Cell Respiration Summary

OVERVIEW OF CELL RESPIRATION

• Goal: Produce energy as ATP.

• Carbohydrates (glucose) are the primary energy source.

• All eukaryotic cells perform cellular respiration.

REACTION COMPONENTS

Reactants:

• Glucose: $C<em>6H</em>{12}O_6$

• Oxygen: $O_2$

  Products:

• Carbon Dioxide: $CO_2$

• Water: $H_2O$

• Note: ATP generated is NOT a product but is energy released.

MITOCHONDRIA STRUCTURE

• Parts:

  • Inner Membrane: Folds (cristae) increase surface area for ATP production.

  • Matrix: Contains DNA, ribosomes; produces its own proteins.

STEPS OF CELL RESPIRATION

1. Glycolysis:

   • Breaks down glucose into pyruvate in the cytosol.

   • Produces 2 ATP (net).

2. Pyruvate Oxidation:

   • Converts pyruvate into Acetyl CoA (producing $CO_2$).

3. Krebs Cycle:

   • Processes Acetyl CoA, generating electron carriers (NADH, FADH2).

4. Electron Transport Chain (ETC):

   • Creates a proton gradient to produce ATP. (34 ATP yield)

GLYCOLYSIS

• Converts 1 glucose to 2 pyruvate.

• Produces a total of 4 ATP, consumes 2 ATP (net yield: 2 ATP).

• Processes 10 steps involving ADP, NAD+, and G3P.

NADH AND FADH2

• Serve as electron carriers, generated primarily in glycolysis and Krebs cycle.

• NADH is utilized in the ETC.

FERMENTATION TYPES

• Lactic Acid Fermentation:

  • Converts pyruvate to lactic acid during O2 deficiency (producing 2 ATP).

• Alcohol Fermentation:

  • Converts pyruvate to ethanol and $CO_2$ (producing 2 ATP), occurs in yeast.

KREBS CYCLE

• Completes oxidation of pyruvate to produce electron carriers.

• Yields:

  • 2 ATP

  • 6 NADH

  • 2 FADH2

• Each turn processes Acetyl CoA (2 turns per glucose).

ELECTRON TRANSPORT CHAIN (ETC)

• Located in the cristae of mitochondria.

• Uses electrons from NADH and FADH2 to pump protons (H+) across the membrane, creating a gradient.

• Facilitates ATP production via oxidative phosphorylation (total of ~36 ATP).

IMPORTANCE OF OXYGEN

• Acts as the final electron acceptor in the ETC.

• Without it, cells cannot produce ATP, leading to energy depletion and cell death.

SUMMARY OF CELL RESPIRATION

• Includes glycolysis, pyruvate oxidation, Krebs cycle, and ETC.

• Produces ATP through substrate-level phosphorylation and oxidative phosphorylation.

In the Pyruvate Oxidation step of cellular respiration, no ATP is produced directly; instead, it produces one molecule of $CO_2$ and converts pyruvate to Acetyl CoA. In the Krebs Cycle, a total of 2 ATP is produced per glucose molecule (as each glucose molecule generates two Acetyl CoA, leading to two turns of the Krebs Cycle). Therefore, the total ATP produced in these two steps combined is 2 ATP.