ETC and Oxidative Phosphorylation Summary

What cofactors does the TCA cycle produce from each acetyl CoA

NADH and FADH2 plus one GTP

Why must NADH and FADH2 be oxidized after being produced in the TCA cycle

To regenerate NAD+ and FAD so the TCA cycle can continue

What gaseous product contains most of the thermal energy released in the TCA cycle

CO2

What role does the ETC play in oxidative phosphorylation

It pumps H+ ions to create a proton gradient for ATP synthesis

Where are hydrogen ions pumped from and to during ETC activity

From the mitochondrial matrix to the intermembrane space

What is the high energy gradient created by proton translocation called

Chemical potential

Through which complex do H+ ions re enter the mitochondrial matrix

Complex V

How is ATP synthesized by Complex V

Mechanical deformation from H+ flow drives ADP and Pi into ATP

What is another name for ubiquinone

Coenzyme Q10

From which complexes do NADH and FADH2 donate electrons

NADH to Complex I and FADH2 to Complex II

Where do electrons go after Complex III

To cytochrome c and then to Complex IV

What accepts electrons at Complex IV

Molecular oxygen O2

What does oxygen form after accepting four electrons at Complex IV

H2O

What enzyme in the TCA cycle is regulated by ADP and ATP

Isocitrate dehydrogenase

How does increased ADP affect the TCA cycle

It activates isocitrate dehydrogenase to speed the cycle

How does increased ATP affect the TCA cycle

It inhibits isocitrate dehydrogenase to slow the cycle

What determines the release of O2 from hemoglobin in tissues

The local partial pressure of oxygen PO2

How do RBCs respond to reduced PO2 in active tissue

They release more oxygen at that location

Does the O2 dissociation curve shift in this physiologic response

No

What is uncoupling in the mitochondria

H+ pumping continues without ATP synthesis

What is a major consequence of uncoupling

Heat production and risk of hyperthermia

What are three causes of mitochondrial uncoupling

Aspirin overdose salicylism certain toxins and DNP

What is DNP and why was it banned

A fat burning uncoupler banned in 1938 for causing hyperthermia

What reactive oxygen species is formed during mitochondrial oxidation

Superoxide ion O2 minus

How is superoxide ion formed

An electron is captured by a molecule of oxygen

Why is superoxide ion harmful

It starts free radical chain reactions that damage cells

What enzyme detoxifies superoxide in the mitochondrial matrix

Manganese dependent superoxide dismutase

What enzyme detoxifies superoxide in the cytosol

Copper zinc superoxide dismutase

What two other enzymes help limit free radical damage

Catalase and glutathione peroxidase

Why is regulation of oxidative phosphorylation important

It matches ATP production with the energy needs of the cell