Transcript Ch. 4: A Tour of the Cell

A Tour of the Cell
Ch. 4
Ms. Haut
INTRODUCTION TO THE WORLD OF
THE CELL
• The microscope was
invented in the 17th
century
• Using a microscope,
Robert Hooke
discovered cells in
1665
• All living things are
made of cells (cell
theory)
http://www.edu365.com/aulanet/comsoc/persones_t
ecniques/Robert_Hooke_archivos/Robert_Hooke.jpg
Principles of the Cell Theory
1. All living things are made of one or more
cells
2. Cells are the basic unit of structure &
function in organisms
3. Cells come only from the reproduction of
existing cells
Microscopes provide windows
to the world of the cell
• The light microscope enables us to see the
overall shape and structure of a cell
Image seen by viewer
Eyepiece
Ocular
lens
Objective lens
Specimen
Condenser lens
Red blood cells
Light source
teaching.path.cam.ac.uk/partIB_pract/NHP1/
Figure 4.1A
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Electron microscopes
• Invented in the 1950s
• They use a beam of
electrons instead of
light
• The greater resolving
power of electron
microscopes
– allows greater
magnification
– reveals cellular details
websemserver.materials.ox.ac.uk/cybersem/getf...
Scanning electron microscope
(SEM)
• Used to see detailed structure of cell surface
Red blood cells
Figure 4.1B
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http://commons.wikimedia.org/wiki/Image:SEM_blood_
cells.jpg
Transmission electron microscope
(TEM)
• Used to examine the internal structures of a
cell
Red blood cell in capillary
commons.wikimedia.org/wiki/Image:A_red_blood_...
Figure 4.1C
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• Cell size and
shape relate
to function
Figure 4.2
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Natural laws limit cell size
• 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
• A small cell has a greater ratio of surface
area to volume than a large cell of the same
shape
30 µm
Figure 4.3
Surface area
of one large cube
= 5,400 µm2
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10 µm
Total surface area
of 27 small cubes
= 16,200 µm2
Categories of Cells
Prokaryotic
Eukaryotic
•Smaller size
•Larger size
•Simpler structure
•More complex structure
•DNA in nucleoid region
(no nucleus)
•DNA in a membrane
bound nucleus
•No membranous
organelles
•Contains membranous
organelles
Prokaryotes
• Enclosed by a
plasma membrane
• Usually encased in
a rigid cell wall
– The cell wall may be
covered by a sticky
capsule
• Inside the cell are its
DNA and other parts
Prokaryotic
flagella
Ribosomes
Capsule
Cell wall
Plasma
membrane
Pili
Nucleoid region
(DNA)
Figure 4.4
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Eukaryotic cells are partitioned
into functional compartments
• 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
• An animal cell
Rough
endoplasmic
reticulum
Smooth
endoplasmic
reticulum
Nucleus
Flagellum
Not in most
plant cells
Lysosome
Centriole
Ribosomes
Peroxisome
Microtubule
Cytoskeleton
Intermediate
filament
Microfilament
Figure 4.5A
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Golgi
apparatus
Plasma membrane
Mitochondrion
The Plasma Membrane:
A Fluid Mosaic of Lipids and Proteins
• The membranes of
cells are composed
of:
•
•
•
Phospholipids
Proteins
Cholesterol
http://bio.winona.edu/berg/ILLUST/memb-mod.jpg
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Plasma Membrane
• Phospholipids form a
two-layered
membrane, the
phospholipid bilayer.
Figure 4.7a
Plasma Membrane
• Most membranes
have specific proteins
embedded in the
phospholipid bilayer.
• Proteins serve a
number of functions
• Transport channels
• Enzymes
Figure 4.7b
Plasma Membrane
• Cholesterol molecules
help keep the
membrane “fluid” at
lower temperatures
http://sps.k12.ar.us/massengale/images/cell20membrane.jpg
Cholesterol
http://www.uic.edu/classes/bios/bios100/lectf03am/cholesterol.jpg
Fluid Mosaic Model
• Fluid part of model:
• Membrane phospholipids and proteins can
drift about in the plane of the membrane.
• Mosaic part of model:
• A diversity of molecules exists within the
membrane
• Phospholipids
• Different proteins
• Cholesterol
Membranes
• The plasma membrane
separates the living cell
from its nonliving
surroundings.
• The cytoplasm contains
organelles
• Most organelles have
membranes
– These compartmentalize
the interior of the cell
– This allows the cell to carry
out a variety of activities
simultaneously
Plant Cells
• A plant cell has some
structures that an
animal cell lacks:
– Chloroplasts
– A rigid cell wall
– Central vacuole
– Plasmodesmata
Nucleus
The nucleus is the cell’s genetic
control center
• The largest organelle is usually the nucleus
• The nucleus is separated from the cytoplasm
by the nuclear envelope
• The nucleus is the cellular control center
– It contains the DNA that directs the cell’s
activities
NUCLEUS
Chromatin
Nucleolus
Two membranes
of nuclear
envelope
Pore
ROUGH
ENDOPLASMIC
RETICULUM
Figure 4.6
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Ribosomes
Many cell organelles are related through the
endomembrane system
• The endomembrane
system is a collection
of membranous
organelles
– Organelles
manufacture and
distribute cell products
– Divides cell into
compartments
Rough endoplasmic reticulum
• The rough ER manufactures membranes
• Ribosomes on its surface are sites where
proteins are made
Transport
vesicle
buds off
4
Ribosome
Sugar
chain
1
Polypeptide
http://micro.magnet.fsu.edu/cells/endoplasmicreticulum/images/en
doplasmicreticulumfigure1.jpg
3
Secretory
(glyco-) protein
inside transport
vesicle
Glycoprotein
2
ROUGH ER
Figure 4.8
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Smooth endoplasmic reticulum
has a variety of functions
• Smooth ER
synthesizes lipids
• In some cells, it
regulates
carbohydrate
metabolism and
breaks down toxins
and drugs
SMOOTH ER
ROUGH
ER
Nuclear
envelope
Ribosomes
SMOOTH ER
Figure 4.9
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
ROUGH ER
Golgi apparatus
• The Golgi apparatus consists of stacks of
membranous sacs
– These receive and modify ER products, then send
them on to other organelles or to the cell membrane
Figure 4.12
Lysosomes digest the cell’s food
and wastes
• A membraneenclosed sac
budded off the Golgi
LYSOSOME
Nucleus
– It contains digestive
enzymes.
