Lysosomes: Structure and Function

Lysosomes

Definition and Function

• Lysosomes are membrane-bound organelles found in eukaryotic cells
• Primary function: cellular digestion and recycling of cellular waste and foreign substances
• Contain digestive enzymes and acids that break down and degrade macromolecules

Structure

• Surrounded by a single membrane
• Internal pH is acidic (around 4.5-5.5) to facilitate enzymatic activity
• Contain a variety of hydrolytic enzymes, including proteases, lipases, and nucleases

Formation and Fusion

• Formed through the fusion of vesicles from the Golgi apparatus and endoplasmic reticulum
• Can fuse with phagosomes (vesicles containing foreign particles or microorganisms) to form phagolysosomes
• Can also fuse with autophagosomes (vesicles containing cellular waste) to form autophagolysosomes

Cellular Processes

• Autophagy: lysosomes break down and recycle damaged or dysfunctional cellular components
• Heterophagy: lysosomes break down and recycle foreign substances and microorganisms
• Cellular defense: lysosomes can fuse with phagosomes to destroy ingested pathogens

Diseases Associated with Lysosomal Dysfunction

• Lysosomal storage diseases: inherited disorders resulting from defective lysosomal enzymes
  • Examples: Tay-Sachs disease, Gaucher disease, Fabry disease
• Other diseases: cancer, neurodegenerative disorders, and immune disorders have been linked to lysosomal dysfunction

Lysosomes

Definition and Function

• Membrane-bound organelles found in eukaryotic cells responsible for cellular digestion and recycling of cellular waste and foreign substances
• Primary function involves breaking down and degrading macromolecules using digestive enzymes and acids

Structure

• Single-membrane organelle with an internal acidic pH (around 4.5-5.5) to facilitate enzymatic activity
• Contains a variety of hydrolytic enzymes, including proteases, lipases, and nucleases

Formation and Fusion

• Formed through the fusion of vesicles from the Golgi apparatus and endoplasmic reticulum
• Can fuse with phagosomes to form phagolysosomes and break down foreign particles or microorganisms
• Can also fuse with autophagosomes to form autophagolysosomes and break down cellular waste

Cellular Processes

• Autophagy: lysosomes break down and recycle damaged or dysfunctional cellular components
• Heterophagy: lysosomes break down and recycle foreign substances and microorganisms
• Cellular defense: lysosomes can fuse with phagosomes to destroy ingested pathogens

Diseases Associated with Lysosomal Dysfunction

• Lysosomal storage diseases: inherited disorders resulting from defective lysosomal enzymes
• Examples of lysosomal storage diseases: Tay-Sachs disease, Gaucher disease, Fabry disease
• Lysosomal dysfunction has also been linked to cancer, neurodegenerative disorders, and immune disorders

Newton's Laws

• An object at rest remains at rest, and an object in motion remains in motion, unless acted upon by an external force (Law of Inertia)
• Force is equal to mass multiplied by acceleration (F = ma), where:
  • F is force in Newtons (N)
  • m is mass in kilograms (kg)
  • a is acceleration in meters per second squared (m/s²)
• For every action, there is an equal and opposite reaction (Law of Action and Reaction)

Inertia

• Inertia is the tendency of an object to resist changes in its motion
• There are two types of inertia:
  • Translational Inertia: resistance to changes in linear motion
  • Rotational Inertia: resistance to changes in rotational motion
• Examples of inertia include:
  • A car maintaining its velocity on a flat road
  • A spinning top maintaining its rotational motion

Friction

• Friction is a force that opposes motion between two surfaces in contact
• There are four types of friction:
  • Static Friction: friction between two surfaces that are not moving relative to each other
  • Kinetic Friction: friction between two surfaces that are moving relative to each other
  • Rolling Friction: friction between a rolling object and a surface
  • Fluid Friction: friction between an object and a fluid (e.g., air or water)
• Factors that affect friction include:
  • Surface Roughness: rougher surfaces increase friction
  • Normal Force: increasing the normal force between surfaces increases friction
  • Surface Area: increasing the surface area in contact increases friction