Cell Respiration

Balanced Aerobic Cellular Respiration Equation

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

Outer Membrane of the Mitochondrion

Protects and defines the shape.

Inner Membrane of the Mitochondrion

Contains enzymes for the electron transport chain (ETC) and ATP synthase.

Matrix of the Mitochondrion

The innermost part, where the Krebs cycle takes place.

Cristae

Folds of the inner membrane that increase surface area for the ETC.

Aerobic Respiration

Requires oxygen and produces 36-38 ATP per glucose molecule.

Anaerobic Respiration

Does not require oxygen and produces 2 ATP per glucose molecule.

Glycolysis

Breaks down glucose into pyruvate; occurs in the cytoplasm.

Krebs Cycle (Citric Acid Cycle)

Breaks down pyruvate, producing electron carriers and ATP; occurs in the mitochondrial matrix.

Electron Transport Chain (ETC)

Uses NADH and FADH2 to generate ATP; occurs in the inner mitochondrial membrane.

Why Glycolysis is Considered Anaerobic

It doesn’t require oxygen, making it the oldest step in cellular respiration.

ATP Synthesis in the ETC

Protons flow back through ATP synthase, converting ADP and Pi into ATP.

Organisms Capable of Krebs Cycle & ETC

Eukaryotes (animals, plants, fungi) and some prokaryotes (e.g. some bacteria).

Glycolysis Inputs

Glucose, 2 ATP, NAD⁺.

Glycolysis Outputs

2 Pyruvate, 4 ATP (net 2), 2 NADH.

Krebs Cycle Inputs

2 Pyruvate, NAD⁺, FAD, ADP.

Krebs Cycle Outputs

6 CO₂, 8 NADH, 2 FADH₂, 2 ATP.

Electron Transport Chain Inputs

NADH, FADH₂, O₂, ADP + Pi.

Electron Transport Chain Outputs

Water, ATP.

ATP Yield from Glycolysis

2 ATP (net) and 2 NADH.

ATP Yield from Krebs Cycle

2 ATP (per glucose).

ATP Yield from ETC

Up to 34 ATP.

Function of Electron Transport Chain

Electrons pump protons across the membrane to create a gradient that drives ATP synthesis.

Final Electron Acceptor in ETC

Oxygen, forming water with electrons and protons.

Purpose of Fermentation

To regenerate NAD⁺, required for glycolysis in the absence of oxygen.

Alcoholic Fermentation

Produces ethanol and CO₂; occurs in yeast and some bacteria.

Lactic Acid Fermentation

Produces lactic acid; occurs in muscle cells of humans and some bacteria.

Reversibility of Lactic Acid Fermentation

Can be reversed because lactic acid can be converted back to pyruvate.

Reversibility of Alcoholic Fermentation

Irreversible because ethanol cannot be easily converted back to pyruvate.

Examples of Organisms in Alcoholic Fermentation

Yeast and some bacteria.

Examples of Organisms in Lactic Acid Fermentation

Muscle cells in humans and some bacteria.

Switching Between Aerobic and Anaerobic Respiration During Exercise

Fermentation aids energy production when oxygen supply is exceeded during intense exercise.

Aerobic Respiration Definition

Preferred energy method when oxygen is available.

Anaerobic Respiration Definition

Used when oxygen demand exceeds supply.

Breathing Definition

The process of taking in oxygen and releasing carbon dioxide.

Respiration Definition

The process by which cells produce energy (ATP) from glucose and oxygen.

Electronegative Definition

A measure of an atom’s ability to attract and hold onto electrons.

Fermentation Definition

The metabolic process that regenerates NAD⁺ under anaerobic conditions.