bio 4.4 12

Anaerobic Processes

Processes that yield energy without the use of oxygen.

Fermentation

A metabolic process that converts sugar to acids, gases, or alcohol, without the use of an electron transport chain. It uses an organic molecule as a final electron acceptor.

Alcohol Fermentation

A process in which pyruvate is decarboxylated and oxidizes NADH, producing CO2, ethanol, and regenerating NAD+.

Lactate Fermentation

A process in which pyruvate reacts with NADH to form lactate and regenerate NAD+.

Lactate Threshold

The point at which lactate production exceeds its clearance from the bloodstream.

Aerobic Respiration

A respiration process using oxygen to convert glucose into ATP, producing a total of 38 ATP.

ATP Yield in Fermentation

Fermentation produces a low ATP yield of 2 ATP (from glycolysis) compared to the 38 ATP in aerobic respiration.

Electron Transport Chain

A series of protein complexes and other molecules that transfer electrons through redox reactions to create a proton gradient.

Oxygen Debt

The amount of oxygen required after exercise to restore the body to its resting state, often resulting from lactate fermentation.

Oxidative Metabolism

Metabolic pathways that use oxygen to produce ATP through the oxidation of fuel molecules.

Two Main Ways Cells Oxidize Fuel for ATP

Fermentation and anaerobic respiration.

Anaerobic Respiration (Mechanism Detail)

Uses an electron transport chain that employs an inorganic substance instead of oxygen to accept electrons.

Role of Yeast and Bacteria in Fermentation

They use fermentation to oxidize NADH into NAD+ instead of using an electron transport chain.

Forms of Fermentation in Eukaryotes

Alcohol (ethanol) fermentation and lactate (lactic acid) fermentation.

Equation for Alcohol Fermentation (Simplified)

\text{pyruvate} + \text{NADH} + \text{H}^+ \rightarrow \text{NAD}^+ + \text{CO}_2 + \text{ethanol}

Overall Equation for Alcohol Fermentation (Glycolysis + Fermentation)

\text{glucose} + \text{2 ADP} + \text{2 P}\text{i} \rightarrow \text{2 ATP} + \text{2 CO}2 + \text{2 ethanol}

Application of Alcohol Fermentation in Baking

Yeast ferments sugar to produce \text{CO}_2 (makes dough rise) and ethanol (evaporates during baking, expanding bubbles for a light texture).

Natural Occurrence Example of Alcohol Fermentation

Happens in rotting fruit, potentially leading to alcohol ingestion by birds.

Explanation for Low ATP Yield in Fermentation

Ethanol, a very energy-rich compound, is produced as waste, meaning much energy from glucose remains unused.

Why Fermentation is Easily Outcompeted

Organisms performing aerobic respiration extract 19 times more energy (38 ATP vs. 2 ATP) from the same food.

When Lactate Fermentation Occurs in Muscle Cells

During demanding activity when ATP need surpasses the oxygen supply rate to the electron transport chain.

What Happens to Excess Pyruvate in Cytosol During Lactate Fermentation

It's converted to lactate, regenerating NAD+ to sustain high glycolysis and ATP production.

Fate of Lactate Fermentation Products After Exercise

The reaction reverses, regenerating pyruvate and NADH, which are then oxidized by the citric acid cycle and electron transport chain.

Primary Location of Lactate Fermentation

The cytosol.

How Lactate is Cleared from Muscles

Transported to the liver and oxidized back to pyruvate to prevent muscle buildup.

Oxygen Debt Mitigation Strategy

Taking deeper and more frequent breaths to supply large quantities of oxygen.

Location of Electron Transport Chain in Anaerobic Prokaryotes

On internal membrane systems derived from the plasma membrane.

Inorganic Electron Acceptors Used by Anaerobic Prokaryotes (besides O2)

\text{SO}4^{2-} , \text{NO}3^- , and \text{Fe}^{3+} .

Typical Habitat for Organisms Using Non-Oxygen Electron Acceptors

Underground environments.

Cause of Rotten Egg Smell in Wetlands

Hydrogen sulfide ( \text{H}_2\text{S} ) released by sulfur-reducing bacteria performing anaerobic respiration.