Lecture 22 ETC

Question 1

What is the purpose of the ETC

Answer 1

To create a proton gradient (with high concentration outside of the matrix to power ATP synthase

Question 2

Can ATP synthase still work without the ETC if there is another way to keep the proton gradient?

Answer 2

Yes

Question 3

What is created or used in all of these pathways?
1. glycolysis
2. Gluconeogenesis
3. Citric acid cycle
4. PPP
5. AA degradation
6. Fatty Acid Synthesis
7. Fatty acid degradation

Answer 3

1. glycolysis- ATP
2. Gluconeogenesis- ATP consumed
3. Citric acid cycle- NA(D)PH made
4. PPP - NA(D)PH consumed
5. AA degradation - FADH2 made
6. Fatty Acid Synthesis - FADH2 consumed
7. Fatty acid degradation- Acetyl CoA made

Question 4

What are the 6 types of electron carriers we talk about in ETC

Answer 4

NAD, FAD/FMN, Coenzyme Q (ie ubiquinone), Hemes, Fe-S clusters, Cu centers

Question 5

What is the final electron acceptor in the ETC

Answer 5

Oxegen

Question 6

What happens to the reduction potential of electron carriers as electrons move through the electron transport chain?

Answer 6

The ETC is like a ladder of electron carriers with a diffrent reduction potential, the reduction potential INCREASES with each step

Question 7

How many electrons and protons can FAD/FMN carry?

Answer 7

(1 and 1 or 2 and 2)
FADH carries 1e and 1 proton
FADH2 carries 2e and 2p

Question 8

How many e- can NAD carry

Answer 8

2e and 1p

Question 9

What are the three names for the three diffrent oxidation states of coenzymeQ?

Answer 9

quinone – fully oxidized form

Semiquinone – partially reduced, radical intermediate (one electron and one proton added)

hydroquinone - fully reduced form (two electrons and two protons added)

Question 10

How many e and p and CoQ hold

Answer 10

1 and 1 or 2 and 2
QH= 1e and 1p
QH2= 2e and 2p

Question 11

Are hemes irreversibly bound?

Answer 11

yes they are tightly of covalently bound to proteins

Question 12

is NAD irreversibly bound to its proteins?

Answer 12

no, its reversibly associated and soluble with proteins.

Question 13

Is FAD tightly bound to its proteins?

Answer 13

yes

Question 14

Is CoQ tightly bound to proteins?

Answer 14

no, is reversibly associated with proteins.

Question 15

Why does Coenzyme Q have a membrane-soluble tail?

Answer 15

Coenzyme Q has a long isoprenoid tail that makes it lipophilic, allowing it to move freely within the inner mitochondrial membrane’s lipid bilayer. This mobility is essential for shuttling electrons between Complexes I/II and Complex III in the electron transport chain.

Question 16

How many e and p do hemes carry

Answer 16

only 1 electron

Question 17

How can you tell if a Heme is carrying a electron or not?

Answer 17

If iron is reduced form Fe(III)+e- —> to Fe(II)

Question 18

What is a cytochrome

Answer 18

An example of a protein with a bound heme

Question 19

How many p and e can iron sulfur clusters carry and how can you tell if its carrying

Answer 19

can only hold 1e- per iron in fe-S cluster if its in Fe(II) mode instead of Fe(III) mode

Question 20

what amino acid are Fe-S clusters covalently bonded to?

Answer 20

Cysteine (which give its sulfur)

Question 21

how may e and p can Cu centers hold?

Answer 21

1 e-

Question 22

how is a Cu center bound to its protein?

Answer 22

Covalently bonded to proteins by cysteine side chain

Question 23

How can you tell if a cu center is carrying its e-?

Answer 23

ifs its in 2 Cu^+1 mode

(2Cu^1.5 + e- —> 2Cu^+1)

Question 24

Overall which e- carriers are irreversibly bound and which are not

Answer 24

Irreversibly bound: FAD, Heme, Iron sulfur clusters,

can freely dissociate: NAD, coenzyme Q

Question 25

whats an example of a ETC inhibitor?

Answer 25

Cyanide, carbon monoxide

Question 26

whats an example of a ETC interceptor and how does it do it? (ie takes the election sand stop ETC)

Answer 26

Ferricyanide, competes with reduction potential of next e- carrier and steals electrons

Question 27

what is the flow of electrons by electron carriers in the ETC?

Answer 27

NADH-CoQ-succinate-CoQ-Cytochrome C-o2

Question 28

-What is purpose of complex 1? - input of substrate or e- carrier? -output of e- carrier? - number of H+ (protons) pumped?

Answer 28

- (=NADH-Ubiquinone oxidoreductase) to oxidize NADH on the matrix side, moves electrons from FMN though Fe-S clusters onto Q, pumps 4 protons out in the process as well as 2 more for QH2 - NADH -QH2 -4 PROTONS OUT

Question 29

-What is purpose of complex 2? - input of substrate or e- carrier? -output of e- carrier? - number of H+ (protons) pumped?

Answer 29

-(succinate dehydrogenase from the citric acid cycle) is to turn scuuonate into fumerare for the citric acid cycle but then takes the reduced electron carrier that it just made (FADH2) and transfers these onto coenzyme Q to make QH2. -Succinate -QH2 -0

Question 30

-What is purpose of complex 3? - input of substrate or e- carrier? -output of e- carrier? - number of H+ (protons) pumped?

Answer 30

-(ubiquinone-cytochrome c reductase) Oxidizes QH2 and reduces cytochrome C. However cytochrome C can only carry 1 electron and QH2 is carrying 2 electrons you have to do the Q cycle to break it up -QH2 -Cytochrome C - 4 protons

Question 31

-What is purpose of complex 4? - input of substrate or e- carrier? -output of e- carrier? - number of H+ (protons) pumped?

Answer 31

-(cytochrome C oxidase) oxidized cytochrome c to reduce o2 to 2 waters (you run complex 4 twice) -Cytochrome C -2 Water -2 protons

Question 32

why does oxygen have to be in its o2^-2 (peroxide) form to accept the last electrons of the ETC?

Answer 32

because if it was neutral it would not be inclined to do any chemistry, it has to be reactive.

Question 33

How many protons will you pump into the intermembrane space if you start with NADH?

Answer 33

10

Question 34

How many protons will you pump into the intermembrane space if you start with FADH2?

Answer 34

6

Question 35

How many protons required for each ATP?

Answer 35

4 (10/2.5 and 6/1.5 are both 4)