PROTEINS & ENZYMES

proteins

are the most abundant biological macromolecules, occurring in all cells and all

parts of the cells.

20 amino acids.

The proteins of every organism, from the simplest bacteria to human beings, are

constructed from the same ubiquitous set of __________________

Proteins

are polymers of amino acids, with each amino acid residue joined to its neighbor

by a specific type of covalent bond.

glycine

All amino acids, except _________, are chiral and have the L-configuration at the α carbon.

proline and cysteine

Hydroxyproline and cystine are synthesized from ______ and ______, respectively, after the protein chain has been synthesized

dipolar ions (zwitterions)

In a dry solid state, amino acids exists as _______________

equilibrium

In aqueous solution an __________ exists between the dipolar ion, the cationic and

the anionic forms of the amino acid

2.3

pKa of alanine (for ionization of carboxyliccid proton) is ____

9.7

pKa of alanine (for ionization of a proton from the protonated amino group) is ___

peptides

The polymer of amino acids is called ________

peptide bonds

The amide linkages are the ____________

Primary structure

_____________ refers to the exact sequence of

amino acid along a protein chain

Secondary and tertiary structures

refer to the further bending and folding of the primary structure

Quaternary structure

refers to the aggregation of more than one polyamide chain

enzymes

Natural catalysts (biological catalysts) in the form of proteins.

Catalyst

a substance that speeds up a chemical reaction and is not changed by the

reaction.

Enzymes

• Produced by living organisms to increase the rate of an immense and diverse set of chemical reactions required for life.

• Involved in all processes essential for life such as DNA replication and transcription, protein synthesis, metabolism and signal transduction, etc.

• There are hundreds of different ________ but each _______ speeds up only one kind of reaction. They are specific.

Oxidoreductases

catalyzes oxidation and reduction of substrates.

Transferases

catalyzes a shift of chemical group from donor to acceptor substrates.

Hydrolases

catalyzes hydrolysis reactions (breaking of bonds)

Lyases

catalyzes removal or addition of chemical groups to substrates

Isomerases

catalyzes intramolecular rearrangements

Ligases

catalyzes combination of substrates

Enzyme activity

mole of substrate converted to product per unit time.

• Rate of appearance or rate of disappearance

Non-competitive inhibitors

bind to enzyme at another site than the active site.

Uncompetitive inhibitors

can only bind to the E-S complex (the intermediate step).

ALLOSTERIC REGULATION

When a small molecule can act as an effector or regulator to activate or inactivate an action of protein, the protein is said to be under ______________