L16 Cell Master-in-class-online-V01 PDF

Slide 1 L16 Cell Read the syllabus Each slide should have the number in the upper right for later references Download lectures from D2L before class − Any text not in black (Green, Blue, Red, etc.) are not typically on the D2L PowerPoint Blue is often drawn or written by hand...

Slide 1 L16 Cell Read the syllabus Each slide should have the number in the upper right for later references Download lectures from D2L before class − Any text not in black (Green, Blue, Red, etc.) are not typically on the D2L PowerPoint Blue is often drawn or written by hand − Anything I write/draw on the screen, board, etc., is not on D2L, but you will need to know − Purple: Not on exams, but interesting information − If you have trouble with the color code, please let me know Students will sit in assigned table during regularly scheduled classes  Slide 2 The cell: You heard this before Cells: the basic structural, functional, and biological unit of all known living organisms A cell is the smallest unit of life Cells are often called the "building blocks of life“ Only cells are alive Cell Theory − That living organisms are made up of cells − Cells are the basic structural/organizational unit of all organisms − That all cells come from pre-existing cells Then where did the first cell come from? − Only active cells are alive Everything is red, you might question after this class  Slide 3 Cell Theory rules All known living things are made up of one or more cell The cell is the fundamental unit of structure and function in all living organisms All living cells arise from pre-existing cells by division Must be able to replicate on their own The activity of an organism depends on the total activity of independent cells Energy flow (metabolism and biochemistry) occurs within cells Organisms of similar species have very similar chemical composition Wrong and outdated but often cited in Textbooks: − Cells contain DNA which is found specifically in the chromosome (There are lots of exceptions, e.g. plasmids) Corrected: − Cells contain DNA in their genome (genomes can be the chromosome, plasmids, etc.) Everything is red, you might question after this class  Slide 4 By definition, viruses are not alive Cell Theory Rules Viruses are not alive All known living things are made up of one or Are not cells more cells All living cells arise from pre-existing cells by Are not cells and are manufactured by cells division Must be able to replicate on their own Are manufactured by the cell and cannot replicate on their own The cell is the fundamental unit of structure and Are not cells function in all living organisms The activity of an organism depends on the total The activity of a virus is depended on the host cell and the activity of independent cells environment Energy flow (metabolism and biochemistry) The virus is inside the cell or outside after cell lysis occurs within cells Organisms of similar species have very similar Viruses are not organisms, nor species chemical composition But similar viruses have similar chemical composition Exposure to one virus, sometimes protects you from another virus Cells contain DNA in their genome Some viruses contain no DNA, these are RNA viruses Some viruses contain no RNA, these are DNA viruses  Slide 5 Are RBCs alive? Are they cells? What about some WBCs? RBCs: red blood cells − Mature RBCs contain no nucleus and no DNA − They have no mitochondria, and thus no mitochondrial DNA RBCs are made in the bone marrow, and they cannot replicate on their own WBCs: white blood cells − Most white blood cells are produced in the bone marrow − Many white blood cells can't divide and reproduce on their own  Slide 6 Mature RBCs questions: answer on board Each person in your group will vote By definition, are mature RBCs or Mature WBCs actually cells? By definition, are they alive by definition? Are they dead cells? − This is not about how you feel, only about the definition Regardless of the definition, do you personally consider them to be cells or not cells? Vote Mature RBCs Mature WBCs Definition Cell or non-cell Alive or dead Feelings Cell or non-cell Alive or dead  Slide 7 What about these human cells? Other mature cells do not contain a nucleus (thus no DNA) − Note: All human cells start with nuclear and mitochondrial DNA Mature skin, hair, and nails contain no nucleus − The nucleus is destroyed during the cornification process (the process of forming a keratinized cell) − Thus, mature hair strands do not have nuclear DNA − The hair follicle (root) contains nuclear DNA  Slide 8 What is life? What are cells?  Slide 9 Are endospores alive? They are not cells Endospore: a dormant, tough, and non-reproductive structure produced by certain bacteria  Slide 10 Endospores: “Hardiest” known form of life to kill. Resistant to: High levels of radiation (ultraviolet and gamma radiation) Extreme pH Extreme pressure Low salt or high salt Desiccation (very little water): do not require water to survive Starvation: They do not require any nutrient (e.g. food) in this state Not cells! Cells make spores Nothing more resilient than spores  Slide 11 Endospores: “Hardiest” known form of life to kill. Resistant to: Extreme cold, only a very small fraction may be killed by the cold Extreme temperatures − Resistant to high temperatures; resistant to boiling − Autoclaves (used to sterile material, common in research labs and hospitals) are set to 121 C (250 F) to kill spores, but it takes time ==> yet it will not kill all the spores!! The high temperature may kill a small fraction, but many survive it The combination of temperature, stream, and pressure is what kills most spores − But some may still survive  Slide 12 Endospores: “Hardiest” known form of life to kill. Resistant to: Lysozymes: No effect on endospores − An antimicrobial enzyme produced by animals (humans) and other organisms − Cleaves the peptidoglycan component of bacterial cell walls, which leads to cell death Chemical disinfectants − Most disinfectants used in household cleaning products have little effect − 10% bleach are effective at killing endospores, but it takes time (15-20 minutes) sterilant alkylating agents such as ethylene oxide (ETO) are also effective Resistant to ALL known antibiotics Spores can be maintained for a VERY long time with nearly no metabolic activity  Slide 13 Endospores can be maintained for a VERY long time Over 9,000 years https://www.ncbi.nlm.nih.gov/pmc/articl es/PMC184555/#:~:text=Bacteria%20o f%20the%20genus%20Thermoactinom yces,the%20oldest%20known%20livin g%20organisms. 