MCAT BIOLOGY

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lace.granatelli
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MCAT BIOLOGY
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2012-12-29 18:30:48
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MCAT BIOLOGY
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  1. Bacteria
    prokaryotic organisms; prokaryotes lack a true nucleus and membrane-bound organelles
  2. Viruses
    not considered living organisms, since they cannot carry out metabolism outside of a host cell
  3. Bacteriophages
    viruses that infect bacteria
  4. Fungi
    lack chlorohyll but are eukaryotic organisms and therefore have membrane-bound organelles
  5. Archaea
    • ex: methogens (prokaryotes that produce methane)
    • extreme halophilies - live at high concentrations of NaCl
    • extreme thermophiles - live where super hot
  6. Prokaryotic plasma membrane is composed of .....
    • phospolipids arranged in lipid bilayer
    • philic head with phobic tail
  7. Prokaryotes have a cell wall to maintain cell shape, protection, & rigidity. Bacteria can be divided into two groups:
    gram-positive and gram-negative
  8. Characteristics of Gram-Positive
    thick cell wall - peptidoglycan
  9. Characteristics of Gram-negative
    thin layer of peptidoglycan between layers of periplasm and coated with lipopolysaccarde and proteins
  10. Oligate anaerobes
    cannot survive in the presence of oxygen
  11. Facultative aerobes
    can survive with or without oxygen
  12. Oligate aerobes
    require oxygen to survive
  13. Photoautotrophs
    • photosynthetic, using light energy to produce their own nutrient molecules.
    • Photosynthetic bacteria use the plasma membrane as the site of photosynthesis
  14. Chemoautotrophs
    use energy derived from inorganic molecules such as ammonia (NH3) or hydrogen sulfide (H2S) to drive nutrient production
  15. Photoheterotrophs
    uses light to generate energy but must obtain their carbon in organic form (glucose)
  16. Chemoheterotrophs
    must consume organic molecules both as an energy source and as a source of carbon
  17. In prokaryotes, transcription and translation occur both in the cytosol....why?
    there is no seperate membrane-bound nucleus
  18. In eukaryotes, transcription takes place where?
    nucleus, where splicing of introns takes place before leaving the nucleus
  19. Genetic transformation takes place when DNA is incorportated into the recipient.  Describe transformation...
    DNA taken up from the enviorment and integrated into the bacterial genome
  20. Genetic transformation takes place when DNA is incorportated into the recipient.  Describe transduction
    genetic material is passed from one bacterial cell to another via a virus .... recombination of bacterial DNA
  21. Genetic transformation takes place when DNA is incorportated into the recipient.  Describe conjugation
    • genetic information is directly transferred from one bacterial cell to another via temportany connection known as a conjugation bridge
    • Cells containing F plasmid are called F+, cells lacking F plasmid are called F-
    • F+ cells extends sex pilli to recipeient F- cell to form the conjugation bridge
  22. transduction, genetic material is passed from one bacterial cell to another via a virus. In generalized transduction....
    DNA from any part of the host's chromosome becomes a part of the viral genome, replacing the viral genome
  23. specilized tranduction works when
    DNA from a specific part of the host's chromosomes becomes part of the viral genome, usually replacing some viral genes
  24. Hfr cells
    when part of the plasmid intergrates into the chromosome
  25. Viruses consists of genetic material surrounded by a protein coat. Viruses are oligate intracelluar partsites, which means....
    • they can express genes and reproduce only within a living host cell
    • Viruses are unable to survive outside of a host cell, since they lack the structures necessary for independent activity and reproduction
  26. Retroviruses are a special group of RNA viruses. When a viral RNA enters the host cell, it is first copied into double-stranded DNA, integrating into the genome of the host cell.  What enzyme does a retrovirus need to copy DNA from RNA?
    • Reverse transcriptase
    • Since animal cells do not contain this, viruses must carry the enzyme with them
    • Since the virus integrates in the genome of the host, it can escape immune detection
  27. What are bacteriophages? They have a polyhedral head and tail appartaus with tail fibers to attach to the host
    virus that infects bacteria
  28. A Bacteriophage infects host cell by attaching to it, releasing enzymes that create a hole in the bacterial cell wall, then inject its DNA into bacterial cell host - once inside, the bacteriophage can reproduce through lytic or lysogenic cycle...what's the difference?
    Lytic- viral DNA is translated and transcribed, weakening the cell wall where it bursts

    Lysogenic-viral DNA becomes integrated into bacterial genome in prophage form, where it lies dormant, until its activated and starts the lytic cycle
  29. Fungi possess cell walls made of ....
    chiton
  30. Glycolipids are similar to phospholipids, except glycolipids have one or more carbohydrates attached to the three-carbon glycerol backbone.  Glycolipids are found in abundance..where?
    in the membranes of myelinated cells composing the human nervous system
  31. What do steriods look like? Name an example
    • four ringed structure
    • hormones, vitamin A, cholestrol which is important for membrane fluidity
  32. Lipoproteins are classified by their density. The greater the ratio of lipid to protein, the lower the density. The major class of lipoproteins in humans are LDL. no question
     
  33. Function of phospholipids?
    structural component of membranes
  34. Function of triacylglycerols?
    store metabolic energy, provide thermal insulation, and padding
  35. Function of steriods?
    regulate metabolic activities
  36. Some fatty acids function to do what
    serve as local hormones
  37. Primary struture of amino acids looks like what?
    a single chain
  38. Secondary structure of amino acids look like what?
    • beta-pleated sheet or alpha-helix - a,helix and the beta-pleated sheets are the secondary structure and contribute to the conforllIation of the protein. All proteins have a pri- mary structure and most have a secondary structure.
    • Beta-pleated sheets: connecting segments of the two strands of the sheet can lie in the same direction (parallel) or in opposite directions (al/liparallel)
    • Alpha-helix: single chain twisted
  39. What does the tertiary structure look like for the amino acids?
    The tertiary structure refers to the three dimensional shape formed when the peptide chain curls and folds
  40. What forces create the tertiary structure for amino acids?
    1.2.3. 4. 5.covalent disulfide bonds between two cysteine an1ino acids on djfferent parts of the chain;electrostatic (ionic) interactions mostly between acidic and basic side chains;hydrogen bonds;van der Waals forces;hydrophobic side chains pushed away from water (toward center of protein)

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