Know the parts of an amino acid◦ 1. Amino group◦ 2. Carboxylic Acid (Carboxylate)◦ 3. R-Group
Amino acids are classified by their R-groups and the groups interaction with water◦ 1.Hydrophobic-The majority of R-groups◦ 2. Polar Uncharged◦ 3. Polar Charged
R-groups composed of only Hydrogen and Carbons
One exception- Methionine contains sulfur, bound only to Carbon
Phenylalanine Methionine
Look for Oxygens and Nitrogens Charged groups will be charged or have a
primary amine or carboxylic acid part.◦ Primary amines are written NH2 and Carboxylic
acids COOH
Amino acids can be proton donors The pH at which the Carboxylate group gives up
its proton is the pK1 and the Amino group is pK2 ◦ pK1 is the point where 50% of the carboxylate groups
are unprotonated, and pK2 is where 50% of the amino groups are unprotonated
Amino acids are good buffers at these points Add them together and divide by 2 to get the
isoelectric point (pI)◦ This is the point where all amino acids in a solution
have zero net charge◦ Amino acids are bad buffers at this point
Peptide Linkages: C-N bond◦ Different order equals different peptides
Ex: Gly-Ala-Pro isn’t the same as Pro-Ala-Gly◦ Number of possible combinations using each AA
once: (Number of Amino Acid)! Ex: tetrapeptide is 4! (4x3x2x1=24)
◦ Number of possible combinations using each AA as many times as we want:
(number of AA)number in polypeptide
Ex: 4 amino acids in a tetrapeptide =44
An amide plane forms around the peptide linkage
C,N,O,H are involved in the formation The double bonded O electrons resonate to
the C-N bond, giving the peptide linkage a partial double bonded characteristic.
Primary◦ Order of the amino acids◦ Ex: ala-gly-asp-leu-lys-phe◦ Main type of interaction: covalent between amino
acids, called peptide bond Secondary
◦ Alpha helix◦ Main type of interaction: hydrogen bonds between
amide planes
Tertiary◦ Main type of interactions: between R-groups◦ H-bonds, Electrostatic, Hydrophobic, Covalent
(disulfide bonds)◦ Specifically, covalent bond called disulfide
Between 2 cysteines’ sulfhydryl R-groups Quaternary
◦ Large molecular weights
Predominate AA: proline and glycine◦ Gly- small R-group for rope-like structure◦ Pro- Oxidizable R-group
Requires Vitamin C; deficiency=scurvy◦ Steps in formation
Immature collagen is hydroxylated (-OH groups added) becoming procollagen Need Vitamin C as reducing agent in this step. If
deficient, the person has scurvy Procollagen is glycolyslated (carbohydrate moeities
added) making tropocollagen Mature collagen formed by crosslinks between
hydroxylated prolines
Bohr Effect
HHb (protonated Hemoglobin) enters lungs◦ Lungs are more basic, so HHb more likely to give up
proton Oxygen (O2) binds to hemoglobin and it gives
up the H+ HHb+ O2+HCO3
- HbO2+H2O+CO2 The bicarbonate is the form that carbon dioxide
goes to the lungs as. It travels in the blood plasma.
All of the reactions occur inside the red blood cell
Oxygenated hemoglobin travels to the tissues where it encounters an acidic enviroment.◦ The acidity is the result of increase carbon dioxide,
which is a metabolic byproduct In an acidic environment, hemoglobin tends
to give up oxygen and bind the protons that are in the tissues◦ Extra protons are there as the result of the acid CO2
◦ Bicarbonate is moved out of the RBC, exchanged with Chloride (Cl-).
Know that pH and Gas Pressures drive respiration
Know which direction the equation is goingH2O + HbO2
- + CO2 HHb + O2 + HCO3-
Which one occurs in the lungs?
Which one occurs in the peripheral tissues?