Overview
This lecture covers the discovery, structure, and functions of cells, including cell theory, types of cells (prokaryotic and eukaryotic), organelles, and cellular membranes.
Discovery and Cell Theory
- All living organisms are made up of cells, the basic unit of life.
- Cells were first observed by Anton van Leeuwenhoek using a microscope.
- Robert Brown identified the cell nucleus.
- Matthias Schleiden and Theodor Schwann proposed that plants and animals are made of cells.
- Rudolf Virchow stated that all cells arise from pre-existing cells.
Types of Cells: Prokaryotic vs. Eukaryotic
- Prokaryotic cells lack a membrane-bound nucleus and membrane-bound organelles (e.g., bacteria).
- Eukaryotic cells have a membrane-bound nucleus and organelles (e.g., plants, animals, fungi).
- Prokaryotes typically have a cell envelope (glycocalyx, cell wall, plasma membrane) and plasmids.
Cell Structure and Organelles
- Eukaryotic cells contain cytoplasm, organelles, and a nucleus with chromosomes (DNA).
- Membrane-bound organelles include mitochondria, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles.
- Non-membrane-bound organelles include ribosomes and centrioles.
- Plant cells have a cell wall, central vacuole, and plastids (chloroplasts, chromoplasts, leucoplasts).
- Animal cells have centrioles and no cell wall.
Cell Membrane and Transport
- The plasma membrane is a lipid bilayer with embedded proteins; described by the fluid mosaic model.
- Selectively permeable: allows certain substances to pass via diffusion, facilitated diffusion, osmosis, or active transport.
- Active transport moves substances against the concentration gradient using ATP (e.g., sodium-potassium pump).
Specialized Structures and Organelles
- Cilia and flagella are extensions for movement, with a 9+2 arrangement of microtubules.
- The endomembrane system coordinates synthesis, packaging, and transport of proteins and lipids.
- Mitochondria are the site of ATP production (cellular respiration).
- Chloroplasts in plants perform photosynthesis and contain stacks of thylakoids (grana).
- Nucleus contains the nucleolus (ribosome synthesis), chromatin (DNA + proteins), and chromosomes.
Key Terms & Definitions
- Cell Theory — all living organisms 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 — lipid bilayer enclosing the cell, controlling substance passage.
- Organelle — specialized cell structure with specific functions.
- Ribosome — non-membrane-bound organelle for protein synthesis.
- Mitochondria — organelle for energy (ATP) production.
- Chloroplast — plant organelle for photosynthesis.
- Nucleus — control center containing genetic material.
- Chromosome — condensed DNA structure containing genetic information.
Action Items / Next Steps
- Review diagrams of plant, animal, and prokaryotic cells.
- Memorize key organelle functions and differences between cell types.
- Prepare for quiz on cell theory and cell structures.