Overview
This lecture introduces the MCAT Biology series with a focus on Chapter 1: The Cell, covering cell theory, eukaryotic and prokaryotic cells, cellular structures, and tissue organization.
Cell Theory
- Cell theory has four main tenets: all living things are made of cells, the cell is the basic unit of life, all cells arise from preexisting cells, and cells transmit genetic material (DNA).
- Historical figures include Robert Hooke (first observed cells), Anton van Leeuwenhoek (first saw living cells), and Rudolf Virchow (cells arise from other cells).
Eukaryotic Cells Overview
- Eukaryotic cells have a true nucleus and membrane-bound organelles.
- They can be unicellular or multicellular, in contrast to always unicellular prokaryotes.
- The cell membrane and organelle membranes are phospholipid bilayers allowing compartmentalized cellular functions.
Major Eukaryotic Organelles & Functions
- Nucleus: Stores DNA, directs RNA and protein synthesis, surrounded by nuclear envelope with nuclear pores for selective transport.
- Mitochondria: Produce ATP via the citric acid cycle and electron transport chain; contain their own DNA and replicate independently (binary fission); support the endosymbiotic theory.
- Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes, synthesizes proteins for export/membranes.
- Smooth ER: Lipid synthesis, detoxification, calcium storage.
- Golgi Apparatus: Modifies, packages, and sorts proteins/lipids, directs them to destinations, and forms lysosomes.
- Lysosomes: Contain degradative enzymes, break down waste, can induce cell death (autolysis).
- Peroxisomes: Oxidize fatty acids and detoxify harmful substances.
Cytoskeleton
- Made of microfilaments (actin; cell shape, movement, cytokinesis), microtubules (tubulin; transport, cilia, flagella, mitosis), and intermediate filaments (mechanical strength, organelle anchoring).
Tissue Formation
- Eukaryotic cells form specialized tissues for division of labor.
- Epithelial tissue: Covers body, lines cavities, forms parenchyma; classified by layers (simple, stratified, pseudostratified) and shape (cuboidal, columnar, squamous).
- Connective tissue: Supports, forms stroma, produces extracellular matrix (collagen, elastin), provides structural integrity.
Key Terms & Definitions
- Cell theory — Core principles defining cells and their role in life.
- Eukaryote — Organism with membrane-bound nucleus and organelles.
- Prokaryote — Organism lacking nucleus and membrane-bound organelles.
- Organelle — Specialized cell subunit with specific functions.
- Cytoskeleton — Protein filament network providing structural support and movement.
- Parenchyma — Functional tissue of an organ.
- Stroma — Supportive framework of connective tissue.
Action Items / Next Steps
- Review the supplied summary table of organelles and their functions.
- Prepare for detailed study of prokaryotic cells, cell division, and viruses in the next lesson.