84.Which of the following amino acids would most likely be found on the surface of a protein molecule?

A. Alanine B. Arginine
C. Isoleucine D. Leucine
E. Phenylalanine

The correct answer is B. This question requires two logical steps. First, you need to appreciate that hydrophilic amino acids are more likely to appear on the surface of a protein molecule, whereas hydrophobic amino acids are most likely be found in the interior. Next, you need to figure out which of the amino acids listed is hydrophilic. If you recall that arginine is a basic amino acid that is positively charged at physiologic pH, you should be able to answer this question right away.

All the other choices have neutral side chains and are uncharged at physiologic pH. They would most likely be found in the hydrophobic core of the protein structure. Alanine (choice A), isoleucine (choice C), and leucine (choice D) all have aliphatic side chains; phenylalanine (choice E) and tryptophan have aromatic side chains.

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83.Which of the following will cause reduction of the size of the pulp chamber in mid-life?

A. Formation of primary dentin
B. Formation of secondary dentin
C. Internal resorption
D. External resorption
E. Pulp fibrosis

The correct answer is B. Primary dentin (choice A) surrounds the pulp chamber when the tooth is
first formed and erupts. It is the initial dentin that makes up the base of both the crown and root. If the
young tooth has a given size pulp chamber, further dentin formation, secondary dentin, later in life, will
begin to fill the chamber with dentin, making it smaller. Internal resorption (choice C) is loss of dentin,
resulting in a larger pulp chamber. External resorption (choice D) involves the exterior of the root and
does not change the pulp chamber size. Pulp fibrosis (choice E) would change the histology of the cells in the chamber, but not the chamber's size


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82.Towne’s projection is a:

a. A-p view b. P-a
c. Lateral d. Panoramic

Ans: a. Antero-posterior view

This view is primarily used to observe the occipital area of skull and sometimes the

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