Interest Grabber
Section 7-1
Are All Cells Alike?
All living things are made up of cells. Some organisms are composed of only
one cell. Other organisms are made up of many cells.
1. What are the advantages of a one-celled organism?
2. What are the advantages of an organism that is made up of many cells?
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Section:
Section Outline
Section 7-1
Discovery of the Cell
7–1
Life Is Cellular
A. The Discovery of the Cell
1. Early Microscopes
2. The Cell Theory
B. Exploring the Cell
C. Prokaryotes and Eukaryotes
1. Prokaryotes
2. Eukaryotes
•
There are several scientists that are responsible for understanding the
cell. They are:
1.  Robert Hooke - Observed a piece of cork and saw thousands of
empty spaces. Coined the term “cell” because they reminded him
of the small rooms in the monastery.
2.  Anton van Leeuwenhoek - first person to observe living cells.
3.  Matthias Schleiden - All plants are made of cells.
4.  Theodor Schwann - All animals are made of cells.
5.  Rudolf Virchow - New cells come only from other cells.
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The Cell Theory
Microscopes
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.
• Compound light microscope - uses two lenses to
focus on an image through which light passes through.
• Transmission Electron Microscope - sends a beam
of electrons through a microscopic slice of a specimen.
• Scanning Electron Microscope - sends a beam of
electrons over the surface of an object to produce a 3-D
image.
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1
Prokaryotes
Eukaryotes
• They are cells that have genetic material that is not
contained in a nucleus.
• Usually larger and more complicated than prokaryote
cells.
• Contain a nucleus in which their genetic material is
separated from the rest of the cell.
• Contain dozens of structures and internal membranes.
• Example - bacteria
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Section:
Prokaryotic and Eukaryotic Cells
Section 7-1
Interest Grabber
Section 7-2
Cell membrane
Cytoplasm
Division of Labor
Prokaryotic Cell
Cell membrane
Cytoplasm
Nucleus
Eukaryotic Cell
Organelles
A cell is made up of many parts with different functions that work together.
Similarly, the parts of a computer work together to carry out different
functions.
Working with a partner, answer the following questions.
1. What are some of the different parts of a computer? What are the
functions of these computer parts?
2. How do the functions of these computer parts correspond to the
functions of certain cell parts?
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Section Outline
Section 7-2
7–2 Eukaryotic Cell Structure
Comparing the Cell to a Factory
• The cell is made up of many
tiny structures that act similar
to specialized organs.
• The structures are known as
organelles.
• Biologist split the eukaryotic
cell into two parts:
–  Nucleus
–  Cytoplasm (jelly-like
substance outside the
nucleus.)
A.
Comparing the Cell to a Factory
B.
Nucleus
C.
Ribosomes
D.
Endoplasmic Reticulum
E.
Golgi Apparatus
F.
Lysosomes
G. Vacuoles
H.
Mitochondria and Chloroplasts
1.
Mitochondria
2.
Chloroplasts
3. Organelle DNA
I. Cytoskeleton
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2
Nucleus
Parts of the nucleus
• The nucleus is compared to
the main office of the factory.
• It is the control center.
• The nucleus contains nearly
all the cell’s DNA and with it
the coded instructions for
making proteins and other
important molecules.
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Parts of the nucleus
Ribosomes
• The nucleus contains granular material made up of DNA
bound to proteins called chromatin.
• During cell division, this chromatin condenses to form
thread-like structures called chromosomes.
• The nucleus also contains a small, dense region called the
nucleolus which is responsible for the assembly of
ribosomes.
•  One of the most important
products of the cell is the
making of proteins.
•  Proteins are assembled on
ribosomes.
•  Ribosomes are small particles of
RNA and protein found in two
places throughout the cell:
1.  Endoplasmic Reticulum
2.  Cytoplasm
•  In the factory, they are the
machines that produce the
product.
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Endoplasmic Reticulum
• The nucleus is surrounded
by a nuclear envelope.
• The envelope contains
many different pores that
allow materials such as
proteins, RNA, and other
molecules to travel to and
from the rest of the cell.
• Just like the memos,
instructions and blueprints
move in and out of the office.
• Rough ER
•  The endoplasmic reticulum is
the site where lipid
components of the cell
membrane are assembled,
along with proteins and other
materials that are exported
from the cell.
•  There are two types of ER’s:
1.  Rough ER
2.  Smooth ER
• Rough ER is responsible for
producing proteins that are
exported from the cell.
