Biology Cellular Respiration (Exam 2)

Cellular Respiration

The process cells use to break down organic molecules and transfer their energy into ATP.

Mitochondrion

Organelle where most stages of aerobic cellular respiration occur in eukaryotic cells.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for ATP production.

Intermembrane Space

Space between the inner and outer mitochondrial membranes where protons accumulate during electron transport.

Mitochondrial Matrix

Innermost compartment where pyruvate processing and the Krebs cycle occur.

NAD⁺

Electron carrier that accepts high-energy electrons and hydrogen to become NADH.

NADH

Reduced electron carrier that delivers high-energy electrons to the electron transport chain.

FAD

Electron carrier that accepts electrons and hydrogen to become FADH₂.

FADH2

Reduced electron carrier that delivers electrons to the electron transport chain.

Substrate-Level Phosphorylation

Direct transfer of a phosphate group from an organic molecule to ADP to produce ATP.

Oxidative Phosphorylation

ATP production using energy from the electron transport chain to create a proton gradient that drives ATP synthase.

Glycolysis

First stage of cellular respiration; splits one glucose molecule into two pyruvate molecules in the cytoplasm.

Net ATP from Glycolysis

Two ATP per glucose, after subtracting the two ATP invested.

Pyruvate Processing

Each pyruvate is converted into acetyl-CoA, releasing CO₂ and producing NADH.

Pyruvate Processing Outputs

Per glucose: two acetyl-CoA, two CO₂, and two NADH.

Acetyl-CoA

Molecule that carries a two-carbon acetyl group into the Krebs cycle.

Citric Acid Cycle

Series of reactions in the mitochondrial matrix that oxidizes acetyl-CoA and transfers energy to electron carriers.

Citric Acid Cycle Outputs

Per glucose: four CO₂, six NADH, two FADH₂, and two ATP (or equivalent GTP).

Carbon Dioxide in Cellular Respiration

Waste product released during pyruvate processing and the Krebs cycle as carbon atoms from the original fuel are oxidized.

Electron Transport Chain (ETC)

Series of membrane proteins that transfer electrons through redox reactions and use the released energy to pump protons across a membrane.

Final Electron Acceptor

Oxygen, which accepts electrons and combines with protons to form water.

Water in Cellular Respiration

Forms when oxygen accepts electrons and protons at the end of the electron transport chain.

Proton Gradient

Difference in proton concentration and electrical charge across a membrane that stores potential energy.

ATP Synthase

Membrane protein that uses energy from proton flow to combine ADP and inorganic phosphate into ATP.

Why NADH Produces More ATP Than FADH₂

NADH donates electrons to Complex I, allowing more proton pumping; FADH₂ enters at Complex II and bypasses Complex I.

Heterotrophs

Organisms that obtain organic molecules from other organisms or their products for energy and carbon.

Active Transport in ATP Production

The electron transport chain uses energy from electrons to pump H⁺ (protons) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.

Facilitated Diffusion in ATP Production

H⁺ flows down its electrochemical gradient through ATP synthase back into the mitochondrial matrix. This flow provides the energy ATP synthase uses to make ATP from ADP and phosphate.

Uncouplers

Substances that allow protons (H⁺) to cross the inner mitochondrial membrane without passing through ATP synthase, reducing the proton gradient and decreasing ATP production.

ETC Disruptors

Substances that block electron transfer through the electron transport chain, reducing proton pumping and decreasing ATP production.

ATP Synthase Inhibitors

Substances that block ATP synthase, preventing protons from flowing through it and reducing ATP production.