Lecture 5 - How Proteins form 3D structures + Intro to Enzymes

What are the two types of secondary protein structure?

a helix, b pleated sheet

What is an α-helix?

coiled structure held together by hydrogen bonds

Where are α-helices commonly found?

transmembrane proteins that cross the lipid bilayer

What is a β-pleated sheet?

strands of the same polypeptide lying side by side

What holds a β-pleated sheet together?

hydrogen bonds between backbones

What makes up much of the structure of globular proteins?

b pleated sheets

What is tertiary structure?

overall 3d shape of a polypeptide chain

What stabilises tertiary structure?

interactions between amino acid side chains

What four types of interactions can stabilise tertiary structure?

hydrogen bonds, ionic bonds, hydrophobic interactions, disulfide bridges

What is quaternary structure?

protein made up of two or more polypeptide chains

Can the polypeptides in a quaternary protein be the same or different?

yes, same or different

What holds the polypeptides together in quaternary structure?

interactions between their side chains

What are examples of proteins with quaternary structure?

collagen, haemoglobin

What are chaperonins?

proteins that assist other proteins with correct folding

What can chaperonins do to incorrectly folded proteins?

refold or mark them for destruction

What happens when a protein is denatured?

loses its secondary, tertiary and quaternary structure and normal 3d shape

What interactions can be disrupted during denaturation?

hydrogen bonds, ionic bonds, hydrophobic interactions, disulfide bonds

How does heat cause denaturation?

breaks weak bonds

How does pH cause denaturation?

changes ionization pattern of r groups

What do reducing agents do during denaturation?

reduce disulfide bonds to sh groups

How do organic solvents cause denaturation?

disturb hydrophobic and hydrophilic interactions

How do detergents cause denaturation?

disrupt hydrophobic interactions

What is renaturation?

denatured proteins return to functional shape when denaturing agent is removed

What does hydrolysis do to proteins?

breaks peptide bonds

What is activation energy?

energy required to start a reaction

Why might bonds need to be broken during a reaction?

so new bonds can form

How do enzymes affect activation energy?

lower activation energy

How does lowering activation energy affect a reaction?

increases rate of reaction

Are enzymes consumed by the reactions they catalyse?

no, can be used again

Why is an enzyme's 3D structure important?

determines its activity