Section 3-1 Looking at Cells

Light Microscope A microscope that uses a beam of light passing through one or more lenses to magnify an object Used to view living cells

Electron Microscopes A microscope that uses a beam of electrons passing through one or more lenses to magnify an object Used to study the tiniest structures inside the cell or the cell surface Cells are not living

Terms Micrograph – an image produced by a microscope Magnification – the ability to make an object appear larger than its actual Resolution – a measure of the clarity of an image Both high magnification and good resolution are needed to view the details of an object clearly. Poor resolution under high magnification will cause an image to be blurry.

Compound Light Microscope Uses 2 lenses Most powerful – 2000X – allows viewing objects that are 0.5μm in diameter. To determine magnification: Multiply the ocular lens strength by the objective lens strength Ocular – 10X; Objective – 40X Magnification = 400X

Electron Microscope Can magnify objects up to 200,000X Used to study very small structures within the cell Living cells cannot be viewed by an electron microscope because electron beam and specimen have to be in vacuum chamber so the beam does not bounce off air particles

Transmission Electron Microscope (TEM) Electron beam is directed at a very thin slice of a specimen stained with metal ions Can reveal cell’s internal structure Black and white images Computers add artificial color

Scanning Electron Microscope (SEM) Electron beam is focused on a specimen coated with a very thin layer of metal Gives 3-dimensional image of cell’s surface Images – black and white; computers add artificial color

Scanning Tunneling Microscope Uses a needle-like probe to measure different voltages caused by electrons that leak, or tunnel, from the surface of he object being viewed. Computers track movement of probe across object. Can view objects as small as an atom. Computer generates a 3D image.

Five Scientists that Contributed to the Development of the Cell Theory Robert Hooke – Developed the compound Microscope and illumination system; noticed that cork was made of compartments or “cells” – first to coin the term cell. Matthais Schleiden – along with Schwann, developed the theories that cells are the basic unit of life , cells are alive and all living things are made of cells. Theodor Schwann - along with Schleiden, developed the theories that cells are the basic unit of life , cells are alive and all living things are made of cells.

Five Scientists that Contributed to the Development of the Cell Theory Rudolph Virchow – all cells arise from other cells Anton van Leeuwenhoek – “Father of Microbiology”; discovered bacteria, protists; simple microscope; very talented at grinding lenses for microscopes

HOMEWORK Active Reading Worksheet Section 3-1 Review Questions page 54