Crash Course Biology: Cellular Respiration

Introduction

• Mitochondria are often referred to as the "powerhouse of the cell."
• They convert energy from food and oxygen into ATP, the energy currency of cells.
• Cellular respiration is the process that enables this energy conversion.

Role of ATP

• ATP (adenosine triphosphate) acts like a rechargeable battery for cells.
• It powers cellular processes crucial for maintaining homeostasis.
• Humans require over 100 pounds of ATP daily, highlighting its importance.

Types of Respiration

• Aerobic Respiration: Utilizes oxygen to release energy and store it in ATP.
• Anaerobic Respiration: Energy release without oxygen (e.g., bacteria).
• Fermentation: Anaerobic process used in food and drink production like sourdough and kombucha.

Cellular Respiration Process

Stage 1: Glycolysis

• Occurs in the cytoplasm.
• Breaks down glucose into pyruvate, producing 2 ATP and NADH.
• Involves 10 enzymatic reactions.

Stage 2: Citric Acid Cycle (Krebs Cycle)

• Occurs in mitochondria.
• Pyruvate is oxidized, producing CO2, ATP, NADH, and FADH2.
• Each glucose molecule results in two cycles.

Stage 3: Oxidative Phosphorylation

• Occurs in mitochondria.
• Involves electron transport chain and ATP synthase.
• Produces the bulk of ATP (around 30 ATP per glucose molecule).
• Creates a proton gradient used to power ATP synthase.

Summary of Cellular Respiration

• Glycolysis: Glucose → Pyruvate + ATP + NADH
• Citric Acid Cycle: Pyruvate → CO2 + ATP + NADH + FADH2
• Oxidative Phosphorylation: NADH + FADH2 + O2 → ATP + H2O

Importance

• Cellular respiration is fast, generating millions of ATP molecules per second per cell.
• Mitochondria are essential for this process, affirming their role as the "powerhouse of the cell."

Next Topic

• Upcoming lecture will focus on Photosynthesis, a crucial chemical process on Earth.

Additional Resources

• Educators can access resources at biointeractive.org/crashcourse.
• Support Crash Course through Patreon.