Early Microscopy Robert Hooke developed first documented microscope He discovered cell walls of cork and coined the name “cells.” His was a simple light microscope.
Electron Microscopes Use expensive technology to “bounce” electrons off the specimen to produce very highly magnified images. The specimens are killed in the process. Computers are used to enhance color (like this dust mite)
Light Microscopes Light Microscopes use a light source to view specimen Multiple “objectives” are used to produce a variety of magnifications Total magnification = Eyepiece power X Objective power
Cell MovementCells have structures to help them move: Cilia – short hair-like extensions that occur in large numbers Flagella – long, whip- like extensions that occur singly or in pairs.
What limits cell size? DNA Overload – each cell has a limited amount of material. More “stuff” creates too much demand. Difficulty exchanging materials –each cell is limited by the surface area to volume ratio.
Movement through the membrane Diffusion – particles move from areas of greater concentration to areas of lesser concentration. Continues until equilibrium is reached No energy required by the cell
Movement through the membrane Osmosis – the movement of water through a selectively permeable membrane. Continues until both solutions are isotonic No energy required by cell Osmotic pressure: 1. Hypotonic: below strength 2. Hypertonic: above strength
Movement through the membrane Facilitated diffusion - small protein channels in the membrane allow specific molecules to flow through No energy required by the cell
Movements that require Energy Active Transport uses protein channels to move specific molecules against the gradient Endocytosis – engulfs “big stuff” Exocytosis – expelling pockets of “big wastes”