CHEM10006 Lecture Notes - Lecture 20: Ozone Depletion, Methionine, Atp Hydrolysis
31 May 2018
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Wednesday, 29 March 2017
Week 5 Chemistry Notes
Reduction of O2
-Radical involved- toxic!
-Reactive species give off H+ as they are protonated
-Makes dangerous species (e.g. hydrogen peroxide)
-Protective enzymes destroy toxic intermediates
SOD: superoxide dismutase
-Oxygen essential but superoxide can damage cells
-SOD abundant in aerobic organisms
-Can destroy superoxide ions (O2-) and protect against radical damage
-Active site contains Cu(II) and Zn(II)
Sulfur
Present in amino acids (Cys and Met) (sp3 hybridised)
Oxidation state in S is -2
Oxidation of compounds with Sulfur is favoured
SO2, SO3 dissolves in water to make H3SO4 and H3SO4
ACID RAIN- SO2 and NO2 dissolve in air
-pH lowered : kills aquatic life, corrosion of structures, release toxic metal from
sediment
!1
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Wednesday, 29 March 2017
BIOGEOCHEMICAL CYCLE OF SULFUR
SO4 ^2- is the soluble/oxidised form of S in nature
Absorbed by cells and incorporated into Cysteine and Methionine and then into
proteins
Nitrogen: Group 15
80% atmosphere
N2 (10 electron system)
Stable (triple bonds)
Compounds containing Nitrogen are unstable as they want to form stable N2
FIXATION
Difficult to incorporate into living tissue —> unreactive
Reduced to NH3 (into AA’s, proteins and nucleic acids) by nitrogenase enzyme
SOLUBLE
Nitrogen fixing bacteria (using metals)
Denitrifying bacteria respire on nitrogen and put back into atmosphere
Hydrides: Ammonia NH3 and Hydrazine N2H4
Oxides: Many oxidation states (many radicals)
Nitrous acid (unstable/weak)
NO (radical) - regulatory molecule, nerve function,
reg. blood pressure (dilation of blood vessels)
-Inhibits blood clotting (mosquitoes)
-Nasal sinuses
!2
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Wednesday, 29 March 2017
-Excess NO is toxic
-NOx production endothermic (increase rate and equilibrium with high temp.)
-NO2 diffuses to upper atmosphere- catalyses ozone depletion (UV)
-NO2 catalyses formation of O3 in photochemical react.
—> produces other pollutants
-O3 reacts with hydrocarbons: deleterious (pollutant)
(photochemical smog)
Phosphorus Group 15
In DNA, bones/teeth, ATP/ADP, minerals (Calcium Phosphate)
Hydride- PH3 (tetrahedral), analogous to NH3 but weaker base, gas
Element- Allotropes, white phosphorus P4 (very reactive, highly strained structure)
forms oxides- relieves strain
-Makes phosphoric acid (weak triprotic acid)
-Dissociate in a series of steps (from neutral, anionic charge goes up of Ka goes down)
- With heat H3PO4 condenses- polyphosphoric acid (reacts with base to form
polyanions)
-Dangerous in environment
!3
find more resources at oneclass.com
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Document Summary
Reactive species give off h+ as they are protonated. Oxygen essential but superoxide can damage cells. Can destroy superoxide ions (o2-) and protect against radical damage. Present in amino acids (cys and met) (sp3 hybridised) So2, so3 dissolves in water to make h3so4 and h3so4. Acid rain- so2 and no2 dissolve in air. Ph lowered : kills aquatic life, corrosion of structures, release toxic metal from sediment. So4 ^2- is the soluble/oxidised form of s in nature. Absorbed by cells and incorporated into cysteine and methionine and then into proteins. Compounds containing nitrogen are unstable as they want to form stable n2. Dif cult to incorporate into living tissue > unreactive. Reduced to nh3 (into aa"s, proteins and nucleic acids) by nitrogenase enzyme. Denitrifying bacteria respire on nitrogen and put back into atmosphere. No (radical) - regulatory molecule, nerve function, reg. blood pressure (dilation of blood vessels) Nox production endothermic (increase rate and equilibrium with high temp. )
