Download Eukaryotic cells

Chapter 4
A Tour of the Cell
PowerPoint® Lectures for
Campbell Essential Biology, Fourth Edition
– Eric Simon, Jane Reece, and Jean Dickey
Campbell Essential Biology with Physiology, Third Edition
– Eric Simon, Jane Reece, and Jean Dickey
Lectures by Chris C. Romero, updated by Edward J. Zalisko
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10 m
1m
Length of some
nerve and
muscle cells
10 cm
Chicken egg
Unaided eye
Human height
1 cm
Frog eggs
Plant and
animal cells
10 mm
1 mm
100 nm
Nucleus
Most bacteria
Mitochondrion
Smallest bacteria
Viruses
Ribosomes
10 nm
Electron microscope
100 mm
Light microscope
1 mm
Proteins
Lipids
1 nm
0.1 nm
Small molecules
Atoms
Figure 4.3
The Two Major Categories of Cells
• The countless cells on earth fall into two categories:
– Prokaryotic cells — Bacteria and Archaea
– Eukaryotic cells — plants, fungi, and animals
• All cells have several basic features.
– They are all bound by a thin plasma membrane.
– All cells have DNA and ribosomes, tiny structures that build proteins.
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CATEGORIES OF CELLS
Prokaryotic Cells
• Smaller
• Simpler
• Most do not have organelles
• Found in bacteria and archaea
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Eukaryotic Cells
• Larger
• More complex
• Have organelles
• Found in protists, plants,
fungi, animals
Figure 4.UN12
• Prokaryotes
– Are smaller than eukaryotic cells
– Lack internal structures surrounded by membranes
– Lack a nucleus
– Have a rigid cell wall
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• Eukaryotes
– Only eukaryotic cells have organelles, membrane-bound structures that
perform specific functions.
– The most important organelle is the nucleus, which houses most of a
eukaryotic cell’s DNA.
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Plasma membrane
(encloses cytoplasm)
Cell wall (provides rigidity)
Capsule (sticky coating)
Prokaryotic
flagellum
(for propulsion)
Ribosomes
(synthesize
proteins)
Nucleoid
(contains DNA)
Pili (attachment structures)
Figure 4.4a
An Overview of Eukaryotic Cells
• Eukaryotic cells are fundamentally similar.
• The region between the nucleus and plasma membrane is the
cytoplasm.
• The cytoplasm consists of various organelles suspended in fluid.
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• Unlike animal cells, plant cells have
– Protective cell walls
– Chloroplasts, which convert light energy to the chemical energy of food
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Ribosomes
Cytoskeleton
Centriole
Lysosome
Not in most
plant cells
Flagellum
Plasma
membrane
Nucleus
Mitochondrion
Rough
endoplasmic
reticulum (ER)
Golgi
apparatus
Idealized animal cell
Smooth
endoplasmic
reticulum (ER)
Figure 4.5a
Cytoskeleton
Central
vacuole
Cell wall
Chloroplast
Mitochondrion
Nucleus
Not in
animal cells
Rough endoplasmic
reticulum (ER)
Ribosomes
Plasma
membrane
Smooth
endoplasmic
reticulum (ER)
Channels between
cells
Golgi apparatus
Idealized plant cell
Figure 4.5b
MEMBRANE STRUCTURE
• The plasma membrane separates the living cell from its nonliving
surroundings.
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The Plasma Membrane: A Fluid Mosaic of
Lipids and Proteins
• The membranes of cells are composed mostly of
– Lipids
– Proteins
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• The lipids belong to a special category called phospholipids.
• Phospholipids form a two-layered membrane, the phospholipid
bilayer.
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Outside of cell
Hydrophilic
head
Hydrophobic
tail
Hydrophilic
region of
protein
Outside of cell
Hydrophilic
head
Proteins
Phospholipid
bilayer
Hydrophobic
tail
Phospholipid
Cytoplasm (inside of cell)
(a) Phospholipid bilayer of
membrane
Hydrophobic
regions of
protein
Cytoplasm (inside of cell)
(b) Fluid mosaic model of
membrane
Figure 4.6
• Most membranes have specific proteins embedded in the
phospholipid bilayer.
• These proteins help regulate traffic across the membrane and
perform other functions.
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• The plasma membrane is a fluid mosaic:
– Fluid because molecules can move freely past one another
– A mosaic because of the diversity of proteins in the membrane
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Cell Surfaces
• Plant cells have rigid cell walls surrounding the membrane.
• Plant cell walls
– Are made of cellulose
– Protect the cells
– Maintain cell shape
– Keep the cells from absorbing too much water
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THE NUCLEUS AND RIBOSOMES:
GENETIC CONTROL OF THE CELL
• The nucleus is the chief executive of the cell.
– Genes in the nucleus store information necessary to produce proteins.
– Proteins do most of the work of the cell.
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Structure and Function of the Nucleus
• The nucleus is bordered by a double membrane called the nuclear
envelope.
• Pores in the envelope allow materials to move between the
nucleus and cytoplasm.
• The nucleus contains a nucleolus where ribosomes are made.
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Nuclear
envelope
Nucleolus
Pore
TEM
Chromatin
TEM
Ribosomes
Surface of nuclear envelope
Nuclear pores
Figure 4.8
• Stored in the nucleus are long DNA molecules and associated
proteins that form fibers called chromatin.
• Each long chromatin fiber constitutes one chromosome.
• The number of chromosomes in a cell depends on the species.
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DNA molecule
Proteins
Chromatin
fiber
Chromosome
Figure 4.9
Ribosomes
• Ribosomes are responsible for protein synthesis.
