Cellular Respiration Overview

Cellular Respiration

• Living organisms require energy to function, even at a microscopic level.
• Cellular respiration is the process that converts chemical energy stored in organic molecules (like glucose) into energy that cells can use, called Adenosine Triphosphate (ATP).
• Reactants of cellular respiration: glucose (C6H12O6) and oxygen (O2)
• Product of cellular respiration: carbon dioxide (CO2), water (H2O), and energy (ATP)
• Cellular respiration occurs in three stages:
  • Glycolysis: occurs in the cytoplasm, splitting glucose into two pyruvate molecules and producing 2 net ATP, 2 NADH, and 2 pyruvate acids. This stage can happen with or without oxygen (aerobic or anaerobic).
  • Krebs Cycle (Citric Acid Cycle): occurs in the matrix of mitochondria, further breaking down pyruvate and producing 2 net ATP, 6 CO2, 8 NADH, and 2 FADH2. This stage requires oxygen.
  • Electron Transport Chain: occurs in the inner membrane of mitochondria, generating the majority of ATP (34 ATP). This stage requires oxygen.
• ATP is the primary energy currency of the cell, used to power essential cellular processes.
• Energy carriers involved in cellular respiration:
  • Adenosine Triphosphate (ATP)
  • Nicotinamide Adenine Dinucleotide (NAD)
  • Flavin Adenine Dinucleotide (FAD)

Types of Cellular Respiration

• Aerobic Respiration: requires oxygen to break down glucose, creating a large amount of ATP (38 ATP).
  • Equation: Glucose + Oxygen → Carbon Dioxide + Water + Energy
• Anaerobic Respiration: occurs in the absence of oxygen, less efficient, producing a small amount of ATP (2 ATP).
  • Equation (Muscles): Glucose → Lactic Acid + Energy
  • Equation (Yeast): Glucose → Ethanol + Carbon Dioxide + Energy
• Key differences between aerobic and anaerobic respiration:
  • Oxygen requirement: Aerobic requires oxygen, anaerobic does not.
  • Location: Aerobic occurs in cytoplasm and mitochondria, anaerobic primarily in cytoplasm.
  • Efficiency: Aerobic is more efficient (38 ATP), anaerobic is less efficient (2 ATP).
  • Products: Aerobic produces CO2 and H2O, anaerobic produces lactic acid (animals) or ethanol and CO2 (yeast).

Photosynthesis

• Photosynthesis is the process that converts light energy into chemical energy (sugars), used by living organisms.
• Occurs in plants and some algae.
• Three main events:
  • Sunlight is converted into chemical energy.
  • Water (H2O) is split into oxygen (O2).
  • Carbon dioxide (CO2) is fixed into sugars (C6H12O6).
• Leaf structure: Chloroplasts contain chlorophyl, a green pigment that absorbs light energy for photosynthesis. Chloroplasts contain flattened discs called thylakoids, stacked into structures called grana. Stroma is the fluid inside the chloroplast.
• Process:
  • Plants absorb water through roots.
  • Leaves take in carbon dioxide from the air.
  • Leaves capture light energy.
  • Light energy is used to convert water and carbon dioxide into sugars and oxygen.
  • Oxygen is released into the air.
  • Plants use sugars for growth.
• Importance:
  • Provides food source for many organisms.
  • Provides energy for life processes.
  • Maintains atmospheric CO2 levels and produces O2.

Importance of Cellular Respiration and Photosynthesis

• Cellular respiration provides energy for the function of all living organisms.
• Photosynthesis is crucial for the production of food, oxygen, and the regulation of atmospheric gases.

SDG Connections

• SDG 3: Good Health and Well-Being:
  • Cellular respiration is fundamental for good health, providing energy for all bodily functions.
• SDG 13: Climate Action:
  • Promoting photosynthesis, especially in urban environments, can contribute to reducing CO2 levels and mitigating climate change.