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Metabolism > Oxidative Stress > Flashcards

Oxidative Stress Flashcards

1
Q

What is oxidative stress?

A

Imbalance of free radicals causing damage to the body

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2
Q

What are free radicals?

A

Atoms or molecules that contain one or more unpaired electron

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3
Q

What are RNS?

A

Reactive nitrogen species

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4
Q

What are the RNS?

A

Nitric oxide - NO●

Peroxynitrite - ONOO-

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5
Q

What are ROS?

A

Reactive oxygen species

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6
Q

What are the ROS?

A

Superoxide - O2●-

Hydrogen peroxide - H2O2

Hydroxyl radical - OH●

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7
Q

What is the most damaging free radical?

A

OH●

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8
Q

How to ROS cause damage to DNA?

A

ROS reacts with base
- modified base = mispairing

ROS reacts with sugar
- strand break

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9
Q

How does ROS cause damage to proteins?

A

Fragmentation of backbone

Modify amino acids = change in protein structure
- effect disulphide bonds

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10
Q

What are disulphide bonds?

A

Bones between thiol groups on cysteine

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11
Q

What is the role of disulphide bonds?

A

Important in folding and stability of some proteins

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12
Q

How does ROS cause damage to lipids?

A

Free radical extracts hydrogen atom from lipid membrane

Lipid radical formed - can react with oxygen to form peroxyl radical

Chan reaction as peroxyl radical extracts hydrogen from nearby fatty acid

Membrane integrity fails

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13
Q

What are endogenous causes of oxidants?

A

Electron transport chain
Nitic oxide synthases
NADPH oxidases

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14
Q

What are exogenous causes of oxidants?

A

Radiation
Drugs
Toxins

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15
Q

How does the electron transport chain form ROS?

A

Electrons can escape chain and react with oxygen to form superoxide

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16
Q

How do nitric oxide synthases form oxidants?

A

Converts arginine to citrulline producing nitric oxide (NO●)

17
Q

What is nitric oxide used for?

A

Signalling molecule

  • vasodilation
  • neurotransmission
18
Q

What are the types of nitric oxide synthase?

A

iNOS - inducible nitric oxide synthase
- produces NO for phagocytes

eNOS - endothelial nitric oxide synthase
- signalling

nNOS - neuronal nitric oxide synthase
- signalling

19
Q

What is a respiratory burst?

A

Rapid release of superoxide and H2O2 to destroy bacteria - part of defence system

20
Q

What are cellular defences against oxidants?

A

Superoxide dismutase (SOD)

Catalase

Glutathione

Free radical scavengers

21
Q

How is SOD a defence?

A

Converts superoxide to H2O2 and oxygen

22
Q

How is catalase a defence?

A

Converts H2O2 to water and oxygen

23
Q

What cofactors does SOD need?

A

Copper
Zinc
Manganese

24
Q

How is glutathione a defence?

A

Reduced form = GSH

GSH reacts with GSH to form GSSG (glutathione peroxidase) - using a e- from ROS

GSSG reduced back to GSH (glutathione reductase) which uses electrons from NADPH

25
Q

What are the free radical scavengers?

A

Vitamin E

Vitamin C

Metabolism (10 decks)

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