Download Ch 3 – Cell Structure The Cell Theory

10/1/2008
Chapter 3
Cells Under the Microscope
Electron microscopes have much higher magnifying and resolving powers
than light microscopes.
Ch 3 – Cell Structure
Biology – Periods 2, 3, 4, & 6
Mrs. Stolipher
• Cell size and
shape relate
to function
Figure 4.2
Chapter 3
Natural laws limit cell size
The Cell Theory
The Cell Theory has three parts:
1. All living things are made of one or more
cells.
• At minimum, a cell must be large enough to house the
parts it needs to survive and reproduce
• The maximum size of a cell is limited by the amount of
surface needed to obtain nutrients from the
environment and dispose of wastes
2. Cells are the basic units of structure and
function in organisms.
3. All cells arise from existing cells.
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• A small cell has a greater ratio of surface area
to volume than a large cell of the same shape
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.
30 µm
10 µm
Surface area
of one large
cube
= 5,400 µm2
Total surface
area
of 27 small
cubes
= 16,200 µm2
Figure 4.3
Common Cell Features
Prokaryotes
ALL 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
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.
Eukaryotic cells are partitioned into
functional compartments
Two Groups of Prokaryotes
• Early in the history of life, two different groups of
prokaryotes evolved—eubacteria (which are
commonly called bacteria) and archaebacteria.
• Eubacteria are prokaryotes that contain a
chemical called peptidoglycan in their cell walls.
• All other life forms are made up of one or
more eukaryotic cells
• These are larger and more complex than
prokaryotic cells
• Eukaryotes are distinguished by the
presence of a true nucleus
• Archaebacteria are prokaryotes that lack
peptidoglycan in their cell walls and have unique
lipids in their cell membranes.
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Eukaryotic Cells
Eukaryotic cells have:
• A nucleus which contains the cell’s DNA
• Other internal compartments called
organelles.
Eukaryotic Cells
• 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.
The Cell Membrane
• The cell (plasma) membrane controls the cell’s
contact with the environment
• 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.
Chapter 3
Section 2 Cell Features
Comparing Prokaryotes and
Eukaryotes
Watch video clip
Ch 3 – Sect 2 – vc10
Eukaryotic Cells, continued
The cytoskeleton’s
network of
protein fibers
anchors the cell’s
organelles and
other
components of
the cytoplasm.
The Cell Membrane, continued
Cell membranes are made of a double layer of
phospholipids, called a bilayer.
• A phospholipid is a lipid made of a phosphate
group and two fatty acids.
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The Cell Membrane, continued
The Nucleus - cell’s genetic control
center
• Generally the largest organelle
• 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.
• is surrounded by a double membrane called the
nuclear envelope, which separates the nucleus from
the cytoplasm
• Scattered over the surface of the nuclear envelope are
many small channels called nuclear pores.
Chapter 3
The Nucleus, continued
Overview: Many cell organelles are related through the
endomembrane system
• The endomembrane system is a collection
of membranous organelles
– These organelles manufacture and distribute
cell products
– The endomembrane system divides the cell
into compartments
– Endoplasmic reticulum (ER) is part of the
endomembrane system
Section 3 Cell Organelles
Nucleus of a Cell
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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Ribosomes and the Endoplasmic
Reticulum, continued
The ER moves proteins and other substances within
eukaryotic cells.
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.
Smooth endoplasmic reticulum has a
variety of functions
• The rough ER manufactures membranes
• Ribosomes on its surface produce proteins
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Transport
vesicle
buds off
Riboso
me
Sugar
chain
• Smooth ER synthesizes lipids
• In some cells, it regulates carbohydrate
metabolism and breaks down toxins and drugs
protein
inside
transport
vesicle
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Glycoprotein
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Figure 4.8
2
ROUGH
ER
Polypept
ide
Ribosomes and the Endoplasmic
Reticulum, continued
SMOOTH ER
ROUGH
ER
Nuclear
envelope
Ribosomes
SMOOTH ER
ROUGH ER
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.
