Life is CellularChapter 7
http://web.jjay.cuny.edu
Key Concept: Cells are the basic unit of life
Macrophages engulfing bacteria © Eye of Science/Photo Researchers, Inc.
History
•Lenses and microscopes:▫Late 1500s – Italy: merchants develop
magnifying lenses to examine the quality of cloth
▫1600s – Holland: lenses combined to form microscopes and telescopes
The cell theory grew out of the work of many scientists and improvements in the microscope.
History
•Lenses / Microscopes▫1665 – Robert Hooke (England)
built compound microscope – looked at thin sections of cork – called the small chambers that he saw “cells”
© The Granger Collection, New York
smithlifescience.com
http://sebastianharmuth.fastpage.name/foundhookemicroscopesrobertusing/
http://www.cork.pt/cork-stoppers.html
http://lensonleeuwenhoek.net/microscopes.htm
History•Lenses and microscopes:
▫1674 – Anton van Leeuwenhoek used a single-lens microscope to observe pond water. To his amazement, he found a whole new world of microorganisms.
http://lensonleeuwenhoek.net/overview.htm
http://www.museumboerhaave.nl/collectie/e_voorwerpen/aalkijker.html
© The Granger Collection, New York
History• Looking at cells
▫1838 – Matthias Schleiden: all plants made of cells
▫1839 – Theodor Schwann: all animals made of cells
▫1855 – Rudolf Virchow: observed onion root tip cells and concluded that new cells could only be produced by division of existing cells
© The Granger Collection, New York
The Cell TheoryThe Cell Theory has three principles:•All living things are made of cells.
Nowicki
The Cell TheoryThe Cell Theory has three principles:•All living things are made of cells.•Cells are the basic units of structure
and function in living things.
Nowicki
The Cell TheoryThe Cell Theory has three principles:•All living things are made of cells.•Cells are the basic units of structure
and function in living things.•New cells are produced from pre-
existing cells.
Nowicki
Life is Cellular
•Most cells are 2-20 micrometers, about 1-10% of the diameter of a human hair.
•Mycoplasma bacterial cell: 0.1 micrometer
•Very large cells: human egg cell, amoeba proteus, skeletal muscles.
•http://learn.genetics.utah.edu/content/begin/cells/scale/
Cell Types
•Cells fall into two broad categories, depending on whether they contain a nucleusNucleus: a large membrane-enclosed
structure that holds the cell’s genetic material (DNA)
Prokaryotes EukaryotesDo not have nuclei Contain nuclei
Cell Types
•Both Prokaryotes and Eukaryotes:▫Come in a variety of
shapes and sizes▫Cells tend to be
microscopic▫All cells are
enclosed by a membrane
▫All cells are filled with cytoplasm prokaryote cell © Dr. Kari Lounatmaa/Photo
Researchers, Inc.
cell membrane
cytoplasm
Cell Types
•Eukaryotic cells ▫Have a nucleus▫Have dozens of
structures and internal membranes
▫Plants, animals, fungi, and protists are eukaryotes
nucleus
cell membrane
organelles
Cell Types
•Prokaryotic cells ▫Do not have a
nucleus▫Do not have
membrane-bound organelles
▫The organisms we call bacteria are prokaryotes
Bacterium(colored SEM; magnification 8800x)
cell membrane cytoplasm
Cell Types – Summary Prokaryotes Eukaryotes
• Genetic material is not contained in a nucleus• Does not have membrane-bound organelles• Bacteria
• Genetic material is contained in a nucleus • Does contain membrane-bound organelles• Plants, animals, fungi, and protists
Both prokaryotic and eukaryotic cells : 1. Tend to be microscopic 2. Are enclosed by a membrane 3. Are filled with cytoplasm 4. Contain DNA
Liver Cell
http://library.thinkquest.org/C004535/eukaryote_examples.html
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Plant and Animal Cells•Both plant and animal cells contain a
variety of organelles. ▫Organelles: specialized organs inside
the cell, also called “little organs”
http://www.goldiesroom.org/Note%20Packets/03%20Cytology/00%20Cytology--WHOLE.htm
Plant and Animal Cells•Some structures are specific to either
plant cells or animal cells only▫What structures do plant cells have
that animal cells do not?
http://www.goldiesroom.org/Note%20Packets/03%20Cytology/00%20Cytology--WHOLE.htm
Cell Wall
Chloroplasts
Plant and Animal Cells
•Plant Cells▫Plant cells
have cell walls and chloroplasts
Plant and Animal Cells
•Plant Cells▫A cell wall
provides rigid support
▫Chloroplasts convert solar energy to chemical energy
Images Produced by Light Microscopes
Amoeba Streptococcus bacteria Anthrax bacteria
Human cheek cells Plant cells Yeast cells
Images Produced by Electron Microscopes
Cyanobacteria (TEM) Lactobacillus
(SEM)Campylobacter
(SEM) Deinococcus(SEM)
House ant Avian influenza virus Human eyelash Yeast
Using Microscopes to Visualize the Three Shapes of Bacteria
•Cocci (round)•Bacilli (rod)•Spirilla (spiral)
Light microscope:Three shapes of bacteria
taken with an SEM
BacilliCocciSpirilla