Ch 3 and 4 questions Flashcards
(16 cards)
When the pH of a solution is below the pI of amino acids contained within that solution, these amino acids will have \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. no net charge (neutral) a neutral to negative charge all uncharged groups a positive to neutral charge
a positive to neutral charge
Three amino acids that have positively charged R groups at neutral pH are \_\_\_\_\_\_\_\_\_\_\_\_\_. K, R, H D, R, M H, R, E P, F, Y K, R, P
K, R, H
The term specific activity differs from the term activity in that specific activity _____________.
is measured only under optimal conditions.
is the activity (enzyme units) of a specific protein.
is the activity (e.g. enzyme units) in milligrams of protein.
refers only to a purified protein.
refers to proteins other than enzymes.
is the activity (e.g. enzyme units) in milligrams of protein.
Which of the following is not a property of amino acids?
amino acids have varied chemical nature
amino acids are non-reactive
amino acids have the ability to make large polymers (many amino acids that are linked)
amino acids have acid-base properties
amino acids are non-reactive
Which of the following amino acids would be most soluble in water (H2O)? Phenylalanine Isoleucine Proline Aspartate Valine
Aspartate
Which of the following amino acids can self-react through a covalent linkage? Cysteine Arginine Tryptophan Proline Cystine
Cysteine
Which of the following would you expect to be a component of a protein? D-phenylalanine D-glucose D-glycine L-alanine
L-alanine
A D-amino acid would interrupt an α-helix made of L-amino acids. Another naturally occurring hindrance to the formation of an α-helix is the presence of:
a nonpolar residue near the carboxyl terminus.
two Ala residues side by side.
a positively charged Lys residue.
a negatively charged Arg residue
a Pro residue.
a Pro residue.
Ehlers-Danlos Syndrome can be characterized by all of the following except:
a mutation that affects the protein fibroin
hyperextensible joints
highly extensible skin
scoliosis
a mutation that affects the enzyme that hydroxylates lysines
a mutation that affects the protein fibroin
Which of the following amino acids are highly represented in silk fibroin?
Alanine and histidine are highly represented
Alanine and Glycine are highly represented
Glycine and phenylalanine are highly represented
Proline and lysine are highly represented
Proline and Alanine are highly represented
Alanine and Glycine are highly represented
Which of the following is the strongest alpha helix former? arginine proline alanine histidine lysine
alanine
Amino acid residues commonly found in positions 2 or 3 of a β- turn are \_\_\_\_\_\_\_\_\_\_. Gly and Phe Pro and Gly Ala and Gly two Cys Ala and Pro
Pro and Gly
Which of the following is true about protein folding?
Proteins have lower potential energy in their native conformations than at the beginning of the folding process
Proteins have more potential energy once they have assumed their native conformations
Proteins have more internal entropy (within the protein structure) after assuming their native conformations
Proteins typically take many hours to fold into their final native conformations
Proteins never assume transient (partially folded) intermediates before assuming their native conformations
Proteins have lower potential energy in their native conformations than at the beginning of the folding process
What is TRUE about the rotation of bonds in a protein backbone?
All bonds in the backbone have restricted rotation and partial double-bond character.
The rotation is free only about the peptide bond. The other bonds are restricted by steric hindrance and the presence of proline residues.
The bond between the carbonyl carbon and nitrogen is restricted. Other bonds are free to rotate depending only on steric hindrance or the presence of proline residues.
The rotation is free about all bonds in the backbone, except for the bond between the nitrogen and the alpha carbon in proline residues.
The bond between the carbonyl carbon and nitrogen is restricted. Other bonds are free to rotate depending only on steric hindrance or the presence of proline residues.
Ramachandran determined the "allowed" values of the phi and psi angles primarily by considering \_\_\_\_\_\_\_\_. Steric hindrance Hydrogen bonding effects pKa values of the amino acids The hydropathy of amino acids
Steric hindrance
Which of these statements is NOT true about β-sheets?
The side-chains of all amino acids point to the same side of the sheet.
The range of allowed phi and psi angles is broader than for those in the α-helix.
The polypeptide chains in the sheet are nearly fully extended.
In antiparallel sheets the hydrogen bonds between adjacent strands are nearly perpendicular to the backbones of the strands.
The side-chains of all amino acids point to the same side of the sheet.
