Lecture Notes: Lysosomes and Mitochondria

Lysosomes

Structure and Composition

• Origin: Produced by the Golgi apparatus.
• Structure: Single membrane organelle.
• Contains: Hydrolytic enzymes which break down proteins, carbohydrates, and lipids.
• Size: Varies from 100 nanometers to 1000 nanometers.

Visibility

• Light Microscope:
  • Lysosomes may be visible due to their size range.
  • Difficult to see clearly due to their single membrane structure.
  • Visible as granulations in neutrophils under light microscope.
• Electron Microscope:
  • Provides clearer visibility of the lysosome structure.

Function

• Breakdown: Responsible for breaking down old or damaged organelles, e.g., mitochondria.
• Process: Enzymes from lysosome fuse with the organelle and break it down.
• Outcome: Parts may be repurposed or excreted from the cell.

Mitochondria

Structure

• Membrane: Double membrane organelle.
  • Outer Membrane: Smooth.
  • Inner Membrane: Folded, called cristae.
• Origin: Derived from prokaryotes (endosymbiotic theory).
• Contains:
  • 70S Ribosomes.
  • Circular Naked DNA.
• Matrix: Fluid-filled space for chemical reactions like aerobic respiration.

Comparison with Nucleus

• Nuclear Membrane: Also double membrane.
  • DNA: Linear with histone proteins (chromatin).
  • Connection: Rough endoplasmic reticulum can connect to nuclear membrane, has 80S ribosomes.

Function

• ATP Production: Mitochondria are the 'powerhouse' of the cell, producing ATP.
• Role of ATP: Essential for muscle contraction, protein synthesis, antibody production, and active transport.

Visibility

• Light Microscope: Mitochondria can be stained but detail is limited.
• Electron Microscope:
  • Provides detailed images.
  • Visible structures: outer and folded inner membrane, matrix.

Note on Ribosomes

• Types:
  • 70S Ribosomes: Found in mitochondria, slightly smaller.
  • 80S Ribosomes: Found on rough endoplasmic reticulum.
• Unit: 'S' refers to Svedberg unit (density).

Additional Points

• Mitochondria Memes: Known as the "powerhouse of the cell" in popular culture.