Amino Acids Flashcards
(79 cards)
1
Q
How many natural occurring standards amino acids ?
A
20
- alpha- amino acids
2
Q
pKa Carboxy group
A
~ 2
3
Q
pKa Amino group
A
~9.5
4
Q
Charge of amino (NH3) groups at physiological conditions (pH=7.4)
A
POSITIVE
- The pH is lower than pKa for the amino group. Therefore, most of the amino- groups are protonated.
5
Q
Charge of carboxylic (COOH) groups at physiological conditions
A
NEGATIVE
- The pH is higher than the pKa for the carboxylic group. Therefore, most of the carboxylic groups are deprotonated
6
Q
At physiological conditions (pH=7.4), all amino acids are in which form? (there are exceptions)
A
ionized form
- zwitterionic:
- positive charge- amino
- negative charge- carboxylic
- Net charge= 0
7
Q
Isoelectric Point (pI)
A
- amino acid is on its zwitterionic form
- pH at which an amino and a carboxylic group are both charged. And, the sum of their charges is equal to 0.
8
Q
Glycine
A
bends and turns
OR
tightly packed chains of fibrous proteins like collagen
9
Q
Branched chain amino acids
A
VIL
- Val
- Ile
- Leu
10
Q
Sulfur containing amino acids
A
- Methionine
- Cys (disulfide bonds- oxidative condensation)
11
Q
Proline
A
- Imino acid: amino group is enclosed in a ring
- NOT found in alpha- helix, is a helix breaker
12
Q
Aromatic Amino Acids (aromatic rings)
A
- Trp
- Phe
- Tyr
13
Q
Basic amino acids, positively charged
A
- Arg
- Lys
14
Q
Histidine
A
- imidazole ring
- weak basic
- physiological buffer
15
Q
Acidic amino acids, negatively charged
A
- Asp
- Glu
16
Q
Hydroxyl (OH) containing
A
- Ser
- Thr
- Tyr
17
Q
Non- polar, uncharged, aliphatic amino acids
A
- Gly
- Ala
- Pro
- Val
- Leu
- Ile
18
Q
Polar, uncharged amino acids/ Hydrophillic
A
Asn
Gln
Ser
Thr
19
Q
Hydrophillic
A
Acidic and basic AAs and polar uncharged.
20
Q
Titration curves
A
Illustrate changes in amino acid structure that occur as the pH of the solution is changed from <1 to 14 (pH) with a strong base
21
Q
predominant basic amino acids (pKa> 10)
A
Arg Lys
22
Q
Semi- essential amino acids
A
Required ONLY during positive nitrogen balance conditions
23
Q
Define Essential Amino Acids
A
cells cannot synthesize them, they have to be ingested
24
Q
Define nitrogen balance
A
is the (normal) condition where the amount of nitrogen incorporated into body each day exactly equal the amount excreted
25
Define Positive nitrogen balance conditions
When the amount of nitrogen incorporated into body each day exceeds the amount excreted
26
Conditions of negative nitrogen balance need Essential AAs
* protein malnutrition
* dietary deficiency of at least 1 essential AA
* Starvation
* uncontrolled diabetes
* Infection
27
What are the Essential amino- acids?
8 (TV TILL PM) Trp (W) Val (V) Thr (T) Ile (I) Leu (L) Lys (K) Phe (F) Met (M)
28
What are the non- essential amino acid
8 Asp (D) Glu (E) Gly (G) Asn (N) Gln (Q) Ala (A) Ser (S) Pro (P)
29
normal pH blood?
7.4
30
amino at 7.4
protonated
31
carboxy at 7.4
deprotonated
32
His
+/- pKa buffer
33
pH equation
pH= pKa when [HA]=[A-]
34
Sickle cell anemia
Glutamate (polar) is substituted by Valine (hydrophobic) at B- subunit
35
Blood protein that works for transporting molecules
Albumin
36
How the Separation of proteins is performed?
