Cell Biology Lecture Notes

Key Concepts

• Cells: Smallest living units of an organism.
• Common Features of All Cells:
  • Cell membrane: Separates the cell from its environment.
  • Cytoplasm: Jelly-like fluid inside the cell.
  • DNA: Genetic material of the cell.

Types of Cells

1. Eukaryotic Cells

• Definition: Cells with organelles, including a nucleus.
• Characteristics:
  • More complex and advanced.
  • Examples: Cells found in plants and animals.

2. Prokaryotic Cells

• Definition: Cells without a nucleus or membrane-enclosed organelles.
• Characteristics:
  • Contain genetic material not enclosed in a nucleus.
  • Always unicellular (e.g., bacteria).

Organelles

• Definition: Specialized parts of a cell with distinct functions.

Nucleus

• Function: Control center of the cell.
• Contains:
  • DNA (genetic material)
  • Chromatin (spread-out DNA)
  • Nucleolus (site of ribosome production)

Ribosomes

• Function: Synthesize/make proteins.
• Location:
  • Free in cytoplasm or attached to the rough Endoplasmic Reticulum (ER).

Endoplasmic Reticulum (ER)

• Types:
  • Rough ER: Has ribosomes attached.
  • Smooth ER: Lacks ribosomes.
• Function: Transport materials like proteins synthesized by ribosomes.

Golgi Apparatus

• Function: Receives proteins from ER, customizes them, and prepares for use.
• Process: Folding proteins and adding materials like lipids/carbohydrates.

Vacuoles

• Function: Store different materials (e.g., central vacuole in plant cells stores water).

Lysosomes

• Function: Garbage collectors that take in damaged cell parts.
• Components: Filled with enzymes to break down debris.

Mitochondria

• Function: Powerhouse of the cell, site of cellular respiration.
• Product: ATP molecules for cell’s energy.
• Note: More mitochondria in energy-demanding cells.

Cytoskeleton

• Function: Maintains cell shape.
• Components:
  • Microfilaments (thread-like, protein)
  • Microtubules (thin hollow tubes)

Chloroplasts

• Function: Site of photosynthesis in plants.
• Characteristics: Contains chlorophyll (green pigment).

Cell Wall

• Function: Provides shape, support, and protection to plant cells.
• Note: Animal cells do not have a cell wall.

Unique Cell Structures

• Cilia: Microscopic hair-like projections in the respiratory tract that help expel particles.
• Flagella: Tail-like structures that aid in cell movement. Only sperm cells in humans have flagella.

Summary

• Eukaryotic cells: Have a nucleus and membrane-enclosed organelles (plant and animal cells).
• Prokaryotic cells: Unicellular, no nucleus/membrane-bound organelles (e.g., bacteria).
• All cells have a cell membrane, cytoplasm, and genetic material. Both plant and animal cells have mitochondria; only plant cells have chloroplasts.