Download 4. A Tour of the Cell

Chapter 4
A Tour of the Cell
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Art of Looking at Cells
• Artists have long found inspiration in the visual
richness of the living world
• Conversely, scientists use art to illuminate their
findings
– Micrographs show structures as scientists
see them
– Drawings can emphasize details
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
INTRODUCTION TO THE CELL
4.1 Microscopes provide windows to the world of
the cell
• A light microscope (LM) enables us to see the
overall shape and structure of a cell
– Passes visible light through a specimen
– Can study living cells and cells and tissues
that have been stained
– Can magnify only about 1,000 times
Video: Euglena
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-1a
Eyepiece
Ocular
lens
Objective lens
Specimen
Condenser
lens
Light
source
• Magnification is the increase in the apparent
size of an object; for example, 1,000X
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Resolution is a measure of the clarity of an
image
– A light microscope can resolve objects as
small as 2 m
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The electron microscope (EM) allows greater
magnification than LM and reveals cellular
details
– Uses a beam of electrons rather than light
– Has much greater resolution than LM (2
nm)
– Can magnify up to 100,000 times
– Cannot be used with living specimens
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Scanning electron microscope (SEM) studies
detailed architecture of cell surfaces
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Transmission electron microscope (TEM)
studies the details of internal cell structure
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Modifications to LM use different techniques to
enhance contrast and selectively highlight
cellular components
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4.2 Most cells are microscopic
• Cells vary in size and shape
– Minimum is determined by the total size of
all the molecules required for cellular
activity
– Maximum is limited by the need for
sufficient surface area to carry out functions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-2a
Human height
Length of some
nerve and
muscle cells
Chicken egg
Frog egg
Most plant and
animal cells
Nucleus
Most bacteria
Mitochondrion
Mycoplasmas
(smallest bacteria)
Viruses
Ribosome
Proteins
Lipids
Small molecules
Atoms
• A small cell has a greater ratio of surface area
to volume than a large cell of the same shape
• The microscopic size of most cells ensures a
sufficient surface area across which nutrients
and wastes can move to service the cell
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-2b
10 m
30 m
30 m
Surface area of one
large cube = 5,400 m2
10 m
Total surface area of 27
small cubes = 16,200 m2
4.3 Prokaryotic cells are structurally simpler than
eukaryotic cells
• There are two kinds of cells
– Prokaryotic (bacteria, archaea)
– Eukaryotic (protists, plants, fungi, animals)
• All cells share some common features
– Plasma membrane
– DNA
– ribosomes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-3a
Prokaryotic cell
Nucleoid
region
Nucleus
Organelles
Eukaryotic cell
• Prokaryotic cells
– Usually relatively small, relatively simple
cells
• Do not have a membrane-bound nucleus
• DNA is coiled into a nucleoid region in the
cytoplasm
• Cytoplasm includes ribosomes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Other prokaryotic structures
– Plasma membrane
– Complex cell wall
– Capsule, pili, prokaryotic flagella in some
forms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-3b
Prokaryotic
flagella
Ribosomes
Capsule
Cell wall
Plasma
membrane
Nucleoid region (DNA)
Pili
4.4 Eukaryotic cells are partitioned into functional
compartments
• Eukaryotic cells are usually larger than
prokaryotic cells (10-100 (m diameter)
– Distinguished by a true nucleus
– Contain both membranous and
nonmembranous organelles
• Compartmentalize metabolism
• Increase membrane surface area for
reactions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Animal cells
– Are bounded by the plasma membrane
alone
– Lack a cell wall
– Contain centrioles and lysosomes
– Often have flagella
Video: Cytoplasmic Streaming
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-4a
Rough
endoplasmic
reticulum
Smooth
endoplasmic
reticulum
Nucleus
Flagellum
Not in most
