Amino Acids Structure: HydrophobicHydrophilic Properties

1
Amino Acids Structure Hydrophobic/Hydrophilic
Properties

• Barshaina Lamar, Ankur Patel, Japhia Jacobo

2
Amino Acids

• Building Blocks of Proteins
• There are 20 standard amino acids

3
Chemical Structure

• With the exception of proline, they all have this
  basic structure
• Two Functional Groups
• Hydrogen
• R - Group
• The R group varies for each amino acid giving it
  its own unique property

4
General Properties

• Zwitterions
• Occurs when functional groups undergo ionization
  in water
• At Physiological pH (7.4)
• Maintains overall neutral charge
• Amino Group Protonates
• Carboxyl Group Deprotonates

5
Amino Acids Classification

• R Group Classified
• Non-polar
• Polar
• Aromatic
• Acidic
• Basic

6
Nonpolar

• Generally non-reactive
• Important in 3D structure of proteins
• Cluster inside of molecules
• Hydrophobic, Neutral and Aliphatic

7
Polar - Uncharged

• Side Chains contain
• Oxygen
• Sulfur
• And/or Nitrogen
• Hydrophilic and Neutral

8
Aromatic

• Contains a benzene-like ring structure
• Bulky and Neutral
• Phenylalanine Highly Hydrophobic
• Tyrosine Polar, weakly acidic
• Tryptophan - hydrophobic

9
Polar - Acidic

• Highly hydrophilic
• Negatively Charged
• R Groups
• Carboxylic Acid Donates H

10
Polar - Basic

• Highly Hydrophilic
• Positively Charge
• Histidine can be charged or uncharged
• catalytic mechanism of enzymes

11
Peptide Bonds

• Dehydration Synthesis - Loss of Water formation
  of Peptide Bond
• Hydrolysis Addition of water results in the
  loss of Peptide bond

12
D / L Configurations

• a-carbon is asymmetric optically active
•  D- and L-
• configuration around the chiral a carbon
• L-amino acids naturally found in all proteins
• D-amino acids some bacterial cell wall peptide
  structures
• Geometry can affect reactivity of enzyme

13
Resources

• Free thought http//www.freethought-forum.com/im
  ages/anatomy2/aminoacid.jpg. Acc Jan 08
• Plant and Soil http//plantandsoil.unl.edu/cropt
  echnology2005/UserFiles/Image/siteImages/AminoAcid
  LG.gif. Acc Jan 08
• http//www.le.ac.uk/by/teach/biochemweb/tutorials/
  aminoacidstruct.html
• University of Arizona Biochemistry
  http//www.biochem.arizona.edu/classes/bioc462/462
  a/NOTES/Amino_Acids/Fig5_13peptidebond.GIF. Acc
  Jan 08
• Nelson, D. Cox, M. Principles of
  Biochemisty4th ed. P14 21.