Overview
This lecture provides an overview of cell structure and function, including why cells are small, the differences between prokaryotic and eukaryotic cells, and the roles of key organelles.
Cell Size and Structure
- Cells are small to allow efficient diffusion of materials like oxygen and carbon dioxide.
- There is an optimal cell size: too small can't fit vital material, too large slows diffusion.
- Cells are complex, featuring a cytoskeleton for structure and transport.
Microscopes and Cell Discovery
- Cells were invisible to scientists until the invention of microscopes.
- Optical microscopes use light and lenses, while electron microscopes use magnets and electrons for higher magnification.
- Electron microscopes require specimens to be dead; new fluorescent microscopes allow for live imaging with dyes.
Types of Cells
- Two main types: prokaryotic (no nucleus) and eukaryotic (has nucleus).
- Bacteria and archaea are prokaryotic; plants, animals, fungi, and protists are eukaryotic.
- All cells have DNA, a cell membrane, cytosol, and ribosomes.
Eukaryotic Cell Organelles and Functions
- Nucleolus: Assembles ribosomes inside the nucleus.
- Nucleus: Contains DNA and regulates cell activity; has pores for material exchange.
- Ribosome: Builds proteins; differs in prokaryotes and eukaryotes.
- Vesicle: Membrane-bound container for transporting materials.
- Rough Endoplasmic Reticulum (ER): Produces proteins and membranes; covered in ribosomes.
- Golgi Apparatus: Modifies, packages, and ships proteins like a UPS center.
- Cytoskeleton: Provides structural support; includes microtubules (compression) and microfilaments (tension).
- Smooth ER: Produces lipids and detoxifies substances.
- Mitochondria: Generates ATP energy; contains its own DNA, evidence for endosymbiotic theory.
- Vacuole: Stores water in plants; maintains turgor pressure; smaller in animals.
- Cytosol: Fluid containing dissolved materials and solutes; supports concentration gradients.
- Lysosome: Contains digestive enzymes; responsible for breaking down material and apoptosis (cell death).
- Centrioles: Help organize cell division; form spindle fibers that move chromosomes.
Key Terms & Definitions
- Diffusion — passive movement of molecules from high to low concentration.
- Cytoskeleton — network of protein fibers for cell structure and movement.
- Organelle — specialized structure within a cell with a specific function.
- Prokaryotic Cell — cell lacking a nucleus (bacteria, archaea).
- Eukaryotic Cell — cell with a nucleus (plants, animals, fungi, protists).
- Apoptosis — programmed cell death, often via lysosome enzymes.
Action Items / Next Steps
- Review and memorize the functions and locations of each organelle.
- Create flashcards for organelle names and functions for practice.
- Pause and quiz yourself on the major organelles and their roles.