Transcript BSCS Chapter 06 - HonorsBiology2015-16

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Chapter Introduction
The Basic Unit of Life
6.1 Cell Study and Technology
6.2 Two Basic Types of Cells
Cell Structure
6.3 Prokaryotic Cell Structure
6.4 Eukaryotic Cell Structure
Multicellular Organization
6.5 Cooperation Among Cells
6.6 Division of Labor
6.7 Systems
Chapter Highlights
Chapter Animations
Learning Outcomes
By the end of this chapter you will be able to:
A Explain the basic tenets of the cell theory.
B Predict the possible effects of improved
technology on the study of cells.
C Distinguish between prokaryotic and
eukaryotic cells.
D Identify prokaryotic cell structures and explain
functions of eukaryotic organelles.
E Describe ways in which cells cooperate with
each other.
F Summarize the advantages of multicellular
organization.
Cell Structures and Their Functions
 How many different
structures can you see
in these cells?
 What functions could
they have?
A micrograph of Paramecium aurelia, x100
Cell Structures and Their Functions
• Cells are so complex that we
are continually learning more
about how they are made
and how they work.
• Biologists are making rapid
progress toward unlocking
the mysteries of the cell.
• In this chapter, you will learn
what research has revealed
about the cell so far.
A micrograph of Paramecium aurelia, x100
The Basic Unit of Life
6.1 Cell Study and Technology
• Whatever their size, all living things are composed
of cells—the basic unit of life.
• Many biologists contributed data and ideas that led
to the cell theory, which can be stated in two parts:
1. Cells, or products made by cells, are the unit of
structure and function in organisms.
2. All cells come from preexisting cells.
Examples of the variety of cells that make up all organisms (color added).
Unicellular (single-celled) bacteria, x20,000
Unicellular algae, x150
Photosynthetic cells in a leaf, x200
Cells from the liver of a salamander, x400
The Basic Unit of Life
6.1 Cell Study and Technology (cont.)
• Once the cell theory was established, scientists
began to study cell structure and function in detail.
• Some cell structures are too small to see without
the electron microscope, which was developed in
the 1930s.
• Electron microscopes reveal very tiny cell parts and
even some large molecules down to 0.5 nm—a
magnification of more than a million.
Transmission electron
microscope (a) and
scanning electron
microscope (b), with
typical images of similar
white blood cells produced
by each. Note the
differences in the images
produced of the same
subject (color added).
a
b
The Basic Unit of Life
6.1 Cell Study and Technology (cont.)
• The major drawback of the electron microscope
is that the steps needed to prepare samples for
examination kill any living cells before they can
be observed.
• Scanning tunneling microscopes can be more
powerful than electron microscopes and do not
require such harsh treatment of samples.
• Both the electron and scanning tunneling
microscopes can reveal only surface features.
Cells differ in size but
average 10 to 20 µm
in diameter. Note that most
cells are too small to be
seen with the unaided eye.
The Basic Unit of Life
6.2 Two Basic Types of Cells
• Living cells can be separated into
two groups, prokaryotes and
eukaryotes, that differ in structure.
• Prokaryotes—the bacteria—
are the simplest living cells
and are found almost anywhere
on Earth.
• Prokaryotic organisms are
nearly always unicellular.
• Prokaryotes range in size
from about 0.3 µm to 5 µm
in diameter.
Many prokaryotes are
visible in this scanning
electron micrograph of the
point of a pin. x290
The Basic Unit of Life
6.2 Two Basic Types of Cells (cont.)
• The cells of eukaryotes are larger (10–50 µm)
and more complex than prokaryotes.
• Eukaryotic cells can form multicellular organisms
such as plants, animals, and fungi.
• Eukaryotic cells have many parts, each with a
specific function, that gives them the flexibility to
develop into hundreds of specialized cell types.
• The membrane-enclosed nucleus is the most
obvious difference between prokaryotes and
eukaryotes.
Note the greater structural complexity of the eukaryotic cell (an amoeba) and its
many membrane enclosed parts, or organelles.
