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Homework Help: The enzyme reverse transciptase is critical for?

  1. Sep 12, 2007 #1
    4. The enzyme reverse transciptase is critical for?

    A. converting the RNA genome of a virus into the DNA form of the host cell.
    B. converting the RNA genome of a bacterium into the doble stranded RNA form.
    C. replacig the uracil with the thymine in DNA strands.
    D. replacing the broken phosphodiester bonds formed after viral attack in the host cell genome.
    E. all of the above

    5. Which of the following processes are part of gene expression?

    A. replication of DNA to make a copy
    B. DNA transcribed to RNA
    c. RNA translated to make protein
    D. a and b
    E. b and c

    6. How was the defecct in cystic fibrosis discovered?

    A. Researchers searched for a gene ain a chromosomal region likely to included the defective gene
    B. Researchers used mouse models to identify a human gene
    C. researchers discovered the protein and proved it was missing in humans with cystic fibrosis
    D. all of the above
    E. none of the above
    Last edited: Sep 13, 2007
  2. jcsd
  3. Sep 13, 2007 #2
    1. oxygen actually has 2 lone pairs in the water molecule; it uses 2 out of its 6 outermost electrons in bonding with hydrogen, leaving the 4 electrons, i.e. 2 lone pairs. i think you're right about the 4 h-bonds. 2 h-bonds due to the two lone pairs and 2 h-bonds due to the two hydrogen atoms having the high partial positive charge.

    3. right, all three of them

    5. gene expression has to do with proteins. c should be the right answer.

    i'm not so sure about 2. and i dunno about 4 and 6.
  4. Sep 13, 2007 #3
    thanks Kushal,

    I have one more question to ask u

    which of the following accurately lists the proper for these cells compentets in increasing size??
    A. protein, proton, ribosome, mitochondira, bacteria......................
    : B. proton, protein, mitochondria, ribosome, bacteria
    C. proton, protein, ribosome, mtochondria, bacteria
    D. protein, proton, ribosome, mitochondria, bacteria
    E. proton, protein, bacteria, ribosome, mitochondira

    I think the answer is E because Bacteria is Prokaryotes...it's before Eukaryotes....what do u think???
  5. Sep 13, 2007 #4


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    Think about it.

    E states that a bacteria is smaller than a ribosome

    What is a ribosome and what is the purpose of a ribosome?
  6. Sep 13, 2007 #5

    ribosome is used for protein synthesis. But bacteria = prokaryotes...ribosome and mitochondria are eukaryotes. I think E is the right anwer.
  7. Sep 14, 2007 #6
    Hint: Bacteria contain ribosomes.

    What should that tell you about their relative sizes?
    Last edited: Sep 14, 2007
  8. Sep 14, 2007 #7
    Dear Bomba, Kushal, and Ismith,

    I have another question

    The most important buffering system for maintain proper blood PH is

    A. charge on the amino acid
    B. the bicarbonate buffer system of Co2, carbonic acid and bicarbonate
    C. Phosphate groups of serum phosphorproteins
    D. all of the above

    First, I picked B because Co2 + H2o = H2C03 PKA = 6.1

    BUT when i think about phosphate H2po4- = H+ + hpo4- PKA 7.2 intracellus PH is around 7.4 so equal amounts of acid / base...therefore, this one work too

    Amino acid contain many Co2 and NH3 groups. Several group have PKA close to 7.4....so this could maintain PROPER BLOOD PH, too.

    Am i right?? so the answer is ALL OF THE ABOVE?
  9. Sep 14, 2007 #8
    ribosomes are really tiny structures, about 20-30 nm. protons are even smaller of course. proteins are in between them.

    bacteria is an organism. it should be larger!!

    to help you out, protons are smallest. proteins are molecules, they 'consist' of protons. ribosomes are organelles which consist of molecules(rRNA). mitochondria are also organelles but much larger(there's an endosymbiont theory saying that mitochondria as well as chloroplasts, were prokaryotes) and finally you bacteria whioch are organisms after all.

