Amino Acids and Proteins5
Amino Acids and Proteins Amino Acids and Proteins
Larry Scheffler Larry Scheffler
Lincoln High School Lincoln High School
Portland OR Portland OR
Protein
Protein
Protein adalah golongan senyawa organik
Protein adalah golongan senyawa organik
makromolekuler yang tersusun dari asam-
makromolekuler yang tersusun dari asam-
asam amino, dengan unsur penyusunnya asam amino, dengan unsur penyusunnya adalah C H O N , kadang- kadang adalah C H O N , kadang- kadang mengandung unsur S dan P. mengandung unsur S dan P.
Istilah protein berasal dari bahasa Yunani
Istilah protein berasal dari bahasa Yunani“Proteos” berarti mempunyai peranan “Proteos” berarti mempunyai peranan penting. penting.
Fungsi Protein
Fungsi Protein
Fungsi Protein : Fungsi Protein :
1. Membangun sel baru
1. Membangun sel baru
2. Mempertahankan sel
2. Mempertahankan sel
3. Mengganti sel yang telah Tua
3. Mengganti sel yang telah Tua Protein sangat diperlukan dalam sintesis
Protein sangat diperlukan dalam sintesis
enzim, hormon dalam tubuh. Oksidasi 1 g
enzim, hormon dalam tubuh. Oksidasi 1 g
protein dapat menghasilkan 4 kalori. protein dapat menghasilkan 4 kalori.
Penggolongan Protein
Penggolongan Protein
Berdasarkan susunan molekulnya protein dapat Berdasarkan susunan molekulnya protein dapat digolongkan menjadi 3 golongan: digolongkan menjadi 3 golongan:
1. Protein Sederhana
1. Protein Sederhana Adalah golongan protein yang tersusun dari asam-
Adalah golongan protein yang tersusun dari asam- asam amino saja. asam amino saja.
Contoh : albumin; globilin; glutalin; Histon.
Contoh : albumin; globilin; glutalin; Histon.
2. Protein Komplek
2. Protein Komplek Adalah golongan protein, yang tersusun dari asam-
Adalah golongan protein, yang tersusun dari asam- asam amino dan senyawa lain non asam amino, asam amino dan senyawa lain non asam amino, seperti H seperti H 3 3 PO PO 4 4 dan Karbohidrat. Contoh : Nukleo dan Karbohidrat. Contoh : Nukleo protein; Chromoprotein; Lipoprotein; Glukoprotein protein; Chromoprotein; Lipoprotein; Glukoprotein Fosfoprotein; Metallo Protein. Fosfoprotein; Metallo Protein.
Amino Acids Amino Acids
Amino acids have both Amino acids have both
a carboxyl group a carboxyl group
- -COOH -COOH
an amino group an amino group
- -NH -NH 2 2 in the same molecule.. in the same molecule..
- H 2 O
Amino Acid Structure
Amino Acid Structure
The general formula of an amino acid is The general formula of an amino acid is shown here shown here
The group designated by The group designated by
R R is usually a is usually a carbon chain but other carbon chain but other structures are also structures are also possible possible
Amino Acid Structure Amino Acid Structure
on the 3 on the 3 rd rd carbon from carbon from the carboxyl group the carboxyl group
are on the 2 are on the 2 nd nd carbon carbon
are on the carbon are on the carbon adjacent to the carboxyl adjacent to the carboxyl group. group.
Amino acids may be Amino acids may be characterized as characterized as
amino acids depending amino acids depending on the location of the on the location of the amino group in the amino group in the carbon chain. carbon chain.
, or , or
, ,
Amino Acids - Proteins Amino Acids - Proteins
Amino acids are the building blocks of Amino acids are the building blocks of proteins. Proteins are natural proteins. Proteins are natural polymers of successive amino acids polymers of successive amino acids
There are 20 different amino acids There are 20 different amino acids that make up human proteins that make up human proteins
amino acids amino acids
Amino acids found in Amino acids found in proteins are proteins are
amino acids amino acids .
.
The amino group is The amino group is always found on the always found on the carbon adjacent to carbon adjacent to the carboxyl group the carboxyl group
Amino Acid Functions
Amino Acid Functions
1.1. Amino acids are the building blocks of Amino acids are the building blocks of proteins proteins 2.
2. Some amino acids and their derivatives Some amino acids and their derivatives function as neurotransmitters and other function as neurotransmitters and other regulators regulators
Examples Include Examples Include
L-dopamine L-dopamine
Epinephrine Epinephrine
Thyroxine Thyroxine
Amino Acids and Proteins Amino Acids and Proteins
Amino acids Amino acids forming proteins forming proteins may be may be characterized as characterized as
Acidic, Basic, or Acidic, Basic, or neutral neutral depending on depending on the character of the character of the side chain the side chain attached. attached.
Acidic Amino Acids Acidic Amino Acids
There are There are two acidic two acidic amino acids. amino acids.
