Professor Andrews - Energetics

Question 1

What three metabolic pathways do species use

Answer 1

1) Fermentation - unique to MO
2) Respiration
3) Photosynthesis - unique to plants

Question 2

Compare fermentation & respiration

Answer 2

• Fermentation results in a mixture, balance of red/ox source therefore more inefficient than respiration
• Fermentation - Most of the energy remains in the product so low ATP yield whereas in respiration more of the energy is released meaning high ATP yield
• Fermentation only organisms grow slower
• Substrate level phosphorylation happens in fermentation organisms meaning no ETC
• Wide range of organic compounds can be fermented

Question 3

What can’t be fermented?

Answer 3

Very reduced/oxidised compounds as a balance of redox is needed

Question 4

What compound is best for fermentation?

Answer 4

Carbohydrates

Question 5

Which molecule is key in fermentation?

Answer 5

Glucose - MO can filter into different pathways

Question 6

What are the 2 parts of glucose fermentation?

Answer 6

1. Glucose —> Pyruvate - get formation of ATP

2. Pyruvate —> end products

Question 7

What 3 pathways are used for converting glucose to pyruvate?

Answer 7

Pathway 1 – Glycolysis - net yields 2 ATP per mol of glucose and 2NADH, most common
Pathway 2 – Phosphoketolase pathway – yields 1 ATP
Pathway 3 – Entner-Doudouroff pathway - yields 1 ATP

Question 8

What step is common to all glucose to pyruvate pathways?

Answer 8

All begin with Glucose —> Glucose-6-phosphate which requires 1 ATP

Question 9

Describe steps of glycolysis

Answer 9

Glucose-6-phosphate —> fructose-6-phosphate
Fructose-6-phosphate —> fructose-1,6-phosphate (uses 1 ATP)
Fructose-1,6-phosphate —> glyceraldehyde-3-phosphate (dihydroxyacetone phosphate)
Glyceraldehyde-3-phosphate —> pyruvate (gaining 4 ATP, 2NADH)

Net gain - 2 ATP per mol glucose, 2NADH

Question 10

Describe steps of phosphoketolase pathway

Answer 10

Glucose-6-phosphate —> 6phospho gluconate (1 NAPD produced)
6-Phospho gluconate —> ribulose-6-phosphate (1 mol NADH produced)
Ribulose-6-phosphate —> Xylulose 5-phosphate
Xylulose 5-phosphate —> Glyceralderhyde-3-phosphate (or acetyl phosphate)
Glyceralderhyde-3-phosphate —> pyruvate (gaining 2 ATP, 1 mol NADH)

Net gain - 1 ATP, 2NADH

Question 11

Describe the steps of Entner-Dondouroff pathway

Answer 11

Glucose-6-phosphate —> 2keto, 3deoxy 6 phospho gluconate (1 NADP produced, water lost)
2Keto, 3deoxy 6 phospho gluconate —> Glyceraldehyde 3 phosphate (or pyruvate)
Glyceraldehyde 3 phosphate —> Pyruvate (2 ATP produced, 1 mol NADH)

Net gain - 1ATP, 2 NADH

Question 12

Why is NADH required?

Answer 12

It is converted back to NAD+ in Stage 2 using pyruvate

Question 13

What fermentation reaction is unique to microbial bacteria?

Answer 13

Terminal Reaction of Glucose Fermentation - Bacteria use pyruvate to regenerate NAD+ (so that the initial reactions can occur). After bacteria ferment Pyruvate —> ethanol there are nine separate possible pathways.

Question 14

Describe pathway 1 - pyruvate to ethanol

Answer 14

Alcoholic fermentation

Occurs with one of the other pathways - EXCEPTION is yeast

Basis of brewery/distilling industrial process - multi-billion pound business

Question 15

Describe pathway 2 - Pyruvate to lactic acid

Answer 15

Lactic acid fermentation

Industrial use in food production - cheese, pickling, yoghurt

Question 16

Describe pathway 3 - Pyruvate to lactic acid + alcohol

Answer 16

Acetyl Phosphate

Industrial use in food production - different taste/feel of a product

Question 17

Describe pathway 4 - Pyruvate to propionic acid formation

Answer 17

Huge amounts of CO2 produced

Industrial use in food production - Swiss cheese (CO2 causes the holes), emmental cheese ‘sweaty sock’ taste

Question 18

Describe pathway 5/5a - Pyruvate to formic acid (HCOOH) to H2+CO2

Answer 18

5A uses enzyme to split HCOOH into H2 & CO2

Bacteria carry this out in a combination - 4 with 5/6 with 5

Question 19

Describe pathway 6 - Pyruvate to succinic acid

Answer 19

Mixed acid ferentation

pH indicates amount and can be used to ID the acid

Question 20

Describe pathway 7 - Pyruvate to 2,3-butenediol

Answer 20

2,3-butenediol fermentation

Neutral compound so less acidic

Identify with methyl red test

Question 21

Describe products of pathway 8/9 - acetone isoproponone, butone fermentation

Answer 21

Major organic solvents before distillation of oil which was more economical