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Biology I 10/18/12
HW: Cell Theory – Write & Restate Take out 7.1 Reading Guide
CHAPTER 7 CELL STRUCTURE & FUNCTION
Objectives
Explain what the cell theory is. Describe how researchers explore
the living cell. Distinguish between eukaryotes and
prokaryotes.
7.1 Life is Cellular
Cells are the basic structural and functional units of life.
They differ in structure and complexity
This idea is relatively new Microscopes were first used around mid-
1600’s The invention of microscopes made the
discovery of the cell possible
Robert Hooke
In 1665, Robert Hooke used an early compound microscope to look at cork
Observed that cork was made up of 1000’s of hollow chambers
Dubbed them cells since they looked like the monastery’s tiny rooms called “cellula”.
Late 1600’s- Dutch textile salesman
Created different types of microscopes
Observed pondwater and found living organisms
Discovered over 5,000 types of microscopic life
Lenses were able to magnify up to 300X
Anton van Leeuwenhoek
The Cell Theory
A fundamental concept: a summary of confirmed discoveries
Cells are the most basic unit and structure of life
All living things are made up of cells New cells are produced from existing
cells
More Discoveries
1839 – German biologists Matthias Schleidan & Theodor Schwann proposed that all organisms are made of
cells.
1855 – German physician Rudolf Virchow Proposed that all cells produce more cells
through time
Exploring The Cell
Three major types of microscopes
1. Light Microscope Magnifies 40-1,000
times Used to magnify objects
that light can pass through
Uses slides
2. Electron Microscopes - Uses electrons to illuminate objects
Magnifies from 30,000 to 9 million times Two types
Transmission – Beam of e- pass through thin slice Images are 2-D Useful to study internal cell structures, large proteins
Scanning – beam of e- scan over surface 3-D images Useful to study external structure
Can only be used to look at dead specimens
3. Scanning Probe Microscopes
Traces surface of sample with a probe
View single atoms, DNA, protein molecules
Can view living things
Cells
Cells come in a variety of shapes Range in size from microscopic bacteria
to giant amoeba
All cells have a cell membrane – outer flexible barrier
All cells have (or had) DNA
Chaos carolinensis – Giant amoeba, approximately 1mm in length
Mycoplasma pneumoniae
Cells
Cell membrane
Nucleus- containing DNA
Eukaryotes- have cells that enclose their DNA in a nucleus Prokaryotes- cells that do not enclose their DNA in a
nucleus
2 Main categories of cells
Nucleus: large, membrane-bound structure that contains the cell’s genetic material in the form of DNA
Prokaryotes
Are generally smaller than eukaryotic cells
Have no nucleus Carry out all of life’s processes Ex: bacteria
Bacillus anthracis
Eukaryotes
Are generally larger and more complex than prokaryotes
Contain dozens of membrane bound structures that are specialized
Nucleus separates DNA from rest of cell Come in a variety of shapes and sizes
Ex: protists, fungi, plant, and animal cells
HW: Cell Theory: Write & Restate
1. Write the 1st part of the cell theory
2. Restate the sentence in your own words
3. Draw a picture to describe the statement
4. Repeat steps 1-3 for 2nd and 3rd sentences.
Example: Write: Each day
the temperature is below 32 degrees.
Restate: It’s freezing everyday!
Draw:Sun Mon Tue Wed Thur Fri Sat