Amino Acid Properties Flashcards
1
Q
How many hydrophobic/insoluable AAs are there?
A
10
2
Q
How many hydrophilic/soluable AAs are there?
A
10
3
Q
How is the polarity of an amino acid determined?
A
by the R-group
4
Q
What are the functions of AAs?
A
- monomers in protein synthesis
- precursors for hormones
- energy source in starvation and low carb diets
5
Q
Amino acids that cannot be made in the body but instead must be consumed are called what?
A
essential amino acids
6
Q
Which are the essential AAs?
A
- lysine
- tryptophan
- phenylalanine
- methionine
- threonine
- leucine
- isoleucine
- valine
- histidine
7
Q
What is a neutral molecule with an equal balance of positive and negative charge called?
A
-zwitterion
8
Q
What are the components of an amino acid that are bound to the alpha carbon?
A
- amino (NH3 +)
- carboxyl (COO-)
- hydrogen
- distinct R group
9
Q
The alpha carbon of AAs is chiral. What does this mean?
A
mirror image is not superimposable
10
Q
A D-isomer or dextrorotary isomer indicates what characteristic?
A
the isomer bends polarized light to the right
11
Q
An L-isomer or levorotary isomer indicates what characteristic?
A
the isomer bends polarized light to the left
12
Q
Almost all amino acids in nature are what type of isomer and what are the exceptions?
A
- L-isomer
- D-alanine and D-glutamic acid are found in peptidoglycan cell wall of bacteria
- D-serine is a neuromodulater
13
Q
Why are most amino acids in nature in the L-isoform?
A
They are more soluble in water
14
Q
L-isomers are also called what in organic chemistry?
A
AAs with S-configuration
15
Q
D-isomers are also called what in organic chemistry?
A
AAs with R-configuration
16
Q
In what direction does molecular weight increase around the alpha carbon in an AA with S configuration?
A
counter clockwise
17
Q
In what direction does molecular weight increase around the alpha carbon in an AA with R configuration?
A
clockwise
18
Q
Which amino acid has no chiral carbon?
A
Glycine
19
Q
What is the water solubility of glycine?
A
it is a non-polar molecule and therefore insoluble although it does not contribute much to hydrophobic interactions
20
Q
What is glycine used for in protein folding?
A
because it’s R group is only a hydrogen, it is great for making tight turns
21
Q
The functional group methyl is found on which amino acid?
A
CH3 is found on Alanine
22
Q
What is the water solubility of Alanine?
A
it is non polar and therefore insoluble
23
Q
Deamination of Alanine results in what molecule?
A
pyruvate which is used in gluconeogenesis
24
Q
Which amino acids are aliphatic?
A
- valine
- leucine
- isoleucine
- methionine (not truly because of S)
- proline
25
What is the shape does the hydrocarbon chain of valine make?
V
26
Which amino acid looks like Valine but with an aliphatic extension?
Leucine
27
What shape does the hydrocarbon chain of Leucine make?
Y
28
What is the water solubility of Valine?
it is non polar and therefore insoluble
29
What is the water solubility of Leucine?
it is non polar and therefore insoluble
30
What is the water solubility of Isoleucine?
it is non polar and therefore insoluble
31
What is the water solubility of Methionine?
it is non polar and therefore insoluble
32
What is the water solubility of Proline?
it is non polar and therefore insoluble
33
What is the water solubility of Phenylalanine?
it is non polar and therefore insoluble
34
What is the water solubility of Tryptophan?
it is non polar and therefore insoluble
35
What is the water solubility of Tyrosine?
it is non polar and therefore insoluble
36
How does Isoleucine differ from Leucine?
They are isomers of one another which means that they have the same chemical formula but different structure. IsoLeucine has a methyl group attached to the beta carbon (shape goes from Y to L), making it a second chiral central.
37
What shape does the hydrocarbon chain of Isoleucine make?
L
38
Which amino acids contain Sulfur?
Methionine, cysteine
39
How is methionine considered non polar when it contains an electronegative atom?
