Lecture 14: Energy Conversion in Mitochondria

Question 1

Why is ATP production called chemiosmotic?

Answer 1

This process is called chemisomotic coupling since chemical bond formation (“chemi”) is linked to membrane transport processes (“osmotic”)

Question 2

2 stages of ATP production?

Answer 2

Stage 1: – High energy electrons are used to set up a proton gradient across the mitochondrial inner membrane Stage 2: – ATP synthase (F-type ATPase) uses the proton gradient to drive ATP production

Question 3

Outer membrane

Answer 3

– Permeable to small molecules

Question 4

Inner membrane

Answer 4

– Cristea – Location of the respiratory chain (electron transport proteins) and ATP synthase

Question 5

Matrix

Answer 5

• Tricarboxylic (TCA) acid cycle, aka Kreb cycle or citric acid cycle • Source of NADH (reduced NAD+, electron for ETS)

Question 6

Food molecules can be broken down into what two things?

Answer 6

-fatty acids -pyruvate

Question 7

Fatty acids and pyruvate are converted to _____ before entering the Krebs (TCA) cycle.

Answer 7

Acetyl-CoA

Question 8

What protein is responsible for dividing mitochondria?

Answer 8

Dynamin

Question 9

The ____ determines the position and timing of mitochondrial fission

Answer 9

ER

Question 10

Mitochondria often align with ___

Answer 10

microtubules

Question 11

Mitochondria are more prevalent in high energy tissues like….

Answer 11

cardiac muscle, sperm tails

Question 12

___ is the primary donor of electrons for the ETS

Answer 12

NADH

Question 13

FADH2 is also utilized as an electron donor, entering at ____

Answer 13

ubiquinone

Question 14

NADH is generated by the catabolism of ___ to CO2 during the TCA cycle

Answer 14

acetyl-CoA

Question 15

Acetyl-CoA is produced from glucose by ___

Answer 15

glycolosis

Question 16

Acetyl-CoA is produced from fatty acids by ___

Answer 16

β-oxidation

Question 17

NADH donates ___ electrons to the ETC

Answer 17

2

Question 18

FADH2 donates ___ electrons to the ETC

Answer 18

4

Question 19

The two components of the electrochemical proton gradient formed by the respiratory chain?

Answer 19

-Proton-motive force due to membrane potential (neg in matrix) -Proton motive force due to PH gradient (basic in matrix)

Question 20

Proton translocating proteins contain…

Answer 20

“proton wires” which are rows of polar or ionic side chains or water molecules spaced at short distances so that proton can jump form one to the other

Question 21

Each subsequent participant in the electron transport chain has an increasingly ___ oxidation reduction (redox) potential

Answer 21

larger

Question 22

NADH readily donates its high energy electrons to ___ bound to proteins within the ETC.

Answer 22

metals

Question 23

Order of proteins in ETC?

Answer 23

Question 24

What are two types of electron carriers?

Answer 24

• cytochromes
• Iron-sulfur proteins

Question 25

Cytochromes

Answer 25

– Contain a covalently-bound heme

– The heme bound iron atom changes from the ferric (Fe3+) to the ferrous (Fe2+) oxidation state whenever it accepts an electron

Question 26

Iron-sulfur proteins

Answer 26

– Sulfur atoms from cysteine side chains within these proteins bind iron in either a 2S:2Fe or 4S:4Fe configuration

Question 27

What are the two mobile electron carriers in the ETC?

Answer 27

• ubiquinone
• cytochrome C

Question 28

Ubiquinone

Answer 28

• Can carry either one or two electrons
• Embedded in the membrane via a long chain isoprenoid
• Helps move proton form matrix to intermembrane space via the Q-cycle

Question 29

Cytochrome C

Answer 29

• A soluble protein with a bound heme prosthetic group
• Shuttles electrons from cytochrome c reductase to cytochrome oxidase

Question 30

What is ubiquinone (Q) converted to as Hydrogens are added to it?

Answer 30

• 1 H (QH*) = ubisemiquinone
• 2 H (QH2) = ubiquinol

Question 31

What Are the Three Large Enzyme Complexes in the Respiratory Chain?

Answer 31

• NADH Dehydrogenase complex

• Cytochrome c reductase (b-c1complex)
• Cytochrome oxidase complex

Question 32

NADH Dehydrogenase complex

Answer 32

Accepts electrons from NADH and passes them through flavin and at least 8 ironsulfur centers to ubiquinone

Question 33

Cytochrome C Reductase (complex III)

Answer 33

• Functions as a dimer
• Each monomer contains 3 hemes bound to cytochromes and an iron-sulfur protein
• Accepts electrons from ubiquinone and passes them to cytochrome c, one at a time

Question 34

Two-step cytochrome C reductase Q-cycle

Answer 34

• Only one e- can be passed to ubiquinone (Q) at a time

Question 35

Cytochrome oxidase complex (complex IV)

Answer 35

• Functions as a dimer
• 2 cytochrome hemes and 2 copper atoms
• Accepts electrons one at a time from cytochrome c
• Passes electrons four at a time to molecular oxygen

Question 36

The ability of cytochrome oxidase complex to hold onto molecular oxygen until it receive all 4 electrons prevents ____

Answer 36

damaging superoxide radical from being released.

Question 37

What is complex II?

Answer 37

succinate dehydrogenase

Question 38

Where is complex II?

Answer 38

• Complex II is the only membrane bound part of the TCA cycle.

• The covalently bound FAD accepts two electrons from succinate forming FADH2
• These electrons move through three iron sulfur clusters to ubiquinone.

Question 39

Beta-oxidation of fatty acids has a much ____ energy yeild than oxidation of glucose

Answer 39

higher

31 NADH : 8 NADH

108 ATP : 30 ATP

Question 40

ATP synthase

Answer 40

• F0F1 ATPase
• Multisubunit integral membrane protein (>500,000 daltons) of the inner mitochondrial membrane
• Works as a rotary catalyst
• As protons move through the enzymes, rotational motion is generated.
• This rotational motion is used to drive protein conformational changes that result in ATP synthesis from ADP and Pi

Question 41

Structure of ATP Synthase?

Answer 41

Question 42

ATP synthase dimers assemble ____

Answer 42

in cristae

Question 43

Voltage gradient drives:

Answer 43

ADP-ATP exchange

Question 44

PH gradient drives:

Answer 44

Pyruvate and phosphate import

Question 45

ADP/ATP carrier proteins localize in the ___

Answer 45

cristae

Question 46

ATP synthase can work in reverse to pump protons

Answer 46

Question 47

_____ uncouple electron transport from ATP synthesis

Answer 47

• Proton ionophores
• These lipid soluble proton carriers eliminate the proton gradient across the mitochondrial inner membrane

Question 48

Cyanide and carbon monoxide are so toxic because they….

Answer 48

inhibit electron transfer in the ETC