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Chapter 2
Cells: The Units of Life
At the conclusion of Chapter 2 (Section 2.3), text book pages 40-44, you should be able to:
Obj 1 - Discuss the history leading to the cell theory
Obj 2 - Explain the difference between the compound light
and the electron microscope
Obj 3 - Explain the importance of the cell theory
25 Sep 2002
homework tonight - read pages 46-48
Quiz (Friday-27Sep02) - concentrate on section 2.3 (pages 40-44)
The Microscope
We've learned that cells are the smallest units capable of carrying out the functions of life. Right? Just how small? Well, you can't see cells when you look at most most plants and animals. You can't see them with the naked eye and you'll need some type of magnifying device to view them.
2 types (Simple or Compound)
- depends on how many lenses they contain
Simple Microscope
- similar to a magnifying glass (only 1 lens)
- Anton Van Leeuwenhoek (mid 1600s), Dutch Scientist,
made a simple microscope that could magnify to 270X
(What does 270X mean?)
Compound Microscope
- Zacharias Janssen (Dutch maker of reading glasses)
developed the first "crude" in 1590
-- put 2 lenses together and got a larger, but "fuzzy"
picture
Compound Light Microscope
- allows light to pass through an object and has 2 or
more lenses
-- eyepiece lens has a magnification of 10X (meaning?)
-- objective lens may have a power of 43X (meaning?)
(some more powerful microscopes can magnify to 2000X)
Inquiring minds want to know...
Can you?
Calculate the total low power and high power magnification of a microscope that has a 8X eyepiece, a 10X objective, and a 40X high power objective?
Other Types
- Stereo Microscope (has an eyepiece for each eye)
-- used to look at thick structures that light can't
pass through (ex. whole insect, leaves, etc.)
- Electron Microscope (uses a magnetic field to bend
beams of electron)
-- can magnify up to 1 000 000X
(see text book page 42, figure 2-9)
-- several kinds
--- Transmission Electron Microscope (TEM)
--- Scanning electron microscope (SEM)
26Sep 2002
Objective 1 - Review the history leading to Cell Theory
Objective 2 - Understand the importance of microscopes
Objective 3 - Discuss the cell theory and explain
significance
homework - study section 2.3 (On-line Quiz/Friday 27 Sep 02)
Historical Perspective - The Cell Theory
Yesterday, we talked about the invention of simple & compound microscopes. Today, we are going to take a few "steps" forward and look at the "Cell Theory"
- 1665, Robert Hooke (English Scientist) made a thin
slice of cork and looked at it under his microscope
-- called what he saw cells
Development of Cell Theory
- 1838, Matthias Schleiden (German Scientist) studied
plants under a microscope
-- concluded that all plants were made of cells
- 1839, Theodor Schwann (German Scientist) concluded that
all animals were made of cells
Together, they were convinced that all living things were
made of cells.
- 1854 (approx.), Rudolph Virchow (German Scientist)
"hypothesized" that new cells don't form on their own.
They divide and form new cells.
Cell Theory
(1) All organisms are made up of cells
(2) Cells are the basic units of structure & function in
all organisms
(3) All cells come from cells that already exist
In your own words, what does the cell theory mean? Why is it important? Has this theory (Cell Theory) stood the "test of time"?
30 Sep 02 - 3 Oct 02
Cell Organization
Objective 1 - diagram an animal cell
Objective 2 - identify the parts & the function of each part
Objective 3 - diagram a plant cell
Objective 4 - identify the parts and the function of each part
2 basic cell types
prokaryotic - no membrane around their nuclear material (unorganized)
eukaryotic - a nucleus with a membrane around it (organized)
Animal Cells
each cell in your body is constantly active (works 24/7)
components
Cell membrane - the structure that forms the outer boundary of the cell and allow only certain materials to move into and out
Nucleus - the structure that directs all the activities
chromatin - (heredity material) located inside the
nucleus contains genetic blueprints for
operations of the cell
nucleolus - involve in making proteins
Cytoplasm - gel-like material inside the cell membrane &
outside the nucleus (constantly moving)
Structures within the cytoplasm of eukaryotic cells that have a specific job or jobs (organelles)
Endoplasmic Recticulum (ER) - a folded membrane thats moves material around in the cell. (takes up a lot of space) - ER can be rough or smooth
ribosome - where protein is made; receive direction
from heredity materil in nucleus
(some ribosomes are scattered in the
cytoplasm & some are attached to the ER,
called Rough ER)
Golgi Bodies - stacks of membrane covered sacs that package and move proteins to the outside of the cell
Mitochondria -where food is broken down and energy is released
lysosome - contains chemicals that digest wastes and worn out cell parts, as well as, break down food
vacuole - where food is stored (somewhat small in animal cells)
Plant Cells
All of the cellular components identified above are present in plant cells. However, I want you to be aware of 2 additional components.
cell wall -
the rigid structure made of cellulose that surrounds a plant cell membrane and supports and protects it.
chloroplasts - plant cell organelles in which light energy is changed in to chemical energy in the form of sugar during the process of photosynthesis.
Chapter 2 Test will be Wednesday - 9 Oct 2002
Are you ready????
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