Biochem 1: Amino Acids and Peptides

Question 1

an amino acid is

Answer 1

a compound that contains both an amino group and a carboxyl group (both are bonded to the alpha-carbon, the one next to the carboxyl group)

Question 2

alpha carbon on amino acid

Answer 2

also bound to hydrogen and the side chain group R

Question 3

what is the R group of an amino acid important for

Answer 3

determines identify of amino acid

Question 4

stereoisomers of amino acids

Answer 4

designated L- or D-

Question 5

stero properties of amino acids

Answer 5

with the exception of glycine, most amino acids are chiral (stereoisomers)
-the vast majority have L-configuration at the alpha carbon

Question 6

non polar side chain amino acids

Answer 6

Ala, Val, Leu, Ile, Pro, Phe, Trp, Met, Gly

Question 7

neutral polar side chain amino acids

Answer 7

Ser, Thr, Tyr, Cys, Gln, Asn

Question 8

acidic side chain amino acids

Answer 8

Glu, Asp

Question 9

basic side chains amino acids

Answer 9

His, Lys, Arg

Question 10

what are amino acids (in terms of titrations)

Answer 10

are weak, diuretic (or triprotic) acids that can be titrated with base

Question 11

what are the charges of the amino and carboxyl group

Answer 11

carboxyl group (-) and amino group (+) are charged at neutral pH

Question 12

what is special about “free amino acids”

Answer 12

alpha-carbon and a-amino groups have titratable protons (some side chains so as well)

Question 13

individual amino acids can be linked by forming

Answer 13

covalent bonds

peptide bonds

Question 14

define peptide bond

Answer 14

the amide bond between the alpha-carboxyl group of one amino acid and alpha-amino group of another amino acid

Question 15

peptide bonds between amino acids are formed by

Answer 15

dehydration synthesis

Question 16

geometry of peptide bond

Answer 16

the four atoms of a peptide bond and the two alpha carbons joined to it lie in a plane with bond angles of 120 degrees about C and N

Question 17

to account for this geometry, a peptide bond is most accurately represented as a

Answer 17

hybrid of two contributing structures

resonance structures

Question 18

2 examples of biologically active peptides

Answer 18

aspartame: Asp-Phe-methyl ester
glutathione: gamma- Glu-Cys-Gly

Question 19

glutathione: gamma- Glu-Cys-Gly

Answer 19

biologically active peptide

• tripeptide with an unusual gamma-carboy peptide bond linkage
• important reductant in cells, it helps to protect proteins from oxidative damage