MCB 150 FINAL EXAM STUDY GUIDE
MCB 150 FINAL EXAM STUDY GUIDE MCB 150
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This 10 page Study Guide was uploaded by Jessica Logner on Wednesday April 13, 2016. The Study Guide belongs to MCB 150 at University of Illinois at Urbana-Champaign taught by Bradley G Mehrtens in Summer 2015. Since its upload, it has received 189 views. For similar materials see Molecular and Cellular Biology in Biology at University of Illinois at Urbana-Champaign.
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Date Created: 04/13/16
MCB 150 FINAL EXAM Uses of microtubules movement and organelle positioning intracellular transport segregation of chromosomes spindle fibers propulsion and cell movement cilia/flagella Formation of microtubules rigid hollow tubes of tubulin protofilaments vertical sticks of alpha and beta tubulin dimers 13 form circle to make tubulin Polarity of microtubules polymerization possible at both ends, MOSTLY occurs at plus end in vivo, negative end normally anchored GTP cap of mictrotubules GTP bound beta tubulin prevents subunits from peeling away, favors polymerization over depolymerization How does binding tubulin influence the formation of microtubules? induces depolymerization b/c no available tubulin Ex: nonspecific tubulin affects Colcemine Ex: targets most rapidly dividing cells chemo drugs How does binding microtubules affect their formation? microtubules are much more stabilized Ex: targets rapidly dividing cells Microtubule organizing centers where new MT originate from Ex: centrosome in animal cells Centrioles 9triplet arrangement A > B > C tubule from inside out, B and C are incomplete 2 per animal cell, perpindicular to each other pericentriolar material amorphous collection of proteins on which MTs emenate gamma tubulin tubulin at point of contact w/ centrioles that is foundation for MTs What is the role of microtubules in nerve cells? Give the cell a stable polarity oriented the same way in axons oriented in opposite directions in dendrites Kinesins long, thin, flowery end move toward plus end Dyneins two legs for "walking" move toward minus end Functions of motor proteins intracellular vesicle transport positioning organelles distributing pigment molecules stable arrangement seperation of sister chromatids and centrosomes Cilia and flagella structure 9+2 arrangement of an axoneme minus end gets anchored in basal body (physically the same as centriole) radial spoke proteins connect to central pair from 9 outer pairs dyneins connect neighboring pairs How do cilia and flagella move? Dyneins anchored at both ends try to walk toward minus end by hydrolzying ATP, pull toward plus end The Cell Theory The cell is the fundamental unit of life All living organisms are made of one or more cells All cells come from preexisting cells Four distinct processes of cell life cycle Cell growth G1 DNA replication S Distribution of replicated chromosomes Mitosis Cell division Mitosis and cytokinesis DNA synthesis in interphase in eukaryotes vs. prokaryotes done only during S phase in euke done continuously in bacteria Time spent in each phase in human cell 11 hours in G1 8 hours in S 4 hours in G2 1 hour in M Other examples of cell cycle in different organisms Yeast cells do it in 90 min. Early embryonic cells divide w/o growing What happens when adult cells stop dividing but are still metabolically active? Enter G0 phase, do metabolism but not dividing Some of these cells can bring themselves back into G1 How does one detect Sphase? radioactive thymine being incorporated into cells Prophase centrosomes migrate to opposite ends of the cell, MT build spindle fibers chromosomes begin to condense disassemble the nuclear envelope How is the nuclear envelope disassembled? must get rid of nuclear pores, nuclear envelope, and lamina key proteins get phosphorylated no individual proteins get hydrolyzed, just lose affinity for neighbors What happens to nuclear lamins during nuclear disassembly A and C are loose and floating, B stays in vesicles because originally embedded in membrane Prometaphase Chromosomes finish condensing Nucleus partial/full disassembly MTs connect to centromere of sister chromatids at kinetochore Chromosomes line up along metaphase plate Astral MTs extend from centriole toward outer edges of cell Kinetochore MTs attach to kinetochore of sister chromatids Polar MTs go toward middle of cell but don't make contact with sister chromatids Metaphase cohesins between sister chromatids breakdown Anaphase A seperate sister chromsomes to opposite sides of cell motor proteins in kinetochore move them away dyneins walk toward minus end of microtubule at centriole Anaphase B push spindle poles away from one another less risk of trapping chromosomes on wrong side requires dyneins and kinesins kinesins attach tails to each other and push microtubulues out, plus ends continue polymerizing Anchored dyneins walk toward minus end of astral microtubules, pull microtubule past