chap 3 Flashcards
Proteins are ____polymers of a-amino acids
Heteropolymers
Naming AA start from
alpha carbon( center of aa)
all AA alpha carbons have an acdic, basic and alpha hydrogen connected to a-carbon EXCEPT
Proline, has a ring, its ring is VERY CONSTRAINING
Name the AA for these groups
Aromatic Nonpolar aliphatic ,phobic Polar, uncharged Pos charge Neg charge
Aromatic: Phe, Tyr, Tryp
Nonpolar: Val, Iso, Leu, Pro, Gly, Ala, Met
Polar: Ser, The, Arginine, Glutamine, Cysteine
Pos: His, Lys, Arg
Neg: Arg, Glu
What is the unique feature about aromatic side chains
they ABSORB UV light at 270-280 , this is due to conjugation
What is the unique feature about polar side chains
They can for hydrogen bonds , while
cysteine for disulfide bond =cystine covalent bond very strong
Asparagine and glutamine are or are not good bases
ARE NOT goodbases, that is why they are not protonated, has amide at end
Adenlyation
is the process of attaching an AMP molecule to a protein side chain by covalent bonding.
Proteins 4 major biological functions
Catalysis-enzyme
transport : hemoglobin
Structure : collagen/keratin
Motion: myosin/cilia
Humans only function with L or D Steroisomers?
L steroisomers , cells are able to specifically synthesize L-isomer of AA because the active site of enzymes are asymmetric – cause their rxns they catalyze to be sterospecific
Are the active sites of enzymes asymmetric?
YES, causes the rxn they catalyze to be sterospcific ( favors L)
carbon closes to the carbxoxyl group is the
alpha carbon
which amino acid starts all protein sequences
methionine
WHAT FUNCTIONAL GROUP DOES HISTIDINE HAVE ?
aromatic imizidole group. histidine facilitates many enzyme catalyzed rxn by serviving as a proton acceptor or donator
what is the most common regulatory modification, post translational modification of AA in proteeins
Phosphorylations
Reversible AA modification are involved in regulation of PROTEIN ACTIVITY
The a-helix is disrupted
PROLINE RESIDUES, in which the ring imposes GEOMETRIC CONSTRAINTS , and by regions in which numerous amino acid residues have charged groups or large, bulky side chains.
side chains of the amino acid residues in an a-helix extend
OUTWARD, from the central
axis of the rodlike structure. This allows the formation of high tensile strength fibrillary
proteins.
An a-helix is generated when each carbonyl of a peptide bond forms
hydrogen bond between c=o and -NH
___ formed by hydrogen bonds between two extended polypeptide chains or between two regions of a single chain that folds back on itsel
B-sheets
between the carbonyl of one peptide bond and the–NH of another.
chains can runn in parallel or opp directions
Post-translational modifications alter
alter the charge on proteins and the interactions between amino acid resi-
dues, altering the three-dimensional configuration and, thus, the function of the protein.
Proteins from the extracellular environment are degraded within
lysozomes
Material enters the cell by endocytosis.
b. The endocytic vesicle fuses with the lysosome to form the phagolysosome.
c. The proteolytic enzymes within the lysosome digest the endocytosed material into
peptides.
d. These peptides can then be completely degraded or, in some cases, presented to cells
of the immune system.
DEFINITION= At neutral pH ( pH=7) the carboxy group is deprotonated but the amino group is protonated. The net charge is ZERO.
Zwitterions
At what ph is , the carboxy group is protonated and the amino acid is in the cationic form.
At Acidic pH (ph<7.4)
At what ph is the amino group is neutral (NH2 instead of NH3) and the amino acid is in the anionic form.
At alkaline pH (pH>7.4),
