Choose the correct answer 1.1 Globular proteins are usually all __________ 1. in
ID: 196316 • Letter: C
Question
Choose the correct answer 1.1 Globular proteins are usually all __________ 1. insoluble in water. 2. roughly spherical. 3. folded so that the hydrophobic amino acids are in the interior of the molecule. 4. hydrophobic, since side chains are exposed to the water. 1.2 The pKa of isoleucine’s -carboxyl group and -amino group are 2.3 and 9.8 respectively. Calculate the isoelectric point. 1. 2.3 2. 6.0 3. 9.8 4. The isoelectric point cannot be calculated without the pKa value for the side chain 1.3 A protein's particular conformations are all _______. 1. the result of the overall three-dimensional architecture of the protein. 2. achieved by breaking and reforming covalent bonds 3. achieved by rotations about each single bond along the peptide backbone 4. the result of amino acid side chain interactions 1.4 Which of the following is the most common function for fibrous proteins 1. Enzymes 2. Structural roles 3. Carrier Molecules 4. Enzymes and carrier molecules 1.5 -helices and -strands are components of a protein’s ______structure. 1. Primary 2. Secondary 3. Tertiary 4. Quaternary
Explanation / Answer
#1.1 Globular proteins are usually (all) 2 roughly spherical , 3 folded so that the hydrophobic amino acids are in the interior of the molecules.
Note: If you have to pick only option, choose 2. Roughly spherical.
The axial ratio (length / width ratio) of the fibrous proteins is usually greater than 10. The axial ratio (length / width ratio) of the globular proteins is usually 3- 10. Relative abundance of hydrophilic or polar residues are present on the surface of protein. The hydrophilic residues on surface interact with polar aqueous environment and make the molecule solvated in it. A globular protein that is soluble in water. Most protein enzymes are globular protein.
A fibrous protein is usually elongated and insoluble in water. Provides structure or support. Fibrous proteins like keratin (nail, hair, hoof, in skin, etc.), muscle fibers (biceps, triceps, body parts and organs, etc.), etc. provide structural support.
#1.2 The pKa of isoleucine’s -carboxyl group and -amino group are 2.3 and 9.8 respectively. Calculate the isoelectric point. 6.0
pI of isoleucine = (pKa1 + pKa2) / 2 = (2.3 + 9.8) / 2 = 6.05
Note: The side chain of Ile is NOT ionizable, so it’s pKa value is not assigned.
#1.3 A protein's particular conformations are all 1 the result of the overall three-dimensional architecture of the protein, 4 the result of amino acid side chain interactions
# The protein’s conformation is its overall 3D folding. The 3D folding of a proteins is because of purely non-covalent interactions like H-bonds, ionic interactions, van de Waals’ interactions, hydrophobic interactions among the side chains of amino acids.
# There is NO breaking/forming of new covalent bonds (except formation of disulfide bonds in some) for establishing protein conformation.
# Rotations around peptide bond give rise to characteristic secondary structures.
# 1.4 Which of the following is the most common function for fibrous proteins 2. Structural roles
1.5 -helices and -strands are components of a protein’s 2. Secondary