Cell Biology Lecture Notes

Introduction to Cells

• Cells: smallest living units of an organism
• Common features of all cells:
  • Cell membrane: separates inside of the cell from its environment
  • Cytoplasm: jelly-like fluid within the cell
  • DNA: genetic material of the cell

Categories of Cells

1. Eukaryotic Cells
   • Contain organelles (nucleus, other specialized parts)
   • Found in plants and animals
   • More advanced and complex
2. Prokaryotic Cells
   • Do not have a nucleus or membrane-enclosed organelles
   • Genetic material not contained within a nucleus
   • Unicellular organisms (e.g., bacteria)

Organelles and Their Functions

• Organelles: specialized parts of a cell with unique jobs

Nucleus

• Control center of the cell
• Contains DNA (genetic material)
• Chromatin: spread-out form of DNA in nuclear membrane
• Chromosomes: condensed DNA structures during cell division
• Nucleolus: makes ribosomes

Ribosomes

• Synthesize or make proteins
• Located in cytoplasm or attached to endoplasmic reticulum (ER)

Endoplasmic Reticulum (ER)

• Rough ER: has ribosomes attached
• Smooth ER: no ribosomes attached
• Membrane-enclosed passageway for transporting materials (e.g., proteins)

Golgi Apparatus (Golgi Body)

• Customizes proteins received from ER by folding them or adding other materials (lipids, carbohydrates)

Vacuoles

• Sac-like structures storing different materials
• Central vacuole (plant cells): stores water

Lysosomes

• Garbage collectors for damaged or worn-out cell parts
• Filled with enzymes to break down cellular debris

Mitochondria

• Powerhouse of the cell
• Site of cellular respiration to make ATP (energy molecules)
• Cells needing more energy have more mitochondria

Cytoskeleton

• Maintains cell shape
• Composed of microfilaments (protein) and microtubules (hollow tubes)

Chloroplasts

• Found in photoautotrophic organisms (e.g., plants)
• Site of photosynthesis
• Contains chlorophyll (green pigment)
• Plant cells also have a cell wall for additional support and protection

Unique Structures in Some Cells

• Cilia: Hair-like projections in the human respiratory tract to trap and expel inhaled particles
• Flagella: Tail-like structure for cell movement; seen in some bacteria and human sperm cells

Summary

• Eukaryotic cells: plant and animal cells with nucleus and membrane-enclosed organelles
• Prokaryotic cells: unicellular organisms without nucleus and organelles
• All cells have a cell membrane, cytoplasm, and genetic material
• Only plant cells have chloroplasts, but both plant and animal cells have mitochondria