Chapter 3: Proteins

Cell’s building blocks and execute the majority of cell’s functions.

RubisCo

Collagen

A polypeptide is a chain of amino acids linked together by peptide bonds.

A peptide bond is a covalent bond that forms between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of another amino acid during a condensation reaction.

Disulfide bridges, also known as disulfide bonds, are covalent bonds that form between two sulfur atoms in different cysteine residues within a protein or peptide.

A hydrogen bond is a relatively weak, non-covalent interaction that occurs between a hydrogen atom covalently bonded to an electronegative atom (such as nitrogen, oxygen, or fluorine) and another electronegative atom in a different molecule or within the same molecule.

An ionic bond is a type of chemical bond that forms between two atoms or ions with significantly different electronegativities.

Hydrophobic interactions are interactions between nonpolar molecules or regions of molecules that occur in the presence of water.

Amino acids are organic compounds that serve as the building blocks of proteins.

Dipolar ions

• It contains an extra COOH group.

• Aspartic acid, Glutamic acid.

• It contain extra NH2 group.

• Histidine, Lysine, Arginine.

• It contains one NH2 group and one COOH group.

• Asparagine, serine, tyrosine, etc.

Glycine, Alanine, Valine, Isoleucine, Leucine

Serine, Threonine

Cysteine, Methionine

Aspartic acid, Asparagine, Glutamic acid, Glutamine

Leucine, Arginine, Histidine

Phenylalanine, Tryptophan, Tyrosine

Proline

no charge on the R-groups

charge on the R-group

• Not synthesized in our bodies.

• Need to be taken in our diets.

Synthesized in their body cannot be taken in diet.

Produced at a very slow rate can be synthesized by the adult body but not in growing children.

Made up of amino acids.

Made up of protein + nonprotein part.

• Primary: Due to denaturation of protein.

• Secondary: formed due to digestion.

All 20 essential amino acids are present.

One/two essential amino acids lacking.

made up of one polypeptide chain.

made up of two/more polypeptide.

It is a linear chain of amino acids linked by peptide bonds.

It comprises of alpha helix and beta plated sheet.

a most common type of secondary structure and rigid rearrangement of polypeptide chain.

made up of 2 or more polypeptide chains are held together by intermolecular-H bonding.

protein of tertiary structure are highly folded and globular in nature.

it is made up of two or more than two polypeptide chain

peroxidase

catalase

• enzymes involved in oxidation-reduction reaction.

• alcohol dehydrogenase, cytochrome oxidase.

• Enzyme that catalyze reactions the transfer of functional group.

• e.g.: hexokinase, trans-aminase.

• Enzyme catalyzing hydrolysis of ester, ether, peptides etc.

• These enzyme breaks large molecules into smaller molecules by the introduction/presence of H2O molecules.

• They break specific covalent bonds and remove a group without hydrolysis, oxidation etc.

• e.g. Aldolase, fumarase.

Rearrangement of molecular structure to form isomers.

Enzyme catalysing the synthetic reaction where two molecules are joined together.

consist of only proteins and catalyze their substrate specific reactions.

Made up of protein and non-protein parts.

A prosthetic group is tightly bound organic co-factor.

A coenzyme is a loosely bound/organic co-factor. It can be easily removed.

• According to this theory:

  • Enzymes are rigid and pre-shaped.

  • Substrate fit to the active site just as a key fit into a proper lock.

• Proposed by Kosh land.The monomer

• Most accepted hypothesis on the basis of enzyme action.

• Enzymes are not rigid and pre-shaped.

chemical molecules that inhibit enzyme activity

• Inhibitors are structure similar to substrate.

• They favor lock and key hypothesis.

• Reversible in nature.

• Km increase but Vmax remain constant.

• Some inhibitors do not compete for active site of enzyme but destroy the structure of enzyme, the physical structure of enzyme is altered as a result and do not form enzyme-substrate complex.

• They favor induced-fit theory.

• Irreversible in nature.

• Km remain constant but Vmax change.