In an Electric field proteins are negative and migrate toward the positive electrode
37
Rate of migration of separation of proteins is determined by?
net negative charge more negative = faster
38
pH stomach
1.5 HCl
39
Aspirin pH
3.5 (weak acid)
40
Aspirin at the stomach is ?
largely protonated uncharged therefore it can cross the membrane and be absorbed
41
Diabetes- ketoacidosis
inadequate insulin increased breakdown of fatty acids in the liver
42
Diabetic ketoacidosis
ketone bodies; acetoacetic acid beta- hydroxybutyric acid
43
ketone bodies
produce anions and H+ ions lower blood/ cell pH metabolic acidosis
44
metabolic acidosis
physiological effects of lower blood pH, including renal disease
45
Q: Is the substitution of a glutamate for valine in sickle cell hemoglobin a conservative replacement?
No, is a replacement of an acidic amino acid which is hydrophilic for a non- charged aliphatic AA
46
Q: Is the substitution of an Aspartate for a Glutamate a conservative replacement?
Yes, the AA that is being replaced, is being replaced by one AA that is similar in structure, acidic and charged in blood pH
47
Practice: proteolytic digestive enzyme chymotrypsin cleaves the peptide bonds formed by the carboxyl groups of large, bulky uncharged amino acids. Which amino acids fall into this category?
Phenylalanine (Phe) Tyrosine (Tyr) Tryptophan (Trp)
48
Practice:
* Does the following peptide is able to form an internal disulfide bond?
* Gly- Cys- Glu- Ser- Asp-Arg- Cys
Yes, it has 2 Cysteine AAs
49
Practice: A drug sometimes injected as a local anesthetic has only one ionizable group, an amino group with a pKa of 8.6. it is otherwise hydrophobic, and enters cells through free diffusion. The ionized form of the drug acts by binding to the intracellular domain of an ion channel. A localized infection decreased the pH around the site of injection from 7.4 to 6.8. The binding site of the channel for the drug is most likely to contain which one of the following amino acid side chains?
Drug: 1 ionizable group (an amino with 8.6) Localized infection: pH= 6.8 Binds to an intracellular domain of an ion channel. Drug: binding site of the channel for the drug: Negatively charged aspartyl or glutamyl residue(s)
50
Where do you find hydrophilic amino acids in a transmembrane and globular protein?
outwards
51
Where do you find hydrophobic amino acids in a transmembrane and globular protein?
hidden from water, inside
52
Why Methionine is hydrophobic although contains sulfur?
it doesnt contain an H and is steric hindrant
53
Basic amino acids can form ionic bonds with ?
Acidic amino acids (Arg, Lys, His)
54
Why Pro is called the helix breaker?
because on its presence, it changes the direction of the helix, produces a kink
55
Hydrophillic amino acids
amide groups and OH groups can form Hydrogen bonds and are located at the surface of globular proteins
56
Hydrophobic amino acids
PIMP GAL TV
57
Derived amino acids are product of the
Cystine (union of two Cys) Hydroxy- proline hydroxy- lysine
58
Most common post- translational modifications (enzyme required)
Hydroxylation Phosphorylation Glycosylation Acetylation
59
Hydroxylation
Pro Lys impart strength to collagen
60
Phosphorylation- Metabolic regulation, cell regulation
Ser Tyr Thr
61
Glycosylation: O- linked
Ser and Thr
62
Acetylation
important in gene expression, acetylation of histones at Lys residues
63
pH \> pKa
Deprotonated form for the species (negative form)
64
pH= pKa
Zwitterionic form/ Isoelectric point
65
pH \< pKa
Protonated form predominating for the species
66
semi essential amino acids are required during?
periods of positive nitrogen balance
67
Normal Pattern of Serum Electrophoresis
68
Normal Ectrophoretic Racing
69
Normal Electrophoretic patterns
70
Electrophoretic patterns will change in certain diseases/ conditions
71
Immediate Response Electrophoretic Pattern
72
Delayed Response electrophoretic pattern
73
Hypogammaglobulinemia Electrophoretic Pattern
74
Hepatic cirrhosis electrophoretic pattern
Hepatic cirrhosis = polyclonal gammopathy\*
75
Paraprotein electrophoretic pattern
76
Nephrotic Syndrome Electrophoretic Pattern
77
Protein losing enteropathy electrophoretic pattern
78
79
Conditions of Positive Nitrogen Balance
* pregnancy
* growth
* recovery from surgery or injury
* recovery from negative nitrogen balance
