Reactive oxygen species

Question 1

How do Mitochondria produce Superoxides?

Answer 1

These electrons prematurely reduce oxygen to form superoxide radicals via Oxidative phosphorylation

Question 2

What does Superoxide Dismutase (SOD) do?

Answer 2

Catalyses superoxide radicals reacting - form oxygen and hydrogen peroxide. However, hydrogen peroxide is a ROS.
Catalase rapidly breaks it down into molecular oxygen and water.

Question 3

Which ROS cannot be removed by an enzymatic reaction?

Answer 3

Hydroxyl Radicals produced from Hydrogen Peroxide with the addition of iron ions
Damage cells, particularly membranes

Question 4

How do cells of the immune system release ROS?

Answer 4

Oxidative burst using the enzyme NADPH oxidase

Question 5

What are the cellular defences against ROS?

Answer 5

NADPH is a reducing agent.
Glutathione (GSH) is a tripeptide that acts as an important antioxidant
Oxidised form of GSH is glutathione disulphide (GSSG), and it is recycled via reduction by NADPH to deal with more ROS.
Catalysed by glutathione peroxidise and glutathione reductase.