Biochemistry/Amino Acids

Lesson Goal: Become familiar with the essential amino acids, and understand their functionality. This is essential background to understanding proteins and enzymes

Lesson Plan While completing the readings and listening to the lecture, take notes, especially about the 20 amino acids (commonly found in mammals) and their characteristics. Then relax and memorize the amino acids formula using the asteroid game. Finish the lesson with a quiz over the amino acids.

Suggested Reading: Wikipedia site:w:Amino_acid Biochemistry Textbook: [1] University of Arizona's website with excellent pictures (explore the links) [2]

Free Lectures available at ITunes U

• Good audio lectures are availiable at [3] but there are no pictures to correlate with the speaker.

Memorize your amino acids with an asteroid game: [4]

Finish your lesson with a quiz: [5]

Important Facts from Lesson: Amino Acids: Building Blocks of Proteins

• Amino acids make good proteins because they have the capacity to polymerize, novel acid-base properties, varied structure and chemical functionality in side chains, and occasionally chirality.

Basic Amino Acid Structure:

• zwitterion molecule: the NH3+ is positively charged and the COO- is negatively charged. Attached to this is the R group which varies.

Amino Acids Can Join via Peptide Bonds

• Peptide bonds combine the NH3+ and the COO- by removing a water molecule creating a HN-CO bond
• This bond favors hydrolysis at biological standard state so energy must be added to create peptide bonds.

Common Amino Acids

• 20 amino acids are commonly found in proteins and can be divided by the polarity of the side chains creating the following groups.

1. nonpolar amino acids or hydrophobic amino acids consisting of alkyl R groups: alanine (moderately soluble), valine (moderately soluble), leucine, isoleucine, proline (cyclic structure and water soluble), the sulfuring containing amino acid methionine and two aromatic amino acids, tryptophan and phenylalanine.
2. polar, uncharged amino acids can form some limited hydrogen bonds with water consisting of amide R groups: asparagine and glutamine
3. hydroxyl groups: tyrosine (not very water soluble due to aromatic ring), threonine and serine (moderately soluble) sulfhydryl group of cysteine glycine has only an H for an R group and is polar due to the amino and carboxyl groups
4. acidic amino acids are negative at neutral pH and are important in binding metal ions, carboxyl groups can act as a nucleophile in enzymes, and can also participate in electrostatic bonding interactions. aspartic acid and glutamic acid
5. basic amino acids have a positive charge at neutral pH arginine and lysine are fully protonated at physiological pH and participate in electrostatic interactions in proteins histidine is only 10% protonated at physiological pH and is important as a proton donor and acceptor in enzyme reactions, and acts as a biologically significant buffer.

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