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Biochemistry Help

  1. Oct 2, 2007 #1
    Biochemistry Help :)

    I need help ...can someone help me out plz :)

    1) Denatured proteins
    (‘1’) have higher viscosities than their native conformation counterparts.
    (‘2’) have higher water water-accessible surface area compared to their native
    conformation counterparts.
    (‘3’) have lost their biological activity.
    (‘4’) may have more titrable residues per molecule than their native conformation
    counterparts.

    A) if 1, 2, 3 are correct
    B) if 1 and 3 are correct
    C) if 2 and 4 are correct
    D) if 4 only is correct
    E) if all are correct

    I think the correct answer is A

    3) The forces or bonds broken during the process of denaturation are
    (‘1’) hydrogen bonds.
    (‘2’) electrostatic interactions.
    (‘3’) hydrophobic interactions.
    (‘4’) peptide bonds.

    A) if 1, 2, 3 are correct
    B) if 1 and 3 are correct
    C) if 2 and 4 are correct
    D) if 4 only is correct
    E) if all are correct

    I think correct answer is A because peptide bonds are primary structure. Primary structure remain the same during protein denaturing. Because denaturing means protein unfold.

    4) The a helix
    (‘1’) can be disrupted by high concentrations of urea.
    (‘2’) is left-handed in most naturally occurring proteins.
    (‘3’) can be terminated by proline residues.
    (‘4’) exists only in combination with pleated sheet structures.
    A) if 1, 2, 3 are correct
    B) if 1 and 3 are correct
    C) if 2 and 4 are correct
    D) if 4 only is correct
    E) if all are correct

    I think it's B because hight concentration or urea can disrupt protein ( denature protein). Also, proline has no H; therefore, it's going to discript the structure. Therefore..proline always at the end of the chain

    5) Properties of disulfide bonds include
    (‘1’) cleavage only through reduction by mercaptoethanol, for example.
    (‘2’) stabilization of tertiary structures of proteins..
    (‘3’) stabilization of secondary structures of proteins.
    (‘4’) the joining of polypeptide chains into multisubunit proteins.
    A) if 1, 2, 3 are correct
    B) if 1 and 3 are correct
    C) if 2 and 4 are correct
    D) if 4 only is

    I think it's E...because disulfide bonds can help to link everything together. is it right?


    6) Factors that are of importance in the maintenance of an a helix are
    (‘1’) constituent amino acids are of the “L” configuration.
    (‘2’) peptide bonds have a partially planar character.
    (‘3’) the =O and –H components present in each peptide bond are “trans” with
    respect to each other.
    (‘4’) in three dimensions, the =O of the first peptide bond is sufficiently close to the
    –H of the fourth peptide bond in the carboxyl-terminal direction to form a
    hydrogen bond.
    A) if 1, 2, 3 are correct
    B) if 1 and 3 are correct
    C) if 2 and 4 are correct
    D) if 4 only is correct

    A is correct because protein always in L configuration, peptide bond have planar character. This is correct.. =O of first peptide hydrogen bond to amine not carboxyl termninal..so I elimate $4...i think 4 is correct.


    18) Carbon dioxide generated in peripheral tissue is transported to the lungs via the blood stream
    as
    (‘1’) carbamino residues.
    (‘2’) “dissolved” CO2.
    (‘3’) bicarbonate ions.
    (‘4’) carbonate ions.

    A) if 1, 2, 3 are correct
    B) if 1 and 3 are correct
    C) if 2 and 4 are correct
    D) if 4 only is correct


    20) In sickle cell anemia,
    (‘1’) glutamate in position 6 of the b-chain of HbA is substituted by valine.
    (‘2’) HbS is present in red cells, which electrophoretically moves more slowly than
    HbA.
    (‘3’) red cell shapes are distorted and asymmetric.
    (‘4’) HbS forms gel polymers in oxygenated form.
    A) if 1, 2, 3 are correct
    B) if 1 and 3 are correct
    C) if 2 and 4 are correct
    D) if 4 only is correct

    21) Concerning hemoglobin and myoglobin, which binds oxygen and iron changes from Fe2Å to Fe3Å?

    A) hemoglobin
    B) myoglobin
    C) both
    D) neither

    22) Concerning hemoglobin and myoglobin, which demonstrates oxygen bound by iron and a proximal histidyl residue?
    A) hemoglobin
    B) myoglobin
    C) both
    D) neither

    23) Concerning hemoglobin and myoglobin, which ancestral gene evolved at least 475 million
    years ago?
    A) hemoglobin
    B) myoglobin
    C) both
    D) neither
     
  2. jcsd
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