Download - Amino Acids (2) IUA
-
8/2/2019 Amino Acids (2) IUA
1/35
AminoAcids(2)
DepartmentofBiochemistryFacultyofMedicine
InternationalUniversityofAfrica,Khartoum,Sudan
-
8/2/2019 Amino Acids (2) IUA
2/35
Acidbasepropertiesofaminoacids
TheaCOOHandaNH2 groupsareionizable.
thepHofthemedium.
-
8/2/2019 Amino Acids (2) IUA
3/35
Acidbasepropertiesofaminoacids
The Carbox l rou shave Ka valuesofbetween1.8and
2.8
(moreacidic
than
simple
monocarboxylic acids).
The amino rou shave Ka valuesbetween8.8and10.6
dependingontheaminoacid.
Acidicandbasicaminoacidshaveadditionalionizable
groups.
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
4/35
Acidbasepropertiesofaminoacids
-
8/2/2019 Amino Acids (2) IUA
5/35
Acidbasepropertiesofaminoacids
-
8/2/2019 Amino Acids (2) IUA
6/35
AminoAcidshavedistinctdissociationcurves
-
8/2/2019 Amino Acids (2) IUA
7/35
Atitsisoelectric pH(pI),anaminoacidbearsnonet
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
8/35
Atitsisoelectric pH(pI),anaminoacidbearsnonet
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
9/35
Thebufferingactionofaminoacids
-
8/2/2019 Amino Acids (2) IUA
10/35
AminoAcidshavedistinctdissociationcurves
-
8/2/2019 Amino Acids (2) IUA
11/35
AminoAcidshavedistinctdissociationcurves
-
8/2/2019 Amino Acids (2) IUA
12/35
Reactionsofaminoacids
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
13/35
Reactionsofaminoacids
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
14/35
The e tidebond
A. Anamide CN linkageformingthebackboneofall
proteins.
B. Involves two ad acent amino acids liked b
eliminationofH2O.
C. Planner,i.e.theCNinvolvedlieinthesameplane
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
15/35
Thepeptidebond
eam noan car oxy
groupsofaminoacidscan
toformpeptides.
-
8/2/2019 Amino Acids (2) IUA
16/35
Peptidebondformation
-
8/2/2019 Amino Acids (2) IUA
17/35
Pe tidesand roteins
Thesimplestpeptide,adipeptide,containsasingle
aminoacidswitheliminationofwater.
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
18/35
Peptidesandproteins
Proteinsarepolymers ofaminoacidsjoinedbypeptide
bonds.
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
19/35
Peptidesandproteins
- .
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
20/35
Peptidesandproteins
Thenumberandorderofallresiduesinapolypeptide
constituteitsprimarystructureoftheprotein.
-
8/2/2019 Amino Acids (2) IUA
21/35
ProteinStructure
-
8/2/2019 Amino Acids (2) IUA
22/35
Proteins: ordersofstructure
The Primary structure, the sequence of the amino acids in
a po ypep e c a n.
The secondary structure, the folding of short (3- to 30-
residue), contiguous segments of polypeptide into geometrically
.
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
23/35
Proteins: ordersofstructure
The tertiary structure, the three-dimensional assembly of
secondary structure units to form larger functional units.
The quaternary structure, the number and types of polypeptide
un s o o gomer cpro e ns an e r spa a arrangemen .
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
24/35
Proteins: ordersofstructure
The secondary structure.
The two most common types of secondary -helix
structure, the -helix and the -sheet,
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
25/35
Proteins: ordersofstructure
-
Stabilized by hydrogen bonds
ompact
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
26/35
Proteins: ordersofstructure
Stabilized by hydrogen bonds
Is highly extended.
erpara e oran para e .
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
27/35
Proteins: ordersofstructure
.
Indicates how secondary structural featureshelices, sheets,
, , - ,
to form domains and how these domains relate spatially to oneanother.
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
28/35
Proteins: ordersofstructure
Thequaternarystructure
In some cases, proteins are assembled from more than one
, .
Quaternary structure defines the polypeptide composition of an
.
AtifHassanKhirelsied
-
8/2/2019 Amino Acids (2) IUA
29/35
Proteins: ordersofstructure
The quaternary structure
.
Homodimers contain two co ies of the same ol e tide chain
while in a heterodimerthe polypeptides differ.
Greek letters (, , etc) are used to distinguish different subunitsof a hetero-oligomeric protein.
AtifHassanKhirelsied
i d f
-
8/2/2019 Amino Acids (2) IUA
30/35
Proteins: ordersofstructure
The quaternary structure
P i d f
-
8/2/2019 Amino Acids (2) IUA
31/35
Proteins: ordersofstructure
e orces a s a ze pro e ns s ruc ure
Higher orders of protein structure are stabilized primarily by
- .
1. Hydrophobic interactions.
2. Hydrogen bonds.
. a r ges.
4. van der Waal forces
AtifHassanKhirelsied
P t i d f t t
-
8/2/2019 Amino Acids (2) IUA
32/35
Proteins: ordersofstructure
The forces that stabilize roteins structure
Some proteins contain covalent disulfide (S-S) bonds that link thesulfhydryl groups of cysteinyl residues.
AtifHassanKhirelsied
P t i d f t t
-
8/2/2019 Amino Acids (2) IUA
33/35
Proteins: ordersofstructure
P t i d t ti
-
8/2/2019 Amino Acids (2) IUA
34/35
Proteinsdenaturation
Denaturation:isthereversibleruptureofthenon
ofproteinconformationandbiologicalactivity.
AtifHassanKhirelsied
Proteins denaturation
-
8/2/2019 Amino Acids (2) IUA
35/35
Proteinsdenaturation
Thefunctionofaproteinisabsolutelydependenton
.
denaturing theprotein.