4/14/08
Biol 205 Week 3 Lecture 1
TEXT Reading Assignment (covers first
two lecture of this week)
• Chapter 1: pg 5-27 on Cell structure and
function
• Chapter 11: pg 365-377 on membrane
structure
Extra Required reading:
A giant virus that may qualify as "living"
See link on Biol 205 home page
First Quiz is this FRiday April 18th
It will cover reading an lecture material
through today April 14th
It will consist of multiple choice, True/False
and/or short answer questions
1
Today’s lecture: a quick review of the
structure of eukaryotic and prokaryotic
cells, viruses & prions
Rest of Week:
• A primer on membrane structure
• Start an in-depth examination of how
cells reproduce: DNA replication, mitosis,
cytoskeleton and molecular motors
2
What did we talk about the first Week of class?
What did you learn during Week 2?
3
How do eukaryotic cells, prokarytic cells,
viruses and prions differ with respect to scale,
chemical composition and “construction”?
What do living organisms do?
• Reproduction: propagate itself (and its
genetic program) and convert genetic
information to a “usable” form
• Transform energy
• Communicate with other cells and with the
environment
• Maintain an ordered, stable system
• Evolve
All of these processes occur in prokaryotic and
eukaryotic cells!
Do they occur in viruses or prions?
4
First let’s consider issues of scale
(drinking water filters—overhead)
5
Scale: What
“issue” places
a limit on the
size of a
prokaryotic
cell?
6
Know these well and forever:
Milli (m), micro (µ), nano (n)
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Cell as the unit of life:
In the hierarchy of biological organization, the
cell is the simplest collection of matter that is
living
A MUST:
http://www.cellsalive.com/toc.htm
Cool stuff on cell biology:
http://www.cellsalive.com/howbig.htm
The cells of all living matter can be divided into two
basic categories. These categories are:
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Prokaryotes (prenucleus):
• genetic material is not encased in a nucleus
• cytoplasm is not divided into membrane bound organelles
• bacteria and archea
Size range of typical prokaryotic cell
1 - 10 µm
Cytoplasm: the entire contents of a cell
(excluding the nucleus in a eukaryotic cell)
Cytosol: semi-fluid portion of the cytoplasm
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Plasma membrane: membrane that defines the
outer boundary of a cell
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Scientific American Nov/Dec 1999
SEE figure on next page
Bacterial cells--prokaryotes--are often described as “bags of enzymes,”
but closer study reveals several levels of subcellular organization. A
typical Escherichia coli cell, shown above in cross section and magnified
one million times, has several
well-defined compartments.
• The cell is surrounded by two membranes enclosing a periplasmic
compartment that is used for capturing and sorting nutrients and wastes.
• At the center of the cell, densely packed DNA strands are folded into a
compact nucleoid, forming a loosely defined compartment devoted to
storage and use of genetic information.
• The cytoplasm occupies the remaining portions of the cell, and is
filled with ribosomes and many different enzymes.
• Multiprotein complexes are engaged in many tasks. The flagellar motor
turns a long, helical flagellum to propel
the cell through its environment.
• Chaperonins and proteasomes oversee the folding of new proteins and the
disposal of obsolete ones, respectively.
• DNA polymerase copies the genetic information. Some of these complexes
increase efficiency by linking several tasks together: The pyruvate
dehydrogenase complex performs three sequential reactions, delivering
molecules from step to step using a flexible arm.
(Illustration by David Goodsell.)
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Eukaryotes (true nucleus)
• genetic material is encased in a nucleus
• cytoplasm is divided into membrane organelles that carry out
specialized functions
• plants, animals, protists and fungi
[membrane= fat layer with pores]
Size range of "typical eukaryotic cell"
10-100 micrometers (µm) in diameter
Largest human cell - egg cell 100 µm diameter
Frog Egg -- 1 mm or 1000µm
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Nucleus:
• contains the vast bulk of DNA in a eukaryotic cell
• separated from the cytoplasm by the nuclear membrane
• the nuclear membrane is a double membrane -- two
membranes each of which is a lipid bilayer
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Endoplasmic
reticulum
• a network of
membranes
formed of
tubes and
flattened sacs
• forms an
internal
compartment
separate from
the cytoplasm
• continuous
with the
nuclear
membrane
Two types of endoplasmic reticulum:
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• Rough ER has ribosomes attached to the membrane
surface
• these ribosomes produce proteins that will be secreted
by the cell (such as insulin in the pancreas)
16
Smooth ER does not have ribosomes attached to the
membrane surface
• functions in diverse metabolic processes such as
synthesis of lipids, metabolism of some carbohydrates,
and detoxification of drugs and poisons
In the liver especially, enzymes of the smooth ER help
to detoxify sedatives such as phenobarbital and other
barbituates.
Barbituates, alcohol and many other drugs induce the
proliferation of smooth ER and its associated
detoxification enzymes.
This in turn increases the tolerance to the drugs,
meaning that a higher dose is required to achieve a
particular effect.
17
Other compartments:
Golgi apparatus: flattened membraneous sacs
involved in sorting and transporting products of the
endoplasmic reticulum
18
Organelle
• any membrane-bound structure found in the
cytoplasm of eukarotic cells
• performs a specialized function
• internal membranes contain pores to allow
molecules to enter or leave
A Lysosome is a type of organelle:
• membrane-bound sac of hydrolytic enzymes
• cell uses these enzymes to degrade
macromolecules (proteins, nucleic acids,
polysaccharides and fats)
19
Mitochondria:
• sites of cellular respiration
• catabolism (breakdown) of sugars, fats and other
fuels
20
Chloroplasts:
• site of photosynthesis
Will look at the structure and function of these
organelles when we discuss respiration and
photosynthesis
21
How do eukaryotic cells, prokarytic cells,
viruses and prions differ with respect to scale,
chemical composition and “construction”?
What do living organisms do?
• Reproduction: propagate itself (and its
genetic program) and convert genetic
information to a “usable” form
• Transform energy
• Communicate with other cells and with the
environment
• Maintain an ordered, stable system
• Evolve
All of these processes occur in prokaryotic and
eukaryotic cells!
Do they occur in viruses or prions?
22
WHICH OF THESE CELLULAR COMPONENTS
ARE FOUND IN VIRUSES?
23
INFLUENZA VIRUS ~ 200nm in diameter
vRNA = viral genomic RNA
8 segments of single-stranded RNA
24
25
Genetics Home Reference:
http://ghr.nlm.nih.gov/condition=priondisease
26
prion
• small proteinaceous infectious particles which resist
inactivation by procedures that modify nucleic acids
• A protein particle that is capable of causing an
infection or disease. Like viruses, prions are not
capable of reproduction by themselves. ...
Prions are relatively small proteins that display dramatically alternate
conformations for similar primary structures. Abnormal conformations
appear to cause fatal neurological diseases in a wide variety of mammals.
Researchers are discovering the mechanisms behind these
conformational changes, including differences that may lead to species
barriers (or lack thereof) among exposed animals.
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