plant cells
Lycosome
Centriole
Ribosomes
Peroxisome
Microtubule
Cytoskeleton
Intermediate
filament
Microfilament
Golgi
apparatus
Plasma membrane
Mitochondrion
• Plant cells
– Are bounded by both a plasma membrane
and a rigid cellulose cell wall
– Have a central vacuole and chloroplasts
– Usually lack centrioles, lysosomes, and
flagella
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-4b
Nucleus
Rough endoplasmic
reticulum
Ribosomes
Smooth endoplasmic
reticulum
Golgi
apparatus
Microtubule
Central
vacuole
Not in
animal
Chloroplast
cells
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
Intermediate
filament
Microfilament
Cytoskeleton
ORGANELLES OF THE ENDOMEMBRANE SYSTEM
4.5 The nucleus is the cell's genetic control
center
• The nucleus contains the cell's DNA
– Controls cellular activities by directing
protein synthesis
– Forms long fibers of chromatin that make up
chromosomes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The nucleus is separated from the cytoplasm
by the nuclear envelope
– Pores in the envelope control flow of
materials in and out
– Ribosomes are synthesized in the nucleolus
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-5
Nucleus
Chromatin
Nucleolus
Two membranes
of nuclear envelope
Pore
Rough
endoplasmic
reticulum
Ribosomes
4.6 Overview: Many cell organelles are
connected through the endomembrane system
• The endomembrane system is a collection of
membranous organelles
– Divide the cell into compartments
– Work together in the synthesis, storage, and
export of molecules
• Prime example: Endoplasmic reticulum (ER)
– A continuous network of flattened sacs and
tubes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4.7 Smooth endoplasmic reticulum has a variety
of functions
• Smooth endoplasmic reticulum (smooth ER)
lacks attached ribosomes
– Synthesizes lipids
– Processes materials such as toxins and
drugs in liver cells
– Stores and releases calcium ions in muscle
cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-7
Smooth ER
Rough ER
Nuclear
envelope
Ribosomes
Rough ER
TEM 45,000
Smooth ER
4.8 Rough endoplasmic reticulum makes
membrane and proteins
• Rough endoplasmic reticulum (rough ER) is
studded with ribosomes
– Manufactures membranes
– Modifies and packages proteins that will be
• Transported to other organelles
• Secreted by the cell
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-8
Transport vesicle
buds off
Secretary
(glyco-) protein
inside transport vesicle
Ribosome
Sugar
chain
Glycoprotein
Polypeptide
Rough ER
4.9 The Golgi apparatus finishes, sorts, and ships
cell products
• The Golgi apparatus consists of stacks of
flattened membranous sacs
– Receives and modifies substances
manufactured by ER
– Ships modified products to other organelles
or the cell surface
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-9
Golgi
apparatus
“Receiving” side of
Golgi apparatus
Transport
vesicle
from ER
New vesicle
forming
“Shipping”
side of Golgi
apparatus
Transport
vesicle from
the Golgi
Golgi apparatus
4.10 Lysosomes are digestive compartments
within a cell
• Lysosomes are sacs of enzymes that form
from the Golgi apparatus
– Function in digestion within a cell
– Destroy bacteria that have been ingested
into white blood cells
– Recycle damaged organelles
Animation: Lysosome Formation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-10a
Rough ER
Transport vesicle
(containing inactive
hydrolytic enzymes)
Plasma
membrane
Golgi
apparatus
Engulfment
of particle
Lysosome
engulfing
damaged
organelle
“Food”
Lysosomes
Food
vacuole
Digestion
LE 4-10b
Lysosome
TEM 8,500 
Nucleus
LE 4-10c
Mitochondrion fragment
Peroxisome fragment
TEM 42,500 
Lysosome containing
two damaged organelles
CONNECTION
4.11 Abnormal lysosomes can cause fatal
diseases
• Lysosomal storage diseases
– Result from an inherited lack of one or more
lysosomal enzymes
– Seriously interfere with various cellular
functions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4.12 Vacuoles function in the general
maintenance of the cell
• Plant cells contain a large central vacuole
– Has lysosomal and storage functions
• Some protists have contractile vacuoles
– Pump excess water out of cell
Video: Paramecium Vacuole
Video: Chlamydomonas
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-12a
Nucleus
Colorized TEM 8,700 
Chloroplast
Central
vacuole
LE 4-12b
Contractile
vacuoles
LM 650
Nucleus
4.13 A review of the endomembrane system
