Chapter 14: Energy Generation in Mitochondria and Chloroplasts

Vocabulary flashcards covering cellular respiration and photosynthesis mechanisms, ATP accounting, and endosymbiotic theory from Chapter 14.

NADH Dehydrogenase

An inner mitochondrial membrane enzyme complex that accepts electrons from NADH, regenerates $NAD^+$, passes electrons to ubiquinone, and pumps $H^+$ into the intermembrane space.

Cytochrome Oxidase

The terminal enzyme complex of the mitochondrial electron transport chain that receives electrons from cytochrome c, reduces $O_2$ to $H_2O$, and pumps $H^+$ into the intermembrane space.

Standard Redox Potential

A measure of electron affinity where carriers with more negative potentials (e.g., NADH at about $-320\text{ mV}$) donate electrons, and carriers with more positive potentials (e.g., $O_2/H_2O$ couple at about $+820\text{ mV}$) accept electrons.

ATP Yield per NADH

Yields approximately $2.5\text{ ATP}$, based on $10\text{ }H^+$ pumped per electron pair ($4 + 4 + 2 = 10\text{ }H^+$) and a transport/synthesis cost of about $4\text{ }H^+$ per ATP ($\frac{10}{4} = 2.5$).

ATP Yield per $FADH_2$

Yields approximately $1.5\text{ ATP}$, because electrons enter at ubiquinone and bypass the first pumping complex, resulting in about $6\text{ }H^+$ pumped.

Net ATP Yield per Glucose

A total yield of approximately $30\text{ ATP}$ produced from glycolysis ($2\text{ ATP}$, $2\text{ NADH} = 3\text{ ATP}$), pyruvate dehydrogenase ($2\text{ NADH} = 5\text{ ATP}$), and the citric acid cycle ($6\text{ NADH} = 15\text{ ATP}$, $2\text{ FADH}_2 = 3\text{ ATP}$, $2\text{ GTP} = 2\text{ ATP}$).

Inner Membrane Disruption

The collapse of the electrochemical $H^+$ gradient that occurs if the inner mitochondrial membrane becomes permeable to protons, dramatically falling or halting ATP synthesis via oxidative phosphorylation.

Photosystem II (PSII)

A complex in the thylakoid membrane where light absorption and water splitting occur on the thylakoid-space side, releasing $O_2$ and replacing lost electrons.

Charge Separation

The process in photosynthesis where antenna chlorophyll transfers absorbed photon excitation energy to a reaction-center special pair, transferring an excited electron to an acceptor to start electron transport.

Stage 1 of Photosynthesis (Light Reactions)

Photochemical reactions occurring in the thylakoid membrane that utilize light energy and water to generate $O_2$, ATP, and NADPH.

Stage 2 of Photosynthesis (Calvin Cycle)

A cyclic pathway occurring in the chloroplast stroma that consumes $CO_2$, ATP, and NADPH to synthesize organic carbon precursors.

Rubisco

A chloroplast stroma enzyme that catalyzes the fixation of $CO_2$ onto ribulose 1,5-bisphosphate (RuBP), yielding an unstable six-carbon intermediate that splits into two molecules of 3-phosphoglycerate.

Glyceraldehyde 3-Phosphate (G3P)

The net organic carbon product exported from the Calvin cycle; fixing $3\text{ }CO_2$ consumes $9\text{ ATP}$ and $6\text{ NADPH}$ to yield one net molecule of G3P.

Endosymbiotic Theory

The evolutionary model stating that mitochondria descended from an aerobic bacterium and chloroplasts descended from a photosynthetic bacterium acquired by ancestral eukaryotic lineages.

Endosymbiotic Evidence

Organelle features inherited from bacterial ancestors, specifically circular chromosomes, bacterial-like binary fission, bacterial-like ribosomes, and membrane components such as cardiolipin and porins.