Redox

Question 1

What indices are used to measure energy state?

Answer 1

PCr / ATP

PCr / Cr

Pi / ATP

PP = ATP / ADP + Pi

Question 2

What is the overall equation for energy production in the cell?

Answer 2

NADH + H+ + 3ADP + 3Pi + 1/2 O2 –> NAD+ + 3ATP + H2O

Question 3

What is the order with which metabolic fuels generate energy?

Answer 3

ANAEROBIC RESPIRATION (glycolysis / B-oxidation) –> Acetyl CoA

DEHYDRIGENATION of substrates –> H+ & e- transferred to NAD & FAD, C converted to CO2

OXIDATION of NADH & FADH2 in ETC –> release of H & E to reduce O2 to H2O & produce ATP.

Question 4

What is Nrf2 and how does its concentration increase during oxidant stress?

Answer 4

Cap ‘n’ Collar TF (acts on ARE in upstream promoters)

Dephosphorylation of Nrf2
Unblock of interaction with ARE
Prevention of degradation in cytoplasm.

Question 5

What damage do hydroxyl radicals do?

Answer 5

lipid peroxidation of fatty acids in membrane - chain reaction

nucleic acid damage - dsDNA breaks can be fatal or changes in DNA base structure

Question 6

How are peroxynitrites formed and what ar their effects?

Answer 6

By a superoxide radical combining with NO.

Lipid peroxidation

Changes nitrosylation (particularly damaging for membrane lipids).

Question 7

How does the ETC generate ROS’?

Answer 7

1-2% of electrons never complete ETC

leak from Fe-S centres

1 electron reduction of oxygen to form superoxide.

Question 8

What are the main roles of redox reactions within cells?

Answer 8

• Transfer of electrons via oxidoreductase enzymes
• Signalling
• Damage.

Question 9

What is notable about redox states in the cell?

Answer 9

Different cellular compartments have different redox states - implies electron flow between couples and compartments is regulated.
(cytoplasm is most reducing environment, extracellular is least, then ER)

Question 10

What are the effects of ROS’?

Answer 10

STRESS
protein damage, DNA damage, Gene transcription, lipid peroxidation.
SIGNALLING
growth, ion channel, gene transcription, contractile function, O2 sensing and transduction.

Question 11

What is oxidative stress?

Answer 11

Loss of overall negative redox state, disrupting cell functions.