• The various organelles of the endomembrane
system are interconnected structurally and
functionally
Animation: Endomembrane System
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-13
Rough ER
Transport vesicle
from ER to Golgi
Transport vesicle from
Golgi to plasma membrane
Plasma
membrane
Nucleus
Vacuole
Lysosome
Smooth ER
Nuclear envelope
Golgi apparatus
ENERGY-CONVERTING ORGANELLES
4.14 Chloroplasts convert solar energy to
chemical energy
• Chloroplasts are found in plants and some
protists
– Are the site of photosynthesis
– Have a complex membranous structure for
capturing and converting light energy
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-14
Stroma
Chloroplast
Granum
Intermembrane
space
TEM 9,750
Inner and outer
membranes
4.15 Mitochondria harvest chemical energy from
food
• Mitochondria are found in nearly all eukaryotic
cells
– Divided into two membranous
compartments
• Intermembrane space
• Second compartment enclosed by inner
membrane
– Contains fluid mitochondrial matrix
– Membrane folded into cristae
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
– Carry out cellular respiration
• Convert the chemical energy in food to ATP
for cellular work
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-15
Mitochondrion
Outer
membrane
Intermembrane
space
Cristae
Matrix
TEM 44,880
Inner
membrane
THE CYTOSKELETON AND RELATED STRUCTURES
4.16 The cell's internal skeleton helps organize
its structure and activities
• The cytoskeleton is network of three types of
protein fibers
– Microfilaments
• Rods of globular proteins
• Enable cells to change shape and move
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
– Intermediate filaments
• Ropes of fibrous proteins
• Reinforce the cell and anchor certain
organelles
– Microtubules
• Hollow tubes of globular proteins
• Give the cell rigidity
• Anchor organelles and act as tracks for
organelle movement
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-16
Tubulin subunit
Actin subunit
Fibrous subunit
25 nm
7 nm
Microfilament
10 nm
Intermediate filament
Microtubule
4.17 Cilia and flagella move when microtubules
bend
• Eukaryotic cilia and flagella are locomotor
appendages that protrude from certain cells
– Move whole cells or materials across the
cell surface
Video: Paramecium Cilia
Animation: Cilia and Flagella
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The structure and mechanism of cilia and
flagella are similar
– Microtubules wrapped in an extension of the
plasma membrane
• 9 + 2 arrangement
• Extend into basal bodies
• Movement of dynein arms produces
microtubule bending
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-17c
Flagellum
Electron micrographs
of cross sections:
TEM 206,500
Outer microtubule
doublet
Central
microtubules
Radial spoke
Dynein arms
Flagellum
Basal body
(structurally
identical to
centriole)
TEM 206,500
Plasma
membrane
Basal body
CELL SURFACES AND JUNCTIONS
4.18 Cell surfaces protect, support, and join cells
• Cells interact with their environments and each
other via their surfaces
• Many cells are protected by more than the
plasma membrane
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Plant cell walls
– Made largely of cellulose
– Provide protection and support
– Connect by plasmodesmata, channels
through the wall
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-18a
Walls
of two
adjacent
plant cells
Vacuole
Plasmodesmata
Layers
of one plant
cell wall
Cytoplasm
Plasma membrane
• Animal cells
– Embedded in an extracellular matrix that
binds cells together in tissues
– Connect by cell junctions
• Tight junctions bind cells into leakproof
sheets
• Anchoring junctions link cells into strong
tissues
• Gap junctions allow substances to flow from
cell to cell
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 4-18b
Tight junctions
Anchoring junction
Gap junctions
Extracellular matrix
Space between cells
Plasma membranes of adjacent cells
Animation: Tight Junctions
Animation: Desmosomes
Animation: Gap Junctions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
FUNCTIONAL CATEGORIES OF ORGANELLES
4.19 Eukaryotic organelles comprise four
functional categories
• Eukaryotic organelles fall into four functional
categories that work together to produce the
cell's emergent properties
– Manufacturing
– Breakdown
– Energy processing
– Support, movement, and communication
between cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings