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Chapter 3
Cell Structure
Table of Contents
Section 1 Looking at Cells
Section 2 Cell Features
Section 3 Cell Organelles
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Chapter 3
Section 1 Looking at Cells
Objectives
• Describe how scientists measure the length of objects.
• Relate magnification and resolution in the use of
microscopes.
• Analyze how light microscopes function.
• Compare light microscopes with electron microscopes.
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Chapter 3
Section 1 Looking at Cells
Cells Under the Microscope
Measuring Cell Structures
Measurements taken by scientists are expressed in metric units.
The official name of the metric system is the International System
of Measurements, abbreviated SI. The table below summarizes the
SI units used to measure length.
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Chapter 3
Section 1 Looking at Cells
Cells Under the Microscope, continued
• Magnification is the quality of making an image
appear larger than its actual size.
• Resolution is a measure of the clarity of an image.
Both high magnification and good resolution are needed
to view the details of extremely small objects clearly.
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Chapter 3
Section 1 Looking at Cells
Cells Under the Microscope, continued
Electron microscopes have much higher magnifying and resolving
powers than light microscopes.
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Chapter 3
Section 1 Looking at Cells
Parts of a Light Microscope
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Chapter 3
Section 1 Looking at Cells
Types of Microscopes
Light microscopes
form an image when
light passes through
one or more lenses to
produce an enlarged
image of a specimen.
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Chapter 3
Section 1 Looking at Cells
Magnification and Resolution
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Chapter 3
Section 1 Looking at Cells
Types of Microscopes, continued
Electron Microscopes
• Electron microscopes form an image of a
specimen using a beam of electrons rather than
light.
• The electron beam and specimen must be in a
vacuum so that the electron beam will not bounce
off of gas molecules.
• Live organisms cannot be viewed with an electron
microscope.
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Chapter 3
Section 1 Looking at Cells
Types of Microscopes, continued
Transmission Electron Microscope
• An electron beam is directed at a very thin slice of a
specimen stained with metal ions. Some structures
become more heavily stained than others.
• The heavily stained parts absorb electrons, those that
are lightly stained allow electrons to pass through.
• The electrons that pass through strike a fluorescent
screen, forming an image.
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Chapter 3
Section 1 Looking at Cells
Types of Microscopes, continued
Scanning Electron Microscope
• An electron beam is focused on a specimen coated
with a very thin layer of metal.
• The electrons that bounce off the specimen form an
image on a fluorescent screen.
• The image shows three-dimensional details of the
surface of a specimen.
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Chapter 3
Section 1 Looking at Cells
Types of Microscopes, continued
Scanning Tunneling Microscope
• A needle-like probe measures differences in voltage
caused by electrons that leak, or tunnel, from the
surface of the object being viewed.
• A computer tracks the movement of the probe across
the surface of the object.
• The image shows three-dimensional details of the
surface of a specimen.
• Live specimens and objects as small as atoms can
be viewed.
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Chapter 3
Section 1 Looking at Cells
Types of Microscopes
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Chapter 3
Section 2 Cell Features
Objectives
• List the three parts of the cell theory.
• Determine why cells must be relatively small.
• Compare the structure of prokaryotic cells with that
of eukaryotic cells.
• Describe the structure of cell membranes.
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Chapter 3
Section 2 Cell Features
The Cell Theory
The Cell Theory has three parts:
1. All living things are made of one or more cells.
2. Cells are the basic units of structure and function in
organisms.
3. All cells arise from existing cells.
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Chapter 3
Section 2 Cell Features
Cell Theory
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Chapter 3
Section 2 Cell Features
The Cell Theory, continued
Cell Size
Small cells function more efficiently than large cells. If a
cell’s surface area–to-volume ratio is too low,
substances cannot enter and leave the cell well enough
to meet the cell’s needs.
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Chapter 3
Section 2 Cell Features
The Cell Theory, continued
Common Cell Features
Cells share common structural features, including:
•
•
•
•
•
an outer boundary called the cell membrane,
interior substance called cytoplasm,
structural support called the cytoskeleton,
genetic material in the form of DNA
cellular structures that make proteins, called ribosomes
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Chapter 3
Section 2 Cell Features
Cytoplasm
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Chapter 3
Section 2 Cell Features
Prokaryotes
Prokaryotes are
single-celled
organisms that lack a
nucleus and other
internal
compartments. They
have a cell wall, may
have cilia or flagella,
and have a single
circular molecule of
DNA.
