5. use of biological resources

Question 1

what is the role of yeast in breadmaking

Answer 1

if given the correct conditions (like warm, damp surroundings), yeast carries out anaerobic respiration- the yeast produces enzymes that break down the starch in the flour, releasing sugars that can then be used by the yeast for anaerobic respiration. the waste product of this is carbon dioxide, which gets trapped into small air pockets in the dough which causes the dough to rise

Question 2

how does bread rise by using yeast?

Answer 2

the carbon dioxide produced by the yeast during anaerobic respiration is trapped in small air pockets in the dough, causing the dough to rise

Question 3

explain why bread doesn’t contain any alcohol when the waste product of anaerobic respiration is ethanol

Answer 3

any ethanol produced by the yeast is evaporated in the heat
the yeast is also killed by the high temperatures during baking which ensures no further respiration

Question 4

what bacteria is used to make yoghurt

Answer 4

lactobacillus bulgaricus

Question 5

describe how you would make yoghurt

Answer 5

-first, all equipment is sterilised
-milk is pasteurised and then cooled
-bacteria called lactobacillus bulgaricus is added
-the mixture is incubated and kept at 46C (optimum temp)
-lactobacillus respires anaerobically, producing lactic acid
-this lowers the pH and acts as a preservative
-the acid also coagulates the milk protein, which gives yoghurt its texture

Question 6

what are some problems with selective breeding?

Answer 6

• can lead to inbreeding- results in a reduction in the number of alleles in a population- leads to an increased chance of organisms inheriting harmful genetic defects and being vulnerable to new diseases

Question 7

selective breeding answer guideline:

Answer 7

• select the individuals with ‘desirable characteristic’ and breed them together
• choose the offspring with the ‘desired characteristic’ and breed them together
• repeat for many generations

Question 8

name 3 differences between natural selection and artificial selection:

Answer 8

1. N occurs naturally, A only occurs when humans intervene
2. N usually takes a long time to occur, A takes less time
3. N results in development of populations that are better adapted to their environment and survival, A increases vulnerability and decreases immunity