06_Lecture_Presentation

Introduction to Cellular Energy

• Oxygen in Cellular Respiration: Reactant for breaking down sugars, generating ATP and heat.

• Brown Fat: Has a unique function in cellular respiration, generating heat without ATP, crucial for heat production in small mammals, including humans.

Overview of Cellular Respiration

• Cellular Respiration: Process of aerobic harvesting of energy, divided into stages: glycolysis, citric acid cycle, and oxidative phosphorylation.

• Fermentation: Anaerobic alternative for energy harvesting.

Photosynthesis and Cellular Respiration

• Energy Source: In ecosystems, energy originates from the sun.

• Photosynthesis: Converts sunlight into chemical energy; produces sugar and oxygen from CO2 and water.

• Cellular Respiration: Breaks down sugar into CO2 and water, capturing released energy to form ATP.

Breathing and Cellular Respiration

• Difference: Breathing refers to gas exchange, while cellular respiration is the aerobic process of extracting energy from food.

• O2 Supply: Essential for the attenuation of energy through cell respiration.

ATP Production in Cellular Respiration

• Energy Transfer: Cellular respiration converts energy from glucose to ATP, potentially producing up to 32 ATP molecules per glucose, with some energy lost as heat.

• Chemical Process: Breakdown formula for glucose: C6H12O6 + O2 ➜ CO2 + H2O + ATP + Heat.

Human Energy Use

• Continuous Energy Supply: Essential for activities and maintaining body function.

• Energy Balance: Critical to manage energy intake versus expenditure for health.

Energy Extraction from Fuel

• Electron Transfer: Cells extract energy via oxidation of fuel molecules, transferring electrons to NAD+.

• NADH: Carries electrons to an electron transport chain, with energy released assisting ATP synthesis.

Stages of Cellular Respiration

1. Glycolysis: Occurs in the cytosol, converts glucose to pyruvate.

2. Pyruvate Oxidation and Citric Acid Cycle: Takes place in mitochondria, oxidizes pyruvate and generates electrons.

3. Oxidative Phosphorylation: Involves electron transport and chemiosmosis, major ATP generation.

Oxidative Phosphorylation

• Electron Transport: From NADH/FADH2 to oxygen, forming water, while H+ is pumped into the intermembrane space, driving ATP synthesis through ATP synthase.

Brown Fat and Heat Production

• Brown Fat Functionality: Unique mitochondria that convert fuel to heat instead of ATP, re-evaluating its role in adult metabolism.

Glucose and ATP Yield

• Overall Yield: Each glucose molecule can yield about 32 ATP through cellular respiration, inclusive of substrate-level and oxidative phosphorylation.

Fermentation

• Non-Aerobic ATP Production: Enables ATP production in absence of oxygen, leading to lactate in muscle cells or ethanol and CO2 in yeast.

Evolution of Glycolysis

• Ancient Process: Glycolysis is an ancient metabolic pathway occurring in nearly all cells, highlighting its evolutionary significance.

Diverse Fuel Sources

• Fuel for Cellular Respiration: Cells utilize carbohydrates, fats, and proteins for ATP production, adapting to various nutritional sources.