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Chapter 3
Section 2 Cell Features
Parts of a Prokaryotic Cell
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Chapter 3
Section 2 Cell Features
Structure of Cilia and Flagella
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Chapter 3
Section 2 Cell Features
Eukaryotic Cells
Eukaryotic cells have:
• A nucleus which contains the cell’s DNA
• Other internal compartments called organelles.
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Chapter 3
Section 2 Cell Features
Comparing Prokaryotes and Eukaryotes
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Chapter 3
Section 2 Cell Features
Parts of an Animal Cell
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Chapter 3
Section 2 Cell Features
Eukaryotic Cells, continued
•
The cytoskeleton provides the interior framework of
a cell. There are three basic kinds of cytoskeletal
fibers.
1. Microfilaments: long slender filaments made of the
protein actin
2. Microtubules: hollow tubes made of the protein
tubulin.
3. Intermediate fibers: thick ropes made of protein.
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Chapter 3
Section 2 Cell Features
Eukaryotic Cells, continued
The cytoskeleton’s
network of protein
fibers anchors the
cell’s organelles
and other
components of the
cytoplasm.
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Chapter 3
Section 2 Cell Features
Cytoskeleton
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Chapter 3
Section 2 Cell Features
The Cell Membrane
•
The cell membrane is a selectively permeable
barrier that determines which substances enter and
leave the cell.
•
The selective permeability of the cell is mainly
caused by the way phospholipids interact with water.
•
A phospholipid is a lipid made of a phosphate
group and two fatty acids.
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Chapter 3
Section 2 Cell Features
The Cell Membrane, continued
Cell membranes are made of a double layer of phospholipids,
called a bilayer.
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Chapter 3
Section 2 Cell Features
The Cell Membrane, continued
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Chapter 3
Section 2 Cell Features
Phospholipid
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Chapter 3
Section 2 Cell Features
Lipid Bilayer
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Chapter 3
Section 2 Cell Features
Cell Membrane
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Chapter 3
Section 2 Cell Features
Parts of the Cell Membrane
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Chapter 3
Section 3 Cell Organelles
Objectives
• Describe the role of the nucleus in cell activities.
• Analyze the role of internal membranes in protein
production.
• Summarize the importance of mitochondria in
eukaryotic cells.
• Identify three structure in plant cells that are absent
from animal cells.
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Chapter 3
Section 3 Cell Organelles
The Nucleus
• The nucleus is an internal compartment that houses
the cell’s DNA. Most functions of a eukaryotic cell
are controlled by the cell’s nucleus.
• The nucleus is surrounded by a double membrane
called the nuclear envelope.
• Scattered over the surface of the nuclear envelope
are many small channels called nuclear pores.
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Chapter 3
Section 3 Cell Organelles
The Nucleus, continued
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Chapter 3
Section 3 Cell Organelles
The Nucleus, continued
• Ribosomal proteins and RNA are made in the
nucleus.
• Ribosomes are partially assembled in a region of the
nucleus called the nucleolus.
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Chapter 3
Section 3 Cell Organelles
Nucleus of a Cell
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Chapter 3
Section 3 Cell Organelles
Ribosomes and the Endoplasmic Reticulum
• Ribosomes are the cellular structures on which
proteins are made.
• The Endoplasmic Reticulum or ER is an extensive
system of internal membranes that move proteins
and other substances through the cell.
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Chapter 3
Section 3 Cell Organelles
Ribosomes
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Chapter 3
Section 3 Cell Organelles
Ribosomes and the Endoplasmic Reticulum,
continued
• The part of the ER with attached ribosomes is
called the rough ER.
• The rough ER helps transport proteins that are
made by the attached ribosomes.
• New proteins enter the ER.
• The portion of the ER that contains the completed
protein pinches off to form a vesicle.
• A vesicle is a small, membrane-bound sac that
transports substances in cells.
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Chapter 3
Section 3 Cell Organelles
Ribosomes and the Endoplasmic Reticulum,
continued
The ER moves proteins and other substances within eukaryotic
cells.
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Chapter 3
Section 3 Cell Organelles
Endoplasmic Reticulum (ER) and Ribosomes
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Chapter 3
Section 3 Cell Organelles
Ribosomes and the Endoplasmic Reticulum,
continued
Packaging and Distribution of Proteins
• Vesicles that contain newly made proteins move
through the cytoplasm from the ER to an organelle
called the Golgi apparatus.
• The Golgi apparatus is a set of flattened, membranebound sacs that serve as the packaging and
distribution center of the cell.
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Chapter 3
Section 3 Cell Organelles
Golgi Apparatus
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Chapter 3
Section 3 Cell Organelles
Ribosomes and the Endoplasmic Reticulum,
continued
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Chapter 3
Section 3 Cell Organelles
Lysosome
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Chapter 3
Section 3 Cell Organelles
Mitochondria
• Mitochondria are organelles that harvest energy
from organic compounds to make ATP.
