CELLS
Chapter 6- Cell Structure and
Function
A Cell is: the smallest unit that can carry
on all of life’s functions
• Galileo – early 17th century (1600’s)
– Looked at insects
– Detailed sketches of insect eye
I
. The Cell Theory
A. Development of Cell Theory (history)
1. 1500’s- first lenses used by merchants to
determine quality of cloth (look at precision of the
weave)
2. 1600’s- microscope and telescope constructed
a. Anton van Leeuuwenhoekmade simple microscopeobserved living things in pond
water for the first time – Late
1600’s
b. Robert Hooke- looked at thin slice of cork.
Noticed it was made of tiny chambers- called
them “cells”, mid 17th century
Hooke’s work stimulated others
to search for cells in other living
things. It became apparent that
cells were basic units of all living
things
Used compound microscope
• c. Robert Brown– 1820’s, Botanist, first
used word “nucleus” for dark spot in cell
d. 1838- Matthias SchleidenGerman botanist concluded all
plants made of cells
e. 1839– Theodor SchwannConcluded that all animals made
up of cells
f. 1855- Rudolf VirchowRussian physician said
“Where a cell exists, there
must have been a
preexisting cell……..”
B. The Cell Theory-summary of before
mentioned scientists and other biologists
is one of fundamental concepts of biology
1. All living things are composed of cells
2. Cells are the basic units of structure and
function in all living things.
3. New cells are produced from existing cells
II. Basic Cell Structures
A. Cells come in many
shapes and sizes
1. Smallest- 0.2
micrometers (bacteria)
b. Largest- birds egg and giant amoeba
(1000 micrometers)
B. Structures common in most Cells
1. Cell membrane-thin, flexible barrier
around the cell.
a. Many also have cell wall- strong layer
around the cell membrane (found in
plants, algae, fungi, and bacteria)
b. Support and protect cells,
while allowing them to interact
with surroundings.
2. Nucleus-large structure containing cell’s
genetic material- controls cell’s activities
(“brain”)
3. Cytoplasm-Material inside the cell
membrane but not including nucleus. Also
contains many important structures
C. Prokaryotes and Eukaryotes- Scientists divide
cells Into two groups depending on whether
they have a nucleus or not.
1. Prokaryotes-no nucleus
a. Smaller and simpler than
cells of eukaryotes
b. Do have cytoplasm, cell
membrane, ribosomes
c. Still carry out all activities
associated with life
2. Eukaryotes-do contain nucleus and
membrane bound organelles (includes
plants, animals, fungi)
a. Contain cytoplasm and cell
membrane
b. Also contain dozens of
other specialized structures
called organelles (means
tiny organs)
KEY CONCEPT
Technology continually changes the way
biologists work.
Imaging technologies provide new views of life.
Unitl 1600’s, cells were not known to exist!
• A microscope provides an enlarged image of an
object.
– light microscopes (LM)
stoma
2000x
Imaging technologies provide new views of life.
• A microscope provides an enlarged image of an object.
– light microscopes (LM)
– scanning electron microscopes (SEM)
stoma
1500X
Imaging technologies provide new views
of life.
• A microscope provides an enlarged image of an object.
– light microscopes (LM)
– scanning
electron microscopes (SEM)
– transmission electron microscopes (TEM)
stoma
5000X
Microscopes Compared and Contrasted!
Type of
Microscope
Image
Source
Best
Magnifiying
Power
Advantages
Compound
Light
Pass light
through
1500X-2000X Can view
living cells
Scanning
Electron
(SEM)
Passes beam 50,000X
of electrons
over surface
Transmssion
Electron
(TEM)
Passes beam 100,000X
Best
of electrons
(1 text says 2 magnfication
through
of all
millionX!)
Great 3D
details
Disadvantages
Not enough
power, 2D
Works only in
vacuum – no
living cells
Works only in
vacuum – no
living cells,
2D