    sorry i don't know the answer for the above question; i've not done it yet...ooopss
  10. Sep 14, 2007 #9
    Hint: Which of the choices would you expect to find in concentrations
    significant enough--in blood--to potentially buffer its pH?
  11. Sep 14, 2007 #10

    Blood is around 7.4. But all of the PKA from A, B, and C are closed to 74...is it ALL OF THE ABOVE??
  12. Sep 14, 2007 #11
    There is a difference between
    "what is the most important (physiological) buffering system for blood pH"
    "what can be used (artificially) to buffer a solution containing some blood"
    Last edited: Sep 15, 2007
  13. Sep 15, 2007 #12

    I think the answer is all of the above. But when i read the question again..he asked " MOST IMPORTANT BUFFERING SYSTEM " then i think it's only Bicarbonate..blood is extracelluar has PKA around 6.1 that close to Blood PH...on the other hand, phosphate is only for intracelluar.

    amino and phosphate groupalso help to maintain blood PH too but not all amino acid has PKA around 7.4...Also, amino and phosphate are minor not MAJOR to help maintain PH....then i go with BICARBONATE is my final answer :)
    Last edited: Sep 15, 2007
  14. Sep 15, 2007 #13
    Yes, B is correct :)

    Actually, this goes back to my second hint:
    >Which of the choices would you expect to find in concentrations
    significant enough--in blood--to potentially buffer its pH?

    You mentioned that blood is an extracellular fluid. Amino acids are generally stored and used inside of cells, and so are phosphoproteins (which are not related to blood buffering in any reasonably direct way).
    Last edited: Sep 15, 2007
  15. Sep 15, 2007 #14

    Thank you!!!!

    cAN SOMEONE help me to check my PH cal please :)

    1. The pH of .55M aqueous solution of hypobromous acid, HBrO, at 25celcius is 4.45. What is the vale of Ka for HBrO?

    HBr0 + h20 = H30+ + BRO-

    Ph= - log (H+)
    4.48 = -log (H+)
    H+ = .00003

    Ka = (.00003) ( .00003) / (.55 - .00003)
    Ka = 2.0 x 10^-9

    2. The Ka of hydrofluoric acid (HF) at 25 celcius is 6.8 x 10^-4. What is the pH of .35M aqueous solution of HF?

    6.8 x 10^-4 = (x)(x) / (.35-x)
    X = .015091

    Ph= -log (H+)
    ph = -log (.015091)
    pH = 1.81

    3. What is the final pH when 100 mL HCL is added to 900 mL of water?

    (.5m / 1L ) ( 1L / 1000 ml ) (1000 Ml / 1 ) = .05 mol of HCL

    Ka is not given..i went online and found ka for HCL is 1 x 10 ^6

    1x 10^ 6 = (x)(x) / (.05-x)
    X = .o5

    ph = - log (h+)
    Ph = - log (.05)
    PH = 1.3
  16. Sep 16, 2007 #15
    First two are correct :)
    (except for a few minor errors in significant figures)

    *For the last one, you may assume that HCl dissociates
    completely in aqueous solution; hence pH=1
    Last edited: Sep 16, 2007
  17. Sep 16, 2007 #16

    What is the final pH when 100 ML of .5M HCL is added to 900 mL of water?

    A. 1.3
    B. 5.0
    C. 13.0
    D. .5
    D. none of the above

    I didn't see pH = 1 ...is it None of the above?? :( hihihi

    I didn't see
  18. Sep 16, 2007 #17
    The first time you posted this question (your previous post), you did NOT state the concentration of your 100ml HCl solution. Well, so to speak, I assumed that you were dealing with 1M HCl solution; thus, dilution with 900mL of water would yield 0.1M HCl solution, which clearly has
    pH = 1

    But, now that you write out the question more fully--i.e., assigning, in fact, a 0.5M concentration to your 100mL HCl solution--then dilution with 900mL of water would yield 0.05M HCl solution, which clearly has pH = 1.3

    So, yes, the answer is "A"
    Last edited: Sep 16, 2007
  19. Sep 16, 2007 #18
    Thank you :) problem solved :) yeehaaa :)
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