chapter 16.1
DESCRIPTION
Chapter 16.1. Functions of Proteins. SWBAT: Classify proteins by their functions in the cells. Proteins. Proteins are polymers of amino acids chemically bonded to each other All proteins in humans are made up from 20 different amino acids Protein Subclasses are: - PowerPoint PPT PresentationTRANSCRIPT
Chapter 16.1Functions of Proteins
SWBAT: Classify proteins by their functions in the cells
Proteins•Proteins are polymers of amino acids chemically bonded to each other•All proteins in humans are made up from 20 different amino acids•Protein Subclasses are:
• structural, contractile, transport, hormones, enzymes, immunoprotein, AA storage
•Identification: many end with –in, -en, -ase
Table 16.1 – page 534
Chapter 16.2Amino Acids
SWBAT: know the structure of an amino acid and be familiar with the classification of amino acids
AA are all the same with regard to• Central carbon• Amino group• Carboxyl group• Hydrogen Differ with regard to the R-side chain
Anatomy of an Amino Acid
Amino AcidsAt normal body pH (~7.4) the functional groups are
COO-
Remember that carboxylic acids are acids and can lose a proton
NH3+
Remember that amines are bases and can accept a proton
This form of the amino acid is called a zwitterion…which has no net charge (one positive and one negative).
Side Chain (R) Group can be:• Alkyl• Hydroxyl• Thiol• Amino• Carboxyl• Aromatic • Cyclical• Amide
Amino Acid (R) Group
Classification of Amino Acids
Non-polar
Polar
Neutral (not
charged)Positively charged(Basic)
Negatively charged(Acidic)
Charged
Amino Acid
Nonpolar Amino AcidsR can be:• Alkyl side chain• Aromatic side chain
All are nonpolar
amino acids
Polar Amino AcidsR can be: • Hydroxyl (-OH)• Thiol (-SH)• Amide (-CONH2)
All can H-bond with water
Acidic Amino AcidsR will be: Carboxylic acid (-COOH)
Can ionize as a weak
acid
Basic Amino AcidsR group will contain:an amino group that ionizes as a weak base
All are polar amino acids…
All of the alpha amino acids (except glycine) are chiral – can exist as D or L enantiomers
Fisher projections with –COOH at the top and (R) group at bottomL isomer – NH2 group on leftD isomer – NH2 group on right
Amino Acid Stereoisomers
L-serine
D-serine
In biological systems, only L amino acids are in proteins
Homework:
pg 534 16.1 – 16.2
pg 537 16.3 – 16.12