Amino Acids and Peptides

What are Proteins?

Class of biomolecules which perform vital functions for living organisms

What is the structure of a protein?

Primary structure (linear sequence)

Secondary structure (alpha helix, beta sheet)

Tertiary structure

Quaternary structure (multiple subunits)

What are Amino Acids?

“Alphabet” that the structure of a protein is written

How many common Amino acids are there?

20

What joins an amino acid?

Peptide bonds

What is the difference between a Peptide and a Protein?

Determined by weight

What are the parts to an amino acid?

-Carboxyl group

-Amino group

-Hydrogen atom

-R group

What is the common features for Amino Acids?

Alpha carbon and four substituents

Tetrahedral

Chiral alpha carbon

What is an Isomer?

Same formula, different arrangement of atoms

What is a Constitutional Isomer?

(Structural), atoms are bonded differently

What is a Stereo Isomer?

(Spatial), Same structural bonds, rearranged differently in space

What are Enantiomers?

Mirror images of each other

What are Diastereomers?

Not mirror images

What are the two types of enantiomers?

D and L

L are found in real life

What are the classes of Amino Acids?

(Polar) Aliphatic-not aromatic

(Polar) Aromatic-planar, unsaturated rings

(Nonpolar) Uncharged

(Nonpolar) Positively charged

(Nonpolar) Negatively charged

What are the aliphatic R groups?

Glycine, Alanine, Proline, Valine, Leucine, Isoleucine, Methionine

-PROLINE make up beta sheets

What is this?

Glycine

What is this?

Alanine

What is this?

Proline

What is this?

Valine

What is this?

Leucine

What is this?

Isoleucine

What is this?

Methionine

What are the Aromatic R Groups?

Phenylalanine, Tyrosine, Tryptophan

-Absorb UV light at 270-280 nm

-association with “aromas”

What is this?

Tryptophan

What is this?

Tyrosine

What is this?

Phenylalanine

What are the Polar, Uncharged R Groups?

Serine, Threonine, Cysteine, Asparagine, Glutamine

-CYSTEINE can form Disulfide bonds

What is this?

Glutamine

What is this?

Asparagine

What is this?

Cysteine

What is this?

Threonine

What is this?

Serine

What are the Positively Charged R Groups?

Lysine, Arginine, Histidine

-Charge with NITROGEN

What is this?

Lysine

What is this?

Arginine

What is this?

Histidine

What are the Negatively Charged R Groups?

Aspartate, Glutamate

-CARBOXYLIC acids on the R group

What is this?

Aspartate

What is this?

Glutamate

What are Bronsted-Lowry acids?

Proton Donors

What are Bronsted-Lowry bases?

Proton acceptors

What is a Zwitterion?

Molecule having separate positive and negative charges at neutral pH

A lower pKa means?

Stronger acid

Higher pKa means?

Stronger base

What is a buffer?

Resist changes in pH

Critical for overall biological function

What do buffers consist of?

weak acid (HA) and conjugate base (A-)

weak base (B) and its conjugate acid (BH+)

What is the Ka equation?

What is a Titration?

Analytical chemistry technique used to determine the concentration of an unknown solution

What is the isoelectric point?

pH which the net electric charge of a molecule is zero

What is the equivalence point?

amount of added titrant is stoichiometrically equivalent to the amount of analyte in the solution

Are Amino acids natural buffers?

Yes

What does a titration curve for Amino acids look like?

Cation—-Zwitterion—-Anion

What can happen with an imbalance in tear film pH?

Dry eye syndrome and other disorders

DES is a degenerative disease of inflammation, cell damage, and biochemical imbalance

What make up Peptide bonds?

Amide linkages

What are characteristics of Peptide bonds?

Covalent bonds

Formed through condensation reactions

Broken through hydrolysis reactions

What are the 3 dihedral angles with peptide conformations?

phi= C-N, free rotation

psi= C-CO, free rotation

omega= CO-N, no rotation

What are Lipoproteins?

Contain lipids

What are Glycoproteins?

Contain sugars

What are Metalloproteins?

Contain metals

What is Taurine?

Non-proteinogenic AA

Helpful for degenerative retinal diseases

What is Glutatione?

Tripeptide antioxidant

Protecting the lens from oxidative damage that leads to cataract formation