1-29 Mitochondria Oxidative Phosphorylation

Question 1

Mitochondria structure

Answer 1

cristae: folds Matrix: inner fold inside Inner membrane: least permeable membrane in cells inner membrane space only 37 genes are expressed from mitochondrial genome, they express all of their own tRNAs and 2 rRNAs, all of the components of the ETC expressed in mitochondria but some are from the mito genome and some are from nuclear genome ***Most of the components of the mitochondria are made in the nuclear genome*** circular genome, no replication fork, instead you have a origin, DNA pol gamma required (encoded by nuclear genome) amino terminus of proteins (often) have signal sequences to get them in to mitochondria, chaperones inside mito help re-fold proteins that get transported in

Question 2

Voltage dependent anion channe

Answer 2

outer mito matrix, beta barrel structure to send ATP/ADP in and out, the send Pyruvate in, to send citrate out structure is common in bacteria but not in eukaryotes so this shows part of the mito evolution, helps tightly control membrane transport

Question 3

inner mitochondrial membrane transporters

Answer 3

ATP/ADP: ATP/ADP Translocate malate/ phosphate citrate /malate OH- /pyruvate OH- /Phosphate

Question 4

Glyercol 3 phosphate shuttle

Answer 4

Main shuttle mechanism to get reducing agents into inner mito matrix intermembrane mito space: Dihydroxyacetone-P +NADH + H + (from glucose to pyruvate) via Cytosolic glycerol 3 P dehydrogenase -> Glycerol-3-P (enters inner mito membrane) +NAD+ Glycerol3P transported into Inner Mito matrix + FAD via MITOCHONDRIAL GLYCEROL3P DEHYDROGENASE-> FAD2H (ETC) + DihydroxyacetoneP (transported back to inner membrane space)

Question 5

Malate-aspartate shuttle

Answer 5

second shuttling mechanism to get reducing agents into inner mito matrix cytosol: malate–>Mito matrix ; glutamate–>mito matrix matrix: malate + NAD+ -> NADH (ETC) + OAA; + Glutamate via TRANSAMINASE -> aKG + Aspartate (both exit mito through transporters) One transporter couples: malate in, aKG out Second transporter couples: glutamate in, aspartate out

Question 6

Components of ETC

Answer 6

Complex I: NADH dehydrogenase; Fe-S involved NADH->NAD+ protons pumped intermem space

**CoQ picks up H+ to make COQH2 and cycles to Complex II**

Complex II: Succinate dehydrogenase, ETF: Q oxioreductase, Fe-S involved, GLYCEROL 3 PHOSPHASTE DEHYDROGENASE (associates on intermembrane space side to deliver FAD)

**CoQ picks up H+ to make CoQH2 and cycles to complex III**

Complex III: Cytochrom b-c1 complex; Fe-S invoved and Cytochrom b, pumps protons

**Cytochrom c released and moves (only mobile protein component in ETC) to complex IV**

Complex IV: Cytochrom c oxidase; O2 final acceptor of electrons, Cu important, pumps protons

Question 7

Ubiquinone

Answer 7

can carry 2e- and 2H+ through the ETC from comples 1-2 and 2-3

is the only lipid component of ETC

contains hydrophobic hydrocarbon tail from cholesterol biosynthesis

Question 8

Cytochrome c

Answer 8

has a heme with Iron (which carries the e-)

Iron is stabilized/coordinated by sulfers from cysteine AAs

proper folding is essential to keep iron in correct orientation

Question 9

Chemiosmotic theory of oxidative phosphorylation

Answer 9

Proton motive force = change in membrane potential + change in pH

“electrochemical gradient”

intermembrane space same pH as cytoplasm but mito matrix is more basic

Question 10

ATP synthase

Answer 10

uses molecular motion to convert the electrochemical gradiatent –> chemical bound energy in ATP

chemE->mechE->synth ATP

reversible in case no ADP around but need to preserve the H+ gradient for other ATP functions

[ADP] controls the rate of oxygen consumption/ATP synth

Question 11

Inhibitors of Respiratory chain

Answer 11

Malonate, Antimycin A (antibiotics), CO, CN-, H2S, oligomycin

Uncouplers: thermogenin & 2,4-dinotrophenol

Question 12

thermogenin

Answer 12

brown fat cells in babies produce thermogenin (a H+ channel on inner mito membrane that dissapaites H+ gradient from ETC and releases heat instead of producing ATP)

Fatty acids feed this cycle to allow babies to keep warm

adults do not produce brown fat cells/thermogenin

Question 13

2,4-dinitrophenol

Answer 13

transports H+ from inner mito space back to mito matrix therby dissipating gradient and uncoupling ETC from ATP synth

once used as weight loss supplement, but is very dangerous!

Question 14

Calcium sink

Answer 14

mitochondria stores and releases calcium as needed

Question 15

Mitochondrial permeability transition pore

Answer 15

VDAC on outer membrane and ANT on innermembrane come together when apoptosis is triggered to form the mitochon permeability transition pore thus releaseing and inducing apoptosis of cells

Question 16

Production of ROS

Answer 16

Reactive oxygen species: O2 + e- (from leaky ETC) -> SUPEROXIDE -> H2O2 +e- -> HYDROXYL RADICAL; +e- -> H2O

Fenton Reaction: H2O2 + FE+2 -> FE+3 + OH- + HYDROXYL RADICAL

Question 17

Production of NOS

Answer 17

NOS: Arginine via via NITRIC OXIDE SYNTHASE -> citrulline + NITRIC OXIDE –> Nitrogen trioxide (nitrosating agent)

NITRIC OXIDE –> Peroxynitrite (oxidizer) ->penoxynitrous acid-> NO3- + OH- + NO2+ (nitrating agent) + NO2radical (smog)

some Nitric oxide is necessary and good, too much is bad, vasodilator

Question 18

Free radical defenses (3)

Answer 18

1. Glutathione

H2o2 + Glutathione (reduced state) via GLUTATHIONE PEROXIDASE -> H2O + Glutathione (oxidized state)

Glutathione (oxidized state) + NADPH (from PPP) + H+ via GLUCATHIONE REDUCTASE -> Glutathione (reduced state) + NADPH+

2. Superoxide dismutate: superoxide -> H2O2
3. Catalase: H2O2 -> H2O + O2 (in peroxisomes)