Test 2-3

Glycolysis Location

Occurs in the cytoplasm.

Inputs of Glycolysis

Glucose, 2 ATP, 2 NAD⁺.

Outputs of Glycolysis

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

Krebs Cycle Location

Takes place in the mitochondrial matrix.

Main Purpose of Krebs Cycle

To extract electrons via NADH and FADH₂ for the ETC.

Electron Transport Chain Location

Occurs in the inner mitochondrial membrane.

Final Electron Acceptor in Aerobic Respiration

Oxygen (O₂), forming water.

ATP Yield from One Glucose in Aerobic Respiration

Up to 36–38 ATP.

Anaerobic Respiration

A form of respiration where electrons are passed through an ETC, but the final electron acceptor is not oxygen.

Common Final Electron Acceptors in Anaerobic Respiration

Sulfate (SO₄²⁻), nitrate (NO₃⁻), carbon dioxide (CO₂), sulfur.

Organisms that Use Anaerobic Respiration

Some prokaryotes (bacteria and archaea) in low-oxygen environments.

Fermentation

An anaerobic process that uses only glycolysis and extra reactions to regenerate NAD⁺.

Why NADH Cannot Use the ETC in Fermentation

Because oxygen (or an alternate final acceptor) isn't available to receive electrons.

Lactic Acid Fermentation

Pyruvate accepts electrons from NADH, forming lactate and regenerating NAD⁺.

Organisms that Use Lactic Acid Fermentation

Muscle cells (under low oxygen), red blood cells, and yogurt bacteria.

Alcohol Fermentation

Pyruvate is first converted into acetaldehyde and CO₂, then into ethanol using NADH.

Products of Alcohol Fermentation

Ethanol, CO₂, and regenerated NAD⁺.

Organisms that Perform Alcohol Fermentation

Yeasts and some bacteria.

Regeneration of NAD⁺ in Aerobic Respiration

NADH donates electrons to the ETC, and oxygen receives them, forming water.

Regeneration of NAD⁺ in Fermentation

NADH gives electrons to pyruvate (or a derivative), regenerating NAD⁺ without the ETC.

Regeneration of NAD⁺ in Anaerobic Respiration

NADH donates electrons to an ETC, which ends with an inorganic molecule instead of oxygen.

Brown Fat

A type of fat tissue specialized for heat generation (thermogenesis), especially in infants and hibernating animals.

Heat Production in Brown Fat

It contains uncoupling proteins that allow protons to flow back into the matrix without going through ATP synthase, releasing energy as heat.

Thermogenesis

The process of generating heat by proton movement without ATP production, often seen in brown fat.

Uncouplers in the ETC

Proteins or molecules that allow protons to bypass ATP synthase, reducing ATP production and releasing heat.

Effect of Uncouplers on ATP Production

They make ATP production less efficient by dissipating the proton gradient, which results in more heat and less ATP.

ATP Synthase Location

An enzyme complex in the inner mitochondrial membrane that synthesizes ATP as H⁺ ions flow through it.

Driving Force for ATP Synthase

The proton gradient created by the ETC (chemiosmosis).

Chemiosmosis

The process by which protons move down their electrochemical gradient through ATP synthase, powering ATP production.

NAD⁺ Role in Glycolysis

NAD⁺ is reduced to NADH, which carries electrons to the ETC.

Importance of Pyruvate for Krebs Cycle

Converted to Acetyl-CoA, which enters the Krebs cycle.

CO₂ Release from Pyruvate

Pyruvate loses a carbon as CO₂, forming a 2-carbon Acetyl-CoA.

CO₂ Release and Glucose Oxidation

Indicates a reduction in the number of carbon atoms, showing how glucose is gradually oxidized and broken down.

CO₂ Released Per Glucose in Krebs Cycle

4 CO₂ (2 per cycle × 2 cycles per glucose).

Krebs Cycle Products Per Glucose

4 CO₂, 6 NADH, 2 FADH₂, 2 ATP.