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3: Amino Acids

Amino acid structure, types, and roles in protein structure.

LibreTexts reference: Amino Acids and Peptides

Amino Acids and Descriptive Properties

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Match each of the following amino acids with their corresponding descriptions.
Note: Each choice will be used exactly once.

Your Choice Prompt
Drop Your Choice Here 1. tyrosine
Drop Your Choice Here 2. arginine
Drop Your Choice Here 3. histidine
Drop Your Choice Here 4. leucine
Drop Your Choice Here 5. lysine

Drag one of the choices below:

  • A. a aromatic amino acid with a side chain containing a phenol (-C6H6OH) group, derived from phenylalanine
  • B. a positively charged amino acid with a long, flexible side chain containing 3 nitrogen atoms (guanidinium)
  • C. an aromatic amino acid with a side chain containing a 5-membered nitrogenous ring and a pKa close to pH 7
  • D. a non-polar branched chain amino acid that is an isomer of isoleucine
  • E. a positively charged amino acid with a long, flexible side chain containing an amine group
 

Amino Acids from Descriptions

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Which one of the following amino acids correspond to the description 'a negatively charged amino acid with a small, carboxylate (-COOH) side chain'.

 

Ionic Bond Formation in Amino Acid Side Chains

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Based on the chemical properties of amino acid side chains, which pair of amino acids listed below can form an ionic bond between their side chains?

 

Dipeptide Sequences from Descriptions

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peptide_2e22

A dipeptide is made up of two (2) amino acids. The figure above shows one such dipeptide with an unknown sequence. Your task is to find out the two (2) letter sequence of this dipeptide.
Here is a step-by-step guide to help you answer the question:

  1. Consult an amino acid guide for reference. You can find a PDF guide on Blackboard under "Exam and Quiz" in the "Old Exams" section, with the filename bchm_exam-help_sheet.pdf, or search online for a visual guide that shows all 20 amino acids with their single-letter codes.
  2. Identify the amino-terminal end, represented as NH3+ and highlighted in bright green. Distinguish between the general nitrogens in amino acid backbones (denoted as NH) and the nitrogen in amino acid side chains.
  3. The one (1) peptide bonds connecting the two (2) amino acids are highlighted in bright green, making it easier to distinguish the two (2) amino acids.
  4. Examine the side chain for each of the two (2) amino acids to determine their single-letter amino acid code.
  5. List the single-letter amino acid codes in the amino to carboxyl (N→C) direction. This is the standard method for writing peptide sequences.

Select the correct peptide sequence from the options below:

 

Tripeptide Sequences from Structural Descriptions

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peptide_475a

A tripeptide is made up of three (3) amino acids. The figure above shows one such tripeptide with an unknown sequence. Your task is to find out the three (3) letter sequence of this tripeptide.
Here is a step-by-step guide to help you answer the question:

  1. Consult an amino acid guide for reference. You can find a PDF guide on Blackboard under "Exam and Quiz" in the "Old Exams" section, with the filename bchm_exam-help_sheet.pdf, or search online for a visual guide that shows all 20 amino acids with their single-letter codes.
  2. Identify the amino-terminal end, represented as NH3+ and highlighted in bright green. Distinguish between the general nitrogens in amino acid backbones (denoted as NH) and the nitrogen in amino acid side chains.
  3. The two (2) peptide bonds connecting the three (3) amino acids are highlighted in bright green, making it easier to distinguish the three (3) amino acids.
  4. Examine the side chain for each of the three (3) amino acids to determine their single-letter amino acid code.
  5. List the single-letter amino acid codes in the amino to carboxyl (N→C) direction. This is the standard method for writing peptide sequences.

Select the correct peptide sequence from the options below:

 

Peptide Sequences with Four Amino Acids

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peptide_2e4f

A tetrapeptide is made up of four (4) amino acids. The figure above shows one such tetrapeptide with an unknown sequence. Your task is to find out the four (4) letter sequence of this tetrapeptide.
Here is a step-by-step guide to help you answer the question:

  1. Consult an amino acid guide for reference. You can find a PDF guide on Blackboard under "Exam and Quiz" in the "Old Exams" section, with the filename bchm_exam-help_sheet.pdf, or search online for a visual guide that shows all 20 amino acids with their single-letter codes.
  2. Identify the amino-terminal end, represented as NH3+ and highlighted in bright green. Distinguish between the general nitrogens in amino acid backbones (denoted as NH) and the nitrogen in amino acid side chains.
  3. The three (3) peptide bonds connecting the four (4) amino acids are highlighted in bright green, making it easier to distinguish the four (4) amino acids.
  4. Examine the side chain for each of the four (4) amino acids to determine their single-letter amino acid code.
  5. List the single-letter amino acid codes in the amino to carboxyl (N→C) direction. This is the standard method for writing peptide sequences.

Select the correct peptide sequence from the options below:

 

Amino Acids from Chemical Structures

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Which amino acid is represented by the chemical structure shown above?

 

Amino Acids from Chemical Structures (7 Choices)

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Which amino acid is represented by the chemical structure shown above?