Cell Biology Notes

Introduction

• Cells are the smallest living units of an organism.
• All cells share three common components:
  • Cell membrane: Separates the inside of the cell from its environment.
  • Cytoplasm: Jelly-like fluid inside the cell.
  • DNA: Genetic material of the cell.

Categories of Cells

1. Eukaryotic Cells
   • Have organelles, including:
     • Nucleus: Control center of the cell, contains DNA.
     • More advanced and complex (found in plants and animals).
2. Prokaryotic Cells
   • Lack a nucleus and membrane-enclosed organelles.
   • Genetic material is not contained within a nucleus.
   • Always unicellular (e.g., bacteria).

Organelles

• Definition: "Little organ"; specialized parts of a cell with unique functions.

Nucleus

• Contains DNA which dictates cell functions.
• Chromatin: Spread out form of DNA.
• DNA condenses into chromosomes during cell division.
• Contains nucleolus where ribosomes are produced.

Ribosomes

• Synthesizes (makes) proteins.
• Can float freely in cytoplasm or attach to Endoplasmic Reticulum (ER).

Endoplasmic Reticulum (ER)

• Types:
  • Rough ER: Has ribosomes attached.
  • Smooth ER: No ribosomes attached.
• Function: Membrane-enclosed passageway for transporting materials (e.g., proteins).

Golgi Apparatus

• Receives proteins and materials from ER.
• Customizes proteins into usable forms (folding, adding lipids or carbohydrates).

Vacuoles

• Sac-like structures for storing materials (e.g., water in plant cells).

Lysosomes

• Garbage collectors of the cell.
• Contains enzymes to break down damaged cell parts.

Mitochondria

• Powerhouse of the cell.
• Produces ATP during cellular respiration for energy.
• More mitochondria in cells that require more energy.

Cytoskeleton

• Maintains cell shape.
• Composed of:
  • Microfilaments: Thread-like structures made of protein.
  • Microtubules: Thin hollow tubes.

Chloroplasts (in Plant Cells)

• Site of photosynthesis.
• Contains chlorophyll, giving plants their green color.

Cell Wall (in Plant Cells)

• Provides structure, support, and protection.
• Animal cells do not have a cell wall.

Unique Cell Structures

• Cilia: Microscopic hair-like projections (found in human respiratory tract).
  • Helps trap and expel inhaled particles.
• Flagella: Tail-like structures for movement (found in some bacteria and sperm cells).

Summary

• Eukaryotic Cells: Have a nucleus and membrane-enclosed organelles (e.g., plant and animal cells).
• Prokaryotic Cells: Unicellular organisms without a nucleus or membrane-enclosed 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.