• It is called rough because there
are ribosomes found on the
surface of the ER which gives it
a bumpy surface.
• The proteins made by these
ribosomes enter the ER where
they are modified.
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3
Smooth ER
Golgi Apparatus
• Ribosomes are not found on its surface.
• Contains enzymes that perform specialized tasks such as
the synthesis of membrane lipids and the detoxification of
drugs.
• Liver cells have large amounts of smooth ER.
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• Proteins that are made in the
rough ER move into the golgi
apparatus.
• They are a stack of apposed
membranes.
• The function of the golgi
apparatus is to modify, sort, and
package proteins and other
materials from the ER for
storage in the cell or secretion
outside the cell.
• Golgi is the customization shop
where the finishing touches are
put on the product.
Lysosomes
Vacuoles
•  They are small organelles filled with enzymes.
•  They have two major jobs:
1.  Digest or breakdown lipids, carbohydrates, and proteins into small
molecules that can be used by the cell.
2.  Ingest and destroy old and worn-out organelles.
• Vacuoles are the storage area of the cell.
They store things such as water, salts,
proteins, and carbohydrates.
• In plants, there is usually a large central
vacuole
that is filled with liquid. The pressure built up
in the vacuole make it possible to support
heavy structures.
• In single-cell organisms, such as the paramecium, they contain a
contractile vacuole that pumps out excess water to help maintain
homeostasis.
• Homeostasis is the maintenance of a controlled internal
environment.
•
The lysosome can be compared to the cleanup crew of the factory.
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Mitochondria
• Mitochondria are organelles
that convert the chemical
energy stored in food into
compounds that are more
convenient for the cell to use.
• Mitochondria have two
membranes - an outer
membrane and an inner
membrane that is folded up to
create more surface area.
• Mitochondria are inherited from
the cytoplasm of the ovum, or
egg.
• Called the “Powerhouse” of the
cell.
Chloroplasts
• Chloroplasts are organelles
that capture the energy from
sunlight and convert it into
chemical energy in a process
called photosynthesis.
• They act as solar panels. The
chemical that absorbs the
sunlight is a green pigment
called chlorophyll.
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4
Organelle DNA
• Mitochondria and Chloroplasts contain their own genetic
information in the form of small DNA molecules.
• They are believed to be descendants of ancient prokaryotes.
• The idea suggests that the ancient prokaryotes developed a
symbiotic relationship with the eukaryotes and actually took
up residence within the eukaryotic cell.
• This idea is called the endosymbiotic theory.
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Figure 7-11 Cytoskeleton
Section 7-2
Cell membrane
Cytoskeleton
• The cytoskeleton is a network
of protein filaments that helps
the cell to maintain its shape.
The cytoskeleton is also involved
in movement.
• The two main types of protein filaments
–  Microfilaments - thread-like structures made of actin.
–  Microtubules - hollow structures made of tubulins.
•  Play an important role in cell division.
•  Make up centrioles, cilia, and flagella.
Endoplasmic
reticulum
Microtubule
Microfilament
Ribosomes
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Mitochondrion
Venn Diagrams
Section 7-2
Prokaryotes
Eukaryotes
Cell membrane
Contain DNA
Animal Cells
Centrioles
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Plant Cells
Cell membrane
Ribosomes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell Wall
Chloroplasts
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5
Figure 7-5 Plant and Animal Cells
Section 7-2
Figure 7-5 Plant and Animal Cells
Section 7-2
Animal Cell
Plant Cell
Vacuole
Smooth endoplasmic
reticulum
Ribosome
(free)
Nucleolus
Nucleus
Chloroplast
Ribosome
(attached)
Cell
Membrane
Nuclear
envelope
Nuclear
envelope
Cell wall
Ribosome
(attached)
Ribosome
(free)
Cell
Membrane
Rough
endoplasmic
reticulum
Mitochondrion
Smooth
endoplasmic
reticulum
Nucleolus
Golgi apparatus
Mitochondrion
Golgi apparatus
Nucleus
Centrioles
Rough endoplasmic reticulum
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Interest Grabber
Section 7-3
Section Outline
Section 7-3
7–3
Cell Boundaries
A. Cell Membrane
B. Cell Walls
C. Diffusion Through Cell Boundaries
1. Measuring Concentration
2. Diffusion
D. Osmosis
1. How Osmosis Works
2. Osmotic Pressure
E. Facilitated Diffusion
F. Active Transport
1. Molecular Transport
2. Endocytosis and Exocytosis
In or Out?
