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Topic 3: Amino Acids

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

Determining Dipeptide Sequence from Structure

Click to show Determining Dipeptide Sequence from Structure example problem

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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:

 

Identification of Amino Acids by Structural and Chemical Properties

Click to show Identification of Amino Acids by Structural and Chemical Properties example problem

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Which one of the following amino acids correspond to the description 'a polar amino acid with a shorter amine-substituted carboxylate (amide) -C(=O)NH2 group'.

 

Amino Acids from Chemical Structures

Click to show Amino Acids from Chemical Structures example problem

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Which one of the following amino acids is represented by the chemical structure shown above?