme / protease is denatured (1)
- active site changes shape, so protein / substrate no longer fits (1)
Question 7
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanSome people cannot digest lactose. Explain how lactase is used to produce lactose-free milk.
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- lactase is an enzyme added to milk (1)
- it breaks down lactose (1)
- into glucose and galactose (both needed) (1)
- so people who are lactose intolerant can drink / digest it (1)
- Max 3
Question 8
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanFermenters are used to make penicillin on a large scale. (a) Name the type of organism that makes penicillin, and one other product made in fermenters. [2] (b) Describe and explain how the temperature and the oxygen concentration are controlled in a fermenter. [3]
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- (a) fungus / Penicillium (1)
- insulin / mycoprotein (1)
- (b) temperature kept at the optimum using a water jacket / cooling water (1)
- heat released by respiration is removed / temperature monitored by a probe (1)
- so enzymes work fast and are not denatured (1)
- sterile air is pumped / bubbled in (1)
- stirrer spreads oxygen through the culture (1)
- oxygen for aerobic respiration, releasing energy for growth (1)
- Max 3 for (b)