Download Proteins – part 1

Proteins – part 1
Proteins
• Our third big biomolecule
• Review:
– the carbohydrate base unit is the
_____________
– the lipid base unit is the ________________
(for the hydrolyzable ones anyway!)
Proteins
• >50% of the dry weight of the body
• 100,000+ compounds
• Types of proteins:
– Catalytic
– Transport
– Regulatory
– Structural
– Contractile
– Protective
– Storage
Protein unit: the amino acid
• Amino acids
– 20 required by mammals
– 10 essential must be from diet
– Four categories:
•
•
•
•
Nonpolar neutral
Polar neutral
Polar acidic
Polar basic
– Natural amino acids are ____stereochemistry!
Practice drawing:
Glycine
Valine
Cysteine
Amino acids in solution
• Zwitterions
• pI and pH
Peptides: chains of amino acids
• 1 amino acid + 1 amino acid = 1 dipeptide
• 1 a.a. + 1 a.a. + 1 a.a. = 1 tripeptide
• Oligopeptide
• Polypeptide
• Proteins
Formation of the peptide bond
O
H2N
CH
C
O
OH
H2N
CH
CH3
C
OH
CH2
C
O
NH2
- H2O
O
H2N
CH
CH3
C
O
NH
CH
C
CH2
C
NH2
OH
dipeptide
O
Peptide sequences
• Name from N terminal to C terminal using
three letter abbreviations
– gly-cys-ala
• Direction matters !!
– gly-cys-ala is different from ala-cys-gly
• Possible constitutional isomers for a given
number of different amino acids = n!
Amino acid exercise:
• Three groups: draw out your share of the
β-endorphin, met-enkephalin, and leuenkephalin amino acid sequence
• Draw from left to right, N-terminus to Cterminus, your amino acids on notecards
using colored stickers
• Link the notecards together, constructing
correct peptide bonds.
Overall charge at physiological pH:______
Extra credit exercise (5 pts)