CP1: Cell response to injury & disease

Question 1

What does ROS & RNS stand for?

Answer 1

ROS: reactive oxygen species
RNS: reactive nitrogen species

Question 2

Define ROS.

Answer 2

highly reactive oxygen species due to an unpaired electron. They are electrophiles that go through chain reactions.

Question 3

Define RNS.

Answer 3

highly reactive nitrogen species due to an unpaired electron. They are electrophiles that go through chain reactions.

Question 4

Define free radical.

Answer 4

highly reactive chemical species with an unpaired electron. They are electrophiles that go through chain reactions.

Question 5

Define electrophile.

Answer 5

chemical species that seeks an electron-rich region.

Question 6

Define oxidative damage.

Answer 6

damage caused by the oxidation (gain of electron) of a cellular component.

Question 7

Define crosslink.

Answer 7

when species form a covalent bond/weak intermolecular interaction that holds them together.

Question 8

Define lipid peroxidation.

Answer 8

when lipid radicals form other lipid radicals by reaction with oxygen. Usually a chain reaction.

Question 9

Define protein adduct.

Answer 9

a complex formed when a protein binds to a chemical molecule.

Question 10

What does the proteasome do?

Answer 10

Degrades oxidised proteins that can’t be refolded

Question 11

How are damaged organelles removed from the cell?

Answer 11

An autophagosome and a lysosome fuse together to form an autophagolysosome.

Question 12

What is the role of vitamin E in the cell?

Answer 12

It prevents/terminates lipid peroxidation.

Question 13

What is the other name for chaperone?

Answer 13

Heat shock proteins

Question 14

What is the role of chaperone?

Answer 14

It protects misfolded proteins and helps them to get the correct folding again.

Question 15

What molecules protect against ROS and what kind of molecule are they?

Answer 15

Glutathione, vitamin C and vitamin E. They are antioxidants

Question 16

Which enzymes neutralise ROS?

Answer 16

Catalase, superoxide dismutase & glutathione peroxidase

Question 17

Which enzymes generate ROS?

Answer 17

myeloperoxidase & NADPH oxidase in neutrophils

Question 18

Which amino acids are very susceptible to oxidation?

Answer 18

Cysteine & tryptophan

Question 19

Define protein aggregate.

Answer 19

When proteins are bound together.

Question 20

Define antioxidant.

Answer 20

A molecule that can donate electrons to neutralise a radical species.

Question 21

Define chaperone.

Answer 21

A protein found in the ER that helps with refolding misfolded proteins.

Question 22

Define proteasome.

Answer 22

Enzyme that degrades proteins.

Question 23

Define lysosome.

Answer 23

Enzyme that destroys cellular components

Question 24

What is the unfolded protein response?

Answer 24

A response that occurs when unfolded proteins accumulate in a cell that results in increased expression of chaperones & decreased synthesis of proteins by the ER.

Question 25

What is ER stress?

Answer 25

When the ER has too much demand or problems with protein synthesis.

Question 26

Define autophagy.

Answer 26

A defence mechanism that removes a whole damaged organelle or a large protein aggregate from the cell.

Question 27

What is respiratory burst?

Answer 27

Large increase in oxygen uptake by neutrophils & other tissue macrophages through NADPH oxidase that reduces oxygen to a superoxide

Question 28

What are external sources of cell injury?

Answer 28

UV X-rays Extreme temps Chemicals Pollution Lifestyle choices Pathogens

Question 29

How do UV rays cause cell damage?

Answer 29

Favours the production of ROS & base oxidation & cross-linking of cytosine & thymine dimers which leads to DNA base mismatch & mutation + stall cell cycle.

Question 30

How do X-rays cause cell damage?

Answer 30

Trigger ROS production & base oxidation + DNA strand breaks which leads to DNA base mismatch & mutation.

Question 31

How do chemicals, pollution & lifestyle choices cause cell damage?

Answer 31

Cause DNA strand breaks + generate ROS, reactive aldehydes & bulky DNA adducts which stall DNA replication machinery

Question 32

What are internal sources of cell injury?

Answer 32

Aerobic respiration Reactive intermediates produced by metabolic reactions Proteolytic/oxidative enzymes Immune cells

Question 33

How is DNA damage repaired?

Answer 33

A sensor protein notices the DNA damage & starts a signalling cascade. A transducer is then recruited to halt the cell cycle & repair the DNA.

Question 34

What is the focus when repairing proteins?

Answer 34

Repair of oxidised cysteine residues & broken disulphide bonds.

Question 35

What happens to irreparable proteins?

Answer 35

They get a ubiquitous tag and are destroyed by lysosomes.

Question 36

What is the process of autophagy?

Answer 36

1) Cell encapsulates the whole damage organelle/large protein aggregate. 2) Autophagosome forms & fuses with a lysosome. 3) This forms an autophagolysosome that destroys the organelle.

Question 37

How do bacteria cause cell injury?

Answer 37

Bacteria have bacterial chaperones that cause protein misfolding. Bacteria compete with the host cell for nutrition & disrupts the cell's homeostasis.

Question 38

How do viruses cause cell injury?

Answer 38

Viruses use the host's cellular machinery to make more proteins which puts stress on the ER. Antiviral defences halts protein synthesis in the ER to prevent production of viral proteins so vital proteins are missing from the cell + leads to accumulation of unfolded proteins that puts stress on the ER

Question 39

How can the immune response cause cell injury?

Answer 39

ROS undergo neutrophil respiratory burst. ROS can produce superoxide if stimulated to do so. Very virulent response that causes tissue damage.