How is a window screen similar to a cell membrane? Read on to find out.
1. What are some things that can pass through a window screen?
2. What are some things that cannot pass through a window screen? Why is it
important to keep these things from moving through the screen?
3. The cell is surrounded by a cell membrane, which regulates what enters and
leaves the cell. Why is it important to regulate what moves into and out of a cell?
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Chapter 7-3
Cell Boundaries
Cell Membrane
• All cells are surrounded by a thin, flexible barrier known as
the cell membrane.
• Many other cells, especially plant cells, produce a strong
supporting layer around the membrane known as the cell
wall.
•  The cell membrane regulates what enters and leaves
the cell and also provides protection and support.
•  The cell membrane is composed of a double-layered
sheet called a lipid bilayer.
•  The lipid bilayer separates the outside surroundings
of the cell with the inside of the cell.
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6
Figure 7-12 The Structure of the
Cell Membrane
Section 7-3
Cell Membrane
• The lipid bilayer is made up of several substances:
1. Lipids
2. Proteins - Form channels and pumps that move
material across the membrane.
3. Carbohydrates - Act like chemical identification cards.
• Because the cell membrane is made up of all these different
molecules which have the ability to move around, scientists
describe the membrane as a “Fluid Mosaic Model.”
• A mosaic is a piece of art that is made up of many pieces
put together to make a picture.
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
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Protein
channel
Lipid bilayer
Cell Walls
• Cell walls are found in plants, algae, fungi, and many
prokaryotes.
• Most cell walls are porous enough to allow water, oxygen,
carbon dioxide, and other substances to pass through easily.
• The main function of the cell wall is to provide support
and protection for the cell.
• Cell walls are made of complex carbohydrates called
cellulose.
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Diffusion Through Cell Boundaries
Measuring Concentration
• One of the most important functions of the cell membrane is
to regulate the movement of dissolved molecules from the
liquid on one side of the membrane to the liquid on the other
side.
•
•
•
•
The cytoplasm in a cell is a solution of many different substances.
Remember a solution is made up of two different parts
1.  Solute - substance that is dissolved
2.  Solvent - substance that is doing the dissolving
The concentration is the mass of the solute in a volume of solution.
Example
•  12 grams of salt in 3 liters of water. What is the concentration?
12 grams
3 liters
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=
4 g/L
7
Diffusion
• Diffusion is the movement of particles from an area where they
are more concentrated to an area where they are less
concentrated.
• If the particles are equal in both areas, they have reached their
equilibrium.
• Because diffusion depends upon random particle movements,
substances diffuse across membranes without requiring the cell to
use energy.
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Selectively Permeable Membrane
Osmosis
• Many substances can diffuse across the membrane, but
some substances are too large or too strongly charged to
cross the membrane.
• For this reason, cell membranes are considered to be
selectively permeable. They allow some substances to cross
through them, but not others.
•
•
1.
2.
3.
Osmosis is the diffusion of water through a selectively permeable
membrane.
Terms of osmosis:
Isotonic - same strength
Hypertonic - above strength
Hypotonic - below strength
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Hypotonic
Osmotic Pressure
Hypertonic
Isotonic
• For organisms to survive, they must have a way to balance the
intake and loss of water.
• Osmosis exerts a pressure known as osmotic pressure on the
hypertonic side of a selectively permeable membrane.
• Because cells are filled salts, sugars, proteins, and other
molecules, they are always hypertonic to fresh water.
• This means the cell will take in water causing it to swell. If it takes
in too much water, it could burst.
• In plant cells, the cell wall prevents the cells from expanding;
preventing the cell from bursting.
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8
Facilitated Diffusion
• Sometimes particles seem to be too large to diffuse through
the cell membrane, but yet still do. How?
• The cell membrane has proteins embedded within the lipid
bilayer.
• These proteins have channels that allow larger molecules to
pass through them.
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Facilitated Diffusion
Section 7-3
Glucose
molecules
High
Concentration
Active Transport
• Sometimes, the cell needs to move particle from low
concentrations to high concentrations.
• Diffusion will not work in this situation so the cell needs to
use energy to move these particles.
• This process is called active transport.
Cell
Membrane
Protein
channel
Low
Concentration
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Figure 7-19 Active Transport
Section 7-3
Molecule to
be carried
Endocytosis
Energy
Molecule
being carried
•  Endocytosis is the process of taking material into the cell
by means of infoldings, or pockets, of the cell membrane.
