Cellular Respiration and Enzyme Function

Embedded in the inner membrane of the mitochondria.
Composed of three transmembrane proteins acting as hydrogen pumps.
Includes two carrier molecules for electron transport between hydrogen pumps.
Thousands of these chains exist in the inner mitochondrial membrane.
Powered by electrons from NADH and FADH₂.
FADH₂ functions as an electron acceptor in the citric acid cycle.
Electron flow through the chain powers proton pumping across the inner membrane.
Electrons combine with hydrogen ions and oxygen to form water at the chain's end.
O₂ acts as the final electron acceptor; its absence halts electron transport, stopping hydrogen ion pumping and ATP production.
Hydrogen ions flow down their gradient through ATP synthase.
ATP synthase uses the proton-motive force (hydrogen ion gradient) to phosphorylate ADP, forming ATP.
The inner mitochondrial membrane is impermeable to hydrogen ions, maintaining the proton-motive force.

Two acetyl CoA molecules are produced per glucose molecule.
Occurs in the mitochondrial matrix.
Completes glucose breakdown, releasing CO₂ as waste.
Each cycle requires one acetyl CoA.
Two cycles are needed to completely oxidize one glucose molecule.
Each cycle produces: 2 CO₂, 3 NADH, 1 FADH₂, and 1 ATP.
Total products from two cycles (per glucose molecule): 4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP.
The six original carbons from glucose are released as CO₂.
Only two ATP molecules are directly produced.
Most of the energy is held in the electrons within NADH and FADH₂.
These electrons are used by the electron transport system.

Protein enzymes have specific three-dimensional shapes affected by pH and temperature.
Non-optimal pH or temperature changes the enzyme's shape, reducing its effectiveness.
Many enzymes need nonprotein helpers called cofactors to function.
Cofactors include metal ions like zinc, iron, and copper, which are crucial for catalysis.
Organic cofactors are called coenzymes; vitamins are examples of coenzymes.
Competitive inhibitors compete with the substrate for the enzyme's active site.
They are often chemically similar to the substrate and reduce enzyme efficiency.
Noncompetitive inhibitors bind to another part of the enzyme, not the active site.
This binding changes the enzyme's shape, making the active site nonfunctional.

Catalysts change reaction rates without being altered themselves.
Enzymes are biological catalysts; most are proteins, but RNA (ribozymes) can also act as enzymes.
Activation energy is the energy needed to start a reaction by breaking reactant bonds.
Enzymes lower the activation energy, speeding up reactions without changing the overall free-energy change.
The substrate is the reactant an enzyme acts upon.

Metabolism transforms matter and energy, following the laws of thermodynamics.
Metabolism is the entirety of an organism's chemical reactions, managing material and energy resources.
Catabolic pathways release energy by breaking down complex molecules into simpler ones (e.g., digestion).
Anabolic pathways consume energy to build complex molecules from simpler ones (e.g., muscle protein synthesis).
Energy is the capacity to do work.
Kinetic energy is the energy of motion.
Potential energy is stored energy due to position or structure.
Chemical energy is potential energy stored in molecules' chemical bonds.