Overview
The lecture explains the structure and functions of cells, the differences between prokaryotic and eukaryotic cells, and the roles of key organelles and the plasma membrane.
Discovery and Cell Theory
- All living organisms are made of cells, the fundamental unit of life.
- Robert Hooke and Anton van Leeuwenhoek first observed cells with microscopes.
- Schleiden and Schwann stated both plants and animals are made of cells.
- Rudolf Virchow added all cells arise from pre-existing cells.
- The cell theory: all organisms are made of cells and their products; cells arise from existing cells.
Prokaryotic vs Eukaryotic Cells
- Prokaryotic cells lack a membrane-bound nucleus and organelles (ex: bacteria, blue-green algae).
- Eukaryotic cells have a membrane-bound nucleus and membrane-bound organelles (ex: plants, animals, fungi, protists).
- Prokaryotes have a single chromosome (circular DNA), plasmids, 70S ribosomes, and may have cell walls.
- Eukaryotes have 80S ribosomes, a cytoskeleton, and organelles like mitochondria and plastids.
Cell Membrane and Cell Wall
- The plasma membrane is a selectively permeable lipid bilayer controlling movement of substances in/out of the cell.
- Plant cells (and some fungi) have a rigid cell wall outside the plasma membrane.
- The fluid mosaic model describes membrane structure and membrane fluidity.
Cytoplasm and Organelles
- Cytoplasm is a semi-fluid matrix containing organelles and is the site of biochemical reactions.
- Membrane-bound organelles include mitochondria (energy production), endoplasmic reticulum (protein/lipid synthesis), Golgi apparatus (packaging/transport), lysosomes (digestion), and vacuoles (storage).
- Non-membrane-bound organelles include ribosomes (protein synthesis) and centrioles (cell division).
- Plastids (found in plants) include chloroplasts (photosynthesis), chromoplasts (pigment storage), and leucoplasts (nutrient storage).
Nucleus and Chromosomes
- The nucleus contains the genetic material (DNA), nucleolus (rRNA synthesis), and is surrounded by a nuclear envelope with pores.
- Chromosomes are made of DNA and proteins; their structure varies based on centromere position.
Key Terms & Definitions
- Cell Theory — All living things are made of cells; cells arise from pre-existing cells.
- Prokaryote — Cell without a membrane-bound nucleus or organelles.
- Eukaryote — Cell with a membrane-bound nucleus and organelles.
- Plasma Membrane — Selectively permeable boundary of the cell.
- Ribosome — Organelle for protein synthesis; 70S in prokaryotes, 80S in eukaryotes.
- Chromosome — DNA-protein structure carrying genetic information.
- Organelle — Specialized structure within a cell with a distinct function.
Action Items / Next Steps
- Review diagrams of prokaryotic and eukaryotic cell structure.
- Memorize key organelle functions.
- Read textbook sections on cell theory, membrane structure, and organelles.