Topic 18 Biological resources continued

Question 1

what is yoghurt?

Answer 1

milk fermented by lactic acid bacteria - lactobacillus bulgaricus -> ferment lactose (sugar present in milk) into lactic acid

Question 2

what does the lactic acid do?

Answer 2

• acidic -> decreases ph + denatures milk proteins so that it coagulates into thick texture
• sours milk for yoghurt taste

Question 3

how is yoghurt made?

Answer 3

1. equipment = heat sterilised to kill bacteria by denaturing enzymes
2. milk pasterised (heated) to kill unwanted bacteria -> contamination could slow production of yoghurt by competing w lactobacillus for lactose in milk
3. milk cooled to 40-45c, and lactobacillus added
4. mixture incubated at temp while bacteria ferment lactose into lactic acid, lowering ph (prevents growth of microorganisms so can be kept for longer)
5. yoghurt stirred and cooled

Question 4

what is yeast?

Answer 4

fungus that can carry out both aerobic and anaerobic respiration
- yeast cells contain enzymes that convert sugars -> ethanol + carbon diocide during anaerobic respiration (fermentation)
- glucose -> ethanol + carbon dioxide

Question 5

How is fermentation used in process of beer making?

Answer 5

• barley grains containing starch are warmed with water to germinate, produce amylase which breaks down starch into maltose
• barley is boiled with water to release sugar
• hops added for flavour
• yeast is added and enzymes convert sugar to alcohol

Question 6

how is yeast used in bread making?

Answer 6

• yeast breakdown glucose in mix to carbon dioxide + ethanol
• co2 creates air bubbles, causing bread to rise
• ethanol evaporated off and yeast killed during baking

Question 7

investigate role of anaerobic respiration by yeast in different conditions cormmmss

Answer 7

c : change temp of water bath
o: keep species of yeast same
R : repeat at each temp
M : measure height of dough in mm before and after 40 mins
S : same type of flour
S : source culture of yeast with same concentration of glucose added

Question 8

investigate role of anaerobic respiration by yeast in different conditions cormmmss

Answer 8

c : change temp of water bath
o: keep species of yeast same
R : repeat at each temp
M : measure height of dough in mm before and after 40 mins
S : same type of flour
S : source culture of yeast with same concentration of glucose added

Question 9

why are fish kept in large cages?

Answer 9

to stop energy being lost due to movement + respiration

Question 10

why are nets used between different speices?

Answer 10

to prevent interspecific predation

Question 11

why are nets used to separate fish by size and age/

Answer 11

to prevent intraspecific predation

Question 12

how can farmers combat the fact that disease spreads easily amongst many fish?

Answer 12

• pesticides or biological control eg wrasse which eat sea lice
• dead fish removed quickly
• antibiotics added

Question 13

what can farmers do to fish diet?

Answer 13

• feed regularly to grow fast as possible
• diet high in protein to get max growht
• contain antibiotics

Question 14

how can farmers combat pollution?

Answer 14

• water filtered to remove faeces which can cause eutrophication due to build up of nitrates
• ph temp and oxygen levels adjusted to maintain optimum conditions

Question 15

how can farmers use selective breeding to increase production?

Answer 15

• large healthy fish that require less food to grow are bred
• ideal fish maximises profit