Cellular Respiration and Energy Release

Flashcards covering the stages, chemical components, and energy yields of aerobic and anaerobic cellular respiration.

Cellular Respiration

The process by which a fuel, usually glucose, is broken down in the presence of oxygen to form $CO_2$, water, and energy.

Respiration Equation

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$ + Heat + ATP

Mitochondrion

The organelle that serves as the site of cellular respiration, containing an inner membrane, outer membrane, crista, and matrix.

Aerobic respiration

A form of respiration that requires oxygen and consists of three stages: Glycolysis, Krebs cycle, and Oxidative phosphorylation.

Anaerobic respiration

A form of respiration that occurs in the absence of oxygen, often used by bacteria and yeast.

Glycolysis

The first stage of respiration which occurs in the cytoplasm outside the mitochondrion, breaking down glucose into pyruvate.

Energy-requiring steps (Glycolysis)

The phase of glycolysis where 2 ATP are invested to activate glucose and its six-carbon derivatives.

Energy-releasing steps (Glycolysis)

The phase of glycolysis where products are split into three-carbon pyruvate molecules, forming ATP and NADH.

Glycolysis Net Energy Yield

A net yield of 2 ATP and 2 NADH per molecule of glucose.

Coenzymes (NAD+ and FAD)

Molecules that accept electrons and hydrogen to become $NADH$ and $FADH_2$, delivering them to the electron transfer chain.

Krebs Cycle

A series of cyclic reactions occurring in the mitochondrion matrix where pyruvic acid is oxidized, releasing energized hydrogen atoms and $CO_2$.

Acetyl-CoA

A two-carbon acetyl unit combined with coenzyme A, formed during preparatory reactions before entering the Krebs cycle.

Citrate

A six-carbon molecule (C6) formed at the start of the Krebs cycle when an acetyl group carried by CoA combines with oxaloacetate.

Oxaloacetate

A four-carbon molecule (C4) that regenerates at the end of the Krebs cycle to allow the cycle to begin again.

Krebs Cycle Products (Per Turn)

Factors produced include 2 $CO_2$, 3 $NADH$, 1 $FADH_2$, and 1 ATP.

Oxidative Phosphorylation

The final stage of aerobic respiration in the mitochondrion where energy from electron transfers is used to form ATP and water is produced.

ATP Synthase Complex

A structure in the mitochondrion that powers ATP formation using the flow of H+ ions down their concentration gradient.

Chemiosmotic Model

A model describing the process of making ATP using the energy from an H+ gradient created across the mitochondrial membrane.

Typical Energy Yield (Aerobic)

A total of 36 ATP per molecule of glucose (2 from Glycolysis, 2 from Krebs, and 32 from Electron Transport Phosphorylation).

Efficiency of Aerobic Respiration

Approximately 39 percent, with 270 kcal captured in 36 ATP out of 686 kcal released, while the rest is lost as heat.

Fermentation Pathways

Anaerobic pathways that begin with glycolysis and yield only 2 ATP, serving mostly to regenerate $NAD^+$.

Lactate Fermentation

An anaerobic process in animals where pyruvic acid is converted into lactic acid.

Alcoholic Fermentation

An anaerobic process in plants, bacteria, and yeast where pyruvic acid is converted into alcohol (ethanol) and $CO_2$.