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Biochemistry > Chapter 3-Amino Acids and Peptides > Flashcards

Chapter 3-Amino Acids and Peptides Flashcards

1
Q

How many amino acids are found in proteins?

A

20

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2
Q

General structure of an amino acid consists of:

A

amino group and carboxyl group that are both bonded to the alpha carbon

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3
Q

amino group

A

NH2 group

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4
Q

carboxyl group

A

-COOH functional group that dissociates to give -COO minus and H ion

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5
Q

sterochemistry

A

branch of chemistry that deals with the three d shape of molecules

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6
Q

side chain group

A

portion of amino acid that determines its identity

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7
Q

chiral

A

non-superimposable mirror images

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8
Q

what is the amino acid that lacks a chiral center (aka achiral)

A

glycine

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9
Q

stereoisomers

A

molecules that differ from each other only in their configuration (3D shape); aka optical isomers

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10
Q

L- and D-amino acids

A

amino acids whose stereochemistry is the same as the stereochemical standards L- and D-glyceraldehyde

L- amino on left
D- amino on right

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11
Q

What form are the amino acids in proteins?

A

L

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12
Q

List the non polar hydrophobic amino acids.

A 
Methionine 
Tryptophan
Phenylalanine
Isoleucine 
Leucine 
Proline
Alanine
Valine 
Glycine
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13
Q

List the polar uncharged amino acids.

A 
Threonine 
Cysteine 
Tyrosine
Serine
Asparagine
Glutamine
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14
Q

List the acidic amino acids.

A

aspartic acid

glutamic acid

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15
Q

List the basic amino acids.

A

Histidine
Lysine
Arginine

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16
Q

alipathic

A

absence of benzene ring or related structure

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17
Q

proline is often called

A

imino acid

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18
Q

is an indole ring aromatic?

A

yes

19
Q

which is a stronger acid: phenol or alipathic alcohol

A

phenol

20
Q

what forms disulfides

A

thiol groups in cysteine

21
Q

disulfide bridges are formed in what type of reaction

A

oxidation reduction

22
Q

when a carboxyl group loses a proton what forms

A

carboxylate anion

23
Q

hydroxyproline and hydroxylysine are found in

A

collagen

24
Q

thyroxine

A
  • differs from tyrosine in that it has an extra iodine containing aromatic group on the side chain
  • produced by thyroid gland only
  • formed by post-translational modification of modification of tyrosine residues in thyroglobulin
25
Q

zwitterion

A

electrically neutral (equal positive and negative charges)

26
Q

neutral amino acids do not exist in the form….

A

without charged groups

27
Q

what does a titration curve indicate?

A

the reaction of each function group with hydrogen ion

28
Q

diprotic

A

two protonated groups

29
Q

electrophoresis

A

method for separating molecules on the basis of ratio charge to size

30
Q

isoelectric pH (pI)

A
  • a pH at which the molecule has no net charge

- molecule will not migrate an electric field

31
Q

pI equation

A

=pKa1 + pKa2
_________
2

32
Q

what type of bond links amino acids (very general)

A

covalent

33
Q

residues

A

portions of monomer units included in polymers after splitting out water between the linked monomers

34
Q

peptide bond

A

amide bond between amino acids in a protein

steps:
- two amino acids
- water removal
- formation of CO-NH bond

35
Q

peptides

A

molecules formed by linking two to several dozen amino acids by amide bonds

36
Q

amide

A

name for a compound formed by the reaction between an amino group and a carboxyl group

37
Q

polypeptide chain

A

backbone of protein; formed by linking amino acids by peptide bonds

38
Q

the _____ of the peptide bond lead to a planar group

A

resonance structures (because of the double bond in the resonance structure there really is no significant rotation)

39
Q

direction of a peptide chain

A

N—->C

40
Q

peptides can play a role in?

A

hormones

41
Q

non polar side chains contain:

A

mostly alipathic or aromatic hydrocarbons

42
Q

amino acids that have electrically neutral polar side chains containing of

A

electronegative atoms: sulfure, oxygen & nitrogen

43
Q

which two amino acids have carboxyl groups in their side chains?

A

glutamic acid and asparatic acid

Biochemistry (7 decks)

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