Chp 7: Cell Structure and Function 7. 1 Microscopes, Cell Theory 7 Chp 7: Cell Structure and Function 7.1 Microscopes, Cell Theory 7.2 Organelles 7.3 Cell Membrane

Microscopes Chapter 7.1

Microscopes invented in the late 1500s. Robert Hooke Microscopes invented in the late 1500s. Looked at cork and saw it had “a lot of little boxes” The boxes looked like little rooms that monks lived in called cells, so he called them “cells”. (1665)

Two Types of Microscopes Light Microscope- light passes through one or more lenses to produce an enlarged image Electron Microscope- forms an image using a beam of electrons rather than light

Micrograph- Images produced by a microscope Microscopes Cont… Micrograph- Images produced by a microscope Micrographs will often include the resolution as well as what kind of micrograph it is (LM) Light micro (TEM) Transmission electron micro) (SEM) scanning electron micro.)

Magnification- is the ability to make an image appear larger than its actual size. Ex. 200x: 200 times larger than its actual size Resolution- is a measure of the clarity of a image. **High magnification and good clarity are needed to see objects clearly.

Compound Light Microscope Have lower magnification but can be used to view living cells. Compound means uses two lenses Objective lens- closest to the object, collects light (ex.40x) then sends image to…. Ocular lens (ex.10x) in the eyepiece Both lenses magnify. When put together… 40 x 10 = 400x (total magnification)

Light Microscopes Total magnification of up to 2,000x. They can view things as small as .5 micrometers in diameter. To see smaller, the wavelength of the light beam must be shorter than visible light.

Needs to be a vacuum so electrons don’t bounce off atoms in the air Electron Microscopes Can have a magnification of up to 200,000x- can study structures inside of cells Needs to be a vacuum so electrons don’t bounce off atoms in the air Because a vacuum is needed, can’t view living cells with an electron microscope

Transmission Electron Microscope An electron beam is directed at a thin slice of specimen that is stained with metal ions Some structures stain more heavily than others Heavy stained parts absorb electrons Lightly stained parts allow electrons to pass through that then hit a screen behind to reveal the image. Always in black and white

Scanning Electron Microscope Show 3-D Specimen is coated and electrons bounce off onto a sheet to show image Also in black and white but can be put into different colors to show different structures

1. All living things are made of one or more cells. Cell Theory 1. All living things are made of one or more cells. 2. Cells are the basic units of structure and function in organisms. 3. All cells arise from existing cells.

Prokaryote vs. Eukaryote Prokaryote- a single celled organism that lacks a nucleus and other internal compartments. The only organisms on Earth for 2 billion years. Eukaryote- organism whose cells have a nucleus.