1. amino acids, peptides, and proteins Flashcards
1
Q
What are amino acids?
A
building blocks of proteins
2
Q
What is the general structure of an amino acid?
A
acidic carboxyl group
amino group
hydrogen
R group
3
Q
What part of an amino acids changes depending on the aa?
A
R group
4
Q
What is the central molecule in an amino acid structure?
A
alpha carbon
5
Q
What are the two stereoisomers in amino acids?
A
L and D - glyceraldehyde
6
Q
Which form do amino acids appear in proteins?
A
L amino acids
7
Q
What type of names do amino acids have?
A
three letter code and a one letter code
8
Q
What amino acid is Gly?
A
glycine
9
Q
What amino acid is Ala?
A
alanine
10
Q
What amino acid is Pro?
A
Proline
11
Q
What amino acid is Val?
A
Valine
12
Q
What amino acid is Leu?
A
leucine
13
Q
What amino acid is Ile?
A
isoleucine
14
Q
What amino acid is Met?
A
methionine
15
Q
What amino acid is Phe?
A
phenylalanine
16
Q
What amino acid is Tyr?
A
tyrosine
17
Q
What amino acid is Trp?
A
Tryptophan
18
Q
What amino acid is Ser?
A
serine
19
Q
What amino acid is Thr?
A
threonine
20
Q
What amino acid is Cys?
A
cysteine
21
Q
What amino acid is Asn?
A
Asparagine
22
Q
What amino acid is Gln?
A
glutamine
23
Q
What amino acid is Asp?
A
Aspartate
24
Q
What amino acid is Glu?
A
gluatamate
25
What amino acid is Lys?
lysine
26
What amino acid is His?
histidine
27
What amino acid is Arg?
Arginine
28
What amino acid is E?
glutamate
29
What amino acid is D?
aspartate
30
What amino acid is R?
arginine
31
What amino acid is H?
histidine
32
What amino acid is K?
lysine
33
What amino acid is Q?
glutamine
34
What amino acid is N?
asparagine
35
What amino acid is C?
cysteine
36
What amino acid is T?
threonine
37
What amino acid is S?
serine
38
What amino acid is W?
tryptophan
39
What amino acid is Y?
tyrosine
40
What amino acid is F
phenylalanine
41
What amino acid is M?
methionine
42
What amino acid is I?
isoleucine
43
What amino acid is L
leucine
44
What amino acid is V
valine
45
What amino acid is P?
proline
46
What amino acid is A
alanine
47
What amino acid is G?
glycine
48
What are the five different groups of amino acids?
nonpolar, aromatic, polar, positively charged, negatively charged
49
What are the 7 nonpolar acids?
glycine
alanine
proline
valine
leucine
isoleucine
methionine
50
What is the simplest amino acid?
glycine
51
What is the unique characteristic about nonpolar amino acids?
all but one have aliphatic R groups
52
What is unique about methionine?
has Sulfur in is R group
53
What is unique about
A,V,L, and I amino acids in the nonpolar group?
exhibit the hydrophobic effect
53
What is unique about proline?
cyclic structure
54
What are the three aromatic R-groups?
phenylalanine, tyrosine, tryptophan
55
What characteristic is unique about the aromatic R groups?
all have cyclic structure
56
What is unique about tyrosine?
the OH group can form hydrogen bonds
57
Are the aromatic R groups nonpolar or polar and why?
nonpolar because of their rings
58
What do the side chains in the aromatic R groups do?
absorb UV light
59
What are the five polar R groups?
serine, threonine, cysteine, asparagine, glutamine
60
What can the side chains of the polar R groups do?
form hydrogen bonds
61
What is unique about cysteine?
SH groups form disulfide bonds with themselves through oxidation
62
What property do disulfide residues have?
strongly hydrophobic
63
What is unique about asparagine and glutamine?
amides of aspartate and glutamate
64
What are the two negatively charged R groups?
aspartate and glutamate
65
What part of aspartate and glutamate gives it the negative charge?
COO-
66
What are the three positively charged R groups?
lysine, arginine, histidine
67
Which amino acid group has the longest chains?
positively charged
68
What is unique about lysine?
second primary amino acid
69
What is unique about arginine?
has a positively charged guanidinium group
70
What is unique about histidine?
aromatic imidazole group
71
What are all amino acids able to do?
ionize
72
What does a negative hydropathy index mean?
higher the interaction with water
73
What two portions of an amino acids contain ionizable protons?
carboxylic acid group
amino group
74
What is the pKa of the carboxylic acid group?
low pH
75
What is the pKa of the amino group?
high pH
76
At high pH, how do amino acids exist?
cation form
77
At low pH, how do amino acids exist?
anion form
78
What is the zwitterion form?
middle pKa, molecule contains a positive and negative charge
79
Why is the pKa value for each amino acid different?
other areas of the amino acid can influence it
80
According to the titrations of amino acids, what other roles can they play?
buffers
81
What is the isoelectric point?
pH where the net electric charge is zero
82
In the zwitterionic form, what can the aa act as?
an acid or base
83
What is the isoelectric point formula for amino acids without ionizable side chains?
(pK1 + pK2)/2
84
When pH = pI, what is the charge?
zero
85
When pH > pI, what is the charge?
negative
86
When pH < pI, what is the charge?
positive
87
What are the four characteristics of aa with ionizable side chains?
have a pKa value
buffers
influence the pI
can be titrated
88
What is unique about the titration curves of ionizable side chain amino achids?
there are 3 ionization steps
89
How do you calculate the pI when the side chain is ionizable?
identify the net zero charge, and take the average of the pKr and pK2
90
What is the pKr?
pKa value that defines the acid strength of a zwitterion
91
What is the pK2?
pKa that defines the base strength of the zwitterion
92
What is a peptide?
multiple amino acids joined together
93
How do amino acids form peptides?
polymerization
94
What are the three characteristics of peptide bonds?
covalent
formed through condensation
broken through hydrolysis
95
in the formation or breakage of peptide bonds, what is either used or given off?
H2O
96
What end do you start with when naming and numbering peptides
amino terminus (N-terminal)
97
What is a polypeptide?
many amino acids
98
What is a protein?
thousands of amino acids
99
What are the three ionizable groups in peptides?
N-terminus
C-terminus
some R groups
100
What are the four functions of peptides
hormones
neuropeptides
antibiotics
protection
101
What are three common hormones and pheromones
insulin
oxytocin
sex-peptide
102
What is an example of a neuropeptide?
substance P - pain mediator
103
What is polymyxin and bacitracin examples of
antibiotics
104
What is a conjugated protein?
covalently bound to a nonprotein entity
105
What types of things can bind to polypeptides?
cofactors
coenzymes
prosthetic groups
106
What are cofactors?
functional non-amino acid component
107
What are coenzymes?
organic cofactors
108
What is the function of uncommon amino acids
found in specific tissues and play special roles
109
How are uncommon amino acids generated?
proton motive force
110
What is a modification that can alter protein function?
phosphorylation
111
What amino acid can't be phosphorylated?
cysteine
