Chapter 3 - Amino Acids

Question 1

Biological Function of Proteins

1. What is the literal meaning of the word “Protein”?
2. What are proteins?
3. What are the 7 biological processes of proteins?

Answer 1

1. Protein means “of first importance”. They playa crucial role in the biological process.
2. Proteins are polymers of amino acids.
3. Enzymes - biological catalysts, antibodies - defense proteins, transport proteins, regulatory proteins, structural proteins, movement proteins, nutrient proteins.

Question 2

Protein Building Blocks: The â-Amino Acids

1. What two groups are found in an Alpha-Amino Acid?
2. In what 2 ways are â-amino acids formed? How many are formed?
3. How many â-amino acids are common in nature? What does â (alpha) mean?
4. Of the â-amino acids that form in nature, how many are stereoisomers?

Answer 2

1. These compounds contain both an amine and a carboxyl acid group.
2. Hundreds are formed both naturally and synthetically.
3. 20 are common in nature. Alpha means the amine is adjacent to the carboxylate group.
4. 19 of the 20 are stereoisomers.

Question 3

Amino Acids

1. What 2 groups are are â-carbons attached to?
2. What 3 things does the amino acid have at physiologic pH?
3. What is a zwitterion?
4. What are Amino Acids?
5. What do the two charged groups (the basic amino group and the carboxylic Acid) at the two ends lead to?
6. What can be affected by changing the pH?
7. What is the Isoelectric point?

Answer 3

1. â-carbons are attached to a Carboxylate group and a protonated amino group.
2. • Carboxyl group in -COO, amino group in -NH3+,and a Zwitterion.
3. A zwitterion is a neutral molecule with equal number of + and - charges.
4. Amino Acids are white crystalline solids with high melting points and high water solubilities.
5. This leads to internal proton transfer -> zwitterions
6. By changing the pH, you can affect the net charge on the zwitterions.
7. Isoelectric point is the pH point at which there is no net charge on the zwitterions

Question 4

Stereoisomers of Amino Acids

1. Which carbon of an amino acid is chiral?
2. What common amino acid is NOT chiral?
3. What is the amino acid configuration isolated FROM proteins?
4. What is the most oxidized part of an amino acid molecule and where is it drawn?

Answer 4

1. The â-carbon.
2. Glycine is the only common amino acid that is not chiral
3. “L” is the amino acid configuration isolated from proteins (Only L is found in proteins, D is found in nature).
4. The most oxidized end of the molecule is always drawn at the top.

Question 5

Classes of Amino Acids

1. What is the main cause of the difference between Amino Acids? Can some amino Acids be hydrophobic?
2. What are the 3 subdivided types of Hydrophilic Amino Acids?

Answer 5

1. All difference between amino Acids depend upon their side-chain R groups. Some amino acids are hydrophobic.
2. • Polar, neutral: Have a high affinity for water, but are not ionic at pH7
     - Negatively charged: Have ionized carboxyl groups in their side chains.
     - Positive charged: Basic as the side chain reacts with water to release a hydroxide anion.

Question 6

Names of Common Amino Acids

1. Link these 3 letter Abbreviations with their corresponding Amino Acid
   - Ala
   - Arg
   - Asn
   - Asp
   - Cys
   - Glu
   - Gln
   - Gly
   - His
   - ile

Answer 6

• Alanine
• Arginine
• Asparagine
• Aspartate
• Cysteine
• Glutamate
• Glutamine
• Glycine
• Histidine
• Isoleucine

Question 7

Names of Common Amino Acids

2. Link these 3 letter Abbreviations with their corresponding Amino Acid
   - Leu
   - Lys
   - Met
   - Phe
   - Pro
   - Ser
   - Thr
   - Trp
   - Tyr
   - Val

Answer 7

• Leucine
• Lysine
• Methionine
• Phenylalanine
• Proline
• Serine
• Threonine
• Tryptophan
• Tyrosine
• Valine

Question 8

Hydrophobic Amino Acids

1. What are the 9 Hydrophobic Amino Acids?

Answer 8

1. Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Isoleucine (ile), Phenylalanine (Phe), Proline (Pro), Tryptophan (Trp), Methionine (Met)

Question 9

Polar Neutral Amino Acids

1. What are the 6 Polar Neutral Amino Acids?

Answer 9

1. Serine (Ser), Threonine (Thr), Tyrosine (Tyr), Cysteine (Cys), Asparagine (Asn), and Glutamine (Gln)

Question 10

Charged Amino Acids

1. What are the two Negatively Charged Amino Acids?
2. What are the 3 Positive a charger Amino Acids?

Answer 10

1. Aspartate (Asp) and Glutamate (Glu)

2. Lysine (Lys), Arginine (Arg), Histidine (His)