250 million years http://news.bbc.co.uk/2/hi/sci/tech/9787 74.stm  Slide 14 Endospores: “Hardiest” known form of life to kill. Resistant to: Endospore formation: triggered by adverse external conditions − E.g. starvation, desiccation, large temperature shifts, etc.  Slide 15 Are endospores alive? Are they cells? Metabolic activity is near zero ==> nothing is happening − DNA is not replicating and is not active − RNA is not active − Translation is not active − Most enzymes inside the cell is not active, some enzymes outside the cell are active When a spore reanimates itself into an active cell it is often cited in the literature as “the cell comes back to life”. -- zombie cells − Spores are not cells, yet cells come from them Does not match the cell theory, by definition spores aren’t alive − Spores do not have any apparent reactions occurring inside of them Does not match the cell theory − They are very dry inside All cells require water, but spores do not require water to be maintained  Slide 16 Why should you care about endospores? Anthrax Anthrax is a disease caused by the bacterium Bacillus anthracis This bacteria can kill in many ways Without treatment the risk of death is high: − Skin anthrax: 24% chance of death − Intestinal infection: 25-75% chance of death − Respiratory anthrax: 80% chance of death Even with treatment, respiratory anthrax has a 50-80% chance of of killing The current treatment is antibiotics − Up until the 20th century anthrax would kill 100,000s of people each year It would also kill 100,000s of animals each year Anthrax has been developed as a weapon by several countries such as the USA − In 1969, President Nixon terminates USA biological weapons program  Slide 17 Anthrax https://s3.amazonaws.com/static.wd7.us/f/f7/CutaenousA58.jpg https://phil.cdc.gov/phil_images/20030825/13/PHIL_4504_lores.jpg  Slide 18 Anthrax https://www.cdc.gov/anthrax/symptoms/index.html https://www.researchgate.net/figure/Black-necrotic-tissue- is-present-in-the-upper-eyelid-2-weeks-after- presentation_fig2_279656862  Slide 19 Are synthetic (human-made) cells alive? https://science.sciencemag.org/ content/351/6280/aad6253  Slide 20 Are synthetic (human-made) cells alive? My lab works with the synthetic minimal cell synthesized in 2016 Eliza Peters Former Undergrad, Human Bio 2021, iScience (Cell Press) Dr. Tahmina Hossain major https://pubmed.ncbi.nlm.nih.gov/33997676/ Former grad student  Slide 21 This class is microbiology (the study of microorganisms) Biology is the study of life and their components − But what is consider to be live is not “black and white” We are utilizing something that we do not understand − It is humbling − Don’t worry, we do this all the time  Slide 22 Eukaryotic and prokaryotic cells It is often stated: Prokaryotic cells are much simpler in their internal and external structures − However, it depends on how you look at it − A better way of putting it: In general, prokaryotic cells internal structures are less compartmentalized than eukaryotes and prokaryotes Some prokaryotic structures are quite complex Note that prokaryotes have structures and enzymatic reactions that do not occur in eukaryotes Prokaryotes are far more diverse than eukaryotes  Slide 23 There are lots of prokaryotes Current estimate of number of prokaryotes on earth − ~1,000,000,000,000,000,000,000,000,000,000 − ~10^30 cells (1E+30) There are far more bacteria/archaea on earth than there are stars in the known universe − http://bionumbers.hms.harvard.edu/bionumber.aspx?id=113931 − http://news.bbc.co.uk/2/hi/science/nature/158203.stm There are more unicellular eukaryotes then multicellular eukaryotes Most multicellular eukaryotes have a unicellular life-cycle stage − Even humans have a unicellular life-cycle − Eggs and sperm are unicellular cells (Gametes are reproductive unicells for multicellular organisms)  Slide 24 General comparison Eukaryotic Prokaryotic Sheer numbers Lots Lots more Species Lots Lots more Diversity Lots Lots more Enzymatic reaction types Lots Lots more # of different types of genes Lots Lots more Small organelles Lots Lots Large organelles Lots Few Intelligence Few None Diversity of environmental niches Lots Lots more Carbon sources Few Lots more Nitrogen sources Few (organic only) Lots (organic and inorganic) Use of diverse of elements Lots Lots more Resistant to extremes A few Lots more  Slide 25 Universal genetic code With only a few exceptions all life utilizes the same genetic code − In other words, all organisms follow the same code Similar to how nearly all modern computers use binary code − Cells have different “operating systems” (e.g. Mac, PC, Linux), but all use the same base code 0 and 1 for computers ATGCU for DNA and RNA Same DNA and RNA code for a specific amino acid works in any organism The code for a specific amino acid is encoded on DNA from bacteria to humans − A common language for almost all organisms to translate nucleotide sequences DNA and RNA to amino acid sequences of proteins − For example, we can take a human gene, put it into a bacteria cell, and that cell will produce a human RNA or a human protein (not in a human but in a bacteria) − However, the genetic code is still evolving  Slide 26 Assigned reading is posted on D2L Read the next lecture reading and this one if you have not already done so