Lactic acid and alcohol fermentation, oxidative decarboxylation Flashcards
Pyruvate info
- Simple Alpha keto acid
- Building block for almost all cellular compounds
- Very reactive - Contains 2 reactive groups, a C=O and COOH group
- Both C=O and COOH groups can be further reduced or acted upon to form complex molecules and polymers
List the 2 ways of NAD+ regeneration in anaerobic respiration
Alcohol fermentation in bacteria, yeasts and other microorganisms
Lactic acid fermentation for humans
Why is respiration important
Respiration re-oxidizes NADH to NAD+, NAD+ generated can be used to sustain glycolysis.
When there is sufficient pyruvate produced from glycolysis, Krebs cycle can then go through
List the method where NAD+ can be regenerated in aerobic respiration
Electron transport chain
Alcoholic fermentation
Carboxylation of pyruvate into acetaldehyde via pyruvate decarboxylase, H+ is added and CO2 is removed.
O O
II II
CH3 - C - H CH3 - C - C - O-
Acetaldehyde II
O
Pyruvate
and then acetaldehyde to ethanol via alcohol dehydrogenase where NADH = H+ is used to form NAD+ that binds to the O.
H H
I I
H - C - C - OH
I I
H H
Ethanol
How is ethanol used
Ethanol formed in alcoholic fermentation is a key ingredient in brewing/wine making, which produces CO2 that accounts for most of the carbonation in beer and in champagne.
Glucose -> Ethanol and CO2, releasing 2 ATP via glycolysis.
Lactic acid fermentation chemistry
Under anaerobic conditions
A glucose is broken down into 2 pyruvate via glycolysis, releasing 2 ATP in the process, which is then used to form 2 lactate via lactate dehydrogenase.
Under aerobic conditions
2 lactate is transported into the liver via blood. 2 lactate undergo gluconeogenesis to form glucose using 6 ATP in the process. The glucose can then transported back into the cells for energy use.
Both liver and muscles use lactate dehydrogenase, the reaction is reversible
Cori cycle involving muscle and liver, lactate dehydrogenase
Lactate produced in skeletal muscles via anaerobic respiration during exercise and lactate will be transported via bloodstream to liver.
In the liver, lactate is converted into glucose.
Lactate is formed from pyruvate via lactate dehydrogenase. LDH is found in the muscles.
Conversion of lactate into glucose in muscles
2 lactate undergoes gluconeogenesis and use 6 ATP to form 1 glucose in the liver
Conversion of glucose into lactate in muscles
1 Glucose undergoes glycolysis to form 2 lactate molecules in muscle and releases 2 ATP.
Oxidative decarboxylation and pyruvate dehydrogenase complex
Under high oxygen level conditions, pyruvate is converted into acetyl CoA via pyruvate dehydrogenase, a process known as oxidative decarboxylation. This reaction is irreversible and links glycolysis with the krebs cycle.
pyruvate, the end product of aerobic respiration, is transported from the cytosol into mitochondria via a transport protein and is converted inside the mitochondria to form acetyl CoA via pyruvate decarboxylation complex
Overall formula of oxidative decarboxylation
Pyruvate + CoA + NAD+ -> Acetyl CoA + CO2 + NADH + H+ (H+ is already present inside the cells)
3 fates of pyruvate
Pyruvate can be used to form ethanol and release energy.
It can be used to form lactate.
It can be used to form acetyl-CoA that can undergo further oxidation.
Why we get fat if we eat too much carbohydrates
The conversion of carbohydrates into fats is irreversible and hence, fats will accumulate in the body. An exception to the rule is that glycerol from fatty acid can be used to form glucose.
Irreversible reaction that links glycolysis and TCA.
Chemical conversion of pyruvate into acetyl-CoA
O- I C = O i C = O I CH3 Pyruvate Pyruvate loses Co2, reduces NAD+ to NADH and add a S-CoA. Decarboxylation, oxidation and transfer of coenzyme A.
S - CoA I C = O I CH3 Acetyl CoA
