Cell Biology: Lecture 8; Pyruvate Oxidation and the Krebs Cycle

What does respiration consists of

pyruvate oxidation, krebs cycle, oxidative phosphorolation

Pyruvate oxidation (per glucose)

2NADH + 2CO2 + 2 acetyl CoA

Krebs Cycle

6NADH + 2FADH2 + 2GTP + 4CO2

What takes place in cytoplasm for prokaryotes

glycolysis, fermentation, krebb cycle 

What takes place in plasma membrane

pyruvate oxidation

What takes place external to mitochondria in eukaryotes

glycolysis and fermentation 

What takes place inside mitochondria for eukaryotes

Inner membrane, pyruvate oxidation, respitory chain matrix, krebb cycle 

Purpose of pyruvate oxidation

1) Transports pyruvate to mitochondria, 2) preparing pyruvate to enter the krebb cycle 

Summary of Pyruvate oxidation

pyruvate + NAD+ + CoA → Acetayl CoA + NADH + CO2

Enzyme for pyruvate oxidation

Pyruvate dehydroganase complex, creating acetyl CoA while bringing cell to mitochondria 

Regulation of enzyme of pyruvate oxidation

inhibited by high levels of ATP and high levels of NADH 

Krebb Cycle Net input/output

1 acetyl CoA + 3NAD+ + FAD + GDP + 1Pi → 2CO2 + 3NADH + FADH2 + GTP

Enzyme in step 3 krebb cycle

Isocitrate Dehydrogenase

What is IDH activated by

ADP and NAD+

What is IDH inhibited by 

ATP and NADH 

What is the change in free energy of the Kreb Cycle

Overall it is an exergonic reaction 

What are big drops in energy associated with 

oxidation reaction, oxidation releases a lot energy 

Pyruvate oxidation and Kreb Cycle summary combined

Output: 4NADH + FADH2 + 1ATP + 3CO2

Pyruvate oxidation and Kreb Cycle summary Regulation

Pyruvate dehydrogenase complex; inhibited y ATP NADH and Acetyl CoA

Isocitrate Dehydrogenase; inhibted by ATP and NADH 

What is the multifunctionality of the Kreb Cycle

Products of the kreb cycle can be used as building blocks for fatty acids or amino acids

Why oxygen required for Kreb cycle

it oxidizes teh electron carrier 

What is the primary mechanism for oxidizing NADH to NAD+

oxygen 

What does Oxidative Phosphoralation

Utilize the electronegativity of oxygen (Sulfur/nitrate) to oxidized NADH and FADH2 produces so far 

Sum total of oxidative phosphoralation

10NADH + 2FADH2 + 6O2 + 34ATP + 34Pi → 10NAD+ + 2FAD + 6H2O + 34ATP

Mitochondria in Oxidation Phosphorlyation

1) Distinct environments that are isolated from eachtoher, folding of innermembrane increases the surface area which means more ATP synthase

Oxidative Phosphorylation Parts

1) Oxidation = electron transport, 2) Phosphorylation: ATP production

Free Energy of Oxidation

electrion transport chain, each component is more EN than the last, electron transport is exergonic 

Complex 1

NADH=Q=Reductase (26 protein subunits andmembrane bound/spanning) 

Q; ubiquinone

Mobile electron carrier

Complex 2

Succinate Q reductase 

Complex 3

Cytochrome C reductase

Cytochrome C

mobile E carrier

Complex 4

Cytochrome C oxidase

Least EN to most EN in electron transport chain 

NADH, NADH Q reductase, ubiquinone, cytochrome creductase, Cytochrome C, Cytochrome C oxidase, O2

Chemiosmotic Hypothesis 

1) energy from oxidation is coupled to pumping/active transport of protons into the inner membrane space 

2) diffusion of protons back into the matrix provides sufficent energy to produce ATP 

What is the proton motive force

Intermembrane space have high H+ concentration matrix side has low H+ concentration 

What does electrical and concetration gradient favor

diffusion back to the mitochondria matrix

What is movement of protons coupled with

endergonic production of ATP

What does experiment one look at

can a proton gradient on its own drive ATP synthase by isolated mitochondria

Conclusion for experiment 1

In the absence of electron transport In the absence of electron transport artifical H+ graident is sufficent for ATP synthesis by mitochondria 

What does experiment 2 test

What is the role of ATP synthase in ATP synthesis

Conclusion of Experiment #2

ATP synthase acting as an H+ Channel is necessary for ATP synthase 

How efficent is the process with oxygen

40%

Where does the other 60% go

energy from glucose being lost in form of heat