Glycogen, TCA Cycle and Mitochondria (Lecture 12)

Question 1

outer mitochondrial membrane

Answer 1

porous, ions diffuse

phospholipid synthesis

Question 2

inner mitochondrial membrane

Answer 2

invaginations increase the surface area.

impermeable to ion transport and other molecules

ETC
oxidative phosphoryaltion

Question 3

mitochondrial matrix

Answer 3

PDC 
CAC
Glutamate DH
FA oxidation 
urea cycle 
replication 
transcription/ translation

Question 4

what is oxidative phosphorylation?

Answer 4

protein complexes take e- from NADH and FADH2. the free energy released by the e- is coupled to the transfer of protons from the matrix to the inner membrane space

H+ is pumped by complex I, III, IV
complex II (succinate dehydrogenase) doesn't pump out H+
the reentry of the H+ from the inter membrane space to the matrix is coupled too the rotational torque of ATP synthase to generate energy

Question 5

why is H+ pumped into the inter membrane space?

Answer 5

generate an electrochemical gradient, a proton motive force

Question 6

the ETC transports e- form ____ to _____ potential

Answer 6

low potential to high potential

Question 7

what is special about complex II?

Answer 7

does not pump protons into the matrix

it is invoiced in the CAC

Question 8

what are the redox centers (prosthetic groups) to accept and release electrons? and which complexes are they associated to?

Answer 8

complex I and II are known as flavo proteins, because they contain flavo mono-nucleotide (FMN) and flavin adenine di-nucleotide (FAD) respectively

complex III (and 2) contain cytochromes which functions to accept and release electrons

Question 9

purpose of iron sulphur (Fe-S) centres?

Answer 9

pass along the electrons

the sulphur in the cysteine residues will bid to iron, and Theron gains/loses electrons

Question 10

what is coenzyme Q

Answer 10

e- carrier that is extremely hydrophobic, thus it can diffuse within the mitochondria trial membrane

both electrons form compels I and II feed into coenzyme Q

it will give the e- to complex III

Question 11

what is cytochrome C

Answer 11

hydrophobic carrier to carry e- to complex IV

cytochrome are complexes to metals to allow for the accepting or release of e-

Question 12

where does O2 get reduced?

Answer 12

after H+ have passed complex IV, where it is reduced to H2O

4 e-

Question 13

electron path in the ETC

Answer 13

in complex I, NADH will reduce electrons and pass it to FMN–> Fe-S

OR

succiante carries electrons to FAD–> Fe-S –> cytochrome

coenzyme Q will travel in the mitochondrial membrane to deliver e-

in complex III, e- will be accepted and released by cytochromes coupled to Fe-S

cytochrome C will carry e-

in complex IV, e- will be accepted and released by Cooper (Cu) and cytochromes. eventually, O2 is reduced to water

proton motive force is identified by complex V (ATP synthase), which generates ATP

Question 14

Complex I

Answer 14

NADH -Coenzyme Q reductase

main donor of e- is NADH

the e- will travel down the FMN, iron sulphur centre

e- will reduce coenzyme Q

Question 15

2 functions of complex I

Answer 15

1. catalyses the transfer of 2 e- from NADH to FMN, which then transfers e- to the Fe-S clusters 1 at a time (this oxidized NADH)
2. transfer of 4 H+ into the inner membrane space (reduction of CoQ drives this)

e- transfer causes a conformational change in the transmembrane arm (perpendicular to other proteins) , which supports proton pumping . this back and forth perpendicular movement of th protein, will open/shut the H+ channel

Question 16

proton translocation channel

Answer 16

in complex I

the anti porter like subunits are linked to the distant Q site

when e- enters the coenzyme Q, its reduced and coenzyme Q is negatively charged

this causes a conformational change in the Q site , which is transmitted to the H channels via the long helical arm of Nqo12

