Lecture Notes: Amino Acids and Their Structure

Introduction to Amino Acids

• Amino acids are fundamental to biochemistry and human metabolism.
• They are the building blocks of proteins.

Real-World Example: Hemoglobin

• Hemoglobin is a protein in red blood cells responsible for oxygen transport.
• Red blood cells carry hemoglobin, which picks up oxygen from the lungs and delivers it to tissues.
• Oxygen is used by cells to generate ATP, the energy source for metabolic processes.

Amino Acids as Building Blocks

• Amino acids are to proteins what car components are to cars.
• There are 20 different amino acids that make up various proteins.

Structure of an Amino Acid

• General structure:
  • Amino Group
  • Carboxylic Acid Group
  • Alpha Carbon: central carbon linking the two groups.
  • Hydrogen Atom
  • R Group (Side Chain): unique to each amino acid.

Chirality

• The alpha carbon is a chiral carbon, meaning it has four unique groups attached:
  • Amino Group
  • Carboxylic Acid Group
  • Hydrogen Atom
  • R Group
• Chirality indicates optical activity (ability to rotate polarized light).
• Exception: Glycine, whose R group is a hydrogen atom, does not have a chiral carbon.

Fischer Projections of Amino Acids

• Helps visualize the arrangement of groups around the chiral carbon.
• L-amino acids: amino group is on the left.
• D-amino acids: amino group is on the right.
• L and D forms are enantiomers (mirror images, non-superimposable).
• Only the L-form is found in the human body.

Importance of L- and D- Forms

• Human body utilizes only the L-form of amino acids.

Summary and Review

• Amino acids are crucial for forming proteins like hemoglobin.
• They have a general structure with a chiral central carbon, except for glycine.
• Fischer projections distinguish between L- and D- forms, crucially only L-form is biologically active in humans.