4 - Energy Generation in Mitochondria and Chloroplasts

what are pyruvate and fatty acids converted to in the mito matrix (CAC)?

acetyl CoA

what does acetyl CoA metabolize into in the CAC?

NADH

oxidative phosphorylation

high energy electrons (from NADH) passed along ETC in inner membrane and gave off to O2

ETC

generates a proton gradient across the inner membrane, used to drive production of ATP

where is acetyl CoA made?

mitochondria

glycolysis produces

pyruvate

break down of fats produces

fatty acids

pyruvate and fatty acids enter the mitochondria from the

cytosol

pyruvate and fatty acids are converted into… in the mito matrix

acetyl CoA and CO2

hydride ion

hydrogen with two electrons

a hydride ion removed from NADH is converted into

a proton and two electrons (used in ETC)

stage 1 of chemiosmotic coupling

as electrons are transferred from activated carriers to O2, protons are pumped across the inner mito membrane

net equation for oxidative phosphorylation

2NADH + O2 + 2H+ —> 2NAD+ + 2H2O

three respiratory enzyme complexes in the inner mito membrane

NADH dehydrogenase, cytochrome c reductase, cytochrome c oxidase

protons derived from water are pumped are pumped across the membrane

from the matrix into the intermembrane space

mobile carriers that ferry electrons

ubiquinone (q) and cytochrome c

the electrochemical H+ gradient includes…

• a large force due to the membrane potential (V)

• a smaller force due to the H+ concentration gradient (pH)

the intermembrane space is slightly more ___ than the matrix

acidic (bc higher concentration of protons)

proton motive force

pulls H+ back into the mito matrix using the membrane potential and pH gradient

atp synthase function

acts like a motor to convert energy of protons flowing down their electrochemical gradient to chemical bond energy

ATP synthase is composed of

• F1 atpase: stationary head

• F0: rotating portion

F0

consists of the transmembrane H+ carrier plus a central stalk

F1

stationary head that is secured to inner membrane by the peripheral stalk

can also carry out the reverse rxn (hydrolysis of ATP)

ATP synthase reversibility

can either make ATP by harnessing the electrochemical H+ gradient or pump protons against this gradient by hydrolyzing ATP

how many total atp made per glucose

30

as an electron passes along the ETC, it can…

bind and release a proton at each step

cytochrome c oxidase

a dimer formed from a monomer with 13 different subunits

functional core of the complex encoded by mitochondrial genome

remaining subunits encoded by nuclear genome

heme and copper atom

form at the site where a tightly bound O2 will receive four electrons to make H2O

three conformations of proton pumping

high affinity for H+

low affinity for H+

third?

uncoupling agents

render the membrane permeable to protons, allowing H+ to flow into the mito matrix without passing ATP synthase

UNCOUPLES ETC from ATP synthesis

chemiosmotic processes evolved in stages

1. evolution of an ATPase that pumped protons out of the cell using the energy of ATP hydrolysis

2. evolution of a different proton pump driven by ETC

3. linked these two systems to make an ATP synthase that uses protons pumped by the ETC