chapter 14 - fermentation

Question 1

Fermentation

Answer 1

energy conservation depends on substrate level phosphorylation

Question 2

What are the two major challenges of fermentation?

Answer 2

1. conserves much less energy than respiratory organisms
2. difficult to achieve redox balance.

Question 3

Energy rich compounds

Answer 3

contains energy rich phosphate bonds or CoA

Question 4

What do energy rich compounds allow

Answer 4

1. making of ATP by transferring phosphate bond to ADP by substrate level phosphorylation
2. can produce fatty acids

Question 5

Redox Balance

Answer 5

balancing number of atoms (reactants and products)

Question 6

How do protons get reduced to H2 during fermentation

Answer 6

1. hydrogenlyase
2. hydrogenase
3. electron configuration

Question 7

Alcoholic fermentation

Answer 7

hexose = ethanol + CO2

Question 8

Homolactic fermentation

Answer 8

hexose = lactate + 2H

Question 9

Heterolactic fermentation

Answer 9

hexose = lactate + ethanol + H + CO2

Question 10

Mechanism of homofermmentative lactic acid bacteria

Answer 10

Glucose = 2 lactate + 2H+
- delta G: -196kJ
- yields: 2 ATP

Question 11

Mechanism of heterofermmentative lactic acid bacteria

Answer 11

Glucose = 2 lactate + ethanol + CO2 + H+
- delta G: -216 kJ
- yields: 1 ATP

Question 12

Mechanism of mixed acid fermentation

Answer 12

2 pyruvate + NADH = 2 CO2 + butanediol

Question 13

Mechanism of sugar fermentation by Clostridium

Answer 13

1.5 Glucose + H2O = acetate + butyrate + 3 CO2 + 4H2 + H+
- delta G: -250 kJ
- yields: 3/4 ATP/glucose

Question 14

Obligate anaerobes

Answer 14

cant tolerate 02, produce H2 from fermentation

Question 15

Clostridium

Answer 15

• ferment sugars and amino acids
• ATP synthesis through substrate level phosphorylation
• generates proton motive force

Question 16

Mechanism of Stickland Reaction

Answer 16

Alanine + 2 glycine + 2H2O = 3 acetate + CO2 + 3 NH4+
- delta G: -186kJ
- yields: 3 ATP

Question 17

Mechanism of energy converting Hydrogenase

Answer 17

Glucose + 2 H2O = 2 acetate + 2CO2 + 4H2 + 2H+
- delta G: -216 kJ
- yields: 4 ATP

Question 18

Secondary Fermentations

Answer 18

Uses primary fermentations as substrates

Question 19

Propionibacterium

Answer 19

Can’t produce lactic acid by itself, uses it from fermentation product of lactic acid bacteria

Question 20

Mechanism of Succinate Fermentation

Answer 20

1. succinate is convertd to propinate through decarboxylation of intermediate
2. this releases energy by decarboxylation reaction, used to move 2 Na+ across membrane
3. Energy is then conserved by using a Na+ - linked ATPase

Question 20

Syntropy

Answer 20

2 different microbes cooperate to perform metabolic reaction (most secondary fermentations)

Question 20

What are the two types of electron transfer?

Answer 20

1. Direct: two microbes connect
2. Mediated: through diffusion (H2)

Question 20

Interspecies electron transfer

Answer 20

how microbes undergo syntropy. 1 species usually electron donor, the other, electron acceptor

Question 21

Example of interspecies H2 transfer?

Answer 21

Ethanol fermentation carried out by syntroph has positive free energy so it cant grow in pure culutres

• H2 produced used as electron donor by methanogen to produce methane, the sum of both reactions is exergonic, when cultured both grow.

Question 22

Oxygenase

Answer 22

catalyzes incorporation of O2 in organic compounds

Question 23

Dioxygenase

Answer 23

incorporation of both oxygen atoms

Question 24

Monooxygenase

Answer 24

Incorporation of 1 oxygen atom, the other as H2O

Question 25

Mechanism of Hydrocarbon metabolism

Answer 25

1- hydrocarbon as n-octane
gets oxygenated
2- alcohol as n-octanol
gets dehydrogenated
3- aldehyde as n-octanal
gets dehydrogenated
4- acid as n-octanoic acid

Question 26

Importance of aromatic catabolisms?

Answer 26

Everything gets turned to a catechol before being reduced to enter citric acid cycle