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7-1 Life is Cellular
Key Concepts:
What is the cell theory?
What are the characteristics of prokaryotes and eukaryotes?
I.
The Cell Theory
Date
1590
1665
1674
1838
1839
1855
Scientist
Janssen brothers
(Dutch)
Robert Hooke
(English)
Anton van
Leeuwenhoek
(Dutch)
Matthias Schleiden
(German)
Theodor Schwann
(German)
Rudolf Virchow
(German)
Findings
First microscopes
coined the term “cell”
first to observe living
things with microscope
all plants are made of
cells *
all animals are made of
cells *
all cells come from preexisting cells *
* These findings are known as the cell theory, which
states:
1. All living things are composed of cells.
2. Cells are the basic units of structure and function
in living things.
3. New cells are produced from existing cells.
II. Basic Cell Structures
A. Cell membrane – thin, flexible barrier around a cell;
regulates what enters and leaves the cell
B. Cell wall – strong layer around the cell membrane in
plants, algae, and some bacteria
C. Nucleus – large structure that contains the cell’s
genetic material (DNA) and controls all cell activities
D. Cytoplasm – material inside the cell membrane – but
not including the nucleus
III. Prokaryotes and Eukaryotes
A. Biologists divide cells into two categories: eukaryotes
and prokaryotes. Eukaryotic cells have a nucleus and
prokaryotic cells do not.
B. Prokaryote – single-celled microorganism that lacks a
nucleus; ex. – bacteria
C. Eukaryote – organism whose cells contain nuclei; ex. –
plants, animals, fungi
D. Organelles – specialized structures that perform
important cellular functions within a eukaryotic cell
7-2 Cell Structures
Key Concepts: What are the functions of the major cell structures?
Cell Wall
 provide support & protection for plant cells
 made primarily of cellulose
 animal cells do not have cell walls
Nucleus
 discovered in 1831 by Robert Brown, a Scottish botanist
 controls most cell processes
 contains the hereditary information (DNA)
o Chromatin – granular material visible in nucleus
(uncondensed DNA)
o Chromosomes – threadlike structures in nucleus
(condensed DNA)
 Nucleolus – small, dense region within the nucleus in
which the assembly of ribosomes begins
 Nuclear envelope – double-membrane layer that
surrounds the nucleus
Cytoskeleton
 A network of protein filaments that help the cell to maintain
its shape.
 Also involved in cell movement
 Two types:
1. Microtubules: hollow tubes, 25 nm in diameter
a. forms track along which organelles move
b. form centrioles (animal cells only) – involved in cell
division
c. form hairlike projections (cilia & flagella)
2. Microfilaments: long, thin fibers,7 nm in diameter; help
with movement and support
Organelles in the Cytoplasm
Ribosomes – small particles in the cell on which proteins are
assembled; made of RNA & protein
Endoplasmic Reticulum (ER) – internal membrane system in
which parts of the cell membrane are assembled and some
proteins are modified
 Two types:
1. Rough ER – has ribosomes on surface
2. Smooth ER – no ribosomes on surface
Golgi Apparatus – stack of membranes in which enzymes
attach carbohydrates and lipids to proteins
Lysosomes – organelles filled with enzymes that break down
materials in the cell
Vacuoles – organelles that store materials such as water, salts,
proteins and carbohydrates
Chloroplasts – organelles that use light energy to make food
molecules (photosynthesis); found only in plants
Mitochondria – organelles that use energy from food to make
high-energy compounds that cells use for growth,
development, and movement
Cell Comparison Chart
Structure
Cell Membrane
Cell Wall
Nucleus
Ribosomes
Endoplasmic
Reticulum
Golgi Apparatus
Lysosomes
Vacuoles
Mitochondria
Chloroplasts
Cytoskeleton
Prokaryotic
Cells
Eukaryotic Cells
Animal
Plant
Cell Comparison Chart
Structure
Cell Membrane
Prokaryotic
Cells
Yes
Eukaryotic Cells
Animal
Plant
Yes
Yes
Cell Wall
Yes
No
Yes
Nucleus
No
Yes
Yes
Ribosomes
Yes
Yes
Yes
Endoplasmic
Reticulum
Golgi Apparatus
Lysosomes
No
Yes
Yes
No
No
Yes
Yes
Yes
No
Vacuoles
No
Yes
Mitochondria
No
Small or
None
Yes
Chloroplasts
No
No
Yes
Cytoskeleton
No
Yes
Yes
Yes