Prokaryotic cell
Eukaryotic cell
Cell Structure
6.3 Prokaryotic Cell Structure
• Nearly all prokaryotic cells have:
– a rigid cell wall made of lipids, carbohydrates
other than cellulose, and protein.
– a plasma membrane that encloses the cell.
– one chromosome that is attached to the
plasma membrane in an area of the cell known
as the nuclear region, or nucleoid.
Cell Structure
6.3 Prokaryotic Cell Structure (cont.)
• Most prokaryotes—bacteria—are unicellular but
can associate in clusters, chains, and films.
• In addition, bacteria usually contain one or more
smaller circular DNA molecules called plasmids.
• Some have flagella (singular: flagellum), long,
whiplike extensions made of protein that rotate like
propellers, enabling cells to swim through water or
the body fluids of larger organisms.
The structure of a prokaryotic cell
Cell Structure
6.3 Prokaryotic Cell Structure (cont.)
• Most bacteria have one of three shapes—rod,
sphere, or corkscrew.
cocci (spheres), x45,000
bacilli (rods), x31,000
(note the flagella)
spirochetes (corkscrews),
x700
Cell Structure
6.3 Prokaryotic Cell Structure (cont.)
• Many of the prokaryotic metabolic processes, such
as glycolysis, are similar to those of eukaryotes.
However, others are unique.
• All ecosystems include many types of bacterial
decomposers that help recycle nutrients such as
carbon, nitrogen, and sulfur compounds.
Cell Structure
6.3 Prokaryotic Cell Structure (cont.)
• Many prokaryotes are autotrophs and are important
primary producers in lakes and oceans.
• Although some bacteria can cause human
diseases, such as skin infections and strep throat,
most are beneficial. Bacteria in your intestines help
you digest food.
Cell Structure
6.4 Eukaryotic Cell Structure
• Eukaryotic cells are divided into small functional
parts called organelles.
• Any part of a eukaryotic cell that has its own
structure and function can be considered an
organelle.
• Compartmentation makes eukaryotic cells more
efficient by separating specific processes and
enabling a division of labor within the cell.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• A plasma membrane encloses
the contents of both eukaryotic
cells and prokaryotic cells.
Plasma
membrane
• A cell wall surrounds the
plasma membrane of plant and
fungal cells, as well as some
unicellular eukaryotes.
• Animal cells lack a rigid
cell wall.
Cell wall
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• The nucleus contains the
chromosomes and is a cell’s
genetic control center.
Nucleus
• A double layer of membranes
forms the nuclear envelope, or
nuclear membrane, that
surrounds the chromosomes.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• One or more drops of
concentrated RNA are usually
visible in the nucleus, in bodies
called nucleoli (singular:
nucleolus).
Nucleus
• The nucleoli are the sites where
types of RNA are synthesized.
Nucleolus
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• Within the plasma membrane,
but outside the nucleus, is the
cellular material, or cytoplasm.
Cytosol
• The cytosol is the protein-rich,
semifluid material in the cell
that surrounds and bathes the
organelles.
• The cytoplasm includes the
cytosol and the organelles.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• A network of several types of
very fine protein fibers, known
as the cystoskeleton, helps to
shape the cell and organize
the cytoplasm.
Cytoskeleton
• The cytoskeleton includes
hollow microtubules and
connecting intermediate
filaments.
The cytoskeleton network of proteins in the cytoplasm of eukaryotic cells facilitates
movement and helps the cell maintain its shape.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• Many small bodies composed
of RNA and protein, called
ribosomes, are scattered
throughout the cytoplasm.
ER
• Ribosomes catalyze the
synthesis of a cell’s proteins.
• In eukaryotes, some ribosomes
are attached to a system of
membranes called the
endoplasmic reticulum (ER).
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• The ER membranes form tubes
and channels throughout the
cytoplasm connecting many of
the organelles in the cell.
ER
• Proteins are synthesized at
the ribosomes attached to
the ER.
• Proteins and other substances
are transported through the
ER to their final destinations in
the cell.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• Many substances that are
exported from the cell pass
through the ER to the
Golgi apparatus.
Golgi
apparatus
• Material passing through the
Golgi apparatus is packaged in
vesicles that appear to pinch
off the Golgi membranes.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• Together the ER, Golgi
apparatus, and vesicles
form a connected internal
membrane system.
