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