5.1.3 Yeast in Food Production

Question 1

Microorganisms can be used by humans to produce, what?

Answer 1

foods and other useful substances

Question 2

Microorganisms can be used by humans to produce foods and other useful substances, give one example:

Answer 2

One example of this is the production of bread using yeast

Question 3

What is yeast

Answer 3

Yeast is a single-celled fungus that can carry out both aerobic and anaerobic respiration

Question 4

Name the 6 cells within a Yeast Cell

Answer 4

Ribosomes
Nucleus
Cell Membrane
Cell Wall (Chitin)
Mitochondrion
Cytoplasm

Question 5

When yeast carries out anaerobic respiration, what does it produce?

Answer 5

it produces an alcohol (ethanol) and carbon dioxide

Question 6

Yeast will respire anaerobically if it has access to, what?

Answer 6

plenty of sugar, even if oxygen is available

Question 7

The yeast produces enzymes that break down, what?

Answer 7

starch in the flour, releasing sugars that can then be used by the yeast for anaerobic respiration

Question 8

The carbon dioxide produced by the yeast during anaerobic respiration is, what?

Answer 8

trapped in small air-pockets in the dough, causing the dough to rise (increase in volume)

• The dough is then baked in a hot oven to form bread

Question 9

During baking, what happens to any of ethanol

Answer 9

any ethanol produced by the yeast (as a waste product of anaerobic respiration) is evaporated in the heat

• This is why bread doesn’t contain any alcohol

Question 10

How is the yeast killed during baking

Answer 10

The yeast is killed by the high temperatures used during baking

• This ensures there is no further respiration by the yeast

Question 11

What is the Word Equation for anaerobic respiration in yeast?

Answer 11

Glucose -> Ethanol + Carbon Dioxide

Question 12

What is the chemical equation for Anaerobic Respiration in Yeast

Answer 12

C6H12O6 -> 2C2H5OH + 2CO2