Golgi
apparatus
• The structure of the system
enables it to direct proteins to
target points inside the cell and
to the plasma membrane for
passage out of the cell.
Internal membrane system of a eukaryotic cell
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• Lysosomes are special vesicles
in animal cells and some other
eukaryotes that contain enzymes
that break down the cell’s old
macromolecules for recycling.
Lysosome
• Lysosomes can also fuse with
vesicles formed by endocytosis,
digesting the food particles within.
• Some animal cells have lysosomes
that fuse with the plasma
membrane, releasing digestive
enzymes outside the cell.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
• The vacuoles present in most
plant cells are vesicles that enlarge
as the cells mature.
• Vacuoles contain water, organic
acids, digestive enzymes, salts,
and pigments.
Plant cell
• Up to 90% of the volume of a
mature plant cell may consist of
its vacuole.
Vacuole
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
• Chloroplasts and mitochondria
are double-membrane organelles
involved in energy reactions.
• Photosynthesis occurs in
chloroplasts.
Plant cell
Mitochondrion
• Mitochondria are the major
sites of ATP synthesis in most
eukaryotic cells.
Chloroplast
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Animal
cell
Plant cell
• Centrioles are tubular
structures in the cells of animals
and some fungi and algae that
participate in cell reproduction.
Centrioles
• Centrioles consist of a pair of
cylindrical bundles of
microtubules.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
• Some eukaryotic cells have flagella that are
covered by the plasma membrane and consist of
long bundles of microtubules.
• Enzymes associated with these microtubules
provide energy for the motion of the flagellum by
breaking down ATP.
Parallel bundles of microtubules make up the internal structure of the flagellum.
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
• Cilia are short flagella.
• Eukaryotic flagella and cilia
move cells along by whipping
in an oarlike motion against
the fluid surrounding a cell.
• Cilia can also help move
material along a cell
or tissue.
Scanning electron micrograph
of rows of cilia on a hamster’s
inner ear cells. x6,700
Cell Structure
6.4 Eukaryotic Cell Structure (cont.)
Multicellular Organization
6.5 Cooperation Among Cells
• When one-celled
organisms divide,
some new cells may
remain together in
a cluster.
• In a cluster of cells,
each cell has an
individual life and
may break away
from the cluster at
some point.
Though prokaryotes such as these exist in
clusters, chains, and films and as isolated
cells, each bacterium is still an individual
organism Anabaena, color added. x600
Multicellular Organization
6.5 Cooperation Among Cells (cont.)
• Some unicellular
microorganisms live in
groups called colonies.
• Members of a colony may
interact in ways that give them
advantages over isolated
organisms, but each member
is still a separate organism.
• In some colonies, such as
that of Volvox, a colonial
algae, individual cells take
on specialized roles.
Bacteria in dental plaque biofilm
on an unbrushed tooth. x2,000
Individual cells of a Volvox colony, (a), look like unicellular alga Chlamydomonas,
(b). Volvox colonies, (c), are seen here through the light microscope. x125
a
b
c
Multicellular Organization
6.5 Cooperation Among Cells (cont.)
• Some types of Volvox have delicate strands of
cytoplasm connecting the cells and can coordinate
their motions.
• Volvox has some characteristics of a colony, but it
also has some specialized reproductive cells, and
the two ends of the colony are different.
• Volvox could be considered just barely a
multicellular organism.
Multicellular Organization
6.6 Division of Labor
• Organisms must have enough surface area for the
living cells within to exchange food, wastes, and
other substances with their environment.
• Large plants and animals use structures, such as
blood vessels, lungs, and leaves, that add internal
surface area.
• Structures that enable large organisms to survive
require a number of specialized cell types.
Multicellular Organization
6.6 Division of Labor (cont.)
• All cells must carry on the basic activities of life, but
each type of cell often takes on a special job as well.
– A gland cell is specialized for making certain types
of chemicals.
– A nerve cell is efficient in conducting electric
signals.
– A muscle cell is specialized for movement.
– The cells that form an organism’s outer covering,
or epidermis, may be specialized.
