Biology Day 2 Lecture Notes
A Tour of the Cell
Early microscope: Anthony van Leeuwenhoek – single lens – ca. 1673
Used microscope to look at fungal cells.
The Cell: first person to coin the word ”cell” to describe the tiniest components of
living systems – plants (Robert Hooke)
In modern telescopes, “dyes” are used to see ultraviolet rays
There are many microscopic techniques.
Different images include surface image and cross image
The Electron Microscope
- Resolution limit of light microscope is about 0,2 microns (size of a small
bacterium, remember 1 micron is .001 mm)
- Magnification limit of about 1000 times
- In 1950’s, the introduction of the electron microscope enabled organelles,
viruses, proteins, etc… to be imaged
- The minimum resolution of a light microscope is about 2 microns, the size of
a small bacterium
- Light microscopes can magnify effectively to about 1000 times the size of the
- At higher magnifications, the image blurs
- Take cells apart to study their components
- Centrifuge is used to fractionate cells and separate their major organelles
- Ultracentrifuges are capable of speeds as fast as 150,000 rpm applying forces
over 1 million times the force of gravity
Cell = simplest collection of matter which has all the properties of life
1. Lowest hierarchical level which is alive.
2. Cell is basic unit of life.
3. Cell performs all functions necessary to live and reproduce.
- Occur in virtually every kind of organism
- Some wreck havoc, others cause no disease or outward sign of their presence
- Often highly specific to host
- Can reproduce only when they enter a cell CELLS – TWO BASIC TYPES:
- pro: before and karyote – nucleus – Examples – bacteria, cyanobacteria,
- no nucleus (genetic information in area called nucleoid
- Visible components – plasma membrane, ribosomes, nucleoid, cytoplasm, cell
wall, pill, flagella, mesosomes, photosynthetic membranes
- Bacteria range in size from approximately as small as the largest viruses to
large enough for single cells to be visible