Unit 3 Chapter 1A (Microscopy & Intro to the Cell) Flashcards
(36 cards)
Robert Hooke
First person to look at a plant through a microscope
Cellulae
Tiny compartments
Cell Theory
Living things are composed of cells and all cells come from other cells
Light Microscope
Visible light passes through a sample and glass lens. Passes through the ocular lens and then objective lens.
- Light is bent to magnify image of the specimen
- Earliest type of microscope
- Image projected into eye or camera
Magnification
The increase in an object’s image size
Resolution
Measure of the clarity of an image
- The ability to distinguish 2 nearby objects as being separate
Resolution of a human eye
0.1 - 0.2mm
Resolution of a light microscope
0.2 microns
- Resolution will not improve after its been magnified about 1000x
Electron Microscopes
Focuses beams of electrons through a specimen sample
- Electromagnets bend the electron path & magnify image
- Images are always black & white
- Use began in the 1950s
Scanning EM (SEM)
Studying the detailed architecture of a cell
- Sample is usually coated with thin film of gold
- Electrons excite the gold atoms
- Electrons are scattered and detected by a device that prjects an image into a screen
- 3D Image
Transmission EM (TEM)
Electron beam passed through a thin section of a specimen
- Stains with heavy metal coat certain types of cellular structures
- Electrons are scattered by the more densely stained parts
- Electrons are detected and an image is made
Electron Microscopy Limitation
Can’t be use to look at living samples
- Due to the specimen having to be broken up
Light Microscopy Limitation
Many parts of a cell and some full microorganisms are too small to see
Minimum Size of a Cell
Large enough to store enough DNA, proteins, and structures to survive & reproduce
Max. Size of a Cell
Influenced by geometry
- Enough surface area to service the full cell volume
Surface to Volume Ratio
A large cell has more surface area than a small cell but lower surface-to-volume ratio
Types of Cells
Prokaryotic Cells & Eukaryotic Cells
Prokaryotic Cells
First cells to evolve and lived for about 1.5 billion years before eukaryotic cells evolved
- Bacteria & Archaea
- Small, simple cell structure
Eukaryotic Cells
Evolved from prokaryotic cells about 1.8 billions years ago
- All higher forms of life like plants, animals, fungi
- Larger, more complex cells
Plasma Membrane (Cell Membrane)
Membrane that surrounds the cell. A flexible boundary between the living cell and its surrounding environments.
- Very thin
- Phospholipid bilayer
Characteristics of the Cell Membrane
- Proteins are embedded in the lipid bilayer
- Hydrophobic regions embedded in membrane
- Hydrophilic regions protrude into the aqueous solutions inside or out the membrane
Plasma Membrane Function
Regulates flow of material in and out of cells
What can pass through the Cell Membrane?
- Small non-polar molecules (O2, CO2)
- Polar Compounds (water, ions, etc)
- Large Molecules (polar and non-polar)
Channel Proteins
Forms a tunnel through the cell membrane which helps polar compounds get through.
