cell bio exam 1 - mitochondria and oxidative phosphorylation

the electron transport chain is

a series of electron carriers and three protein complexes found in the inner mitochondrial membrane; when electrons are transferred, protons are pumped across the membrane from the matrix into the intermembrane space

proton gradients, a form of an electrochemical gradient, are used to

power ATP synthase and phosphorylate ATP

chemiosmotic coupling

the mechanism of electron transfers generating energy

evidence for mitochondria and chloroplasts deriving from bacteria

• inner and outer membranes

• contain their own DNA separate from cell genome

• reproduce in a manner similar to prokaryotes

• genes in chloroplasts closely resemble genes found in cyanobacteria

mitochondrial abundance and organization can differ according to

a cell’s function

mitochondrial functions include

• energy production (production of ATP)

• regeneration of NAD+

• provision of precursors for biosynthesis of amino acids, nucleotides, fatty acids

• cell signaling

• regulation of apoptosis

the mitochondrial matrix

• space within inner membrane

• contains hundreds of enzymes

• contains DNA

the mitochondrial inner membrane

• contains proteins in the electron transport chain

• contains ATP synthase

• highly folded to increase surface area and efficiency

the mitochondrial intermembrane space

• contains enzymes that use ATP passing out of the matrix to phosphorylate other materials

• protons pumped into this space from the matrix during oxidative phosphorylation

the first step of catabolism is

the breakdown of large food molecules into small monomers (pyruvate ir fatty acids)

once molecules have been broken down into pyruvate and fatty acids, they travel into the mitochondria and are converted into

acetyl-coA

oxidation of the acetyl in acetyl coA in the (?) generates (?)

citric acid cycle, high energy electrons that are passed onto NADH

each pass of electrons between protein complexes in the ETC provides

energy to pump protons into the intermembrane space

how are proton pumping and redox reactions related?

electrons are transferred between carriers and complexes of the ETC through redox reactions

why are materials in the ETC inclined to keep passing on electrons?

redox potential increases in each subsequent complex/carrier

redox potential is

a measure of a molecule’s tendency to accept or donate an electron

• lower redox potential = lower affinity for electrons → act as electron donor (beginning of electron transport chain has lowest redox potential)

• higher redox potential = higher affinity for electrons → act as electron acceptor (end of electron transport chain has highest)

ubiquinone

• electron carrier in the electron transport chain

• hydrophobic

• located between first (NADH dehydrogenase complex) and second (cytochrome c reductase complex) protein complexes

cytochrome c

• contains heme group - positively charged iron atoms that accept electrons

• between the second (cytochrome c reductase complex) and third (cytochrome c oxidase) complexes

cytochrome c oxidase complex

• final protein complex/electron carriers

• largest electron affinity due to large binding site for oxygen + copper heme group

• transfers its electrons to oxygen → form water and pumps protons into the intermembrane space

proton pumping generates an electrochemical gradient, which means it is now energetically favorable for

protons to move into the mitochondrial matrix (proton-motive force)

the proton-motive force causes

• protons to move through ATP synthase

• conformational changes in subunits of ATP synthase including rotation of rotor

• generates ATP

ADP-ATP exchange between the intermembrane space and matrix is driven by

a voltage gradient

pyruvate and phosphate import from the intermembrane space to matrix is driven by

a pH gradient

complete oxidation of a single glucose molecule leads to the formation of

30 ATP molecules

a (high/low?) ratio of ATP:ADP is maintained within the cell cytosol

high; there is roughly 10x more ATP than ADP