• ATP is the main energy currency of cells. Most ATP
is made inside the mitochondria.
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Chapter 3
Section 3 Cell Organelles
Mitochondria, continued
• Mitochondria have two membranes. The outer
membrane is smooth. The inner membrane is greatly
folded, and has a large surface area.
• Mitochondria have their own DNA. Mitochondria
reproduce independently of the cell. Mitochondrial
DNA is similar to the DNA of prokaryotic cells.
• Mitochondria are thought to be descendents of
primitive prokaryotes.
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Chapter 3
Section 3 Cell Organelles
Mitochondria, continued
Mitochondria have an inner and an outer membrane.
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Chapter 3
Section 3 Cell Organelles
Mitochondrion
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Chapter 3
Section 3 Cell Organelles
Structures of Plant Cells
Plants have three unique structures that are not found
in animal cells:
• Cell Wall
• Chloroplasts
• Central Vacuole
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Chapter 3
Section 3 Cell Organelles
Parts of a Plant Cell
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Chapter 3
Section 3 Cell Organelles
Structures of Plant Cells, continued
• The cell membrane of plant cells is surrounded by a
thick cell wall, composed of proteins and
carbohydrates.
• The cell wall
• helps support and maintain the shape of the cell
• protects the cell from damage
• connects the cell with adjacent cells
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Chapter 3
Section 3 Cell Organelles
Parts of a Cell Wall
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Chapter 3
Section 3 Cell Organelles
Structures of Plant Cells, continued
• Chloroplasts are organelles that use light energy to
make carbohydrates from carbon dioxide and water.
• Chloroplasts, along with mitochondria, supply much
of the energy needed to power the activities of plant
cells.
• Chloroplasts, like mitochondria, have their own DNA
and reproduce independently of the plant cell.
• Chloroplasts, like mitochondria, are thought to be
descendents of ancient prokaryotes.
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Chapter 3
Section 3 Cell Organelles
Chloroplasts
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Chapter 3
Section 3 Cell Organelles
Structures of Plant Cells, continued
Central Vacuole:
• Most of a plant cell’s volume is taken up by a large,
membrane-bound space called the central vacuole.
• The central vacuole stores water and may contain
ions, nutrients, and wastes.
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Chapter 3
Section 3 Cell Organelles
Vacuoles
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Chapter 3
Section 3 Cell Organelles
Comparing Plant and Animal Cells
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Chapter 3
Section 3 Cell Organelles
Summary of Organelles
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Chapter 3
Standardized Test Prep
Multiple Choice
Use the figure below and your knowledge of science to
answer questions 1–3.
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Chapter 3
Standardized Test Prep
Multiple Choice, continued
1. Which structures in this cell are also found in
prokaryotic cells?
A.
B.
C.
D.
A and B
C and D
E and F
A and E
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Chapter 3
Standardized Test Prep
Multiple Choice, continued
1. Which structures in this cell are also found in
prokaryotic cells?
A.
B.
C.
D.
A and B
C and D
E and F
A and E
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Chapter 3
Standardized Test Prep
Multiple Choice, continued
2. Which features of plant cells are missing from this
cell?
F.
G.
H.
J.
cell wall and chloroplasts
Golgi apparatus and mitochondria
rough ER and lysosomes
smooth ER and nucleus
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Chapter 3
Standardized Test Prep
Multiple Choice, continued
2. Which features of plant cells are missing from this
cell?
F.
G.
H.
J.
cell wall and chloroplasts
Golgi apparatus and mitochondria
rough ER and lysosomes
smooth ER and nucleus
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Chapter 3
Standardized Test Prep
Multiple Choice, continued
3. What is the function of the structure labeled A?
A.
B.
C.
D.
making ATP
making carbohydrates
making proteins
moving proteins through the cell
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Chapter 3
Standardized Test Prep
Multiple Choice, continued
3. What is the function of the structure labeled A?
A.
B.
C.
D.
making ATP
making carbohydrates
making proteins
moving proteins through the cell
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Chapter 3
Metric Units of Length and Equivalents
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Chapter 3
Object Size and Magnifying Power of
Microscope
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Chapter 3
Compound Light
Microscope
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Chapter 3
Surface Area–to-Volume Ratio
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Chapter 3
Prokaryotic Cell
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Chapter 3
Eukaryotic Cells
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Chapter 3
The Cell Membrane
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Chapter 3
The Cell Membrane
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Chapter 3
Processing of Proteins
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Chapter 3
Plant Cell
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Chapter 3
Organelles
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