Lesson 10: Cell Biology

Cell Biology Reference

Cell Theory

• All living things are made of cells.
• The cell is the basic unit of life.
• All cells come from pre-existing cells.

Prokaryotes vs Eukaryotes

• Prokaryotes: no membrane-bound nucleus (bacteria, archaea). DNA floats in cytoplasm.
• Eukaryotes: membrane-bound nucleus; complex organelles. Animals, plants, fungi, protists.

Key Organelles

• Nucleus: stores DNA; controls cell activity.
• Mitochondria: cellular respiration; ATP production ("powerhouse").
• Ribosome: protein synthesis.
• ER (Rough/Smooth): protein processing (rough) / lipid synthesis (smooth).
• Golgi Apparatus: modifies and packages proteins for export.
• Chloroplast: (plant only) photosynthesis.
• Vacuole: storage; plant cell central vacuole maintains turgor pressure.
• Lysosome: digests waste using enzymes.

Cell Division

• Mitosis: produces 2 genetically identical daughter cells; for growth and repair.
• Meiosis: produces 4 genetically unique haploid cells (gametes) for sexual reproduction.

Membrane Transport

• Diffusion: high → low concentration; no energy needed.
• Osmosis: water movement across semipermeable membrane.
• Active transport: low → high concentration; requires ATP.