Free CLEP Science and Mathematics Exam Braindumps (page: 12)

Page 11 of 128

All of the following nitrogenous bases make up RNA molecules EXCEPT

  1. adenine
  2. cytosine
  3. thymine
  4. guanine
  5. uracil

Answer(s): C

Explanation:

RNA has bases A, C, G, and U. There is no thymine in RNA.



Proteins such as hemoglobin that are comprised of multiple units, or chains, of amino acids exhibit what type of structure?

  1. Primary
  2. Secondary
  3. Tertiary
  4. Quaternary
  5. Trimeric

Answer(s): D

Explanation:

Multi-subunit proteins are said to exhibit quaternary structure. Tertiary structure refers to the 3-D structure created by the interactions between monomers on a single chain of amino acids. Secondary structure refers to the local alpha helices and beta-pleated sheets that portions of an amino acid chain form as a protein twists up into its overall 3-D shape. The primary structure of a protein is simply the linear order of the amino acid chain that makes up the protein and that dictates that secondary and tertiary structures.



The electron carrier in photosynthesis responsible for ferrying electrons from the chloroplast membrane into the stroma of the chloroplast is

  1. NADPH
  2. NADH
  3. ATP
  4. FADH2
  5. C6H12O6

Answer(s): A

Explanation:

To distinguish between NADH and NADPH, just remember the "P" in NADPH can stand for photosynthesis (in reality, it stands for the word "phosphate"). NADPH is the exclusive electron carrier of photosynthesis, which is responsible for ferrying electrons from the light reaction to the Calvin Cycle. NADH and FADH., are the carriers in cellular respiration, while ATP and the sugar glucose are not electron carriers at all, but energy molecules.



Significant overlap in the sequence of amino acids of the same protein involved in cell division from two different species indicates that

  1. other proteins compared between the two species are unlikely to be similar
  2. the proteins have a common evolutionary origin
  3. the DNA coding for the two proteins will be identical when introns are removed
  4. the two proteins would have identical tertiary structures
  5. the two species do not share a recent common ancestor

Answer(s): B

Explanation:

Similar amino acid sequences mean similar DNA sequences, since DN A codes for proteins. This would indicate that the two proteins have a common evolutionary origin, and if many other proteins between the two species were also closely related in amino acid sequence, it would also show that the two species shared a recent common ancestor. Tertiary structures would not be identical unless the proteins were identical, not just similar, and this structure determines function.






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