Overview
This lecture introduces how cells are studied, compares types of microscopes, outlines cell theory, and explains the significance of cells in organisms.
The Role of Cells in Organisms
- Cells are the smallest unit of living things and form the basis of all organisms.
- In multicellular organisms, similar cells form tissues, which combine into organs, organ systems, and ultimately organisms.
- Cells are classified as either prokaryotic (bacteria, archaea) or eukaryotic (animals, plants, fungi, protists).
Microscopy: Tools for Studying Cells
- Microscopes are essential for studying cells, which are usually too small to be seen unaided.
- Micrographs are images of cells taken with microscopes.
Light Microscopes
- Light microscopes use visible light and lenses to magnify specimens, offering up to 400x magnification (1,000x with oil immersion).
- They are suitable for viewing living cells, but require staining to see cell components, which usually kills the cells.
- Images appear inverted, and specimens must be thin or translucent for light to pass through.
- Dissecting microscopes have lower magnification (20–80x), provide a three-dimensional view, and can examine larger or thicker specimens.
Electron Microscopes
- Electron microscopes use electron beams for higher magnification and resolution.
- Scanning electron microscopes (SEM) scan surfaces, revealing cell surface details; transmission electron microscopes (TEM) show internal structures.
- Preparing specimens for electron microscopy kills the cells.
Cell Theory
- The unified cell theory states: all organisms are made of one or more cells, the cell is the basic unit of life, and all cells arise from existing cells.
- Key contributors include Robert Hooke, Antony van Leeuwenhoek, Matthias Schleiden, and Theodor Schwann.
Careers: Cytotechnologist
- Cytotechnologists examine cells under microscopes to detect diseases, such as cervical cancer, and assist pathologists in diagnosis.
- Early detection by cytotechnologists can improve treatment outcomes.
Key Terms & Definitions
- Cell — The smallest unit of a living organism.
- Prokaryotic — Cells without a nucleus (e.g., bacteria, archaea).
- Eukaryotic — Cells with a nucleus (e.g., animals, plants).
- Microscope — Tool used to magnify small objects like cells.
- Micrograph — An image taken through a microscope.
- Magnification — Degree to which an object’s image is enlarged.
- Resolving Power — Ability to distinguish two close structures as separate.
- Dissecting Microscope — Microscope for viewing larger or three-dimensional specimens at low magnification.
- Electron Microscope — Uses electrons for high-resolution cell imaging.
- Cell Theory — All living things are made of cells, cells are life’s basic unit, and all cells come from other cells.
- Cytotechnologist — Cell specialist who identifies abnormal changes in cell samples.
Action Items / Next Steps
- Try the HowBig interactive to explore cell sizes.
- Review the differences between prokaryotic and eukaryotic cells.
- Summarize the principles of cell theory for study.