Download Cells/Organelles Case

Evidence from the cell
EVIDENCE FROM THE
CELL
Deduction: If the hypothesis of evolution is
correct then the microscopic structure of
organisms should show evidence of
common ancestry.
Test: Look at the microscopic structure
Data: Short History of the Cell
 1665—Robert
 Cells
Hooke—”Micrographia”
Seen in cork
THE CELL THEORY
 1838—M.
 Plants
are made of cells
 1839—T.
Schwann
 Animals
 1858—R.
 “All
Schleiden
are made of cells
Virchow
cells come from cells.”
THE CELL THEORY

Living organisms composed of one or more
cells

Cells, the smallest unit of life

Cells come from pre-existing cells
Organelles are discovered
 Similar
cellular structures exist in all
cells
 Organelles = tiny little “organs” of
the cell
– Nucleus
– Mitochondria
– Chloroplasts (Plants)
– Golgi Apparatus
– Etc
Deduction: If the hypothesis of evolution is correct,
then organisms with the simplest cell structure evolved
first and should appear first in the fossil record.
 Test:
Look at the microscopic
evidence and the fossil record.
 Data:
Two types of cells discovered.
 Prokaryotic
 Eukaryotic
cells
cells
PROKARYOTIC CELLS
(Prokaryotes)
Bacteria & Blue Green
“Algae”

Simplest cells

Smallest cells

Oldest cells
(3.5 Billion Years Old)
EUKARYOTIC CELLS
(EUKARYOTES)

Animals, Plants,
Fungi

Large Cells

Complex Cells
Many membranous
organelles
Recent
(2+ Billion
years old)

EVALUATION
 Data
support the hypothesis of
evolution as all organisms are made of
the same basic structure.
 Cells
probably evolved early since all
organisms have cells.
 And
Prokaryotes probably evolved first
AND NOW LET’S
Becky



Well, Becky thought, being a dorm counselor for
freshmen was not going to be that bad. She got a
free room for the year and the food was plentiful free steaks last week at an outdoor BBQ followed by
a hay ride in a horse-drawn wagon in their welcome
celebration.
But, then again it wasn’t perfect: she had ended up
covered in bug bites; some of the students got sick
from eating steak that was burned on the outside
and raw in the middle; the horses had mucked up
the courtyard and pigeons had roosted on the dorm
roof.
At least tonight, the students were finally settling in
and quieting down, she mused.



The quiet was shattered a few minutes later,
when one of the other counselors, Ann, yelled
through her door.
“Becky, we’ve got a problem. One of the
students found a homeless kitten, and the girl
has been keeping her in her room. I only found
out because the girl, Ellie, just came to my room
complaining of being sick. I felt sick too when I
saw the mess that kitten made. I thought cats
were born housebroken, but I guess not.”
“Anyway, now I think Ellie might really be sick.
She’s feverish and says she’s going to throw up.”




“What do you want me to do?” Becky asked.
“I’m freaking out!” Ann answered. “Forget about
the mess, just help me figure out what to tell
them at the health center. I don’t know what
she’s been exposed to. Or what we’ve been
exposed to for that matter! This is the second girl
this week with aches, fever, and nausea.
“My Mom sent me up with a bunch of medicine,”
Becky answered. “I’ll make a list of where we’ve
been, what we’ve eaten and possibly been
exposed to. Then we can start taking something
right away to keep from getting it, too.”
I don’t care what you do. Let’s just get her to the
health center now!”
Spend a minute and make 3
suggestions as to what is possibly
affecting Ellie.
 1………
 2……..
 3……..
On to the Internet