Although sulfur is electronegative, it's electronegativity is decreased because it is within an aliphatic chain
40
What shape does the hydrocarbon chain of methionine make? Where is the sulfur located in the chain?
I, it is the 3rd out of 4 atoms from the alpha carbon
41
What is the distinguishing structure of Proline?
the secondary amino group, called an imino group
42
What is an imino?
amino group (−NH2) bonded to the alkyl side chain, forming a ring while maintaining the + on the amino group and therefore the neutrality of amino acid
43
What are the 10 hydrophobic molecules?
- Glycine
- Alanine
- the 5 aliphatic amino acids including Valine, Leucine, Isoleucine, Methionine and Proline
- the 3 aromatic amino acids including Phenylalanine, Tryptophan and Tyrosine
44
What does aliphatic mean?
contain a hydrocarbon chain
45
What are the aromatic amino acids?
- phenylalanine
- tryptophan
- tyrosine
46
What is the hydrophobicity rank of the aromatic amino acids?
Phenylalanine>Tryptophan>Tyrosine
47
Why is Tyrosine less hydrophobic (more water soluable) than phenylalanine?
because it contains a hydroxyl group off of the aromatic ring which can give up it's protons
48
What shape does the hydrocarbon chain of phenylalanine make?
Balloon shaped with a single hydrocarbon between the alpha carbon and a benzene ring
49
Which amino acid is recognized by chymotrypsin in the small intestines to hydrolyze peptides?
phenylalanine
50
What is the distinguishing structure of Tryptophan?
the indole ring which contains N
51
Why is Tryptophan less hydrophobic (more water soluble) than Phenylalanine?
Because the indole ring in the R-group of tryptophan contains an electronegative nitrogen and imparts a partial charge, whereas phenylalanine has no electronegative atoms in it's R-group
52
Which amino acids absorb UV light, making them visible with a spectrophotometer at 260-280nm?
the two aromatic amino acids that contain electronegative atoms in their R-group, tryptophan and tyrosine
53
Which amino acid serves as a precursor for melatonin and serotonin?
tryptophan
54
Which amino acids are taken up by skeletal muscle during exercise?
aliphatic amino acids
55
Why is exercise associated with decreased depression and increased sense of well being?
the availability of serotonin in the brain (molecule associated with feelings of elation) is dependent on the availability of it's precursor, tryptophan. to be available, tryptophan must pass the blood brain barrier via amino acid transporters which are not selective for Tryptophan. During exercise, aliphatic amino acids are taken up by skeletal muscle leaving more tryptophan in the blood so it can compete for transport better
56
What shape does the hydrocarbon chain of Tyrosine make?
Balloon shaped with a single hydrocarbon between the alpha carbon and a benzene ring, and a hydroxyl group attached to the opposing carbon of the benzene ring
57
Which amino acid is important in the active sites of enzymes and in signal transduction?
Tyrosine
58
Why is Tyrosine less hydrophobic (more water soluble) than Tryptophan?
Although both contain electronegative atoms, the electronegative oxygen of Tyrosine imparts more of a partial charge than the nitrogen of tryptophan.
59
Which amino acid is a precursor for dopamine and epinephrine?
Tyrosine
60
What is the solubility effect hydroxylations have on Tyrosine?
they make Tyrosine more soluble
61
Which two amino acids have second chiral carbons?
threonine and isoleucine
62
What is the water solubility of Serine?
it is polar and therefore water soluble
63
What is the water solubility of Threonine?
is is polar and therefore water soluble
64
What is the structure of the R-group of Serine?
a single methyl group with one of the hydrogens replaced by a hydroxyl group CH2-OH
65
What is the structure of the R-group of Threonine
a two carbon carbon chain with a hydroxyl group attached to the beta carbon making it a chiral carbon
66
Which amino acids are found in the active sites of enzymes and why?
Serine and Threonine because the H-bonds of their hydroxyl groups help to initiate catalysis
67
Which amino acids are used in signal transduction pathways?
