Lecture Notes: Introduction to Cells and Their Organelles

Basic Characteristics of Cells

• Smallest Living Units: Cells are the smallest living units of an organism.
• Common Features: All cells have:
  • Cell Membrane: Separates the interior of the cell from its environment.
  • Cytoplasm: Jelly-like fluid inside the cell.
  • DNA: Genetic material of the cell.

Types of Cells

Eukaryotic Cells

• Characteristics:
  • Have organelles, including a nucleus.
  • More advanced and complex.
  • Found in plants and animals.

Prokaryotic Cells

• Characteristics:
  • No nucleus or membrane-enclosed organelles.
  • Genetic material not contained within a nucleus.
  • Always unicellular organisms, like bacteria.

Organelles and Their Functions

Nucleus

• Control Center: Contains DNA, which dictates cell functions.
• Chromatin and Chromosomes:
  • Chromatin: Spread-out form of DNA.
  • Chromosomes: Condensed form of DNA for cell division.
• Nucleolus: Produces ribosomes.

Ribosomes

• Function: Synthesize proteins.
• Location: Free in cytoplasm or attached to endoplasmic reticulum (ER).

Endoplasmic Reticulum (ER)

• Types:
  • Rough ER: Ribosomes attached; synthesizes proteins.
  • Smooth ER: No ribosomes attached.
• Function: Transports materials through the cell.

Golgi Apparatus

• Function: Modifies, sorts, and packages proteins for use.
• Process: Proteins emerge from ER in vesicles, folded or combined with lipids or carbohydrates.

Vacuoles

• Function: Sac-like structures that store materials.
• Example: Central vacuole in plant cells stores water.

Lysosomes

• Function: Break down cellular debris with enzymes.

Mitochondria

• Function: Powerhouse of the cell, produces ATP through cellular respiration.
• Presence: Found in both plant and animal cells.

Cytoskeleton

• Components: Microfilaments and microtubules.
• Function: Maintains cell shape.

Chloroplasts

• Function: Site of photosynthesis in plant cells.
• Pigment: Contains chlorophyll, a green pigment.

Cell Wall

• Function: Provides shape, support, and protection.
• Presence: Only in plant cells.

Unique Structures in Some Cells

• Cilia: Hair-like projections in respiratory tract cells, trap particles and expel them.
• Flagella: Tail-like structures for movement, present in some bacteria and human sperm cells.

Summary

• Eukaryotic vs Prokaryotic:
  • Eukaryotic: Animal and plant cells with nucleus and organelles.
  • Prokaryotic: Unicellular organisms without nucleus and organelles.
• Common Traits: All cells have a cell membrane, cytoplasm, and genetic material.
• Photosynthesis & Respiration:
  • Chloroplasts for photosynthesis in plant cells.
  • Mitochondria for respiration in all eukaryotic cells.