There are There are two carboxyl two carboxyl groups and groups and only one only one amino group amino group ( asp ) (glu)
Basic Amino Acids I Basic Amino Acids I
These amino These amino acids are acids are basic. They basic. They have more have more amino groups amino groups than carboxyl than carboxyl groups groups
Basic Amino Acids II Basic Amino Acids II
These amino These amino acids are also acids are also basic. They basic. They have more have more amino groups amino groups than carboxyl than carboxyl groups groups
Neutral Amino Acids I Neutral Amino Acids I
These amino These amino Acids are
Acids are considered considered neutral. There neutral. There is one carboxyl is one carboxyl group per amino group per amino group group (ala) (gly)
Neutral Amino Acids II Neutral Amino Acids II
(Tyr) (Trp) (Cys) (Ser) (Val)
Neutral Amino Acids III Neutral Amino Acids III
(Ile) (Thr) (Asp) (Phe)
(Gln)
Amino Acids and Optical
Amino Acids and Optical
Except for glycine, all amino acids have a
Isomers Isomers
Except for glycine, all amino acids have a chiral carbon atom chiral carbon atom
. Therefore they can . Therefore they can have have optical isomers
optical isomers The amino acids found in
The amino acids found in proteins proteins are all are all levarotatory or L forms levarotatory or L forms .
.
Amino Acids are Amphoteric
Amino Acids are Amphoteric
Amino acids are Amino acids are amphoteric.
amphoteric.
They are capable of They are capable of behaving as both an acid and a base, since they have behaving as both an acid and a base, since they have both a proton donor group and a proton acceptor both a proton donor group and a proton acceptor group. group.
In neutral aqueous solutions the proton typically In neutral aqueous solutions the proton typically migrates from the carboxyl group to the amino group, migrates from the carboxyl group to the amino group,
The Zwitterion The Zwitterion
This dipolar ion form is known as a This dipolar ion form is known as a Zwitterion.
Zwitterion.
Essential Amino Acids Essential Amino Acids
Of the 20 amino acids that make up
Of the 20 amino acids that make up
proteins 10 of them can be proteins 10 of them can be synthesized by the human body synthesized by the human body The other 10 amino acids must be
The other 10 amino acids must be acquired from food sources. These acquired from food sources. These amino acids are known as essential amino acids are known as essential amino acids amino acids
Essential Amino Acids Essential Amino Acids Essential amino acids Essential amino acids
Arginine Arginine
Histidine Histidine Isoleucine Isoleucine
Leucine Leucine Lysine Lysine
Methionine Methionine Phenylalanine Phenylalanine
Threonine Threonine Tryptophan Tryptophan
Valine Valine Non-Essential amino acids Non-Essential amino acids Alanine Alanine (from pyruvic acid) (from pyruvic acid)
Asparagine Asparagine (from aspartic acid) (from aspartic acid) Aspartic Acid Aspartic Acid (from oxaloacetic acid) (from oxaloacetic acid)
Cysteine Cysteine Glutamic Acid Glutamic Acid (from oxoglutaric acid) (from oxoglutaric acid)
Glutamine (from Glutamine (from glutamic acid) glutamic acid) Glycine ( Glycine ( from serine and threonine) from serine and threonine)
Proline
Proline (from glutamic acid) (from glutamic acid)
Serine
Serine (from glucose) (from glucose) Tyrosine Tyrosine (from phenylalanine) (from phenylalanine)
Essential Amino Acids Essential Amino Acids Complete protein Complete protein
Contains all 10 Contains all 10 essential amino acids essential amino acids
Proteins derived from Proteins derived from animal sources are animal sources are complete proteins complete proteins Beans contain some Beans contain some complete protein as complete protein as well well
Incomplete protein Incomplete protein Lack one of more of the Lack one of more of the essential amino acids essential amino acids
Most vegetable proteins Most vegetable proteins are incomplete proteins are incomplete proteins Beans are an exception Beans are an exception to this generalizations to this generalizations
Peptide Bond Peptide Bond
When two amino acids combine, there is
When two amino acids combine, there is
a formation of an amide and a loss of a
a formation of an amide and a loss of a
water molecule water moleculeProteins- Levels of Structure Proteins- Levels of Structure
Amino acids can undergo condensation Amino acids can undergo condensation reactions in any order, thus making it possible reactions in any order, thus making it possible to form large numbers of proteins. to form large numbers of proteins.
Structurally, proteins can be described in four Structurally, proteins can be described in four ways. ways.
Secondary 3. Tertiary 4. Quaternary structure.
Primary Structure Primary Structure
The primary structure of a protein is defined by The primary structure of a protein is defined by the sequence of amino acids, which form the the sequence of amino acids, which form the protein. This sequence is determined by the protein. This sequence is determined by the
base pair sequence in the DNA used to create it.
base pair sequence in the DNA used to create it.