Serine and Threonine
68
What is the water solubility of Cysteine?
it is polar and therefore water soluble
69
What is the difference in structure between Serine and Cysteine?
Cysteine has a sulfhydryl in place of the hydroxyl
70
What is the structure of the R-group in Cysteine?
a single methyl group with one of the hydrogens replaced by a sulfhydryl group CH2-SH
71
Which amino acid can be used as an electron donor and how does it do this?
Cysteine, by creating a bond between the sulfhydryl groups of two Cysteine molecules
72
Which amino acids carry a negative charge at physiological pH?
- Glutamate (Glutamic Acid at pH lower than 4.5)
| - Aspartate (Aspartic Acid at pH lower than 4.5)
73
What is the water solubility of Glutamate?
it is polar and therefore water soluble
74
What is the water solubility of Aspartate?
it is polar and therefore water soluble
75
What happens to the carboxyl group on the R-group of Glutamate at pH below 4.5?
It will still have its +H and is therefore called Glutamic Acid at pH levels below 4.5 because it is still has a proton to donate
76
Which amino acids are intermediates in the Kreb's Cycle?
Glutamate can be deaminated to alpha-ketoglutarate and aspartate can be deaminated to oxaloacetate, which are intermediates in the Kreb's Cycle
77
What is the structure of the R-group in Glutamate?
it is a double carbon chain with a terminal carboxyl group
| CH2CH2COO-
78
What is the structure of the R-group in Aspartate?
it is a single carbon chain with a terminal carboxyl group
| CH2COO-
79
What is the difference in structure between Aspartate and Glutamate?
Aspartate is one carbon shorter than glutamate in its R-group.
*Glue another carbon on the chain of aspartate to make glutamate
80
What happens to the carboxyl group on the R-group of Aspartate at pH below 4.5?
It will still have its +H and is therefore called Aspartic Acid at pH levels below 4.5 because it is still has a proton to donate
81
What is a deamination?
+H3N--C--H (in this case, on an amino acid) turns to C==O
82
What is the difference in structure between Serine and Asparagine?
Asparagine has a carboxamide in place of a hydroxyl
| CH2-CONH2 vs CH2-OH
83
What is the structure of the R-group in Asparagine?
a single carbon, carbon chain with a terminal carboxamide group CH2-CONH2
84
What is the structure of the R-group in Glutamine?
a 2 carbon, carbon chain with a terminal carboxamide group CH2-CH2-CONH2
85
What is the water solubility of Asparagine?
it is polar and therefore water soluble
86
What is the water solubility of Glutamine?
it is polar and therefore water soluble
87
What is the water solubility of Arginine?
it is polar and therefore water soluble
88
What is the water solubility of Histidine?
it is polar and therefore water soluble
89
What is the water solubility of Lysine?
it is polar and therefore water soluble
90
Which amino acids contain carboxamine groups at the end of the R-group?
Asparagine and Glutamine
91
Which amino acids carry a net positive charge at physiologic pH?
Arginine, Lysine and Histidine
92
What is the distinguishing structure of Arginine?
Guanidinium NH-C-NH2NH2+
93
Which amino acid is a nitrogen donor in the urea cycle?
Arginine
94
What is the structure of the R-group in Arginine?
3 carbon, carbon chain with a terminal guanidinium group
| CH2CH2CH2-NH-C-NH2NH2+
95
What is the structure of the R-group in Lysine?
4 carbon, carbon chain with a terminal amine
| CH2CH2CH2CH2NH3+
96
Hinhydrin is a chemical that turns purple when it reacts with what?
free amines, such as the terminal amine in Lysine
97
What is the distinguishing structure of Histidine?
Imidazole group
98
What is the structure of the R-group in Histidine?
a single carbon chain with a terminal imidazole group
99
What are some of the uses of Histidine?
- enzyme catalytic sites
- hemoglobin structural changes
- proton acceptor in blood pH maintenance
100
Why is Histidine a weak buffer a physiologic pH?
The imidazole group has a pKa of 6
