Use of biological resources

Question 1

Anaerobic respiration in yeast equation

Answer 1

Glucose –> carbon dioxide + ethanol

Question 2

How does yeast make bread rise?

Answer 2

Bubbles of carbon dioxide gas (produced by anaerobic respiration of yeast) expand the dough and make it rise

Question 3

Why is ethanol not present in bread?

Answer 3

High temperatures used in bread making mean that the ethanol doesn’t remain in the bread after cooking has finished (it evaporates)

Question 4

How do you measure anaerobic respiration by yeast in different conditions?

Answer 4

Study the production of carbon dioxide

Question 5

How do you test for the presence of carbon dioxide? (2 ways)

Answer 5

Limewater
Hydrogencarbonate indicator

Question 6

Colour of hydrogencarbonate indicator in high CO2 concentration

Answer 6

Yellow

Question 7

Colour of hydrogencarbonate indicator in normal CO2 concentration?

Answer 7

Red

Question 8

Colour of hydrogencarbonate indicator in normal atmospheric CO2 conentration?

Answer 8

Red

Question 9

Describe the steps to investigating the role of anaerobic respiration in yeast in different conditions?

Answer 9

1. Dissolve sugar in previously boiled water.
2. Add yeast and mix to form a suspension.
3. Add a layer of vegetable oil.
4. Connect a delivery tube to a second boiling tube that contains limewater or hydrogencarbonate indicator (to test for CO2)

Question 10

What bacterium is used to make yoghurt?

Answer 10

Lactobacillus bulgaricus

Question 11

What conditions can be used to investigate anaerobic respiration in yeast?

Answer 11

Amount of sugar used
Temperature
Type of sugar

Question 12

Steps of making yoghurt using bacteria

Answer 12

Milk is pasteurised
Lactobacillus bulgaricus is added
Mixture is kept at 46oC
Lactobacillus respires anaerobically producing lactic acid. This lowers the pH and and coagulates the milk protein.
Yoghurt is further cooled to 5oC to help preserve it

Question 13

Why is the milk pasteurised when making yoghurt?

Answer 13

To kill bacteria

Question 13

Why is the mixture kept at 46oC when making yoghurt?

Answer 13

It is the optimum temperature for the bacteria enzymes and ensures they aren’t denatured.

Question 13

How does a lower pH of yoghurt help when lactic acid is formed?

Answer 13

Acts as a preservative.

Question 14

Air filter in fermenter

Answer 14

Filters air coming in, maintaining sterile conditions

Question 14

Stirrers in fermenter

Answer 14

Keeps the broth well-stirred to oxygenate all parts of the fermenter and prevent micro-organisms from settling

Question 14

Cooling jacket in fermenter

Answer 14

Removes heat energy, prevents the fermenter from overheating and the enzymes from denaturing

Question 15

Growth medium in fermenter

Answer 15

Contains all necessary glucose and amino acids for micro-organism growth

Question 16

Super-heated steam

Answer 16

Applied before the fermenter is used, killing unwanted micro-organisms. Leaves only water with no other residues.