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Evidence from the cell

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.

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Evidence from the cell

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  1. Evidence from the cell

  2. EVIDENCEFROMTHE 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

  3. Data: Short History of the Cell • 1665—Robert Hooke—”Micrographia” • Cells Seen in cork

  4. THE CELL THEORY • 1838—M. Schleiden • Plants are made of cells • 1839—T. Schwann • Animals are made of cells • 1858—R. Virchow • “All cells come from cells.”

  5. THE CELL THEORY • Living organisms composed of one or more cells • Cells, the smallest unit of life • Cells come from pre-existing cells

  6. Organelles are discovered • Similar cellular structures exist in all cells • Organelles = tiny little “organs” of the cell • Nucleus • Mitochondria • Chloroplasts (Plants) • Golgi Apparatus • Etc

  7. 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 cells • Eukaryotic cells

  8. PROKARYOTIC CELLS (Prokaryotes) Bacteria & Blue Green “Algae” • Simplest cells • Smallest cells • Oldest cells (3.5 Billion Years Old)

  9. EUKARYOTIC CELLS(EUKARYOTES) Animals, Plants, Fungi Large Cells Complex Cells Many membranous organelles Recent (2+ Billion years old)

  10. 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

  11. AND NOW LET’S

  12. 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.

  13. 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.”

  14. “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!”

  15. Spend a minute and make 3 suggestions as to what is possibly affecting Ellie. • 1……… • 2…….. • 3……..

  16. 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. .

  17. 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.”

  18. Becky’s Internet Search Results – List of Suspects • Influenza Virus: Spread primarily through respiratory droplets from sneezing or coughing. Virus has single strand of RNA surrounded by phospholipid/protein envelope (80-120nm). • 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).

  19. Suspects 1 and 2 • Too small to be seen in a light microscope, electron micrographs are shown below. Suspect 1: Influenza Suspect 2: West Nile Virus http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html http://www.lib.uiowa.edu/hardin/md/cdc/2290.html

  20. 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.

  21. Virus hijacking host system

  22. Clicker Question. Suppose thatEllie has contracted West Nile Virus. Using your Table 1 information which suspect below best matches that profile?

  23. Suspect 3: BacteriumCoxiella burnetii 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. http://microbewiki.kenyon.edu/index.php/Coxiella

  24. 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

  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

  26. Clicker Question. Suppose thatEllie has contracted Coxiella. Using your Table 1 information, which suspect below best matches that profile?

  27. 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.”

  28. 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 29

  29. “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: • Amoxicillin, Penicillin, and other ß-lactams • blocks the enzyme that normally creates links in peptidoglycan molecules • Streptomycin • Blocks prokaryotic ribosomes. • 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.

  30. 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

  31. “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

  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.”

  33. Microscope Analysis Nucleus of Ellie’s cell Pathogens What are they looking at?

  34. EukaryotesProkaryotes 35

  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

  36. 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

  37. 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. .

  38. If these are nuclei and there is no evidence of a cell wall what organism do you think the pathogen is? • Fungus • Protozoan • Bacterium • Virus

  39. 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

  40. 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

  41. Ah, so Ellie is infected with a protozoan. Now what? How do we get rid of it?

  42. Scientists have produced a new drug that can damage mitochondria in protozoan cells. Where is the mitochondrion?

  43. The Mitochondrion • “Power House of the Cell” • Has its own DNA

  44. A: 1 B: 2 C: 3 D: 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?

  45. 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 Toxoplasmagondii cysts in their meat, also.”

  46. 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?

  47. 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!

  48. EUKARYOTES • Eukaryotes • Nuclear membrane • Endoplasmic reticulum • Golgi, lysosomes • Mitochondria • Chloroplasts • 9+2 flagella & cilia • Multiple chromosomes • Must have evolved later after the prokaryotes

  49. What is Important! • 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

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