L9: Proteins - Self Assembly, Interactions Flashcards
Describe the hydrophobic effect in terms of proteins.
- When a protein goes from unfolded (less stable) to folded (more stable).
- Spontaneous reaction
- Gibbs Free energy < 0, thus energetically favourable.
What is denaturation?
- Unfolding of proteins
- Not all proteins can “re-nature” and re-gain function
What is denaturation a result of?
- Disruption of non-covalent interaction
- Can happen by changing pH, temperature, etc.
What makes a protein more stable?
- Strong interactions between side chains = more stable protein.
- Weaker interactions = less stable protein
What role do non-covalent interactions have in folded polypeptide chains?
- Hold the polypeptide chain into the correct structure.
What is the key concept in regards to non-covalent interactions in proteins?
- The interactions can be easily broken.
Why is it important that the non-covalent interactions can be easily broken?
- For different protein functions.
- Changing shape is important for it to be able to accomplish the many tasks it has within the cell (ex. catalyzing reactions, binding a substrate, etc.)
What are integral membrane (transmembrane) proteins?
- Proteins that cross through the lipid bilayer.
What are peripheral proteins?
- Associated w/ the lipid bilayer on either side
- DOES NOT span the lipid bilayer
What are the side groups of the proteins that are exposed to extracellular fluid?
- Charged/hydrophilic
What are the side groups of the proteins that are within the protein?
- Hydrophobic
What are the side groups of the proteins that are in the protein channel?
- Charged/hydrophilic
List the non-covalent interactions from strongest to weakest.
- Ionic
- Ion-PD
- PD-PD
- PD-ID
- ID-ID
What factors may impact non-covalent interactions?
- Size of side chain
- Hydrophobic (ID-ID) interactions (lots of interactions make them very strong)
- Location in the protein (interior vs. exterior, charged and polar side chains tend to interact w/ water vs. nonpolar side chains)
