Lesson 4 : Proteins Flashcards
Proteins is also called ______________ since it is a chain of ___________ linked by ______________.
polypeptide
amino acids
peptide bonds
Characteristics (definition) of proteins
● It is a naturally occurring, unbranched polymer in which the monomer units are amino acids.
● It is a peptide in which at least 40 amino acid residues are present.
● It contains Carbon, Hydrogen, Oxygen, and Nitrogen.
● It sometimes contains Sulfur and Phosphorus.
Function of Protein
● Structural component (skin, hair, muscles)
● Chemical messenger (hormones)
● Disease defense (antibodies)
● Enzymes (catalase, lactase)
Characteristics (definition) of amino acids
● Building blocks of proteins.
● There are 700 different naturally occurring amino acids, but only 20 are normally present in proteins.
There are __ amino acids present in proteins are called the ______________ ____________ ___________.
20
Standard Amino Acids
CHEMICAL STRUCTURE OF AMINO ACIDS
● Amino acid is an organic compound that contains both an amino group and a carboxyl group.
● Amino group acts like a base and tends to be positive.
● Carboxyl group acts like an acid and tends to be negative.
● “R” group is a variable and can range from 1-2 atoms.
● Two amino acids can join to form a dipeptide.
What is a Peptide bond
linkage of carbon and nitrogen.
CLASSIFICATION BASED ON SIDE CHAIN POLARITY
Non-Polar Amino Acids
Polar Neutral Amino Acids
Polar Acidic Amino Acids
Polar Basic Amino Acids
Non-Polar Amino Acids
1 amino group
1 carboxyl group
1 non polar side chain
Polar Neutral Amino Acids
1 amino group
1 carboxyl group
1 polar neutral side chain
Polar Acidic Amino Acids
1 amino group
2 carboxyl group
(1 is part of side chain)
Polar Basic Amino Acids
2 amino group
1 carboxyl group
(1 is part of side chain)
What are the essential amino acids
○ Histidine
○ Isoleucine
○ Leucine
○ Lysine
○ Methionine
○ Phenylalanine
○ Threonine
○ Tryptophan
○ Valine
What are the conditionally non-essential amino acids
○ Arginine
■ Required for growth in children but is not an essential acid for adults.
○ Cystine
○ Glutamine
○ Glycine
○ Proline
○ Tyrosine
What are the non-essential amino acids
○ Alanine
○ Asparagine
○ Aspartate
○ Glutamate
○ Serine
Amino acids have___________ : Right and Left based on the _____________ of the amino group.
mirror images
location
Nature prefers the ______________ of amino acids.
L-isomers
All 20 standard amino acids have chiral centers except __________.
Glycine
What is Chirality
refer to having a mirror image.
it is a molecule that has both positive and negative charges. It is made up of two (or more) functional groups. One of its components has a positive charge and another one with a negative charge.
Zwitterion
the net charge of a zwitterion is
zero
The pH at which an amino acid has no net charge because equal number of positive and negative charges are present.
ISOELECTRIC POINT
Through _____________ ____________ of proteins or amino acids, it produces dipeptide that is linked to carbon-nitrogen bond.
dehydration synthesis
What does IUPAC and what is it’s purpose
International Union of Pure and Applied Chemistry
Helps in naming small peptides.
IUPAC RULES IN NAMING PEPTIDES
RULE 1
● The C-terminal amino acid residue keeps its full amino acid name.
RULE 2
● All the other amino acid residue names ending in -ine or -ic acid will be replaced with -yl, except:
○ Tryptophan - Tryptophyl
○ Cysteine - Cysteinyl
○ Glutamine - Glutaminyl
○ Asparagine - Asparaginyl
RULE 3
● The amino acid naming sequence begins at the N-terminal amino acid residue.
CLASSIFICATION OF PROTEIN: BASED ON NUMBER OF PEPTIDE CHAIN
● Monomeric Protein
● Multimeric Protein
● Monomeric Protein - only one peptide chain is present. ● Multimeric Protein - more than one peptide chain is present.
CLASSIFICATION OF PROTEIN: BASED ON CHEMICAL COMPOSITION
● Simple Protein
● Conjugated Protein
● Simple Protein - only amino acid residues are present.
● Conjugated Protein - one or more non-amino acid entities present in its structure in addition to one or more peptide chains.
The pleated sheet structure of the Beta Sheet is held together by the _______ between the ______ of ______________.
Hydrogen Bonds
amide groups
linear polypeptide chains
The average number of amino acid residues in a typical Beta Sheets is ___ with an average of ___ strands bonding together.
six
CLASSIFICATION OF PROTEIN: BASED ON SHAPE
● Fibrous
● Globular
● Fibrous - have an elongated shape with one dimension much longer than the others.
● Globular - have peptide chains folded into spherical and globular shapes.
What is PROTEIN HYDROLYSIS
● Splits peptide bonds to smaller peptides and amino acids.
● Occurs in the digestion of proteins.
● Occurs in cells when amino acids are needed to synthesize new proteins and repair tissues.
● In the lab, hydrolysis of a peptide requires acid or base, water, and heat.
● In the body, enzymes catalyze the hydrolysis of proteins.
What is PROTEIN DENATURATION
Involves the disruption of bonds in the secondary, tertiary, and quaternary structures.
● Heat and organic compounds
● Acids and Bases
● Heavy metal ions
● Agitation (Whipping or Shaking)
● Heat and organic compounds - break apart H+ bonds and disrupt hydrophobic interactions.
● Acids and Bases - break H+ bonds between polar R groups and disrupt ionic bonds.
● Heavy metal ions - react with S-S (Sulfur-Sulfur) bonds to form solids.
● Agitation (Whipping or Shaking) - stretches peptide chains until bonds break.
