Lecture Notes: Introduction to Cells

Basic Properties of Cells

• Cells are the smallest living units of an organism.
• Common features across all cells:
  • Cell Membrane: Separates the inside of the cell from the environment.
  • Cytoplasm: Jelly-like fluid inside the cell.
  • DNA: Genetic material of the cell.

Categories of Cells

Eukaryotic Cells

• Contain organelles, including a nucleus.
• More advanced and complex.
• Found in plants and animals.

Prokaryotic Cells

• No nucleus or membrane-enclosed organelles.
• Genetic material is not contained within a nucleus.
• Always unicellular, e.g., bacteria.

Organelles and Their Functions

• Organelles: Specialized cell parts with unique functions.

Nucleus

• Control center of the cell.
• Contains DNA.
• DNA dictates cell function and behavior.
• Chromatin: Spread-out form of DNA.
• Chromosomes: Condensed DNA structures for cell division.
• Nucleolus: Produces ribosomes.

Ribosomes

• Synthesize proteins.
• Found in cytoplasm or attached to the endoplasmic reticulum (ER).

Endoplasmic Reticulum (ER)

• Rough ER: Has ribosomes, involved in protein synthesis.
• Smooth ER: Lacks ribosomes.
• Transports materials like proteins.

Golgi Apparatus

• Customizes proteins by folding or adding lipids/carbohydrates.

Vacuoles

• Sac-like structures for storage.
  • Central Vacuole in plants stores water.

Lysosomes

• Garbage collectors of the cell.
• Contain enzymes to break down cell debris.

Mitochondria

• Powerhouse of the cell.
• Produces ATP through cellular respiration.
• Present in both animal and plant cells.

Cytoskeleton

• Maintains cell shape.
• Composed of microfilaments and microtubules.

Chloroplasts (Plant Cells)

• Site of photosynthesis.
• Contains chlorophyll, a green pigment.

Cell Wall (Plant Cells)

• Provides shape, support, and protection.
• Not present in animal cells.

Special Cell Features

• Cilia: Hair-like structures in respiratory tract cells to expel particles.
• Flagella: Tail-like structure in some bacteria and sperm cells for movement.

Summary

• Eukaryotic cells: Plant and animal cells with nucleus and organelles.
• Prokaryotic cells: Unicellular, without nucleus and organelles.
• Common cell features: Cell membrane, cytoplasm, and DNA.
• Chloroplasts in plant cells only, while mitochondria are in both plant and animal cells.