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