Lecture 26- ATP production & oxidative phosphorylation

Question 1

What is metabolism?

Answer 1

Living systems acquire & use free energy in order to carry out their functions

Question 2

2 divides of metabolism

Answer 2

Catabolic
Anabolic

Question 3

Catabolic metabolism

Answer 3

The degradation of nutrients to salvage components & gain energy

Question 4

Anabolic metabolism

Answer 4

The synthesis of biomolecules for simpler components

Question 5

Autotrophs

Answer 5

Synthesis all cellular components from simple molecules

Question 6

Photoautotrophs

Answer 6

Use light to produce carbohydrates which are oxidised giving free energy

Question 7

Chemolithotrophs

Answer 7

Obtain free energy from compound oxidation

Question 8

Heterotrophs

Answer 8

Oxidise carbohydrates, lipids and proteins

Question 9

Classification of oxidising agents

Answer 9

Obligate aerobes- require O₂
Anaerobes- use sulphate or nitrate

Question 10

Vitamins

Answer 10

Organic molecules obtained from diet
Water soluble (coenzyme precursors)
Fat soluble (required in diet eg. vitamin C)

Question 11

Degradative pathways

Answer 11

Often converge on common intermediates
Further metabolised in central oxidadative pathway

Question 12

Biosynthetic pathways

Answer 12

Carry out the opposite
Few metabolites are the starting points

Question 13

Metabolic roles of liver (learn overview)

Answer 13

Metabolism of carbohydrate, lipid, amino acids

Question 14

Metabolic roles of muscle (learn overview)

Answer 14

ATP production for muscle contraction
use glycogen, glucose, fatty acids an ketone bodies as fuel

Question 15

Metabolic roles of brain (learn overview)

Answer 15

Nerve transmission (high ATP requirement)
Use glucose and ketone bodies as fuels not fatty acids

Question 16

Metabolic roles of adipose (learn overview)

Answer 16

Fat synthesis & storage

Question 17

-ve ΔG= ….
ΔG=0 = ….
+ve ΔG= …

Answer 17

-ve ΔG= favourable
ΔG=0 = equilibrium
+ve ΔG= unfavourable- usually require input of ATP

Question 18

Forms of cellular energy curency

Answer 18

Thioester bond-containing compounds
Reduced coenzymes
ATP

Question 19

NAD+ accepts … electron(s) and … proton(s)

Answer 19

2 (donated to ETC)
1

Question 20

FAD+ accepts … electron(s) and … proton(s)

Answer 20

2 (donated to ETC)
2

Question 21

ATP as an energy carrier

Answer 21

Biological importance depends on the free energy change that accompanies cleavage of phosphoanhydride bonds
Standard free energy of hydrolysis is -7.3 kcal/mol
Reactions with large +ve ΔG are possible by coupling with 2nd process with large -ve ΔG

Question 22

Substrate level phosphorylation

Answer 22

Direct addition of phosphate group to ADP to form ATP

Question 23

Oxidative phosphorylation

Answer 23

Energy-rich molecules are metabolised by oxidative reactions
Metabolic intermediates donate electrons to NAD+ & FAD to form NADH + H+ and FADH₂
As e- passes down ETC, they lose free energy- used to pump H+ across inner mitochondrial membrane -> H+ gradient which drives ATP synthesis from ADP + Pi

Question 24

ETC loaction

Answer 24

Inner mitochondrial membrane
impermeable so requires specialised transport systems
Highly convoluted crisae increase surface area
Mitochondrial matrix contains enzymes responsible for oxidation

Question 25

Organisation of ETC

Answer 25

IMM contains 5 separate protein complexes and 2 mobile electron carriers
Ultimately electrons combine with O₂ to form H₂O

Question 26

Complex I

Answer 26

At least 34 polypeptides
NADH binds to Complex I and electrons transferred to CoQ
Electron’s energy loss is used to pump 4H+ across the membrane

Question 27

Complex II

Answer 27

Enzyme of TCA cycle-succinate dehydrogenase
Accept electrons from FADH₂
Transfers electrons to CoQ vis Fe-S proteins
No energy is lost so no protons are pumped at Complex II

Question 28

Coenzyme Q

Answer 28

Small lipid molecule- hydrophobic quinone
Diffuses rapidly with IMM
Accept electrons from FE-S proteins from Complex I and Complex II

Question 29

Complex III & Cyt c

Answer 29

Both cytochrome proteins
Cut C is peripheral protein
Electrons transferred from Complex III to Cut C to Complex IV
At Complex III energy loss is used to pump 4 H+ across inner membrane

Question 30

Complex IV

Answer 30

The only electron carrier in which the heme iron has co-ordination site for O₂
Transfers pair of electrons to 1/2 O₂ which is reduce to form H₂O
2 protons pumped across IMM

Question 31

Why are electrons transferred?

Answer 31

The transfer of electrons does the ETC is energetically favourable
NADH is a strong electron donor
O₂ is a strong electron acceptor

Question 32

Chemiosmotic hypothesis

Answer 32

Proton pumping across the IMM creates a H+ gradient
Drives ATP synthesis via ATP synthase

Question 33

ATP synthase

Answer 33

Protons pumped to the cytosolic side of mitochondrial membrane re-enter the matrix by passing through F₀ proton channel
As protons pass down channel they drive the rotation of the C ring of F₀ which causes conformational change in beta subunit of F₁ domain

Question 34

ATP yield of oxidative phosphorylation

Answer 34

Every pair of electrons from NADH- 2.5 ATP generated
Every pair of electrons from FADH₂- 1.5 ATP generated
So, from one glucose molecule 30 ATP generated by oxidative phosphorylation

Question 35

P/O ratio

Answer 35

Number of ATP molecules formed per oxygen atom

Question 36

Inhibitors of electron transport chain

Answer 36

Prevent the passage of electrons down ETC and so prevent H+ being pumped across IMM
Inhibit ATP synthesis

Question 37

Uncouplers of ETC & ATP synthesis

Answer 37

Chemicals- dinitrophenol
Natural proteins- uncoupling protein (UCPs)

Question 38

Other final electron acceptors

Answer 38

Allow organisms to live in anaerobic conditions
eg. NO₃ which forms NO₂, N₂O or N₂
SO₄ which forms S or H₂S
CO₂ which forms CH₄ (methanogenesis)