Multicellular Organization
6.6 Division of Labor (cont.)
• Hydra is a small, threadlike freshwater animal with
a ring of tentacles at one end.
• The animal’s cells look slightly different and are
different in specialization.
x15
Multicellular Organization
6.6 Division of Labor (cont.)
• Cells of larger organisms are much more distinctive
in appearance.
Muscle cells, color added (a), and red blood cells, color added (b), are
specialized cells in humans.
a
b
x124
x288
Multicellular Organization
6.6 Division of Labor (cont.)
• In multicellular organisms, a group of cells with the
same specialization usually work together.
• Each specialized mass or layer of cells is called
a tissue.
• Different tissues may be organized into organs.
• Organs may be incorporated into systems
of organs.
(a) The heart, blood, and
blood vessels are the
organs that make up an
animal’s circulatory system.
(b) The heart is composed
mostly of cardiac muscle
tissue.
(c) Specialized cells form
cardiac muscle tissue.
Multicellular Organization
6.7 Systems
• In most multicellular organisms, the inner cells
cannot obtain nutrients directly from the outside
environment or pass their wastes directly to the
outside environment.
• Specialized systems are required to handle
deliveries between the environment and the cells.
Multicellular Organization
6.7 Systems (cont.)
• Most specialized systems are necessary for
three reasons:
1. a division of labor occurs among cells,
2. many individual cells cannot work together
without regulation and coordination, and
3. most cells are not in direct contact with the
outside environment.
Multicellular Organization
6.7 Systems (cont.)
• In many organisms, additional specializations have
developed within the organ systems.
• Specialized systems are required to handle
deliveries between the environment and the cells.
• Cells are the lowest level of organization that truly
can be considered living.
Levels of structure in the biosphere
Summary
•
Prokaryotic cells are smaller and less specialized
than eukaryotic cells.
•
The most distinguishing characteristic of eukaryotic
cells is the presence of organelles, which include
the nucleus, mitochondria, chloroplasts, ribosomes,
vacuoles, endoplasmic reticulum, and other
compartments with specific functions in the
eukaryotic cell.
•
Cells may exist alone as unicellular organisms.
•
Cells may be clustered and form multicellular
organisms.
•
Tissues, organs, and systems become more
complex in larger multicellular organisms.
Reviewing Key Terms
Match the term on the left with the correct description.
___
cilia
e
a. specialized mass of cells
___
vacuoles
d
b. extrachromosomal elements
that contain a few genes that
help bacteria survive under
specific conditions.
___
plasmid
b
___
nucleoid
c
___
lysosome
f
c. sites of synthesis and
assembly of rRNA and tRNA
___
tissue
a
d. large vesicle that grows as a
plant cell matures
e. short flagella
f.
vesicle that may fuse with the
plasma membrane and
release digestive enzymes
outside of the cell
Reviewing Ideas
1. What is the major drawback of the electron
microscope?
The major drawback of the electron microscope
is that the steps needed to prepare samples for
examination kill any living cells before they can
be observed.
Reviewing Ideas
2. What is the lowest level of organization that truly
can be considered living? Where does this fall
on the continuum of biological organization?
Cells, the basic unit of life, are about midway on
the continuum of biological organization. They
are also the lowest level of organization that truly
can be considered living.
Using Concepts
3. Why are prokaryotes a vital part of every
ecosystem?
Some prokaryotes are bacterial decomposers that
help recycle nutrients such as carbon, nitrogen,
and sulfur compounds that otherwise would
remain unavailable in wastes and dead organisms.
Using Concepts
4. How does a Hydra survive without a
circulation system?
In a Hydra, all cells are in close proximity to the
outside environment and can directly receive
nutrients and expel waste products.
Synthesize
5. What are the basic requirements to be
considered a multicellular organism?
Aside from having more than one cell, the cells of
a multicellular organism should exhibit signs of
specialization and coordination and division of
labor in their activities.
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Chapter Animations
The structure of a prokaryotic cell
Internal membrane system of a eukaryotic cell
Levels of structure in the biosphere
The structure of a prokaryotic cell
Internal membrane system of a eukaryotic cell
Levels of structure in the biosphere
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