Peptide Bonds and Proteins #19
Name some characteristics of peptide bond
1. Partial double-bond character 2. trans configuration 3. -C=0 and -NH groups of peptide bonds are uncharged but polar 4. charged groups: N-terminus, C-terminus, ionized R-groups
What are the 2 major secondary structures
1. α-Helix 2. β-Pleated Sheet
How many levels of protein structures are there?
4
Sickle Cell anemia
Disease due to change in a single amino acid substitution in Hemoglobin (Val for Glu)
What kind of bonds happen in the tertiary structures
Disulfide bridges, ionic interactions, Hydrophobic interactions, and hydrogen bonds
Ionic Interactions
Carboxyl groups interact with amino groups
Hydrogen bonds
form from a variety of side chains (-OH, -NH2, -OCNH2)
What disrupts salt bridges, bind sulfydryl groups
heavy metal ions
Oxytocin
hormone secreted by the posterior pituitary gland (trade name Pitocin)
Where does the protein folding typically occurs?
in ER
Tertiary structure results results from what
interactions between R groups of the different amino acid residues
name 2 types of β-Pleated Sheet
parallel and anti parallel sheets
How are amino acids linked to form a polypeptide chain?
peptide bonds
What is the precursor for protein digestion
protein denaturation
What happens to the 3D structure when it is broken
protein losses its native sructure
What binds the amino acids ionizable groups followed by H₂O salvation and precipitation
salt concentration
What prevents rotation around bond between carbonyl carbon and nitrogen of the peptide bond?
shorter than a single bond making it rigid and planar
Name 2 parts of quaternary structure
simple and conjugated
What affect salt bridges (stomach acid)
strong acids or bases
Quarternary structure
structure of proteins containing more than one polypeptide chain (subunit)
What determines the the 3D structure and the function of protein?
the Amino acid sequence
What makes the α-Helix very stable and the helical configuration?
the H-bonds
What is the primary structure of proteins
the linear sequence of amino acids (determines the unique 3D shape of Protein)
What type of protein is more spherical and either dissolve in water or form stable suspensions in water
Globular proteins
How can peptide bonds be cleaved using Lysine and Arginine
Trypsin cleaves the peptide bonds with Lys and Arg with (+) charged R groups
What is known as antidiuretic hormone because it stimulates kidneys to retain water
Vasopressin (ADH)
Explain Conjugated proteins
also contain other components called prosthetic groups
Amino acids incorporated into a polypeptide called what
amino acid residues
What plays in the folding process
attraction and repulsion (between side chains)
Explain simple proteins
contain only amino acid residues
What can extreme pH or Temperature do to proteins
disrupt the stabilizing forces (bond) causing the protein to take on a random confirmiation
What are 2 reactions involving amino acids
disulfide and peptide bonds (affects protein structure and function)
When does Tertiary structures usually occur
domains occur when 100-200 AA fold in an independent fashion separate from other parts of polypeptide chain
peptide bonds cannot be broken through
*high heat and high concentrations of urea *hydrolyze a peptide bond (nonenzymatically) *requires a prolonged exposure to a strong base or acid at elevated temperatures
Adrenocorticotropic Hormone (ACTH)
A tropic hormone produced and secreted by the anterior pituitary that stimulates the production and secretion of steroid hormones by the adrenal cortex.
What type of hormone that has 39 amino acid peptide synthesized by the pituitary gland.
Adrenocorticotropic Hormone (ACTH)
H-Bonds occur between the same chain
Intrachain
Fibrous Protein
Composed of long polypeptides that can intertwine with one another to form strong fibers Water soluble
Disulfide bridges
Covalent bond contributes to the stability of the 3D shape of the protein
Name the two primary protein types
Fibrous and Globular
Interchain
H-Bonds occur between 2 different chains
what are example of a conjugated protein with a quaternary structure
Hemoglobin
Zymogens
Inactive forms of enzymes such as trypsinogen, chymotrypsinogen and procarboxypeptidase
When is peptide bond formed?
It is formed between α-carboxyl group of one amino acid and α-amino group of another
What is a Disulfide bond (-S-S-)?
It's a covalent linkage formed when -SH groups of 2 cysteines become oxidized to form a dimer (cystine)
Proteins
Long chains of amino acids linked together by peptide bonds
Protein Denaturation
Loss of its characteristic native structure and function
Hydrophobic interactions
Nonpolar groups are either attracted to each other or forced together by their hydrophobic nature *interior side of the protein
What disrupts hydrophobic interactions
Organic solvents and detergents
What type of structure is linear order in which amino acids are linked together
Primary Structure of protein
Amyloid plaque
Primary component of plaque in Alzheimer's disease 40 AA residues Cleavage of amyloid precursor protein
name all levels of protein structures
Primary, secondary, tertiary, and quarternary
When β-bends reverse chain direction, what does it often contain?
Proline
What causes the kink in α-Helix?
Proline (Pro)
What disrupts disulfide bridges (urea and β-mercaptoethanol)
Reducing agents
Which structures of protein repeat at regular intervals?
Secondary Structure
What is a hydrogen-bonded arrangement of the primary structure of a protein?
Secondary Structure of Protein
dimer
a chemical entity consisting of two structurally similar subunits called monomers joined by bonds that can be either strong or weak.
What does the side chain of cysteine contain?
a sulfhydryl group (-SH)
What temperatures are proteins biologically active
between 0° to 40°
Where does the hydrogen bonds occur within the α-Helix
between C=O group of an amino acid and N-H groups of amino acid 4 residues away
What can happen in misfiling proteins
can accumulate and cause disease
What assist in protein folding
chaperones called heat shock proteins
How are Peptide bonds cleaved by using Chymotrypsin
it uses Tyrosine, Phenylalanine, and Tryptophan with it
α-Helix examples
keratin and myoglobin
vasopressin (ADH)
made in hypothalamus, stored in posterior pituitary; Increases permeability of nephron's collecting duct to water -> increased water reabsorption and increased blood volume; Secreted when plasma osmolarity increases (osmoreceptors) or when blood vol decreases (baroreceptors) Peptide synthesized by the hypothalamus in response to low blood pressure or high blood Na+ concentration
what disrupts hydrogen and salt bridges
mechanical stress
N-terminal of the free amino end of the peptide is written where?
to the left
C-terminal of the free carboxyl end of the peptide is written where?
to the right
Trypsin and Chymotrypsin are secreted as....
trypsinogen and chymotrypsinogen
What happens to the structure of protein when it's denatured
uncoiled
What happens in tertiary structures
when the primary and secondary configurations bend and fold into a specific 3D shape
Which of the 2ndary structure involves a coiled polypeptide chain backbone? It's also most common of polypeptide helices
α-Helix
Which of the 2ndary structure involves in one or more polypeptide chains
β-Pleated Sheet
Which of the secondary structure is less common involving 2 or more polypeptide chains
β-Pleated Sheet