Evidence from the cellEvidence from the cell

EVIDENCEEVIDENCE FROMFROM THE THE CELLCELL

Deduction:Deduction: IfIf the hypothesis of evolution is the hypothesis of evolution is correct correct thenthen the microscopic structure of the microscopic structure of organisms should show evidence of organisms should show evidence of common ancestry.common ancestry.

Test:Test: Look at the microscopic structure Look at the microscopic structure

Data: Short History of the CellData: Short History of the Cell

1665—Robert Hooke1665—Robert Hooke—”Micrographia”—”Micrographia”

Cells Seen in corkCells Seen in cork

THE CELL THEORYTHE CELL THEORY 1838—M. Schleiden1838—M. Schleiden

Plants are made of cellsPlants are made of cells

1839—T. Schwann1839—T. SchwannAnimals are made of cellsAnimals are made of cells

1858—R. Virchow1858—R. Virchow““All cells come from cells.”All cells come from cells.”

THE CELL THEORYTHE CELL THEORY

Living organisms composed of one or more Living organisms composed of one or more cellscells

Cells, the smallest unit of lifeCells, the smallest unit of life

Cells come from pre-existing cellsCells come from pre-existing cells

Organelles are discoveredOrganelles are discovered

Similar cellular structures exist in all Similar cellular structures exist in all cellscells

OrganellesOrganelles = tiny little “organs” of = tiny little “organs” of the cellthe cell– NucleusNucleus– MitochondriaMitochondria– Chloroplasts (Plants)Chloroplasts (Plants)– Golgi ApparatusGolgi Apparatus– EtcEtc

Deduction:Deduction: IfIf the hypothesis of evolution is correct, the hypothesis of evolution is correct, thenthen organisms with the simplest cell structure evolved organisms with the simplest cell structure evolved

first and should appear first in the fossil record.first and should appear first in the fossil record.

Test:Test: Look at the microscopic Look at the microscopic evidence and the fossil record.evidence and the fossil record.

Data:Data: Two types of cells discovered. Two types of cells discovered.Prokaryotic cellsProkaryotic cells

Eukaryotic cellsEukaryotic cells

PROKARYOTIC CELLS PROKARYOTIC CELLS (Prokaryotes)(Prokaryotes)

Bacteria & Blue Green Bacteria & Blue Green “Algae”“Algae”

Simplest cellsSimplest cells

Smallest cellsSmallest cells

Oldest cells (3.5 Oldest cells (3.5 Billion Years Old)Billion Years Old)

EUKARYOTIC CELLSEUKARYOTIC CELLS(EUKARYOTES)(EUKARYOTES)

Animals, Plants,Animals, Plants, FungiFungi

Large CellsLarge Cells

Complex CellsComplex CellsMany membranous Many membranous organellesorganelles

RecentRecent(2+ Billion (2+ Billion years old)years old)

EVALUATIONEVALUATION Data support the hypothesis of Data support the hypothesis of

evolution as all organisms are made of evolution as all organisms are made of the same basic structure.the same basic structure.

Cells probably evolved early since all Cells probably evolved early since all organisms have cells.organisms have cells.

And Prokaryotes probably evolved firstAnd Prokaryotes probably evolved first

AND NOW LET’SAND NOW LET’S

BeckyBecky Well, Becky thought, being a dorm counselor for Well, Becky thought, being a dorm counselor for

freshmen was not going to be that bad. She got a freshmen was not going to be that bad. She got a free room for the year and the food was plentiful - free room for the year and the food was plentiful - free steaks last week at an outdoor BBQ followed by free steaks last week at an outdoor BBQ followed by a hay ride in a horse-drawn wagon in their welcome a hay ride in a horse-drawn wagon in their welcome celebration. celebration.

But, then again it wasn’t perfect: she had ended up But, then again it wasn’t perfect: she had ended up covered in bug bites; some of the students got sick covered in bug bites; some of the students got sick from eating steak that was burned on the outside from eating steak that was burned on the outside and raw in the middle; the horses had mucked up and raw in the middle; the horses had mucked up the courtyard and pigeons had roosted on the dorm the courtyard and pigeons had roosted on the dorm roof. roof.

At least tonight, the students were finally settling in At least tonight, the students were finally settling in and quieting down, she mused.and quieting down, she mused.

The quiet was shattered a few minutes later, The quiet was shattered a few minutes later, when one of the other counselors, Ann, yelled when one of the other counselors, Ann, yelled through her door.through her door.

““Becky, we’ve got a problem. One of the Becky, we’ve got a problem. One of the students found a homeless kitten, and the girl has students found a homeless kitten, and the girl has been keeping her in her room. I only found out been keeping her in her room. I only found out because the girl, Ellie, just came to my room because the girl, Ellie, just came to my room complaining of being sick. I felt sick too when I complaining of being sick. I felt sick too when I saw the mess that kitten made. I thought cats saw the mess that kitten made. I thought cats were born housebroken, but I guess not.”were born housebroken, but I guess not.”

““Anyway, now I think Ellie might really be sick. Anyway, now I think Ellie might really be sick. She’s feverish and says she’s going to throw up.”She’s feverish and says she’s going to throw up.”

