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Organic Chemistry

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Amino Acids and Proteins

Question
9 out of 14
 

Amino acids play an essential role in the physiological processes in our body. They are the main building blocks of the principal structures in our body. Amino acids themselves or in combination with carbohydrates, lipids, etc., form an intricate system of physiologically important structures and functional domains without which life as we know it cannot exist.

From a biological point of view with respect to life forms, only 20 amino acids are important, even though many more are found in nature. Most amino acids are optically active. With the functional groups and their chemical behavior, we can predict certain properties of amino acids such as ionization properties. Amino acids join together to form peptides. Table-1 shows the pKa values of some amino acids.


Table-1

image\28343 ch 28 passage 1.png

image\Ch 28 pass, g2.png


Which of the following are true regarding amino acids?

I. Amino acids have carboxyl group

II. Amino acids have high melting points

III. Some amino acids can have a net positive charge

IV. Some amino acids can have a net negative charge



A I, III & IV only
B I, II & III only
C I, III & IV only
D I, II, III & IV
Ans. D All amino acids have at least one carboxyl group. Hence, statement I is true. Amino acids have high melting points since they can have multiple charges. This results in strong ionic interactions and hence much energy is required to break the ionic interactions between them. Thus it is hard to break the crystal lattice, and they have high boiling points. Hence, statement II is true. Depending on the pH and the particular amino acid's nature, amino acids can have either a net positive charge, a net negative charge, or a net zero charge. Hence, statements III and IV are true.

Amino Acids and Proteins Flashcard List

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