Lecture 307: respiratory chain

Question 1

mitochondria uses O2 to regenerate ____

Answer 1

• NAD+ so all rxns can continue to synthesize NADH

Question 2

glucose oxidation

Answer 2

• 12 reducing equivalents produced [10 NADH and 2FADH2]
• need 1/2 O2 per reducing equivalent
• H2O used and synthesized

Question 3

NADH and FADH2 can be converted to ___ molecules of ATP

Answer 3

• 32

Question 4

NADH

Answer 4

• main donor of e- in cells
• readily dissociates from enzymes [carries e- between enzymes so substrates can be ox/ red]
• can carry ONLY TWO e- at a time
• main donor in oxidative phosphorylation

Question 5

PDH complex and TCA cycle occur in

Answer 5

• mitochondrial matrix

Question 6

e- transport and oxidative phosphorylation occur in ___; also includes ___

Answer 6

• inner membrane

- succinate-dehydrogenase from TCA cycle [involved in e- transport]

Question 7

reduction e- carriers for energy production in respiratory chain

Answer 7

• NADH or FADH2
• complex 1-4 [multiprotein enzyme complexes]
• CoQ
• cytochrome C

Question 8

flavoproteins

Answer 8

• tightly bound FMN or FAD
• can link 1 OR 2 e- at a time
• complexs 1 and 2

Question 9

iron-sulfur proteins

Answer 9

= non-heme iron complexed with sulfur

• Fe-S = 1 iron complexed with 4 cysteine residues
• Fe4-S4 = 4 iron, 4 inorganic sulfur, 4 cysteine residues
• iron = e- carrier [Fe2+ or Fe3+]
• complexes 1, 2 and 3

Question 10

CoQ

Answer 10

• can link 1 OR 2 e-

- lipophilic = located in inner membrane of mitochondria

Question 11

cytochromes

Answer 11

= specific group of heme proteins [heme covalently bound]

- can be a, b or c-types

Question 12

complexes as a, b or c-type cytochromes

Answer 12

• complex 2 = b-type
• complex 3 = b and c-type
• complex 4 = a-type [a1 or a3]

Question 13

cytochrome b and c-types contain what kind of heme

Answer 13

• same heme found in hemoglobin

Question 14

cytochrome a-type contains what kind of heme

Answer 14

• heme variant heme-A = associated with copper ion

Question 15

all heme-bound iron cycles through ___ and ___ bound states

Answer 15

• +3

- +2

Question 16

copper ions associated with heme-a cycle through ___ bound states

Answer 16

• +1

- +2

Question 17

transport of e- is a series of coupled (endergonic/ exergonic)

Answer 17

• exergonic

Question 18

complexes 1, 3 and 4 as proton pumps

Answer 18

= energy USED [from free e-] to pump protons UP their gradient from matrix into intermembrane space

Question 19

complex 5 as a proton pump

Answer 19

= GENERATES energy as protons are pumped DOWN their gradient from intermembrane space to matrix

Question 20

complex 1

Answer 20

= NADH-CoQ reductase

• 45 subunit complex
• contains one bound FMN and 8Fe-sulfur clusters
• PROTON PUMP = transports 4H+ into intermembrane space

Question 21

complex 2

Answer 21

= succinate-CoQ reductase [succinate dehydrogenase complex (flavoprotein; TCA cycle enzyme)]

• 4 subunit complex
• contains 3 Fe-sulfur clusters
• CoQ draws from succinate [e- transferred ONE at a time]
• NOT a proton pump = NO H+ transfer

Question 22

function of CoQ in complex 2

Answer 22

= helps regenerate FAD within the succinate dehydrogenase enzyme = enzyme can keep functioning in TCA cycle

Question 23

both complex 1 and 2 end up dumping e- to ____

Answer 23

• CoQ

Question 24

complex 3

Answer 24

= CoQ: cytochrome c oxidoreductase

• dimer = 10-11 subunit complex
• 2 binding sites = Q0 and Q1 [travels from 0 to 1]
• IS a proton pump = transports 4H+ into intermembrane space
• transfers e- to cytochrome c = each only carries ONE e- each

Question 25

cytochrome c

Answer 25

• intermembrane space side
• respiratory chain = heme prosthetic group; transfers e- between complex 3 and 4
• involved in apoptosis

Question 26

complex 4

Answer 26

= cytochrome c oxidase

• 13 subunit complex
• 2 hemes = a [copper center CuA] and a3 [copper center CuB]
• IS a proton pump = transports 2H+/ NADH (of FADH2) oxidized
• first 3 transfers happen FOUR TIMES
• binuclear heme a3-CuB center = carries FOUR e-

Question 27

incomplete reduction of O2

Answer 27

• 1e- transferred = superoxide radical
• 2e- transferred = hydrogen peroxide
• 3e- transferred = hydroxyl radical [bad !!]
• 4e- transferred = water

Question 28

other metabolic rxns that use O2

Answer 28

• oxygenase aka hydroxylases

- cytochrome P450 monooxygenase

Question 29

which complex converts these H+ to ATP?

Answer 29

complex 4!!