Unit 2 - Alternative Pathways

Question 1

Anaerobic pathway:

Answer 1

-When O2 is lacking, cells rely on glycolysis for energy

Question 2

Anaerobic Pathway: PROBLEM

Answer 2

The cell will run out of NAD+

Question 3

Anaerobic Pathway: THEREFORE

Answer 3

NADH needs a way to be recycled

Question 4

Anaerobic Pathway: FERMENTATION

Answer 4

process where H atoms from NADH r transferred to organic compounds other than an electron transport chain (Oxidizes NADH back to NAD+)

Question 5

two types of fermentation

Answer 5

1) ethanol fermentation
2) lactate fermentation

Question 6

Lactic Acid Fermentation

Answer 6

oxygen is not present
- conversion of 2 mols of pyruvate into lactic acid when O2 is not present
- happens during vigorous muscle exercise
- liver converts lactic acid back into glucose

Question 7

Lactic Acid Fermentation: Occurs in HUMANS when…

Answer 7

demand for ATP exceeds the rate at which oxygen can be supplied

Question 8

Lactic Acid Fermentation:
Process

Answer 8

• pyruvate is converted into lactate
• NAD+ reduced to NADH
• lactate regenerates NAD+ (Oxidizes)
• glycolysis continues

Question 9

Lactic Acid Fermentation: Final rxn

Answer 9

pyruvate + NADH + H = NAD + lactate

Question 10

Glycolysis includes

Answer 10

2 pyruvate mols
- glucose + 2ADP +2pi =2 lactate + 2 ATP
- fermentation only produces 2 ATP

a) lactic acid fermentation occurs in humans

Question 11

Applications of Lactic Acid

Answer 11

• occurs during strenuous exercises when respiration occurs faster than oxygen can be supplied
• burning sensation felt in muscles
• transported through blood from muscles to liver
• O2 levels resume, lactate is oxidized back to pyruvate

Question 12

Oxygen debt

Answer 12

amount of oxygen needed to remove all lactate

Question 13

Alcohol Fermentation

Answer 13

• not in humans
• occurs in bacteria and yeast when oxygen is not available
• conversion of 2 mols of pyruvate into 2 ethanol

Question 14

Facultative anaerobes

Answer 14

can function both aerobically and anaerobically (ie. yeast and some bacteria)

Question 15

Alcohol Fermentation Process (4)

Answer 15

• pyruvate is decarboxylated
• produces acetaldehyde
• acetaldehyde oxidizes NADH to NAD+
• ethanol is produced

Question 16

Alcohol Fermentation Products

Answer 16

• CO2
• Ethanol
• NAD+

Question 17

Alcohol Fermentation final rxn

Answer 17

pyruvate + NADH + H = NAD + CO2 + ethanol

Question 18

alcohol fermentation glycolysis include

Answer 18

glucose + 2 ADP + 2Pi = 2CO2 + 2 ethanol

fermentation produces only 2 ATP

Question 19

Ethanol fermentation application (3)

Answer 19

1) bread
2) alcoholic beverages
3) gasoline

Question 20

BREAD

Answer 20

• leavened by mixing live yeast cells w starches (flour) and water
• yeast cells ferment the glucose from starch and release CO2 and ethanol
• ethanol evaporates during baking

Question 21

ALCOHOLIC BEVERAGES

Answer 21

-yeast cells ferment sugars from fruit juices (WINE)
-yeast cells die when ethanol concentrations reaches 12%

Question 22

GASOLINE

Answer 22

-fermentation of carbohydrate products for the production of ethanol that is added to gasoline

Question 23

Obligate Anaerobes

Answer 23

• cannot survive in the presence of oxygen
• no mitochondria
• contain ETC
• many prokaryotes and protists

Question 24

Obligate Anaerobes: ETC

Answer 24

take place on specialized membranes use another inorganic compound as a final electron acceptor instead of oxygen.
ie. NO3, FE3, SO42-

Question 25

where do we find these organisms?

Answer 25

• soils deep underground and in the sediments of marshes, wetlands, and lake
• rotten egg smell in some wetlands r produced by anaerobic sulphur-reducing bacteria and use SO42- as the terminal electron acceptor