5th topic

What are proteins made of

Amino acids

What determines a protein’s function

Its shape

Why must an active site be precisely folded

To allow proper binding

What happens if a protein’s structure is altered

It loses binding and function

What is the primary structure of a protein

Sequence of amino acids in a polypeptide chain

What type of bond holds the primary structure

Covalent peptide bond (condensation)

What determines the primary sequence of a protein

DNA

Why is the amino acid sequence important

Dictates final 3D shape, helices and sheets formation, solubility, and ligand binding

What is secondary structure

Local folding of the polypeptide chain stabilized by hydrogen bonds

What are the two main types of secondary structure

α-helix and β-sheet

Describe α-helix

Coiled spring shape

Describe β-sheet

Pleated sheet shape

What are the types of β-sheets

Parallel and antiparallel

What stabilizes secondary structures

Hydrogen bonds between backbone atoms

What is tertiary structure

Unique 3D shape of a polypeptide chain

What mainly determines tertiary structure

R group interactions

What interactions stabilize tertiary structure

Hydrophobic effect, ionic bonds, disulfide bonds, hydrogen bonds, van der Waals forces

What is the hydrophobic effect in proteins

Nonpolar R groups cluster inside, hydrophilic R groups face outside

What are disulfide bonds

Covalent links between cysteine side chains in the presence of oxygen

What happens if a protein loses its tertiary structure

Denaturation, protein becomes nonfunctional

What is quaternary structure

Assembly of multiple polypeptide chains (subunits)

What stabilizes quaternary structure

Hydrophobic interactions, hydrogen bonds, ionic bonds, sometimes disulfide bridges

What does quaternary structure create

Functional protein complexes