985870
Description
Flashcards by Gerard Jitechian, updated more than 1 year ago
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Created by Gerard Jitechian
over 12 years ago
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| Question | Answer |
| Virus | an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply ONLY within the living cells of a host. |
| What is the major limitation of a virus? | It can only reproduce using the metabolic machinery of the host cell |
| Why can't viruses reproduce on their own? | DO NOT CONTAIN: 1) Membranes of their own 2) Ribosomes-needed to make proteins 3) Cytoplasm 4) Energy source |
| Are viruses cells? | No. They are noncellular. |
| What kind of genome do viruses have? | DNA or RNA genome. |
| What surrounds a virus? | A protein coat |
| Where do viral protein coats come from? | The host cells |
| What kind of microscope is needed to see a virus? | electron microscope |
| What do viral protein coats facilitate? | The penetration of prospective host cells. |
| Three factors of virus classification | 1) Type of nucleic acid 2) Size and shape 3) Presence / absence of outer envelope |
| What, specifically, do viruses rely once inside host cells? | The host cell's: enzymes, ribosomes, transfer RNA (tRNA), and ATP for its own replication |
| Bacteriophage | Viruses that infect bacterial cells |
| What targeting mechanism do bacteriophages use? | Portions of capsid adhere to specific receptor on the host bacterial cell |
| Lytic cycle (5 stages) | 1) Attachment 2) Penetration 3) Biosynthesis 4) Maturation 5) Release |
| Lysogenic cycle | 1) Becomes integrated into the host genome 2) Becomes latent 3) May later reenter the lytic cycle |
| prophage | viral genetic material already integrated into the host bacterial cell |
| Why are the Lytic & Lysogenic Cycles important in the field of medicine? | They are key factors in targeting drug-resistant bacteria |
| Retroviruses | any of a group of RNA viruses that insert a DNA copy of their genome into the host cell in order to replicate, e.g., HIV. |
| a key enzyme in retroviruses | reverse transcriptase |
| cDNA | a DNA that is complementary to a given RNA which serves as a template for synthesis of the DNA in the presence of reverse transcriptase |
| retrovirus action pathway | 1) viral RNA enters host cell → cDNA reverse transcription 2) cDNA becomes integrated into host DNA and is replicated as host DNA replicates 3) Viral DNA is transcribed; new viruses are produced |
| What cells does HIV infect? | helper T-cells |
| helper T-cell | a cell that influences or controls the differentiation or activity of other cells of the immune system. |
| integrase | virally encoded enzyme responsible for integrating viral DNA into host DNA |
| What allows viruses to jump from one species to another? | Changes in the capsid or spikes of the virus |
| What is the major drawback of anti-viral medications? | They destroy the host cells |
| How do anti-viral medications target infected cells? | They are synthesized to target the enzymes which the virus needs to use for replication |
| Viroid | Naked strands of RNA that lack capsids/Protein coats |
| Prions | misfolded protein molecules with contagious tertiary structures |
| What do prions lack? | genetic material |
| What tissues do prions affect? | They only affect neuronal or brain tissue. |
| Are prion diseases treatable? | No. All are untreatable and extremely fatal. |
| Prokaryote | a microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles |
| Peptidoglycan | a substance forming the cell walls of many bacteria, consisting of glycosaminoglycan chains interlinked with short peptides |
| plasmid | a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium |
| How do prokaryotes reproduce? | Asexually by means of binary fission |
| Conjugation | A method of genetic recombination where a sex pilus forms between two cells and the donor cell passes DNA to recipient cell through it |
| Transformation | A method of genetic recombination where a cell picks up pieces of DNA from the surrounding media in a test tube or dish |
| Transduction | A method of genetic recombination where bacteriophages carry portions of DNA from one bacterial cell to another |
| Bacterial Growth Curve |
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| lag phase | 1st phase of bacterial growth. There is no increase in cell number; however cells are actively metabolizing, in preparation for cell division |
| factor contributing to length of lag phase | growth medium |
| exponential phase (log phase) | 2nd stage of bacterial growth. DNA replication begins and cells begin to divide |
| What factors affect the duration of exponential phase (aka generation)? | the organism itself, the growth medium, and the temperature |
| stationary phase | 3rd stage of bacterial growth. Metabolic activity slows and the cells cease rapid cell division |
| death phase | 4th stage of bacterial growth. Here, cells quickly lose the ability to divide (even if they are placed in fresh medium) |
| Obligate aerobes | Prokaryotes that are unable to grow in the absence of free oxygen |
| Obligate anaerobes | Prokaryotes that are unable to grow in the presence of free oxygen |
| Facultative anaerobes | Prokaryotes that are able to grow in either the presence or absence of free oxygen |
| Mesophiles | Bacteria that grow in ambient/room temp |
| Thermophiles | Bacteria that grow in hot temp. (45oC/ 113 oF) |
| Psychrophiles | Bacteria that grow in cold temp. [grow very slowly] (0 to -15 oC/32-5 oF) |
| Extremophiles | Bacteria that grow in extremely hot temps (100-120oC/ 212-248 oF) |
| What important enzyme is derived from extremophiles? | DNA polymerase from Thermus aquaticus for PCR (polymerase chain reaction ) |
| Halophiles | Bateria that grow in high salt areas |
| Gram stain procedure | A laboratory staining procedure important for distinguishing bacteria based on cell wall structure. Classified as gram positive and negative. |
| Gram-positive bacteria | Appear purple. THICK peptidoglycan on the very outside of their cell walls |
| Gram-negative bacteria | Appear pink. Have a THIN peptidoglycan hidden inside a much more COMPLEX cell wall |
| Three bacterial classes based on shape | spirilli, bacilli, cocci) |
| spirilli | Spiral shaped |
| bacilli | Rod shaped |
| cocci | Round shaped |
| Cyanobacteria | Gram-negative bacteria that undergo photosynthesis |
| lichen | A symbiotic relationship where the cyanobacteria provides the fungus with organic nutrients and the fungus protects the cyanobacteria and supplies it with inorganic nutrients |
| Archaea | Chemoautotrophs, do not contain peptidoglycan, and are related to eukaryotes |
| Chemoautotroph | Oxidize inorganic compounds (i.e., H2 gas, NH3) to obtain the energy needed to break down CO2 into an |
| lipopolysaccharide (LPS) | Gram-negative bacteria have this on their cell walls to protect agaist chemical agents that may destroy it. They are very toxic to animals |
| ENDOTOXIN | Chemical in Gram-negative bacteria released into host only when the bacterial cell wall is destroyed |
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