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UIUC MCB 100 - Ch. 12: Eukaryotic Microorganisms

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MCB 100 1st Edition Lecture 35 Outline of Last Lecture I. Glycolytic facultative anaerobes (cont.) Outline of Current Lecture I. Evolutionary history of eukaryotic microorganisms II. Ecology and distributionIII. Cell structure IV. Eukaryotic genes V. Reproduction Current LectureI. Evolutionary historyi. Appeared after bacteria ii. Probably 2.5-3 billion years agoiii. Mitochondria probably evolved from endosymbiotic aerobic bacteriaiv. Plant chloroplasts probably evolved from endosymbiotic cyanobacteria v. Origin of the cytoplasm and nucleus II. Ecology and distributioni. World wide- diverse habitatsii. Some can grow anaerobically, but majority require oxygen iii. Most are free living, some protozoa and fungi are pathogens iv. Some live in extreme environments (Antarctica, thermal vents, pH 10) II. Cell structure i. Internal membranes- nucleus, endoplasmic reticulum, organellesii. Cell membrane usually contains sterols i. Cholesterol- animalsii. Phytosterol- plants iii. Ergosterol- fungi ii. Multiple linear chromosomes, DNA plus histone proteins iii. Ribosomes = 80S, many associated with endoplasmic reticulum iv. Cell walls tend to be chemically simple If present i. Protozoa lack cell wallsii. Plant cell walls = lignocelluloseiii. Fungi = chitin ii. Eukaryotic genes are usually interrupted by introns; transcripts are spliced to make mRNAs These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iii. Eucaryotic cells have a cytoskeleton- network of microtubules and fibers that determines cell shape and helps move things around in the cell- makes possible: pseudopods, phagocytosis, mitosis, and meiosis iv. Most species can reproduce sexually and have a diploid stagev. Normal cell division = mitosis (complex chromosome sorting)vi. Reductive cell division = meiosis (a diploid cell divides to give haploid cells) vii. Endoplasmic reticulumi. Elaborate membrane network within the cytoplasmii. Continuous with cytoplasmic and nuclear membranesiii. Increases surface area for excretion of proteins iv. Increases surface area for membrane bound enzymesv. Many 80S ribosomes are attached to the E.R. i. Nuclear Membrane i.a. Separates transcription from translation i.b. Eukaryotic mRNAs are extensively modified after translationi.c. Eukaryotic genes are organized into pieces1. Exons are gene parts that encode information for protein synthesis2. Introns are "nonsense" sequences that interrupt eukaryotic genes 3. Both introns and exons are transcribed to make RNA 4. Introns are removed and exons joined together (spliced) i.b. Eukaryotic mRNAs are polyadenylated on the 3' end (poly-A tail)i.c. Eukaryotic mRNAs have modified bases added to the 5' end (capping) i. Membrane bound organelles (mitochondria, hydrogenosomes, kinetoplasts, chloroplasts): i.a. Mitochondria1. Organelles of cellular aerobic respiration2. ETC located in inner mitochondria membrane3. ATP synthase located in inner mitochondrial membrane4. make most of the ATP that is used in the cell (ETC pumps protons into space between inner and outer mitochondrial membranes, PMF is used to generate ATP by ATP synthase)5. Respiratory poisons such as cyanide act by inhibiting the flow of electronsin the mitochondrial ETC 6. Dual membrane7. Contain a small autonomous chromosome8. Contain their own ribosomes 9. Most eukaryotic cells including all plant and animal cells have mitochondria and depend on them for ATP production by aerobic respirationi.a. Hydrogenosome 1. Similar to mitochondria but it carries out an anaerobic redox reaction thatproduces hydrogen 2. A membrane-enclosed organelle that is seen in some anaerobic eukaryotic microorganisms (trichomonas, some protozoa, some fungi)3. Produce H2, acetate, CO2, and ATP4. May have evolved from mitochondria or they may be degenerate mitochondria 5. Often lack mitochondrial genome and have no cristae i.a. Kinetoplast1. Similar to mitochondria but larger; associated with a flagellum2. An independently replicating disk-shaped mass of circular mitochondrial DNA molecules found inside a large mitochondrion3. Associated with the basal body of a flagella 4. Seen only in protozoa of the class Kinetoplastea- trypanosomes and Leishmania 5. May not be directly involved in motility i.b. Chloroplasts 1. Organelles of photosynthesis in plants and algae 2. Dual membrane3. Clorophylls and electron transfer chain of light harvesting apparatus are found in the thylakoid membranes4. Contain a small autonomous chromosome5. Contain their own 70S ribosomes II. Eukaryotic genes (come in pieces) i. Genes are not organized into operonsii. Each gene has its own promoter iii. Expression of gene usually requires several different activator proteins iv. Initial transcript includes both exon sequences, codons that direct protein synthesis, and introns, which interrupt the sensible part of the message v. Intron sequences must be spliced out of the transcript to make a useful mRNA II. Reproductioni. Most are capable of sexual reproductionii. In microorganisms, the haploid form is often the most commonly seen phaseiii. Fusion of two haploid cells (usually of different mating types) forms a diploid zygoteiv. Diploid form may immediately undergo meiosis to yield haploid cells or it may grow as a diploid strain for a while and then cells undergo meiosis v. All organisms that undergo sexual reproduction have both a diploid phase and haploid phasevi. In animal cells- typical body cell is diploid vii. Ovum and sperm cells are haploidviii. Fusion of ovum and a sperm produces a zygote- new diploid individual with genetic material from both of 2 parents ix. Diploid: 2 complete copies of the genome; 2 copies of each chromosomex. Haploid: (monoploid) 1 copy of each chromosome in genome xi. Mitosisi.a. normal cell division, a diploid cell divides to give 2 diploid cells or a haploid cell divides to give 2 haploid cells i.b. Phases of mitosis:1. Interphasea. Time between cell division cycles when cell grows larger, ingests food, makes new proteins, phospholipids, ribosomes, etc. 2. Prophasea. DNA is replicated; chromosome condense into tightly packed bodiesthat are visible in a light microscope as distinct entitiesb. Nuclear membrane disappears 2. Metaphasea. Chromosomes line up on mid cell plateb. Each chromosome is attached to actin microfilaments at the centromere of chromosomec. Fibers that are attached to chromosome are also


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UIUC MCB 100 - Ch. 12: Eukaryotic Microorganisms

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