Flashcards in Session 5 (2) - Byproducts of metabolism Deck (22):
How are ROS's formed?
Some electrons leaked from electron transport chain (1+3), prematurely reducing oxygen to super oxide radicals (O(x2)-. Oxygen molecule with unpaired electron.
What do ROS cause damage to?
DNA, protein and membranes
What enzyme catalyses formation of hydrogen peroxide and oxygen from ROS?
Superoxide Dismutase (SOD)
What is the issue with hydrogen peroxide production?
It is in itself a Reactive Oxygen Species
What enzyme is used to remove H2O2
Enzyme catalase therefore rapidly breaks it down into molecular oxygen and water.
What do you add to H2O2 to form hydroxyl radicals? Give equation.
H2O2 + Fe2+ --> OH- (hydroxyl radicals)
What is the issue with hydroxl radicals?
Highly reactive, damage cell membranes but cannot be elimated by enzymatic reaction.
How are hydroxyl radicals removed?
NADPH provides H+ and converts to water.
How are ROS useful in the body? What enzyme is used in reaction? What happens to cell and surrounding bacterial cells? What system is this used in?
Neutrophils and monocytes can rapidly produce a release of ROS, known as an oxidative burst. NADPH Oxidase is used.
Electrons from NAPH transfer across membrane.
Cell and surround bacterial cells destroyed.
How can oxidizing agents be produced in the body via artificial means?
Primaquine (anti-malarial) and Paraquat (banned herbicide)
What is produced from Arginine in the body? What enzyme is used, and what is it involved in?
NO, produced from arginine via Nitric Oxide synthase.
NO combines with O2 to produce peroxynitrite, which is involved cell damage.
Name five cell defences against ROS other than SOD and catalase
NADPH, glutathione, anti-oxidant vitamins, flavenoids and minerals
What is NADPH, and where is it produced?
reducing agent that is mostly produced by the pentose phosphate pathway.
What is glutathione?
a tripeptide that is usually abundant in cells and acts as an important antioxidant. The thiol (-SH) group in cysteine can donate its H and therefore act as a reducing agent.
How is oxidised glutathione converted bact to reduced form?
What enzmes catalyse the reactions?
glutathione peroxidise and glutathione reductase
Name three anti-oxidant vitamins
Vitamin C, Vitamin E, Vitamin A
How is diabetes mellitus related to ROS?
(Type 1) B cell destruction by ROS
How is alzheimers disease caused by ROS
Protein damage and misfolding by ROS
How are the negative effects of cardiovascular disease compounded by ROS?
Reperfusion causes huge amounts of ROS to be produced. ROS switched on by cells when dying, encouraged by reoxygenation.
Outline cellular defences against following
What is oxidative stress?
When ROS levels are excessive, or not enough anti-oxidants.