Lecture 14: Energy Conversion in Mitochondria Flashcards
Why is ATP production called chemiosmotic?
This process is called chemisomotic coupling since chemical bond formation (“chemi”) is linked to membrane transport processes (“osmotic”)
2 stages of ATP production?
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
Outer membrane
– Permeable to small molecules
Inner membrane
– Cristea – Location of the respiratory chain (electron transport proteins) and ATP synthase
Matrix
• Tricarboxylic (TCA) acid cycle, aka Kreb cycle or citric acid cycle • Source of NADH (reduced NAD+, electron for ETS)
Food molecules can be broken down into what two things?
-fatty acids -pyruvate
Fatty acids and pyruvate are converted to _____ before entering the Krebs (TCA) cycle.
Acetyl-CoA
What protein is responsible for dividing mitochondria?
Dynamin
The ____ determines the position and timing of mitochondrial fission
ER
Mitochondria often align with ___
microtubules
Mitochondria are more prevalent in high energy tissues like….
cardiac muscle, sperm tails
___ is the primary donor of electrons for the ETS
NADH
FADH2 is also utilized as an electron donor, entering at ____
ubiquinone
NADH is generated by the catabolism of ___ to CO2 during the TCA cycle
acetyl-CoA
Acetyl-CoA is produced from glucose by ___
glycolosis
Acetyl-CoA is produced from fatty acids by ___
β-oxidation
NADH donates ___ electrons to the ETC
2
FADH2 donates ___ electrons to the ETC
4
The two components of the electrochemical proton gradient formed by the respiratory chain?
-Proton-motive force due to membrane potential (neg in matrix) -Proton motive force due to PH gradient (basic in matrix)
Proton translocating proteins contain…
“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
Each subsequent participant in the electron transport chain has an increasingly ___ oxidation reduction (redox) potential
larger
NADH readily donates its high energy electrons to ___ bound to proteins within the ETC.
metals
Order of proteins in ETC?
What are two types of electron carriers?
- cytochromes
- Iron-sulfur proteins
Cytochromes
– 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
Iron-sulfur proteins
– Sulfur atoms from cysteine side chains within these proteins bind iron in either a 2S:2Fe or 4S:4Fe configuration
What are the two mobile electron carriers in the ETC?
- ubiquinone
- cytochrome C
Ubiquinone
- 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
Cytochrome C
- A soluble protein with a bound heme prosthetic group
- Shuttles electrons from cytochrome c reductase to cytochrome oxidase
What is ubiquinone (Q) converted to as Hydrogens are added to it?
- 1 H (QH*) = ubisemiquinone
- 2 H (QH2) = ubiquinol
What Are the Three Large Enzyme Complexes in the Respiratory Chain?
• NADH Dehydrogenase complex
- Cytochrome c reductase (b-c1complex)
- Cytochrome oxidase complex
NADH Dehydrogenase complex
Accepts electrons from NADH and passes them through flavin and at least 8 ironsulfur centers to ubiquinone
Cytochrome C Reductase (complex III)
- 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
Two-step cytochrome C reductase Q-cycle
- Only one e- can be passed to ubiquinone (Q) at a time
Cytochrome oxidase complex (complex IV)
- 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
The ability of cytochrome oxidase complex to hold onto molecular oxygen until it receive all 4 electrons prevents ____
damaging superoxide radical from being released.
What is complex II?
succinate dehydrogenase
Where is complex II?
• 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.
Beta-oxidation of fatty acids has a much ____ energy yeild than oxidation of glucose
higher
31 NADH : 8 NADH
108 ATP : 30 ATP
ATP synthase
- 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
Structure of ATP Synthase?
ATP synthase dimers assemble ____
in cristae
Voltage gradient drives:
ADP-ATP exchange
PH gradient drives:
Pyruvate and phosphate import
ADP/ATP carrier proteins localize in the ___
cristae
ATP synthase can work in reverse to pump protons
_____ uncouple electron transport from ATP synthesis
- Proton ionophores
- These lipid soluble proton carriers eliminate the proton gradient across the mitochondrial inner membrane
Cyanide and carbon monoxide are so toxic because they….
inhibit electron transfer in the ETC