Question 17

complex II

Answer 17

coenzyme Q reductase

does not pump H

succinate from the CAC will get oxidized by succinate DH and the e- form succiante will enter the complex

Question 18

the pathways to reduce coenzyme Q

Answer 18

1. complex 1
2. complex 2
3. ETF can receive e- form FAD or dehydrogenase. ETF is then oxidized by ETF-QO. this oxidization will transfer the e- form ETF onto CoQ. this occurs in the matrix
4. glycerol-3-phosphate dehydrogenase oxidizes G3P –> DHAP in the cytosol . the e- are donated to FAD and in turn donated to CoQ

Question 19

complex III

Answer 19

complex III catalyses the reduction of 2 molecules of cytochrome C. it does this by oxidizing coenzyme Q

coenzyme Q can accept 2e-, vat cytochrome C can only accept 1. therefore there a complex cycle to account for this stoichiometry : Q cycle

Question 20

the Q cycle

Answer 20

Q= coenzyme Q = ubiquinone

QH = semi ubiquinone

QH2 = ubiquinol

1. fully reduced coenzyme Q, QH2, wil bind to the Qo site. the protons will be transported to the inter membrane space, but cytochrome c can only accept 1 e-.
2. 1 electron will be sued to reduce cytochrome C, the second electron is put only Q to make QH
3. QH2 binds, 2 H+ go to the inter membrane space, 1 e- reduced cytochrome c and the other will now take QH to make a fully reduced QH2

2 ubiquinol molecules are fully oxidized to Q, only is fully reduced to form QH2, 2 cytochrome c molecules have been fully reduced

Question 21

complex IV

Answer 21

catalyses the transfer of 4 e- from 4 reduced cytochrome c molecules to generate 2H2O

every 2e- donated from NADH will cause 10 H+ pumped

Question 22

respirasome

Answer 22

the etc subunits aggregate together to form a super complex

this is done for efficiency (of e- transfer like channeling) or for the reduction of byproducts (RO species) or to limit the crystallization of complexes

Question 23

lower reduction potential implies

Answer 23

that the molecule is more likely to give up e-

Question 24

higher reduction potential implies

Answer 24

that the molecule is more likely to accept an electron

Question 25

shuttling cytosolic NADH to the mitochondria

Answer 25

cytosolic NADH cannot go into the mitochondria via the cytosol, this it must be put on shuttles

1. Glycerol 3 phosphate shuttl.

transfers cytosolic NADH by putting these e- onto DHAP to make G3P which can pass the membrane. the e- will then be put onto FADH2 to generate DHAP . DHAP will diffuse back into the cytosol

2. malate/aspartarte shuttle.

e- put onto oxaloacetate to make malate (reverse in CAC). malate holds onto the electrons of NADH and can come into the mitochondrial matrix. malate eis oxidized to release the electron onto NADH. oxaloacetate is generated, but it cannot diffuse, thus it will undergo a transamination reaction with glutamate to generate aspartic acid and alpha KG , once out of the mitochondria the reverse transamination reaction will occur to make glutamate and oxaloacetate.

Question 26

Fo ring contains ___ rings, which allows for ___ H+ to pass per subunit. This will generate ___ ATP per turn.

Answer 26

8 rings

1H+/ subunit

3 ATP/ turn

Question 27

how do we calculate the P/O ratio?

Answer 27

to make ATP , Pi is needed to phosphorylate ADP. the import of Pi is done by the importation of a H+ (no electrical disturbances)

we add this extra H+ per ATP (+ 3H) –> 8H+ + 3 H+= 11H+ to make 3 ATP

11/3 = 3.7 protons per ATP

for every 2e- donated to oxygen in the respiratory chain, 10 H+ pumped (complex 1 = 4H+and complex 3/4 = 6H+)

or 6H+ via complex 2

final division

10H+ (equivalent to Oxygen)/3.7 H+ per ATP = 2.7

6H+ (equivalent to Oxygen)/3.7 H+ per ATP = 1.5