Oxidative Stress Flashcards Preview

Phase 1 - S2 Metabolism, Endocrinology, Haematology > Oxidative Stress > Flashcards

Flashcards in Oxidative Stress Deck (58)
Loading flashcards...
1

What diseases can be caused by oxidative stress

Cardiovascular disease, COPD, Cancer, Pancreatitis, MS

2

What are free radicals

An atom or molecule that contains one or more unpaired electrons
They are very reactive and take electrons from other atoms, molecules and ions

3

How does a superoxide form

Addition of an electron to oxygen

4

How is hydrogen peroxide formed

The addition of 2 hydrogen ions and an electron to a superoxide

5

How does a hydroxyl radical form

The addition of an electron and hydrogen to hydrogen peroxide

6

What are the 3 reactive oxygen species

Superoxide
Hydrogen peroxide
Hydroxyl radical

7

What are the 2 nitrogen reactive species

Nitric oxide
Peroxynitrate

8

How is peroxyntirite formed

Reaction of a superoxide and nitric oxide

9

which is the most damaging free radical

hydroxyl radical

10

how do reactive oxygen species damage DNA

- react with the bases leading to mispairing and mutation
- react with the sugar causing strand breakages and mutation

11

the amount of what molecule can be used to measure oxidative damage

8-oxo-dG

12

how do reactive oxygen species damage proteins

- by taking an electron from the backbone leading to fragmentation and degradation
- or the sidechain changing the protein structure which can either cause degradation, loss or gain in function

13

how can disulphide bridges form due to ROS

if ROS take electrons from cysteine residues

14

why can disulphide bonds disrupt function of a protein

as they cause misfolding and crosslinking

15

how to ROS damage lipids

- extract a hydrogen atom from a polyunsaturated fatty acid on the membrane
- the lipid radical then reacts with oxygen to form lipid peroxyl radical
- these cause lipid peroxidation

16

what is lipid peroxidation

a chain reaction of lipid peroxyl radicals stealing electrons off nearby fatty acids

17

why does is the damage to lipids de to ROS dangerous

the lipid bilayer is disrupted and so membrane integrity fails

18

give examples of exogenous sources of oxidants

radiation
pollutants
drugs
toxins

19

true or false: anti malarial drugs are a source of exogenous oxidants

true

20

give examples of endogenous oxidants

electron transport chain
nitric oxide synthases
NADPH oxidases

21

how does the electron transport chain cause the production of oxidants

an electron may escape from the chain and react with dissolved oxygen to form a superoxide

22

what are the 3 types of nitric oxide synthase

iNOS - inducible nitric oxide synthase
eNOS - endothelial nitric oxide synthase
nNOS - neuronal nitric oxide synthase

23

what does nitric oxide synthase do

produces nitric oxide from arginine

24

does nitric oxide synthase require NADPH?

yes and oxygen

25

what does nitric oxide do

it is a signalling molecule which causes vasodilation, neurotransmission and is used in phagocytosis

26

what is respiratory burst

rapid release of superoxide and hydrogen peroxide from phagocytes and peroxynitritie to destroy bacteria

27

outline respiratory burst

- phagocyte produces superoxide from oxygen taking and electron from NADPH using NADPH oxidase
- iNOS produces nitric oxide
- nitric oxide combines with the superoxide to form peroxynitrite
- superoxide also form hydrogen peroxide
- hydrogen peroxide is converted into hypochlorite by myeloperoxidase
- hypochlorite and peroxynitrate are used to kill bacteria

28

what do genetic defects in NADPH oxidase cause

increased susceptibility to bacterial infections

29

what does NADPH oxidase do

causes the production of superoxide from oxygen by adding an electron from NADPH

30

what 2 enzymes defend against ROS

superoxide dismutase and catalase