Lysosomes: Structure and Function

Study Notes

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

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

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

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

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

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

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

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

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

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

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 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 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