Amino Acids: Structure, Properties, and Behavior in Biological Systems

The video tutorial explains the structure and types of amino acids, highlighting their role as protein monomers. It covers the formation of peptide bonds through dehydration synthesis and discusses how pH affects amino acid structure, including the concept of zwitterions. The tutorial also provides examples of different amino acids, such as valine, serine, aspartic acid, phenylalanine, and lysine, and explains their properties based on their R groups.

What is the primary structural feature that makes a carbon atom chiral in an amino acid?

• It is bonded to four different groups.

• It is bonded to two identical and two different groups.

• It is bonded to three different groups.

• It is bonded to four identical groups.

Which type of amino acid is characterized by an R group that is nonpolar and hydrophobic?

• Nonpolar amino acid

• Polar amino acid

• Aromatic amino acid

• Acidic amino acid

What type of reaction leads to the formation of a peptide bond between amino acids?

• Hydrolysis reaction

• Dehydration synthesis reaction

• Reduction reaction

• Oxidation reaction

At what pH is the carboxylic acid group of alanine likely to lose a hydrogen ion?

• Below 2.3

• At 9.7

• At 2.3

• Above 2.3

What is the net charge of an amino acid when the pH is between its two pKa values?

• Depends on the amino acid

• Negative

• Positive

• Zero

What is the term for an amino acid that has both a positive and a negative charge but is overall neutral?

• Cation

• Neutral ion

• Anion

• Zwitterion

How does the charge of an amino acid change under basic conditions?

• It becomes more acidic.

• It remains neutral.

• It becomes more negative.

• It becomes more positive.

What happens to the amino group of alanine when the pH is above 9.7?

• It loses a hydrogen ion.

• It becomes positively charged.

• It gains a hydrogen ion.

• It remains unchanged.

At a pH of 5, what is the predominant form of alanine?

• Fully protonated

• Zwitterion

• Fully deprotonated

• Positively charged

What is the effect of moving one pH unit away from the pKa on the ratio of acid to base forms of an amino acid?

• The ratio remains the same.

• The ratio changes by a factor of 10.

• The ratio changes by a factor of 2.

• The ratio changes by a factor of 5.