– The enzymes break
down
macromolecules
Figure 4.11A
Lysosomal enzymes
• digest food
• destroy bacteria
• recycle damaged
organelles
• function in embryonic
development in
animals
http://sun.menloschool.org/~cweaver/cells/e/lysosomes/lysozome.jpg
Peroxisomes
• Specialized lysosome
containing catalase
• Produces hydrogen
peroxide (H2O2) as
waste product
• Catalase breaks
down toxic H2O2
http://faculty.une.edu/com/abell/histo/peroxisome.jpg
H2O2 ---catalase---> H2O + O2
Vacuoles function in the general
maintenance of the cell
• Plant cells
contain a large
central vacuole
– The vacuole
has lysosomal
and storage
functions
Central
vacuole
Nucleus
Figure 4.13A
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Contractile Vacuole
• Protists may have
contractile vacuoles
Nucleus
– These pump out
excess water
Contractile
vacuoles
Figure 4.13B
Collapsing contractile vacuole of Protozoa
www.microscopy-uk.org.uk/.../vidjuna.html
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
A review of the endomembrane
system
• The various organelles of the
endomembrane system are interconnected
structurally and functionally
Rough
ER
Transport
vesicle
from Golgi
Transport
vesicle
from ER
Plasma
membrane
Vacuole
Nucleus
Lysosome
Smooth
ER
Nuclear
envelope
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Golgi
apparatus
Figure 4.14
ENERGY-CONVERTING
ORGANELLES
• Chloroplasts
• Mitochondria
Chloroplasts
• Chloroplasts are
found in plants and
some protists
• Chloroplasts convert
solar energy to
chemical energy in
sugars
Figure 4.16
Mitochondria
• Mitochondria carry out cellular respiration
– This process uses the chemical energy
in food to make ATP for cellular work
Figure 4.17
Endosymbiosis
– Mitochondria and chloroplasts each contain their own
DNA separate from the nucleus.
– Evidence for Endosymbiosis theory
•
Mitochondria and chloroplasts evolved from
free-living prokaryotes in the distant past.
http://faculty.ircc.edu/faculty/tfischer/images/endosymbiosis.jpg
THE CYTOSKELETON AND
RELATED STRUCTURES
The cell’s internal skeleton helps organize
its structure and activities
• A network of protein fibers makes up the
cytoskeleton
Figure 4.17A
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3 Types of fibers make up the
cytoskeleton
• Microfilaments of actin enable cells to
change shape and move
• Intermediate filaments reinforce the cell and
anchor certain organelles
• Microtubules
– give the cell rigidity
– provide anchors for organelles
– act as tracks for organelle movement
Actin subunit
Tubulin
subunit
Fibrous subunits
25 nm
7 nm
MICROFILAMENT
10 nm
INTERMEDIATE
FILAMENT
Figure 4.17B
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MICROTUBULE
Cilia and flagella move when
microtubules bend
• Eukaryotic cilia and
flagella are locomotor
appendages that
protrude from certain
cells
• A cilia or flagellum is
composed of a core
of microtubules
wrapped in an
extension of the
plasma membrane
http://fig.cox.miami.edu/~cmallery/150/cells/centriole.jpg
http://www.microscopyuk.org.uk/mag/imgjan99/janvid2.gif
www.cco.caltech.edu/~brokawc/Dem
o1/BeadExpt.html
EUKARYOTIC CELL SURFACES
AND JUNCTIONS
Cell surfaces protect, support,
and join cells
• Cells interact with their environments and
each other through their surfaces
• Plant cells are supported by rigid cell walls
made largely of cellulose
– They connect by plasmodesmata, channels that
allow them to share water, food, and chemical
messages
Walls of two
adjacent
plant cells
Vacuole
PLASMODESMATA
Layers of one
plant cell wall
Cytoplasm
Plasma membrane
Figure 4.19A
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Animal cells are embedded in an
extracellular matrix
• It is a sticky layer of
glycoproteins
• It binds cells together
in tissues
• It can also have
protective and
supportive functions
http://kentsimmons.uwinnipeg.ca/cm1504/Image122.gif
• Tight junctions can bind cells together into
leakproof sheets
• Anchoring
junctions link
animal cells
• Communicating
junctions allow
substances to
flow from cell
to cell
TIGHT
JUNCTION
ANCHORING
JUNCTION
COMMUNICATING
JUNCTION
Plasma
membranes of
adjacent cells
Figure 4.19B
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Extracellular
matrix
Acknowledgements
• Essential Biology with Physiology, 2nd ed., by Campbell, Reece, and
Simon, ©2007. These images have been produced from the
originals by permission of the publisher. These illustrations may not
be reproduced in any format for any purpose without express written
permission from the publisher.
• BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by
Campbell, Reece, Mitchell, and Taylor, ©2003. These images have
been produced from the originals by permission of the publisher.
These illustrations may not be reproduced in any format for any
purpose without express written permission from the publisher.
• Background image found at
http://www.paxcam.com/imgs/library/2/thumbnails/slide_19.jpg