Mitochondria in Eukaryotic Cells

Introduction to Mitochondria

• Membrane-enclosed organelles.
• Responsible for producing most of the energy used by the cell.
• Energy produced in the form of ATP (Adenosine Triphosphate).
• Referred to as the "nuclear power plant" of the cell.

Symbiotic Theory

• Explains the origin of mitochondria in eukaryotic cells.
• Eukaryotic cells engulfed a prokaryotic cell, such as bacteria.
• This prokaryotic cell evolved into mitochondria.

Functions of Mitochondria

• Energy Production: Main function is ATP synthesis.
• Programmed Cell Death (Apoptosis): Release molecules that lead to cell death.
  • Important in development (e.g., formation of fingers).
• Calcium Signaling: Interaction with the endoplasmic reticulum membrane.
• Cellular Differentiation: Guides undifferentiated cells into specialized cells (e.g., muscle cells, nerve cells).

Structure of Mitochondrion

• Outer Membrane:

  • Phospholipid bilayer similar to cell membrane.
  • Contains large integral proteins called porins for molecule transport.
  • Allows passage of small molecules like pyruvate and NADH via facilitated diffusion.

• Inner Membrane:

  • High protein concentration, impermeable to ions and small molecules.
  • Contains proteins for transporting molecules into the mitochondrial matrix.
  • Houses electron transport chain (ETC) proteins for setting up electrochemical gradients.
  • Crucial for ATP synthesis.

• Cristae:

  • Infoldings in the inner membrane to increase surface area.

• Intermembrane Space:

  • Region between outer and inner membranes.
  • Concentration of ions and small molecules similar to cytosol.
  • Different protein composition compared to cytosol due to impermeability.

• Mitochondrial Matrix:

  • Contains proteins for the citric acid cycle (Kreb's cycle).
  • Location for ATP production with the help of ETC.
  • Contains mitochondrial DNA and RNA.

Importance of Mitochondrial Structures

• Outer Membrane: Allows necessary molecules to pass into intermembrane space.
• Inner Membrane: Essential for ATP production and maintaining molecule gradients.
• Cristae: Increases the efficiency of inner membrane functions.
• Matrix: Site of critical metabolic processes and genetic material.

Conclusion

Mitochondria are essential organelles in eukaryotic cells, performing key functions from energy production to supporting cellular processes such as apoptosis and differentiation. Understanding their origin, structure, and roles provides insight into their vital contributions to cellular life.