•  The pocket that results breaks loose from the outer portion
of the cell membrane and forms a vacuole within the cell.
•  There are two types of endocytosis
1.  Phagocytosis - Extensions of the cytoplasm surround
a particle and engulf it, forming a food vacuole.
2.  Pinocytosis - Pocket in the cell membrane fills with
liquid and pinches off to form vacuoles.
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9
Phagocytosis
Exocytosis
• Exocytosis is the release of large amounts of materials
from the cell.
• The membrane of the vacuole fuses with the cell membrane
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Interest Grabber continued
Interest Grabber
Section 7-4
Section 7-4
From Simple to More Complex
Many multicellular organisms have structures called organs that have a
specific function and work with other organs. Working together, these
organs carry out the life processes of the entire organism.
1. Some activities cannot be performed by only one person, but need a team of
people. What type of activity requires a team of people to work together in order
to complete a task?
2. What do you think are some characteristics of a successful team?
3. How is a multicellular organism similar to a successful team?
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Section Outline
Section 7-4
Levels of Organization
Section 7-4
7–4
The Diversity of Cellular Life
Muscle cell
Smooth muscle tissue
Stomach
Digestive system
A. Unicellular Organisms
B. Multicellular Organisms
1. Specialized Animal Cells
2. Specialized Plant Cells
C. Levels of Organization
1. Tissues
2. Organs
3. Organ Systems
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10
Videos
Click a hyperlink to choose a video.
Video 1
Diffusion
Diffusion
Osmosis
Passive Transport
Active Transport
Endocytosis and Exocytosis
Click the image to play the video segment.
Video 2
Osmosis
Click the image to play the video segment.
Video 4
Active Transport
Click the image to play the video segment.
Video 3
Passive Transport
Click the image to play the video segment.
Video 5
Endocytosis and Exocytosis
Click the image to play the video segment.
11
Go Online
The latest discoveries in cell study
Cell structure activity
Career links on histotechnologists
Interactive test
Articles on cells
Interest Grabber Answers
1. What are the advantages of a one-celled organism?
A one-celled organism has simpler needs and can respond immediately to
its environment because its entire cell is immersed in its environment.
2. What are the advantages of an organism that is made up of many cells?
In a multicellular organism, different jobs are divided among different
groups of cells that work together. Also, a multicellular organism can
continue to survive even if it loses some of its cells.
For links on cell theory, go to www.SciLinks.org and enter the
Web Code as follows: cbn-3071.
For links on cell membranes, go to www.SciLinks.org and enter the
Web Code as follows: cbn-3073.
Interest Grabber Answers
Working with a partner, answer the following questions.
1. What are some of the different parts of a computer? What are the functions
of these computer parts?
Answers may include: monitor (interfaces with the computer’s
environment), software (instructions for how to carry out different jobs),
CPU (directs the computer's activities), recycle bin or trash can (storage
area for wastes), and so on.
2. How do the functions of these computer parts correspond to the functions
of certain cell parts?
Students should try to link the functions they described in question 1 to the
functions of the different cell structures. The cell needs a way to interface
with its environment (cell membrane), instructions for carrying out different
jobs (DNA), and a CPU to direct the cell’s activities (nucleus).
Interest Grabber Answers
1. What are some things that can pass through a window screen?
Answers may include air, fine dust, and rainwater.
2. What are some things that cannot pass through a window screen? Why is
it important to keep these things from moving through the screen?
Insects, leaves, and other matter that may fall from trees. The screen
keeps out annoying insects and objects that may bring dirt into the home.
3. The cell is surrounded by a cell membrane, which regulates what enters
and leaves the cell. Why is it important to regulate what moves into and out
of a cell?
Materials such as oxygen and food that are needed by the cell have to be
able to get inside the cell. At the same time, excess materials have to leave
the cell.
Figure 7-15 Osmosis
Interest Grabber Answers
Section 7-3
1. Some activities cannot be performed by only one person, but need a team
of people. What type of activity requires a team of people to work together
in order to complete a task?
Answers might include building a human pyramid or constructing an arch
out of blocks.
2. What do you think are some characteristics of a successful team?
Divide up jobs and cooperate well with one another.
3. How is a multicellular organism similar to a successful team?
The functions of the organism are divided up among its parts (organs and
organ systems). All the parts cooperate to carry out all the functions of the
whole organism.
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12
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13