Proteins Part 1 Flashcards
General formula of proteins
CHON
Carbon Hydrogen Oxygen and Nitrogen some sulfur
Greek word of protein and its meaning
Proteios
Of primary importance
Swedish chemist that described and named in 1839
Jons Jakob Berzelius
In 1926 he showed the enzyme urease was a protein
James B. Sumner
Basic unit of proteins
Amino acids
It is a naturally-occuring, unbranched polymer in which the monomer units are amino acids
Protein
Most abundant molecules in the cells of humans
Protein
Elemental composition of proteins
CHON
Average nitrogen content of proteins is
15.4%
Present in some specialiazed proteins
Iron Fe
Phosphorus P
An organic compound that contains both an amino NH2 and Carboxyl COOH groups attached to same carbon atom
Amino acid
the R side chain determines the ___ of amino acids
Classification
R side chain may vary
In size shape charge acidity functional groups present hydrogen bonding ability and chemical reactivity
Based on common r groups there are
20 standard amino acids
r groups are non polar
Non polar amino acids
Number of standard amino acids are non polar
8 of the 20
R groups are polar
Polar amino acids
Three types of polar amino acids
Polar neutrak polar acidic and polar basic
R side with 2 COOh
Polar acidic
Contains polar but neutral side chains
Polar neutral
Contains amino group as part of the side chains
Polar basic
Smallest amino acid
Achiral only= no isomerism
Glycine
A
ALA
Alanine
Arg
R
Arginine
ASP
D
Aspartic Acid
Asn
N
Asparagine
Cys
C
Cysteine
Glu
E
Glutamic Acid
Gln
Q
Glutamine
Gly
G
Glycine
His
H
Histidine
Ile
I
Isoleucine
Leu
L
Leucine
Lys
K
Lysine
Met
M
Methionine
Phe
F
Phenylalanine
Pro
P
Proline
Ser
S
Serine
Thr
T
Threonine
Trp
W
Tryptophan
Tyr
Y
Tyrosine
Val
V
Valine
Not synthesized by humans, can only be obtained in Food
Essential Amino Acids
It is required for growth in children but is not an essential amino acid for adults
Arginine
Essential amino acids for
Adult
Children
9-Adult
10- children
Metabolic fates
Exclusively ketogenic
K- Lysine
L-leucine
Metabolic fates
Both ketogenic and glucogenic
I- isoleucine
T-threonine
W-tryptophan
Y-tyrosine
F- phenylalanine
A protein that contains all of the essential amino acids in the same relative amounts in which the body needs them and examples
Complete dietary protein
Example Casein from milk and proteins in meat fish and eggs
From animal sources
Protein that does not contain adequate amounts relative to the bodys needs of one or more of the essential amino acids
Incomplete dietary protein
Protein from plant sources
Gelatin (Arg)
Common Limiting amino acid (LAA)
Lysine- wheat rice oats
Methionine-beans and peas
Tryptophan-corn and beans
Only complete dietary protein from plant
Soyq
Two or more incomplete dietary proteins that when combined provide an adequate amount of all essential amino acids relative to the body
Example
Complementary dietary proteins
Rice and beans
Amino acids found in nature as well as in proteins are what isomers?
L-isomers
Ile and Thr have ___ chiral center
2
Physical properties of proteins
Pure form- white crystalline
Decompose before they melt
Not very soluble in water
An ion with positive and negative charges on the same molecule
Zwitterion
The only standard amino acid with a sulfhydryl group -SH
Cysteine
Mild oxidizing agents dimerizes to form a
Cystine molecule
Two cysteine residues linked via a covalent disulfide bond
Cystine
21st amino acid
Selenocysteine
Aliphatic amino acids
LIVAG
Leucine
Isoleucine
Valine
Alanine
Glycine
The only achiral
R group is H
Smallest amino acid
Glycine
R group is methyl
Alanine
Also known as branched chain amino acids
Valine
Leucine
Isoleucine
R group is isopropyl
Valine
R group is isobutyl
Leucine
R group is secbutyl
Isoleucine
Amino acids with alcohol
Serine
Threonine
Acidic amino acids
Double COOH
Aspartic Acid
Glutamine
Basic amino acids
Lysine
Arginine
Histidine
Cysteine
Cystine
Guanido
Sakaguchi test
Arginine
Imidazole ring
Polydiazo test
Histidine
Sulfur containing amino acids
Cysteine
Cystine
Methionine
Double sulfur linkage
Cystine
Test for methionine
Fohls test or
Lead acetate
+ Dark matter or Black ppt
Aromatic amino acids
Phenylalanine
Tyrosine
Methylbenzene
Test is xanthoproteic test (Nitric acid)
What positive?
Phenylalanine
+yellow
The only phenolic amino acid
Phenol compound
Test is millons test
Tyrosine
Aromatic amino acids (WYF)
Tryptophan
Has an indole ring
Hopkins cole test `
Tryptophan
Known as imino acid
2ndary amino acid
Test is ninhydrin test
Proline
Has an -OH group
Secondary amino acids
Hydroxyproline
Under proper conditions amino acids can bond together to produce an
Unbranched chain of amino acids
Name of the bond between amino acids and
Peptides
Bond between two amino acids
Dipeptide
Bond between 10-20 amino acids
Oligopeptide
Bond between large number of amino acid
Polypeptide
Every peptide has a
N-terminal end and a c-terminal end
The number of isomeric peptides possible increases rapidly as the length of the
Peptide chain increases
Small peptides are biochemically active
Hormones
Neurotransmitter
Antioxidants
Best known peptide hormone
Oxytocin
Known as the love hormone
Can cause uterine contraction during labor when a woman is about to give birth to her child
Oxytocin
Vasopressin which controls amount of water in the urinary tract
Anti diuretic hormone or ADH
Oxytocin and ADH are produced by which gland
Pituitary gland
(Nine amino acid residues) with six of the residues held in the form a loop by a disulfide bond between two cysteine residues
Nonapeptide
Biochemically important small peptides
Small peptide neurotransmitters
Pentapeptide
Glutathione
They are pentapeptide (5) neurotransmitters produced by the brain and bind receptors within the brain
Also helps reduce pain
Enkephalins
Best known enkephalins
Met-enkephalin
Leu-enkephalin
Tyr-Gly-Gly-Phe-Met
Met-enkephalin
Tyr-Gly-Gly-Phe-Leu
Leu-enkephalin
A tripeptide
Present is in high levels in most cells
Regulator of oxidation-reduction reactions
Glutathione
Glu-Cys-Gly
Glutathione
An antioxidant and protects cellular contents from oxidizing agents such as peroxides and superoxides
Highly reactive forms of oxygen often generated within the cell in response to bacterial invasion
Glutathione
General definition
A protein is a naturally occuring unbranched polymer in which the monomer units are amino acids
Specific definition
A protein is a peptide in which at least 40 amino acid residues are present
Common proteins contain
400-500 amino acid residues
small proteins contain
40-100 amino acid residues
Several proteins with _____ amino acid residues are known
> 10,000
Contains one peptide chain
Monomeric protein
Contains more than one peptide chain
Multimeric protein
( protein subunits)
A protein in which only amino acid residues are present
Simple proteins
A protein that has one or more non-amino acid entities (prosthetic groups) present in its structure
Conjugated proteins
Contain lipid prosthetic groups
Lipoproteins
Contain carbohydrate groups
Glycoprotein
Contain a specific metal as prosthetic group
Metalloproteins
