Transcript The Cell - MDC Faculty Home Pages

Biology
A Guide to the Natural World
Chapter 4 • Lecture Outline
Life’s Home: The Cell
Fifth Edition
David Krogh
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4.1 Cells as Life’s Fundamental Unit
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Cells as Life’s Fundamental Unit
• With the possible exception of viruses,
every form of life on Earth either is a cell or
is composed of cells.
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Cells as Life’s Fundamental Unit
• Cells come into existence only through the
activity of other cells.
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4.2 Prokaryotic and Eukaryotic
Cells
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Prokaryotic and Eukaryotic Cells
• All cells can be classified as prokaryotic or
eukaryotic.
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Prokaryotic and Eukaryotic Cells
• Prokaryotic cells either are bacteria or
another single-celled life-form called
archaea.
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Prokaryotic and Eukaryotic Cells
• Setting bacteria and archaea aside, all other
cells are eukaryotic.
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Prokaryotic and Eukaryotic Cells
• Eukaryotic cells have most of their DNA
contained in a membrane-lined
compartment, called the cell nucleus,
whereas prokaryotic cells do not have a
nucleus.
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Prokaryotic and Eukaryotic Cells
• Eukaryotic cells tend to be much larger than
prokaryotic cells. They have more of the
specialized internal structures called
organelles than do prokaryotic cells.
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Prokaryotic and Eukaryotic Cells
• Many eukaryotes are multicelled organisms,
whereas all prokaryotes are single-celled.
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Prokaryotic cells
Eukaryotic cells
DNA
spread through much of cell
within membrane-bound nucleus
much smaller
much larger
always single-celled
often multicellular
only one type of organelle
many types of organelles
Size
Organization
Organelles
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Figure 4.2
4.3 The Eukaryotic Cell
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The Eukaryotic Cell
• There are five principal components to the
eukaryotic cell: the nucleus, other
organelles, the cytosol, the cytoskeleton,
and the plasma membrane.
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The Eukaryotic Cell
• Organelles are “tiny organs” within the cell
that carry out specialized functions, such as
energy transfer and materials recycling.
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The Animal Cell
nuclear pores
The nucleus contains
DNA
the cell’s primary
nuclear envelope
complement of DNA.
nucleolus
The smooth endoplasmic reticulum
is the site of the production of lipid
molecules such as estrogen and
testosterone.
free ribosomes
plasma membrane
cytoskeleton
Mitochondria are the powerplant
organelles that extract energy
from food and put it into a form
cells can use.
lysosome
The folds of the rough endoplasmic
reticulum form a set of chambers
within which proteins are processed.
transport vesicle
All the cell’s structures outside the
nucleus are immersed in a jelly-like
fluid called the cytosol. Composed
mostly of water, the cytosol is a
location for countless chemical
reactions carried out within the cell.
How are cell proteins
sorted and shipped, so
that they end up at the
right location? Partly
through the work of the
Golgi complex.
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Figure 4.4
The Eukaryotic Cell
• The cytosol is the jelly-like fluid outside the
nucleus in which these organelles are
immersed.
• The cytosol should not be confused with the
cytoplasm, which is the region of the cell
inside the plasma membrane but outside the
nucleus.
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The Eukaryotic Cell
• The cytoskeleton is a network of protein
filaments.
• It functions in cell structure, cell movement,
and the transport of materials within the
cell.
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The Eukaryotic Cell
• The plasma membrane is the outer lining of
the cell.
• A membrane can be defined as the flexible,
chemically active outer lining of a cell or of
its compartments.
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The Eukaryotic Cell
Components of eukaryotic cells
nucleus
other organelles
cytosol
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cytoskeleton
plasma membrane
Figure 4.3
4.4 A Tour of the Animal Cell’s
Protein Production Path
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Tour of the Animal Cell’s Protein
Production Path
• Information for the construction of proteins
is contained in the DNA located in the cell
nucleus.
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The Protein Production Path
• This information is copied onto a length of
messenger RNA (mRNA) that departs the
cell nucleus through its nuclear pores and
goes to the sites of protein synthesis,
structures called ribosomes, which lie in the
cytoplasm.
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The Protein Production Path
• Many ribosomes that receive mRNA chains
process only a short stretch of them before
migrating to, and then embedding in, one of
a series of sacs in a membrane network
called the rough endoplasmic reticulum
(RER).
