A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)
Cells Are Small (1-100 um)
Magnification and Resolution in Microscopy
• Magnification is the ability of a microscope to enlarge
an image.
-Magnification is almost unlimited on a microscope.
• Resolution is the ability of a microscope to clearly
define the details of what it is looking at.
-Resolution limits the usefulness of high magnification
since once an object becomes blurry; greater magnification
doesn't help. Light microscopes are limited to 1000X.
-Microscopes that use lower wavelengths of electromagnetic
energy, like electron microscopes, have better resolution of
tiny details and can be used at higher magnifications
(100,000X).
The Microscopic World of Cells
•
Cells were first discovered in 1665 by Robert Hooke.
•
The accumulation of scientific evidence led to the cell
theory which has two main tenets:
1. All living things are composed of cells.
2. All cells are formed from previously existing cells.
•
Organisms are either:
–
Single-celled, such as most bacteria and protists
–
Multicellular, such as plants, animals, and most fungi
Types of Microscopes
•
Light Microscopes use visible light and
optical lenses
–
Limited to 1000X because of low
resolution
–
Require little or no electrical power to
operate
Euglena
Types of Microscopes
• Electron microscopes (EMs) use a
beam of electrons and magnetic lenses
– Much higher resolving power than
the light microscope and can magnify
up to 100,000X.
– Types of Electron Microscopes
• The scanning electron
microscope (SEM) is used to
study the detailed architecture
of the surface of a cell.
• The transmission electron
microscope (TEM) is useful
for exploring the internal
structure of a cell.
A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)
The Two Major Categories of Cells
• The countless cells on
earth fall into two
categories:
– Prokaryotic cells, such
as bacteria
– Eukaryotic cells, such
as protist, fungal, plant,
or animal cells
Comparison of Prokaryotic and Eukaryotic Cells
A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)
Prokaryotic Cells Are Small and Simple
A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)
Eukaryotic Cells are Larger and More Complex
Eukaryotic Cells are Larger and More Complex
A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)
Membrane Structure
•
The plasma membrane separates the living cell from its nonliving
surroundings
•
Phospholipids form an impermeable bilayer
•
Proteins provide transport channels and other functions
Structures Found Outside the Cell Membrane in Eukaryotes
• Plant cells have rigid cell walls of cellulose
– Provide protection, maintain cell shape, and keep
cells from absorbing too much water.
• Animal cells have an extracellular matrix
– Holds cells together in tissues and protects and
supports them.
A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)
Organelles Within A Eukaryotic Cell
The Nucleus: Information Storage and Control of the Cell
• The nucleus is
the library of
the cell.
• Chromosomes
(books) within
the nucleus
store
instructions on
how to run the
cell
Ribosomes Make Proteins Using Genetic Instructions
Copy of instructions
from the nucleus
A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)
The Endomembrane System: Manufacturing and
Distributing Cellular Products
• Many of the membranous organelles in the cell
belong to the endomembrane system.
The Endoplasmic Reticulum
• The endoplasmic
reticulum (ER)
– Lipid synthesis
factory, including
phospholipids for
cell membrane
– Routing system
for delivery of
proteins (subway
system)
A Tour of the Cell, Part I
CHAPTER 4
Microscopes as Windows on Cells
o Types of Microscopes
o Magnification and Resolution
 Categories of Cells
 Features of Prokaryotic Cells
 Features of Eukaryotic Cells
o Membrane Structure
o Nucleus and Ribosomes
o Endoplasmic Reticulum (ER)