.
Ellie was quickly sent to the health center, but
Becky being Becky, did an Internet search and
found 5 possible suspects that could be causing
Ellie’s illness. She made a table with the various
characteristics of disease agents.
Her table looks like Table 1 in the next slide.
Does it make sense?
Add any details you missed so that when you
hear the results of the health center tests you will
be able to figure out what was making Ellie sick.
CHARACTERISTIC
Virus
Bacteria
Protozoa
What differences exist in the type
and shape of the genetic material?
RNA or DNA
Circular DNA
DNA in linear
chromosomes
What differences exist in the
structure that provides an outer
protective barrier?
Proteins with or
without lipids
Phospholipid
membrane with
or without cell wall
Phospholipid
membrane
without cell wall
What differences exist in
reproduction?
Only reproduces
inside other cells
Asexual
Both sexual and
asexual
What differences exist in size?
nanometer
About 1 µm size
5-100 µm
What drugs can treat infections?
Enzyme inhibitors
Antipeptidoglycans,
Drugs that affect
organelles or
enzymes that
only protists
have.
The Usual Suspects
• “I can’t afford to get sick,” said Ann, “I’m
carrying 23 hours. Maybe Ellie just has
the plain old flu.”
• “If she does, I’ve got some Tamiflu,”
Becky volunteered. “Flu is a virus. I’ve
actually got two suspects that are
viruses.”
Becky’s Internet Search
Results – List of Suspects
1. Influenza Virus: Spread primarily
through respiratory droplets from
sneezing or coughing. Virus has
single strand of RNA surrounded by
phospholipid/protein envelope (80120nm).
2. West Nile Virus: Spread by
mosquitoes that have previously fed
on infected birds. 20% of infected
people show symptoms. Single
stranded RNA, phospholipid/protein
envelope (50nm).
Suspects 1 and 2
•
Too small to be seen in a light
microscope, electron micrographs are
shown below.
Suspect 1: Influenza
http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html
Suspect 2: West Nile Virus
http://www.lib.uiowa.edu/hardin/md/cdc/2290.html
Suspects 1 & 2:
Viruses
Size
– Smallest Organisms (50nm)
– 100 times smaller than bacteria
Composition
– Outer shell: repetitive protein often inserted
into a lipid envelope (responsible for
recognition and infection of host cell.)
– Protected interior that contains genetic
material (DNA or RNA) with important protein
enzymes required for duplication.
Cannot reproduce by itself
– hijacks a host cell to replicate itself.
Virus
hijacking
host system
Clicker Question. Suppose that Ellie has contracted
West Nile Virus. Using your Table 1 information which
suspect below best matches that profile?
Suspects
Circular Nucleus
DNA
Divides
asexually
Size
Cell
Wall
Sexual
Reproduction
A
+
-
+
1µm
+
-
B
-
+
+
10µm
-
+
C
-
-
-
0.1µm
-
-
D
-
+
+
5µm
+
+
Suspect 3: Bacterium
Coxiella burnetii
0.3-0.5 µm gram-negative bacterium that can only survive
inside cells and causes 1-2 week Q-fever. Infection occurs 23 weeks after inhalation of barnyard dust. Coxiella are often
found in livestock and are excreted in milk, urine, and feces.
http://microbewiki.kenyon.edu/index.php/Coxiella
Prokaryotes
• Unicellular
• Reproduce asexually
• Composition
– Protected interior (cytoplasm) that
contains genetic material (one circle of
DNA) as well as complexes of protein
enzymes to carry out necessary functions
of gathering energy, manufacturing
proteins (ribosomes), etc…
25
Prokaryotes
• Size
– 0.2-10 micrometer (µm)
• Composition
– Phospholipid membrane, many contain
cell wall composed of peptidoglycan
(positive for chemical Gram stain,) those
with little or no peptidoglycan called gram
negative (like Coxiella).
26
Clicker Question. Suppose that Ellie has contracted
Coxiella. Using your Table 1 information, which suspect
below best matches that profile?
Suspects
Circular Nucleus
DNA
Divides
asexually
Size
Cell
Wall
Sexual
Reproduction
A
+
-
+
1µm
+
-
B
-
+
+
10µm
-
+
C
-
-
-
0.1µm
-
-
D
-
+
+
5µm
+
+
Ellie’s Diagnosis
Initial Identification: The health center
collected blood samples from Ellie and
observed her cells under a microscope. They
identified foreign structures with DNA and
outer membranes. The cells were gram
negative and about 1/10 the size of her cells.
“Ah, ha!” Becky said. “That matches one of my
suspects. I knew those were a health hazard.
I just need to re-check the size thing. This
internet chart compares our cells to viruses
and stuff.”
Metric Review
• 1 meter (m) = ~3 feet
• 1 meter (m) = 1000 millimeter (mm)
• 1 millimeter (mm) = 1000 micrometer (µm)
(smallest size distinguished by naked eye)
• 1 micrometer (µm) = 1000 nanometer (nm) (only
seen with light microscope)
• 1 mm poppy seed = (1000 µm/mm) = 1000 µm29
“That’s great,” Becky said. “My Mom sent me 3 different
antibiotics to kill bacteria.”
Given the description of Ellie’s test results, which
antibiotic will definitely NOT work:
A. Amoxicillin, Penicillin, and other ß-lactams
– blocks the enzyme that normally creates links in
peptidoglycan molecules
B. Streptomycin
– Blocks prokaryotic ribosomes.
C. Ciprofloxacin hydrochloride (Cipro)
– Blocks bacterial DNA gyrase enzyme needed to
counteract excessive twisting of DNA that occurs
when circles of DNA are unwound to be copied
into DNA or RNA.
Becky decided that the doctor ought to
treat Ellie with Cipro because she
believed the pathogen was
•
•
•
•
A) A virus
B) A bacterium
C) A fungus
D) A protozoan
“Wait a minute!” Ann said. “The doctor said
the blobs in Ellie’s blood were 1/10th the size
