Life Is Cellular

Learning Objectives §  State the cell theory. §  Describe how the different types of microscopes work. §  Distinguish between prokaryotes and eukaryotes.

Discovery of the Cell

Robert Hooke (1665) – Examined a slice of cork through a compound

microscope – saw tiny, hollow, room-like structures – called these structures “cells” because they

reminded him of the rooms where monks lived – only saw the outer walls (cell walls). Why?

Cork Under a Microscope

The Discovery of the Cell Anton van Leeuwenhoek was the first to observe living microorganisms.

Dutch fabric merchant; looked at blood, rainwater, teeth scrapings. Called what he saw “animalcules”

The Cell Theory (Schleiden, Schwann, Virchow)

1.  All living things are made up of cells. 2.  Cells are the basic units of structure and function in

living things. 3.  New cells are produced from existing cells.

Exploring the Cell Most microscopes use lenses to magnify the image of an object by focusing light or electrons.

•  Modern compound light microscopes have improved to magnify objects 1500x using two lenses and a beam of light

•  Electron microscopes use a beam of electrons to magnify objects 500,000 times!

Electron Microscopes

Two types of electron microscopes:

•  transmission

•  scanning

Scanning Electron Microscope (SEM) Scans the surface of cells to show their three-dimensional shape

T cells Scanning electron micrograph of T lymphocyte (right), a platelet (center) and a red blood cell (left)

Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) This work is in the public domain in the United States

Transmission Electron Microscopes (TEM)

Sends electrons through a specimen to show the parts inside the cell

B- & T-lymphocytes https://embryology.med.unsw.edu.au/

Micrographs A micrograph is a photo of an object seen through a microscope.

Light Microscope Transmission Electron Microscope

Scanning Electron Microscope

Micrographs Review Scanning Electron Microscope Light Microscope Transmission Electron Microscope Light Microscope Using Fluorescent Stain

Cell Size Certain units of measurement are used for tiny objects, such as cells.

Prokaryotes and Eukaryotes

Nucleus Nucleus

Cell Membrane Cell Membrane

Cell Membrane

Review •  All living things are made up of cells. •  Cells are the basic units of structure and function in

living things. •  New cells are produced from existing cells.

Eyepiece – lens magnifies 10x

Stage – Supports the specimen slide

Arm – Always carry with one hand on the arm and one on the base

Coarse Adjustment – moves stage up or down to bring specimen into focus Fine Adjustment – allows for precise focusing

Base – supports the scope

Light Source – provides the light that shines through the stage

Diaphragm – controls the amount of light reaching the stage

Stage Clips – hold the specimen slide to the stage

** Objective Lenses – magnify by 4x, 10x, 40x, or 100x

Revolving Nosepiece – holds and rotates objective lenses

Body Tube – supports the eyepiece and objectives

** Since the eyepiece had a magnification of 10x, the total magnification when using the 4x objective lens would be 40x. When using the 10x objective lens, the total would be 100x. When using the 40x lens, the total would be 400x.