The sequence for bovine insulin is shown below The sequence for bovine insulin is shown below
The secondary structure describes the way that the
Secondary Structure Secondary Structure
The secondary structure describes the way that the
chain of amino acids folds itself due to intramolecular chain of amino acids folds itself due to intramolecular hydrogen bonding hydrogen bondingTwo common secondary structures are the Helix and the sheet
Tertiary Structure Tertiary Structure
The tertiary structure The tertiary structure maintains the three maintains the three dimensional shape of dimensional shape of the protein. the protein.
The amino acid chain The amino acid chain
(in the helical, pleated (in the helical, pleated or random coil form) or random coil form) links itself in places to links itself in places to form the unique twisted form the unique twisted or folded shape of the or folded shape of the protein. protein.
Tertiary Structure
Tertiary Structure
There are four ways in which parts of the amino acid There are four ways in which parts of the amino acid chains interact to stabilize its tertiary shape.. They include: chains interact to stabilize its tertiary shape.. They include: I. I.
Covalent bonding
Covalent bonding
, for , for example disulfide bridges example disulfide bridges formed when two cysteine formed when two cysteine molecules combine in which molecules combine in which the –SH groups are oxidized: the –SH groups are oxidized: II. II.
Hydrogen bonding
Hydrogen bonding
between between polar groups on the side chain. polar groups on the side chain. III. III.
Salt bridges
Salt bridges
(ionic bonds) (ionic bonds) formed between –NH formed between –NH 2 2 and – and –
COOH groups COOH groups
Quaternary Structure Quaternary Structure
Many proteins are not single strands Many proteins are not single strands
The diagram below shows the quaternary structure of The diagram below shows the quaternary structure of an enzyme having four interwoven amino acid strands an enzyme having four interwoven amino acid strands
The natural or native structures of
The natural or native structures of proteins may be altered, and their proteins may be altered, and their
biological activity changed or destroyed
biological activity changed or destroyed
by treatment that does not disrupt the by treatment that does not disrupt the primary structure. primary structure. Following denaturation, some proteins
Following denaturation, some proteins will return to their native structures under will return to their native structures under proper conditions; but extreme proper conditions; but extreme conditions, such as strong heating, conditions, such as strong heating, usually cause irreversible change. usually cause irreversible change.
Denaturing Proteins Denaturing Proteins
Denaturing Proteins
Denaturing Proteins hydrogen bonds are broken by increased Heat Heat (coagulation of egg white albumin on frying.) translational and vibrational energy.
Ultraviolet Ultraviolet Similar to heat
Radiation Radiation (sunburn) salt formation; disruption of hydrogen bonds.
Strong Acids or Strong Acids or (skin blisters and burns, protein precipitation.) Bases Bases competition for hydrogen bonds.
Urea Urea (precipitation of soluble proteins.) (e.g. ethanol & acetone) change in dielectric Some Organic Some Organic constant and hydration of ionic groups. Solvents Solvents protein.) (disinfectant action and precipitation of
A small change in A small change in the sequence of the sequence of the primary the primary structure can have structure can have a significant a significant impact on protein impact on protein structure
structure In sickle cell
In sickle cell anemia a glutamic anemia a glutamic acid is replaced by acid is replaced by a valine in the a valine in the amino acid amino acid sequence sequence
Sickle Cell Anemia Sickle Cell Anemia
Ninhydrin Reaction
Ninhydrin Reaction
Triketohydrindene hydrate, commonly known as
Triketohydrindene hydrate, commonly known as
, reacts with amino acids to form a reacts with amino acids to form a
purple colored imino derivative, This derivative
purple colored imino derivative, This derivative
forms a useful test for amino acids, most of which forms a useful test for amino acids, most of which are colorless. are colorless.
Protein Tests: Biuret Protein Tests: Biuret
Biuret reagent is a light blue Biuret reagent is a light blue solution containing Cu solution containing Cu 2+ 2+ ion ion in an alkaline solution. in an alkaline solution.
Biuret turns purple when Biuret turns purple when mixed with a solution mixed with a solution containing protein. The containing protein. The purple color is formed when purple color is formed when copper ions in the biuret copper ions in the biuret reagent react with the reagent react with the peptide bonds of the peptide bonds of the polypeptide chains to form a polypeptide chains to form a complex. complex.
Xanthroprotic Test Xanthroprotic Test
Concentrated Nitric acid will form a yellow
Concentrated Nitric acid will form a yellow
complex with tryptophan and Tyrosine side complex with tryptophan and Tyrosine side chains in proteins chains in proteins
Disulfide Bridge Test
Disulfide Bridge Test
Disulfide bridges will react with Pb Disulfide bridges will react with Pb 2+ 2+ ion from lead acetate in an acidfied ion from lead acetate in an acidfied solution. A black precipitate indicates solution. A black precipitate indicates the presence of disulfide-bonded the presence of disulfide-bonded cysteine in proteins. cysteine in proteins.