Figure 4.9
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The Golgi apparatus finishes, sorts, and
ships cell products
Chapter 3
Section 3 Cell Organelles
Golgi Apparatus
– The Golgi apparatus is a set of flattened, membrane-bound
sacs that serve as the packaging and distribution center of the
cell.
– These receive and modify ER products, then send them on to
other organelles or to the cell membrane
Lysosomes digest the cell’s food and
wastes
• Lysosomes are
sacs of digestive
enzymes budded
off the Golgi
• Lysosomal enzymes
LYSOSOME
Nucleus
– digest food
– destroy bacteria
– recycle damaged
organelles
– function in
embryonic
Connection: Abnormal lysosomes can
cause fatal diseases
Rough ER
Transport vesicle
(containing inactive
hydrolytic enzymes)
Plasma
membrane
Golgi
apparatus
• Lysosomal storage diseases are hereditary
– They interfere with other cellular functions
– Examples: Pompe’s disease - genetic disorder caused by a deficiency or
dysfunction of the lysosomal hydrolase which breaks down glycogen. The build-up of glycogen
causes progressive muscle weakness throughout the body and affects various body tissues,
particularly in the heart, skeletal muscles, liver and nervous system.
Engulfment
of particle
Lysosome
engulfing
damaged
organelle
“Food”
– Tay-Sachs disease - occurs when harmful quantities of a fatty acid derivative called a
ganglioside accumulate in the nerve cells of the brain. It is usually fatal.
LYSOSOMES
Food
vacuole
Digestion
Figure 4.11B
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A review of the endomembrane system
• The various organelles of the
endomembrane system are interconnected
structurally Trans
and functionally
Transpo
Rough
ER
port
vesicl
e
from
ER
rt
vesicle
from
Golgi
Nuclear
envelope
Lysoso
Golgi me
appara
tus
• Mitochondria are organelles that harvest
energy from organic compounds (food) to
make ATP.
• Mitochondria carry out cellular respiration
– This process uses the chemical energy in food to
make ATP for cellular work
• ATP is the main energy currency of cells. Most
ATP is made inside the mitochondria.
Vacu
ole
Nucleus
Smo
oth
ER
Plasm
a
membr
ane
Mitochondria
Figure 4.14
Mitochondria, continued
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.
– They reproduce independently of the cell.
– Mitochondrial DNA is similar to the DNA of
prokaryotic cells.
• Mitochondria are thought to be descendents of
primitive prokaryotes.
Structures of Plant Cells
Structures of Plant Cells – cell
wall
Plants have three unique structures that are not
found in animal cells:
• The cell membrane of plant cells is
surrounded by a thick cell wall, composed of
proteins and carbohydrates.
• Cell Wall
• The cell wall
• Chloroplasts
• helps support and maintain the shape of the cell
• protects the cell from damage
• Central Vacuole
• connects the cell with adjacent cells
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Structures of Plant Cells chloroplasts
• are organelles that use light energy to
make carbohydrates from carbon
dioxide and water.
• along with mitochondria, supply much
of the energy needed to power the
activities of plant cells.
• like mitochondria, chloroplasts
– have their own DNA and reproduce
independently of the plant cell.
– are thought to be descendents of ancient
prokaryotes.
Nucleus
Structures of Plant Cell –
central vacuole
• Most of a plant cell’s volume is taken up by a
large, membrane-bound space called the
central vacuole.
• Functions in general maintenance of the cell
• The central vacuole stores water and may
contain ions, nutrients, and wastes.
• Protists (single celled eukaryotes) may have
contractile vacuoles
– Which work to pump out excess water
Rough
endoplasmic
reticulum
An animal cell
Ribosomes
Rough
endoplasmic
reticulum
Smooth
endoplasmic
reticulum
Golgi
apparatus
Central
vacuole
Cytoskeleton
Chloroplast
Nucleus
Flagellum
Microtubule
Not in
animal
cells
Smooth
endoplasmic
reticulum
Not in most
plant cells
Lysosome
Microfilament
Cell wall
Ribosomes
Mitochondrion
Microtubule
Cytoskeleton
Plasma membrane
Figure 4.5B
Golgi
apparatus
Plasma
membrane
Microfilament
Mitochondrion
Figure 4.5A
Summary of Organelles
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