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The Protein Production Path
• The polypeptide chains produced by the
ribosomal “reading” of the mRNA
sequences are dropped from ribosomes into
the internal spaces of the RER.
• There, the polypeptide chains fold up, thus
becoming proteins, and undergo editing.
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Tour of an Animal Cell
Suggested Media Enhancement:
Tour of an Animal Cell
• To access this animation go to folder
C_Animations_and_Video_Files
and open the BioFlix folder.
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The Protein Production Path
• Some ribosomes are not embedded in the
RER but instead remain free-standing in the
cytosol.
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The Protein Production Path
• Materials move from one structure to
another in the cell via the endomembrane
system.
• Here a piece of membrane, with proteins or
other materials inside, can bud off from one
organelle, move through the cell, and then
fuse with another membrane-lined structure.
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The Protein Production Path
• Membrane-lined structures that carry
cellular materials are called transport
vesicles.
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The Protein Production Path
• Once protein processing is finished in the
rough ER, proteins undergoing processing
move, via transport vesicles, to the Golgi
complex.
• They are processed further and marked for
shipment to appropriate cellular locations.
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The Golgi Complex
Golgi complex
1. Transport vesicle from
RER fuses with Golgi
2. Protein undergoes more
processing in Golgi
cisternae
cisternal
space
vesicle
Side chains are edited (sugars
may be trimmed, phosphate
groups added).
3. Proteins are
sorted and
shipped…
to cytosol
for export
out of cell
to plasma
membrane
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Figure 4.9
4.5 Cell Structures Outside the
Protein Production Path
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Cell Structures Outside the Protein
Production Path
• The smooth endoplasmic reticulum is a
network of membranes that functions to
synthesize lipids and to detoxify potentially
harmful substances.
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Lysosomes and Cellular Recycling
• Lysosomes are organelles that break down
worn-out cellular structures or foreign
materials that come into the cell.
• Once this digestion is completed, the
lysosomes return the molecular components
of these materials to the cytoplasm for
further use.
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lysosome
worn-out
organelle
digestive
enzymes
1. Lysosome fuses
with worn-out
organelle.
2. Organelle
broken down.
5. Usable molecules
recycled to make
new organelles.
3. Small
molecules
returned to
cytosol.
4. Waste
molecules
expelled from
cell.
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Figure 4.10
Mitochondria and Energy
• Mitochondria are organelles that function to
extract energy from food and to transform
this energy into a chemical form the cell can
use, the molecule ATP.
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Mitochondria and Energy
Mitochondrion
food
oxygen
outer
membrane
inner
membrane
water
carbon dioxide
ATP
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Figure 4.11
4.6 The Cytoskeleton: Internal
Scaffolding
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The Cytoskeleton: Internal
Scaffolding
• Cells have within them a web of protein
strands, called a cytoskeleton.
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The Cytoskeleton: Internal
Scaffolding
• The cytoskeleton provides the cell with
structure, facilitates the movement of
materials inside the cell, and facilitates cell
movement.
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The Cytoskeleton: Internal
Scaffolding
• There are three principal types of
cytoskeleton elements.
• Ordered by size, going from smallest to
largest in diameter, they are microfilaments,
intermediate filaments, and microtubules.
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(a) Microfilaments (in red)
(b) Intermediate filaments
7 nm
10 nm
25 nm
Main function: changes
Main function: maintenance
in cell shape
of cell shape
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(c) Microtubules
Main functions: maintenance
of cell shape, movement of
organelles, cell mobility
(cilia and flagella)
Figure 4.12
Microfilaments
• Microfilaments are made of the protein
actin.
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Microfilaments
• They help the cell move and capture prey
by forming rapidly in the direction of
movement and decomposing rapidly at their
other end.
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Microfilaments
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Figure 4.13
Intermediate Filaments
• Intermediate filaments provide support and
structure to the cell.
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Microtubules
• Microtubules play a structural role in cells
and facilitate the movement of materials
inside the cell by serving as transport
“rails.”
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Microtubules
• Cilia and flagella are extensions of cells
composed of microtubules.
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Cilia
• Cilia extend from cells in great numbers,
serving to move the cell or to move material
around the cell.
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Flagella
• By contrast, one—or at most a few—
flagella extend from cells that have them.
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Flagella
• The function of flagella is cell movement.