them Telophase Relax chromosomes Break down MT reform nuclear envelope w/ phosphatases Lac operon Negatively regulated by glucose presence Positively regulated by lactose presence What are the functions of the products of the lac operon? Beta galactosidase breaks up lactose Permease uses proton gradient to bring lactose into the cell Transacetylase acetylizes lactose to make CoA How does lactose regulate the lac operon? binds to the repressor protein and keeps it from binding to the operator When is the lac operon functioning at top efficiency? Glucose is absent and lactose is present How does the presence of glucose regulate the lac operon? cAMP concentration inversely proportional to concentration of glucose CAP activated by cAMP and binds to promoter to transcribe How are the products of the lac operon affected by translational regulation? (1) mRNA stability: mRNA gets degraded from the 3' end, (2) transacetylase degraded first strength of SD sequence is proportional to distance from sequences Betagal>permease>transA Regulation of protein activity Codon usage bias: using uncommon codons slows down translation Allosteric and feedback inhibition Obligate intracellular parasites can persist on own BUT can only reproduce when inside a host cell What is the structure of a virus? protein coat (capsid), a few enzymes, nucleic acids for genes What is the basic structure of a virus genome? Few dozen to hundreds of genes RNA or DNA, ss or ds linear or circular single or multiple intact of segmented What is the most common form of the virus genome? linear dsDNA most common phage in bacteria Receptors (Virus attaching to animal cell) Proteins in envelope interact w/ receptors on the host cell Envelope fuses with membrane like vesicle Endocytosis of virus Host cell brings virus in and gets surrounded, when pH drops in early endosome virus has conformational change and it escapes Replicative cycles of viruses Phages normally just inject their nucleic acids Early gene expression is enzymes needed to replicate itself Virulent T4 phage life cycle Attaches to e coli Injects DNA into cytoplasm Some genes get expressed right away late viral mRNA produced replicate virus DNA DNA and capsids are assembled into new viruses, lyse cell What genes are expressed right away in virulent T4? produces early viral mRNA produces nuclease to degrade host genome and reduce competition produces enzymes that modify the sigma factor of the host RNA polymerase to look for viral promoters Temperate phages Can do the same thing as virulent phages or can lay dormant for awhile Why would a virus choose the lysogenic (temperate) cycle? cell is immune to infection cell turns of lysis proteins phage is spliced in genome (prophage) Cell copies prophage to pass onto daughter cells How does a virus leave the lysogenic cycle? excised from host genome and goes down lytic pathway What happens if a virus gets locked into lysogeny? active genes in prophage confer properties to host cell e.g. botulism, scarlet fever What's missing for RNA viruses in a host cell? they can't directly produce RNA from RNA to replicate themselves, host cells have nothing to do this Solution: replicase Positive sense RNA RNA can be translated directly to make replicase, makes alternating negative/positive sense RNA Negative sense RNA RNA is complementary to desired mRNA, can't be translated directly Needs a complementary strand made by replicase first, brought in capsid w/ negative sense Retroviruses makes dSDNA out of own RNA, integrates this into host genome to produce more of own RNA How do retroviruses use reverse transcriptase to create dsDNA from RNA? (1)Uses host nucleases to create temp DNARNA hybrid (2)Uses RnaseH on rev. trans. to degrade the RNA part of hybrid (3) ssDNA made into dsDNA with same process 2x How does viral DNA from the reverse transcriptase enter the nucleus? (1) Integrase holds onto DNA, has an NLS for entering (2)Integrase targest specific spot to put viral DNA in genome HIV Polyprotein eukaryotes don't do polycistronic translation, internal HIV protease cuts it up into individual proteins Why does HIV mutate so quickly? Reverse transcriptase has no proofreading and constantly makes mistakes What are plasmids? extrachromosomal, circular, dSDNA a few to a dozen genes that aren't essential can be found in multiple copies need host machinery to replicate Where are plasmids found and how are they useful? Prokaryotes, yeasts, plants, protozoans E.g. genes that help bacteria survive in inhospitable conditions Plasmid Conjugation Oneway transfer of plasmids b/w bacteria. Give a few and then make more What is the largest impact of trading plasmids? Antibiotic resistance Ex: Penicillin resistance at 90% Using restriction enzymes for genetic engineering Cut plasmid at very specific sequence, recognizes unmethylated plasmids can estimate where they cut and size of fragments use ligase to rejoin in another plasmid/host DNA
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