Free radicals

Question 1

define free radical

Answer 1

any species (atom or molecule) that is capable of independent existence and contains one or more unpaired electrons.

Question 2

what are the consequences of radicals targeting DNA?

Answer 2

apoptosis or necrosis

Question 3

what are the consequences of radicals targeting DNA?

Answer 3

apoptosis or necrosis

Question 4

where do free radicals come from?

Answer 4

they’re derived from either normal metabolic processes in the human body or from external sources.

Question 5

what external/environmental sources produce free radicals?

Answer 5

UV light, smoking, air pollution, ionising raditation.

Question 6

what kind of radiation has high tissue penetration?

Answer 6

x-rays and gamma rays

Question 7

how does ionising radiation cause damage in the cells?

Answer 7

free radicals can split water in the cells into hydrogen and hydroxyl radicals.

Question 8

which cells are susceptible to ionising radiation?

Answer 8

gastrointestinal cells, fetal cells, bone marrow cells and lymph nodes

Question 9

name O2*−

Answer 9

superoxide

Question 10

how is O2*− super oxide produced?

Answer 10

40% leakage of electrons from electron transport chain

Question 11

name H2O2

Answer 11

hydrogen peroxide

Question 12

how is H2O2 hydrogen peroxide produced?

Answer 12

not a radical - but it liberates OH

Question 13

name RO*

Answer 13

organic radical

Question 14

name OH*

Answer 14

hydroxyl radical

Question 15

how is RO* produced?

Answer 15

produced from attack of C=C bonds​

Question 16

how is OH* produced?

Answer 16

generated from H2O2 from Fenton reaction​

Question 17

name RCOO*

Answer 17

peroxyl radical

Question 18

how is RCOO* produced?

Answer 18

generated from lipid attack

Question 19

name HOCL

Answer 19

hypochlorus acid

Question 20

how is HOCL produced?

Answer 20

respiratory burst

Question 21

what cellular structure is most likely to be exposed to the hydroxyl radical?

Answer 21

mitochondria

Question 22

what is nitrosative stress?

Answer 22

refers to the joint biochemical reactions of NO and O2*− when an oxygen metabolism disorder occurs in the body.

Question 23

name some of the effects of ROS on cellular structures.

Answer 23

damaged membrane - increased permeability, damaged mitochondria - reduced ATP production, DNA damage - mutations, protein misfolding.

Question 24

why are membranes and lipids susceptible to damage from ROS?

Answer 24

they are polyunsaturated fatty acids

Question 25

3 stages of a radical chain reaction

Answer 25

initiation, propagation, termination

Question 26

what is lipid peroxidation?

Answer 26

a process under which free radicals attack lipids containing carbon-carbon double bonds.

Question 27

what does lipid peroxidation cause?

Answer 27

decrease in membrane fluidity, damage to membrane proteins (receptors and their function!!), increase in “leakiness” to K+ and Ca2+.

Question 28

what is produced when a radical attacks guanine in DNA?

Answer 28

8-OHdG , deoxyguanosine. It is mutagenic and the biomarker of carcinogenesis.

Question 29

what happens when a radical attacks guanine in DNA?

Answer 29

Impaired protein synthesis. This base pair trans version of guanine is notable in some forms of cancer.

Question 29

what are the 3 stages of cellular change/adaptation?

Answer 29

proliferation, apoptosis, necrosis

Question 30

what does ROS-DNA damage cause?

Answer 30

strand breakage, purine, pyrimidine, or deoxyribose modifications in base pairs and cross-linkage.

Question 31

what can DNA damage lead to?

Answer 31

replication errors, induction of transcription.

Question 32

how do radicals initiate atherosclerosis?

Answer 32

damage blood vessel walls