To Prepare And Show The Production Of Alcohol By Yeast Flashcards Preview

*Biology: Experiments > To Prepare And Show The Production Of Alcohol By Yeast > Flashcards

Flashcards in To Prepare And Show The Production Of Alcohol By Yeast Deck (23)
Loading flashcards...
1
Q

Why must this investigation be carried out under anaerobic conditions?
(2)

A

Alcohol is only produced under anaerobic conditions

If aerobic conditions no alcohol will be produced

2
Q

How did you ensure conditions were anaerobic?

A

Layer of paraffin oil on top of boiled glucose solution and yeast

3
Q

Suggest a suitable control for this experiment.

A

Add no yeast

4
Q

How did you know fermentation was taking place?

A

Bubbles of carbon dioxide will be seen in the limewater

5
Q

Why might limewater be used in this experiment?

A

Limewater turns milky in the presence of carbon dioxide

6
Q

Name the molecule from which lactic acid is produced by glycolysis.

A

Pyruvate (pyruvic acid)

7
Q

In what part of the cell does the Krebs Cycle occur?

A

Mitochondrion

8
Q

Suggest how you would know the glucose is used up.

A

No more bubbles are produced

9
Q

Explain why boiled yeast is suitable as a control for this experiment?

A

Heat denatures enzymes

10
Q

Give an alternative control other than boiled or no yeast.

A

Distilled/deionized water

11
Q

What affect does the absence of limewater have on the experiment?

A

No affect on experiment

12
Q

Explain why the absence of limewater doesn’t affect the experiment?

A

Limewater is only present to test for carbon dioxide

13
Q

State one factor apart from temperature that must be kept constant when repeating the experiment, what needs to be the exact same when repeating the experiment.
(2)

A

Same concentration of glucose

Same concentration of yeast

14
Q

Name one industry that depends on fermentation.

A

Brewing/baking

15
Q

Name one end product of the brewing industry.

A

Alcohol

16
Q

Name one substance that yeast can use to make ethanol.

A

Sugar

17
Q

What substance, other than ethanol, is produced by the fermentation by yeast.

A

Carbon dioxide

18
Q

Suggest a suitable temperature for this experiment.

A

30 degrees Celsius

19
Q

Why does the production of ethanol eventually stop?

3

A

Sugar is used up

Alcohol kills yeasts

Yeast dies

20
Q

Name the reagent(s) used to demonstrate that alcohol (ethanol) has been produced and the colour change associated with a positive test,
(2)

A

Acidified potassium dichromate - orange to green

Iodoform test -Potassium iodide solution - colourless - then sodium hypochlorite solution - brown -orange then colourless - heat at 50-60 degrees then yellow crystals form

21
Q

Describe the iodoform test.

7

A

Filter the solution

Place some of filtrate into a test tube

Add an equal volume of potassium iodide solution - colourless

Add sodium hypochlorite solution - brown-orange colour then becomes colourless

Place test tube in a water bath at 50-60 degrees for 4 to 5 minutes

Remove test tube and allow to cool

Pale yellow crystals form of a chemical called iodoform which indicates ethanol is present

22
Q

Describe the discontinued test for alcohol.

3

A

Acidified potassium dichromate is added to the filtered solution

The test tube is placed in a warm water bath

If alcohol is present the colour changes from orange to green

23
Q

What substrate did you use?

A

Sugar/glucose