““What do you want me to do?” Becky asked.What do you want me to do?” Becky asked.

““I’m freaking out!” Ann answered. “Forget about I’m freaking out!” Ann answered. “Forget about the mess, just help me figure out what to tell the mess, just help me figure out what to tell them at the health center. I don’t know what them at the health center. I don’t know what she’s been exposed to. Or what she’s been exposed to. Or what we’vewe’ve been been exposed to for that matter! This is the second girl exposed to for that matter! This is the second girl this week with aches, fever, and nausea. this week with aches, fever, and nausea.

““My Mom sent me up with a bunch of medicine,” My Mom sent me up with a bunch of medicine,” Becky answered. “I’ll make a list of where we’ve Becky answered. “I’ll make a list of where we’ve been, what we’ve eaten and possibly been been, what we’ve eaten and possibly been exposed to. Then we can start taking something exposed to. Then we can start taking something right away to keep from getting it, too.”right away to keep from getting it, too.”

I don’t care what you do. Let’s just get her to the I don’t care what you do. Let’s just get her to the health center now!”health center now!”

Spend a minute and make 3 Spend a minute and make 3 suggestions as to what is possibly suggestions as to what is possibly

affecting Ellie.affecting Ellie.

1………1……… 2……..2…….. 3……..3……..

On to the InternetOn to the Internet Ellie was quickly sent to the health center, but Ellie was quickly sent to the health center, but

Becky being Becky, did an Internet search and Becky being Becky, did an Internet search and found 5 possible suspects that could be causing found 5 possible suspects that could be causing Ellie’s illness. She made a table with the various Ellie’s illness. She made a table with the various characteristics of disease agents. characteristics of disease agents.

Her table looks like Table 1 in the next slide. Does Her table looks like Table 1 in the next slide. Does it make sense?it make sense?

Add any details you missed so that when you Add any details you missed so that when you hear the results of the health center tests you will hear the results of the health center tests you will be able to figure out what was making Ellie sick.be able to figure out what was making Ellie sick.

..

CHARACTERISTIC Virus Bacteria Protozoa

What differences exist in the typeand shape of the genetic material?

RNA or DNA Circular DNA DNA in linearchromosomes

What differences exist in thestructure that provides an outerprotective barrier?

Proteins with orwithout lipids

Phospholipidmembrane withor without cell wall

Phospholipidmembranewithout cell wall

What differences exist inreproduction?

Only reproducesinside other cells

Asexual Both sexual andasexual

What differences exist in size? nanometer About 1 µm size 5-100 µm

What drugs can treat infections? Enzyme inhibitors Anti-peptidoglycans,

Drugs that affectorganelles orenzymes thatonly protistshave.

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 (80-120nm).

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).

http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html

Suspects 1 and 2

• Too small to be seen in a light microscope, electron micrographs are shown below.

Suspect 2: West Nile VirusSuspect 1: Influenzahttp://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 DNA

Nucleus Divides asexually

Size Cell Wall

Sexual Reproduction

A + - + 1µm + -

B - + + 10µm - +

C - - - 0.1µm - -

D - + + 5µm + +

Suspect 3: BacteriumCoxiella burnetii

http://microbewiki.kenyon.edu/index.php/Coxiella

0.3-0.5 µm gram-negative bacterium that can only survive inside cells and causes 1-2 week Q-fever. Infection occurs 2-3 weeks after inhalation of barnyard dust. Coxiella are often found in livestock and are excreted in milk, urine, and feces.

25

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…

26

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).

Clicker Question. Suppose that Ellie has contracted Coxiella. Using your Table 1 information, which suspect

below best matches that profile?

Suspects Circular DNA

Nucleus Divides asexually

Size Cell Wall

Sexual Reproduction

A + - + 1µm + -

B - + + 10µm - +

C - - - 0.1µm - -

D - + + 5µm + +

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.”

Ellie’s Diagnosis

29

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 µm

A. Amoxicillin, Penicillin, and other ß-lactams– blocks the enzyme that normally creates links in

peptidoglycan moleculesB. 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.

“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:

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

32

A: Yes

B: No

“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?”

Microscope AnalysisBecky 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 AnalysisNucleus of Ellie’s cell

Pathogens

What are they looking at?

35

Eukaryotes Prokaryotes

DNA Linear strands within membrane-bound nucleus

single circle in “nucleoid region

Size 5-100 µm 0.2-10 µm

Organization often multicellular, some have cell walls (no peptidoglycan)

usually single-celled, 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

Suspect 4: Fungus

Cryptococcus neoformans

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

http://www.scq.ubc.ca/wp-content/uploads/2006/08/neoformans2.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.

http://www.roche.com/pages/facets/2/toxmoplasma.jpg

Cyst in tissue loaded with protozoans

Back to the InternetBecky 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) Fungus

B) Protozoan

C) Bacterium

D) Virus

• 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

They quickly discovered treatments for eukaryotic pathogens

A: Presence of DNAB: Presence of ß-glucan-containing cell wallsC: Presence of celluloseD: Presence of peptidoglycan cell walls

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?

• 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

A: 1B: 2C: 3D: 4

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?

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 acat

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 complexPlants Fungi Animals

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