What is the role of mitochondria in eukaryotes?
It utilizes oxygen to extract energy from organic molecules for cellular processes
What is mitochondrial fusion/fission?
- mitochondria can merge: (fusion) or split (fission) from each other.
The difference between anaerobes and aerobes
- Anaerobes: oxygen-independent metabolism to utilize energy
- Aerobes”: using oxygen to extract more energy from organic molecules
How is mitochondrial fission initiated?
- Mitochondrial fission is triggered by ER tubules which tightens the mitochondria
Mitochondria functions
- Associated with fatty acids for ATP production
- Amino acid synthesis
- Regulate the uptake/release of Ca2+
- Controls cell death (apoptosis)
Two main domains of the inner mitochondrial membrane
- Inner boundary domain - rich in protein transporters
- Cristae - ATP synthesis
The two parts created by the mitochondrial membrane
- Matrix (ribosomes and DNA for mitochondrial proteins) and the intermembrane space
What happens to Pyruvate after glycolysis in aerobic respiration
- Goes in the mitochondria to be decarboxylated = Acetyl-CoA in the TCA (Calvin) cycle
What happens in the TCA Cycle?
- Pyruvate is oxidized to Acetyl CoA
- Acetyl CoA (2C) + oxaloacetate (4C) = citrate (6C)
- Citrate => isocitrate (isomer)
- Isocitrate is oxidized, CO2 released = 1NADH and a-Ketoglutarate (5C)
- a-Ketoglutarate is oxidized, CO2 is released = 1NADH and succinyl-CoA (4C)
- Succinyl-CoA is converted to succinate by ATP/GTP
- Succinate is oxidized to fumerate = 1FADH2
- Fumerate + H2O = malate
- Malate is oxidized to oxaloacetate and the cycle begins
The role of reducing coenzymes in ATP production
NADH and FADH2 donate electrons to the ETC chain during ATP synthesis
- NADH produces 3 ATP molecules and FADH2 produces 2 ATP
What is chemiosmosis in mitochondria
- The coupling H+ movement across in the inner membrane for ATP synthesis by ATP synthase
What is oxidative phosphorylation
- ATP synthesis using energy released from electrons in the ETC
What are strong reducing and oxidizing agents
- Reducing agents: they have a weak affinity for electrons and strong oxidizing agents have a high affinity for electrons
The different types of electron carriers
- Flavoproteins: carry e- with their FAD (NADH or succinate dehydrogenase)
- Cytochromes: have heme groups where the Fe is oxidized (lose e- =>Fe3+)
- 3 Copper (Cu) atoms: alternate between Cu2+/Cu3+
- Ubiquinone: (CoQ) 5C lipid-soluble molecule that transfers e- between complexes
- Iron-sulfur proteins: [2Fe-2S] could be linked to cysteine to transfer e- within complexes
Electron transport chain
- The carriers are arranged in an increased (+) redox potential order
- Each carrier is reduced by the previous carrier and oxidized by the next carrier
- O2 is the final e- acceptor, which is reduced by water
Steps to the ETC (electron transport chain)
- Arranged from complex I,III,II,IV (energy status)
- Complex I: NADH dehydrogenase ([Fe-S] complex). NADH (4H+) donates 2e- which is transferred to CoQ (2+4H+ from matrix -> IMS (intermembrane space, high [H+])
- Complex III: cytochrome bc1, e- from CoQ (now ubiquinol) => cyt b (2H+)
- Complex II: Succinate dehydrogenase ([Fe-S] complex) succinate => fumerate. 2e- from comp. II => CoQ = > cyt bc1 (cyt b) => CoQ => cyt c
- Complex IV: cyt c oxidase, e- from cyt c + O2 + H+ = H2O, (2H+) to IMS (overall 10 H+)
- ATP synthase: helps H+ flow back into the matrix (against their [gradient]) which produces 1 ATP from 4 H+
What are the products of O2 reduction in Complex IV of the ETC
For every O2 molecule reduced;
- 4 H+ forms 2 H2O
- 4 H+ are in the IMS
Two main ways to measure O2 in the blood
- Clark electrode: measures voltage across metal contacts
- Pulse oximeter: uses color measurement to assess blood O2 levels
Two components of the proton-motive force
- The ∆pH (pH gradient) between the matrix and the IMS
- The separation of charge across the membrane = (electric potential)
- This force drives ATP synthesis
The main subunits of ATP synthase
- The F1 particle: (catalytic subunit) with 3 sites for ATP synthesis (3alpha, 3beta, gamma, delta, epsilon)
- The F0 particle: embedded in the inner membrane. has a channel for proton conduction (a,b2,c9-15) protons move through the F0 complex, c ring of the gamma subunit rotates, making the ß subunit rotate = ATP synthesis
The binding change mechanism of ATP synthesis
- Energy from H+ movement changes the binding affinity of ATP synthase = ATP synthesis i by rotational catalysis
- The binding affinity of the 3ß catalytic sites have different affinities for ATP (L ;loose,T; tight,O; open)
- The ß subunit rotates 360º changing its conformation, with ATP synthesis happening in the T conformation
- 4 H+ for 1ATP, 3ATP per cycle: 12 H+ per cycle
Roles of the proton-motive force
- ATP synthesis
- Facilitated mitochondrial diffusion of Ca2+
Peroxisomes
- Membrane-bound vesicles that oxidize long fatty-acid chains, synthesize plasmalogens (class of phospholipids), and break down hydrogen peroxide (catalase)
- In plants; glyoxysomes, convert stored fatty acids => glucose
