tertiary structure of globular proteins

Question 1

characteristics of globular proteins

Answer 1

• no regular repeating amino acid sequences (unlike fibrous)
• higher order structural organization (3 and 4)

Question 2

Tertiary (3) structure

Answer 2

• 3D arrangement of protein due to folding of localized secondary (2) structure
• usually a-helices and B-sheets to allow for longer-range interactions
• long range interaction between two secondary folded structures

Question 3

what are the longer range interactions between B-sheets and a-helices?

Answer 3

Interactions between side chains

Question 4

What are the interactions that occur between side chains

Answer 4

• hydrogen bond
• Disulfide bond (covalent)
• ionic bond (saltbridge)
• Hydrophobic interactions/van der waals (dispersion forces, temporary induced dipoles)

Question 5

Formation of disulfide involves what?

Answer 5

oxidation, as you’re losing H bonds and gaining bonds to S instead.

Question 6

Amino acid side chains in globular proteins are distributed by what

Answer 6

• polarity.
• allow for an increase in entropy of surroundings by putting nonpolar on the inside, hydrophobic effects (tendency for nonpolar substances to aggregate and avoid water)

Question 7

Where are polar amino acids located?

Answer 7

on the outside of globular proteins to interact with water.
this is not always the case, as this would mean all active sites would have to be external. DO have to have polar amino acids on the inside

Question 8

How to offset the effect of polar molecules on the inside when that is where nonpolar amino acids are located?

Answer 8

can put metal, hydrogen bonding.

Question 9

When are nonpolar amino acids on the outside of a protein

Answer 9

transmembrane protein, hormones…
Hemoglobin with multiple subunits, need the subunits to be stuck together with nonpolar interactions