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(a) Transport monorails
transport
vesicle
motor
proteins
microtubule
(b) Cilia
(c) Flagellum
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Figure 4.14
4.7 The Plant Cell
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Tour of a Plant Cell
Suggested Media Enhancement:
Tour of a Plant Cell
• To access this animation go to folder
C_Animations_and_Video_Files
and open the BioFlix folder.
© 2011 Pearson Education, Inc.
The Plant Cell
• Plant cells have most of the structures found
in animal cells—ribosomes, a cell nucleus,
a rough ER, and so forth—although plant
cells do not have the lysosomes found in
animal cells.
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The Plant Cell
• Plant cells have three structures not found in
animal cells:
• a cell wall
• a large central vacuole
• the organelles called chloroplasts
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The Plant Cell
Plant cells have a cell
wall, chloroplasts, and a
central vacuole, while
cytoskeleton
animal cells do not.
nuclear envelope
nuclear pores
nucleus
DNA
nucleolus
rough endoplasmic
reticulum
smooth endoplasmic
reticulum
free ribosomes
cell wall
chloroplast
Golgi complex
cytosol
plasma membrane
central vacuole
mitochondrion
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Figure 4.17
The Central Vacuole
• The central vacuole stores nutrients and
degrades waste products.
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The Cell Wall
• The cell wall gives the plant structural
strength and helps regulate the intake and
retention of water.
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Chloroplasts
• Chloroplasts are the sites of photosynthesis.
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Chloroplasts
water
carbon dioxide
minerals
outer membrane
inner membrane
sugar (food)
oxygen
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Figure 4.19
The Structure of Cells
Animation 4.1: The Structure of Cells
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4.8 Cell-to-Cell Communication
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Cell-to-Cell Communication
• Cells are able to communicate with each
other through special structures.
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Communication Among Plant Cells
• Plant cells have channels, called
plasmodesmata, that are always open and
hence have the effect of making the
cytoplasm of one plant cell continuous with
that of another.
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Communication Among Animal Cells
• Adjacent animal cells have channels, called
gap junctions, that are composed of protein
assemblages that open only as necessary.
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Communication Among Animal Cells
• These gap junctions allow the movement of
small molecules and electrical signals
between cells.
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Plant tissues
(a) Plasmodesmata
plasmodesmata
Animal tissues
In plants, a series of tiny pores
plasma
between plant cells, the
membrane plasmodesmata, allow for the
cell walls
movement of materials among
cells. Thanks to the
cytoplasm plasmodesmata channels, the
cytoplasm of one cell is
continuous with the cytoplasm
of the next; the plant as a whole
can be thought of as having a
single complement of
continuous cytoplasm.
gap junction
(b) Gap junctions
plasma
In animals, protein assemblies
membranes come into alignment with one
cytoplasm another, forming communication
channels between cells. A
cluster of many such
assemblies—perhaps several
hundred—is called a gap
junction.
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Figure 4.20
Table 4.1
Structures in Plant and Animal Cells
Function and Location
Name
Function and Location
Nucleus
Site of most of the cell’s DNA
Location: Inside nuclear envelope
Mitochondria
Transform energy from food
Location: Cytoplasm
Nucleolus
Synthesis of ribosomal RNA
Location: Nucleus
Rough endoplasmic reticulum
Protein processing
Location: Cytoplasm
Ribosomes
Sites of protein synthesis
Location: Rough ER, Free-standing in
cytoplasm
Smooth endoplasmic
reticulum
Lipid synthesis, storage; detoxification of
harmful substances
Location: Cytoplasm
Cytoskeleton
Maintains cell shape, facilitates cell
movement and movement of materials
within cell
Location: Cytoplasm
Vesicles
Transport of proteins and other cellular
materials
Location: Cytoplasm
Cytosol
Protein-rich fluid in which organelles and
cytoskeleton are immersed
Location: Cytoplasm
Central vacuole
(in plant cells only)
Nutrient storage, cell pressure
maintenance, pH balance
Location: Cytoplasm
Golgi complex
Processing, sorting of proteins
Location: Cytoplasm
Chloroplasts
(in plant cells only)
Photosynthesis
Location: Cytoplasm
Lysosomes (in animal cells
only)
Digestion of imported materials and cell’s
own used materials
Location: Cytoplasm
Cell walls
(in plant cells only)
Limit water uptake; maintain cell
membrane shape, protect from outside
influences
Location: Outside plasma membrane
Name
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Table 4.1