• Ribosome components are made in the nucleolus but assembled in
the cytoplasm.
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• Ribosomes may assemble proteins:
– Suspended in the fluid of the cytoplasm or
– Attached to the outside of an organelle called the endoplasmic reticulum
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How DNA Directs Protein Production
• DNA directs protein production by transferring its coded
information into messenger RNA (mRNA).
• Messenger RNA exits the nucleus through pores in the nuclear
envelope.
• A ribosome moves along the mRNA translating the genetic
message into a protein with a specific amino acid sequence.
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DNA
Synthesis of
mRNA in the
nucleus
mRNA
Nucleus
Cytoplasm
Movement of
mRNA into
cytoplasm
via
nuclear pore
Synthesis of
protein in the
cytoplasm
mRNA
Ribosome
Protein
Figure 4.12-3
THE ENDOMEMBRANE SYSTEM:
MANUFACTURING AND DISTRIBUTING
CELLULAR PRODUCTS
• Many membranous organelles forming the endomembrane
system in a cell are interconnected either
– Directly or
– Through the transfer of membrane segments between them
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The Endoplasmic Reticulum
• The endoplasmic reticulum (ER) is one of the main
manufacturing facilities in a cell.
• The ER
– Produces an enormous variety of molecules
– Is composed of smooth and rough ER
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Nuclear
envelope
Ribosomes
TEM
Rough ER
Smooth ER
Ribosomes
Figure 4.13
Rough ER
• The “rough” in the rough ER is due to ribosomes that stud the
outside of the ER membrane.
• These ribosomes produce membrane proteins and secretory
proteins.
• After the rough ER synthesizes a molecule, it packages the
molecule into transport vesicles.
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Proteins are
often modified in
the ER.
Secretory
proteins depart in
transport vesicles.
Ribosome
Vesicles bud off
from the ER.
Transport
vesicle
Protein
A ribosome
links amino acids
into a
polypeptide.
Rough ER
Polypeptide
Figure 4.14
Smooth ER
• The smooth ER
– Lacks surface ribosomes
– Produces lipids, including steroids
– Helps liver cells detoxify circulating drugs
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The Golgi Apparatus
• The Golgi apparatus
– Works in partnership with the ER
– Receives, refines, stores, and distributes chemical products of the cell
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“Receiving” side of
Golgi apparatus
Transport vesicle
from rough ER
“Receiving” side
of Golgi
apparatus
New
vesicle
forming
“Shipping” side
of Golgi
apparatus
Transport
vesicle
from the
Golgi
Plasma
membrane
New vesicle forming
Figure 4.15
Lysosomes
• A lysosome is a sac of digestive enzymes found in animal cells.
• Enzymes in a lysosome can break down large molecules
• Lysosomes can also
– Destroy harmful bacteria
– Break down damaged organelles
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Vacuoles
• Vacuoles are membranous sacs that bud from the
– ER
– Golgi
– Plasma membrane
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• Contractile vacuoles of protists pump out excess water in the cell.
• Central vacuoles of plants
– Store nutrients
– Absorb water
– May contain pigments or poisons
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LM
Vacuole filling with water
LM
Vacuole contracting
Colorized TEM
(a) Contractile vacuole in Paramecium
Central vacuole
(b) Central vacuole in a plant cell
Figure 4.17
Chloroplasts
• Most of the living world runs on the energy provided by
photosynthesis.
• Photosynthesis is the conversion of light energy from the sun to
the chemical energy of sugar.
• Chloroplasts are the organelles that perform photosynthesis.
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• Chloroplasts have three major compartments:
– The space between the two membranes
– The stroma, a thick fluid within the chloroplast
– The space within grana, the structures that trap light energy and convert
it to chemical energy
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Inner and outer
membranes
Space between
membranes
Granum
TEM
Stroma (fluid in chloroplast)
Figure 4.19
Mitochondria
• Mitochondria are the sites of cellular respiration, which produce
ATP from the energy of food molecules.
• Mitochondria are found in almost all eukaryotic cells.
• An envelope of two membranes encloses the mitochondrion.
These consist of
– An outer smooth membrane
– An inner membrane that has numerous infoldings called cristae
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TEM
Outer
membrane
Inner
membrane
Cristae
Matrix
Space between
membranes
Figure 4.20
THE CYTOSKELETON: CELL SHAPE AND
MOVEMENT
• The cytoskeleton is a network of fibers extending throughout the
cytoplasm.
• The cytoskeleton
– Provides mechanical support to the cell
• Maintains its shape
• The cytoskeleton contains several types of fibers made from
different proteins:
– Microtubules
–
Are straight and hollow
–
Guide the movement of organelles and chromosomes
– Intermediate filaments and microfilaments are thinner and solid.
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LM
(a) Microtubules
in the cytoskeleton
LM
(b) Microtubules
and movement
Figure 4.21
Cilia and Flagella
• Cilia and flagella aid in movement.
– Flagella propel the cell in a whiplike motion.
– Cilia move in a coordinated back-and-forth motion.
– Cilia and flagella have the same basic architecture.
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Colorized SEM
(a) Flagellum of a human sperm cell
Colorized SEM
Colorized SEM
(b) Cilia on a protist
(c) Cilia lining the
respiratory tract
Figure 4.22
Evolution Connection:
The Evolution of Antibiotic Resistance
• Many antibiotics disrupt cellular structures of invading
microorganisms.
• Introduced in the 1940s, penicillin worked well against such
infections.
• But over time, bacteria that were resistant to antibiotics were
favored.
• The widespread use and abuse of antibiotics continues to favor
bacteria that resist antibiotics.
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