of her cells. Could they be Coxiella?”
A: Yes
B: No
32
Microscope Analysis
Becky and Ann talked together outside the Ellie’s room at the
student health center the next morning. They were pouring
over photographs of blood stains.
“Look at this, Becky. They can’t be bacteria!”
“You’re right!” Becky exclaimed. “I wish I hadn’t started taking
the antibiotics. The little crescent shaped structures that I
thought were the bacteria are too big,
“And look at their insides, they can’t be bacteria. Maybe they
are some kind of protozoan parasite or maybe a fungus.”
Microscope Analysis
Nucleus of Ellie’s cell
Pathogens
What are they looking at?
Eukaryotes Prokaryotes
DNA
Size
Organization
Linear strands within
membrane-bound nucleus
single circle in “nucleoid
region
5-100 µm
0.2-10 µm
often multicellular, some have
usually single-celled,
cell walls (no peptidoglycan) some have peptidoglycan
cell walls
Metabolism
usually need oxygen to exist
may not need oxygen to
exist
Organelles
membrane bound organelles
like mitochondria
no organelles, different
ribosomes
Examples
plants, animals, protists, fungi
bacteria, archaea
35
Suspect 4: Fungus
Cryptococcus neoformans
http://www.scq.ubc.ca/wp-content/uploads/2006/08/neoformans2.jpg
2.5-10 µm encapsulated fungus found in decaying pigeon or chicken
droppings. The cells have a cell wall. Inhaled as spores that eventually
spread to the brain causing meningoencephalitis. Has a black pigmented
layer that can be seen sometimes on bird seed.
http://microgen.ouhsc.edu/images/Heuser_bud.png
http://www.naturalhistorymag.com/0705/images/0705Samplings_Cryptococcus.jpg
Eukaryote Suspect 5:
Toxoplasma gondii (Protozoan)
• 4-6 µm single-celled protozoan parasite of mammals &
birds.
• Most likely through ingesting undercooked meat.
• Sexual life cycle occurs in cats, so infection can follow
contact with cat feces. Usually no symptoms in cats.
Cyst in tissue
loaded with protozoans
http://www.roche.com/pages/facets/2/toxmoplasma.jpg
Back to the Internet
Becky and Ann left the health clinic and headed
to the library and the computer.
“The organisms in Ellie’s blood don’t look like
either of your suspects, Becky.”
“Well, maybe they would look different when
they are in the blood.”
They started scanning Google.
.
If these are nuclei and there is no evidence
of a cell wall what organism do you think the
pathogen is?
A)
B)
C)
D)
Fungus
Protozoan
Bacterium
Virus
They quickly discovered treatments for
eukaryotic pathogens
• Pyrimethamine, Sulfonamides
– Interferes with enzymes used to make the folic acid
needed to make thymine and uracil nucleotides
needed to make RNA & DNA.
– Antifungals
– Polyenes combine with ergosterol (component of
fungal and some bacterial membranes) disrupt and
break membranes.
– Inhibits ß-glucan found in cell walls of some fungi
So: If
Pyrimethamine, Sulfonamides: Interfere with enzymes
used to make the folic acid needed to make thymine and
uracil nucleotides.
Polyenes combine with a component of fungal and some
bacterial membranes, disrupt and break them.
One of these drugs specifically affects one of the two
eukaryotic suspects. Which test of Ellie’s blood would help
you tell which eukaryotic suspect she was infected with?
A: Presence of DNA
B: Presence of ß-glucan-containing cell walls
C: Presence of cellulose
D: Presence of peptidoglycan cell walls
• Ah, so Ellie is infected with a protozoan.
• Now what? How do we get rid of it?
Scientists have produced a new drug that can damage
mitochondria in protozoan cells. Where is the mitochondrion?
The Mitochondrion
• “Power House of the Cell”
• Has its own DNA
Number of Membranes: Scientists have
produced a new drug that can damage
mitochondria in protozoan cells, but they must
modify it to get it across phospholipid
membranes. Through how many phospholipid
membranes would the drug have to pass to get
from the blood stream into the center of a
protozoan’s mitochondrion?
A: 1
B: 2
C: 3
D: 4
Ellie’s Prognosis
“Well, Ellie’s responding well to the pyrimethamines that the
doctors prescribed,” Becky commented to Ann while checking
her email a few days later.
“Her parents seemed to appreciate that we got her such quick
medical treatment. Do you think we should warn the other
students? They might have eaten some Toxoplasma gondii
cysts in their meat, also.”
Ellie’s Prognosis
“They are probably already infected,” Becky answered. “I
learned that something like 25-40% of American adults are
already infected with Toxoplasma gondii. It’s more of an
issue for women. You know, they can’t scoop their cat’s
litter box when they’re pregnant because the cat poop
contains them, and infection causes birth defects in
thousands of children.”
“You don’t think Ellie is…” Ann began….
“Don’t go there. I don’t know and I don’t want to know.”
Are you a
cat
person?
EVOLUTIONARY PERSPECTIVE
• Prokaryotes
•
•
•
•
•
•
DNA, RNA, fats, proteins, carbohydrates
Chlorophyll
Plasma membrane
Cytosol=Cytoplasm
Ribosomes
Chromosome (single)
All of this must have evolved early in the history of
earth!
EUKARYOTES
• Eukaryotes
•
•
•
•
•
•
•
Nuclear membrane
Endoplasmic reticulum
Golgi, lysosomes
Mitochondria
Chloroplasts
9+2 flagella & cilia
Multiple chromosomes
Must have evolved later after the prokaryotes
• The difference between
Prokaryotes & Eukaryotes
• The functions of the cell organelles
• The sequence: Suggests Evolution
Prokaryotes—3.5 BYA
Very small
Structurally simple
Eukaryotes—2 BYA
Larger
Structurally complex
Plants Fungi Animals
Next time