Overview
This lecture provides an overview of cell structure, types of cells, and the functions of major organelles, highlighting how cell components relate to their functions.
Why Cells Are Small
- Cells are small so materials can efficiently diffuse in and out.
- There is an optimal size: small enough for efficient diffusion, large enough to contain necessary components.
- DNA and cellular machinery must fit inside the cell.
Microscopes and Cell Discovery
- Cells were invisible to scientists until microscopes were invented.
- Optical microscopes use light and lenses to magnify images.
- Electron microscopes use magnets to focus electrons for higher magnification.
- Electron microscopy requires specimens to be dead and sometimes coated with metal.
- Fluorescent optical microscopes use dyes to visualize living and dead cells.
Types of Cells
- Prokaryotic cells lack a nucleus; only bacteria and archaea are prokaryotic.
- Eukaryotic cells have a nucleus; include plants, animals, fungi, and protists.
- All cells have DNA, a cell membrane, cytosol, and ribosomes.
Eukaryotic Cell Organelles and Functions
- Nucleolus: Area inside the nucleus where ribosomes are assembled.
- Nucleus: Contains DNA; controls cell activities through genetic information.
- Ribosome: Builds proteins; consists of small and large subunits.
- Vesicle: Membrane-bound container that moves materials in the cell.
- Rough Endoplasmic Reticulum (Rough ER): Produces proteins and membranes; ribosomes attached.
- Golgi Apparatus: Modifies, packages, and ships proteins; like the cell’s shipping center.
- Cytoskeleton: Provides structural support; consists of microtubules (compression) and microfilaments (tension).
- Smooth Endoplasmic Reticulum (Smooth ER): Produces lipids; detoxifies toxins.
- Mitochondria: Generates ATP energy; believed to be from endosymbiotic origin; has own DNA.
- Vacuole: Large in plant cells for storing water and maintaining pressure; small in animal cells.
- Cytosol: Fluid with dissolved solutes inside the cell; contains concentration gradients.
- Lysosome: Contains digestive enzymes; breaks down material and involved in cell death (apoptosis).
- Centriole: Helps with cell positioning and spindle formation during cell division; absent in higher plants.
Key Terms & Definitions
- Diffusion — passive movement of substances from high to low concentration.
- Organelle — specialized structure within a cell with a specific function.
- Apoptosis — programmed cell death.
- Endosymbiotic theory — explains mitochondria's origins as formerly independent bacteria.
Action Items / Next Steps
- Review and memorize the functions and locations of major cell organelles.
- Make flashcards for organelle names, structures, and functions for self-testing.