Biochem Exam 3 UPDATED ACTUAL Questions and CORRECT Answers
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Course
Biochem
Institution
Biochem
Biochem Exam 3 UPDATED ACTUAL
Questions and CORRECT Answers
Observe the ribbon structure of pepsin. To do this, click the green-outlined box at the bottom
of the player. Green x's will appear over your selection. Then go to the dropdown menu and
on the "Display" line, click the "Toggle Ribbo...
Biochem Exam 3 UPDATED ACTUAL
Questions and CORRECT Answers
Observe the ribbon structure of pepsin. To do this, click the green-outlined box at the bottom
of the player. Green x's will appear over your selection. Then go to the dropdown menu and
on the "Display" line, click the "Toggle Ribbon for selection" icon. Then click the "Toggle
CPK for selection" icon to remove the space-filling display. To remove the green x's, click
"Clear Selection" on the "Misc" line of the dropdown menu.
Determine the relative proportions of secondary and quaternary structure(s). What best
describes these structures? - CORRECT ANSWER✔✔- The major secondary structures are
beta sheets, and there is no quaternary structure.
Which of the following correctly describes the biochemistry of the amino acids at the termini
of pepsin? - CORRECT ANSWER✔✔- two nonpolar amino acids at the N-terminus and one
polar amino acid at the C-terminus
The catalytic acitivity and/or conformational stability of this protein is likely dependent upon
_____________of peripheral amino acid side chains. These side chains are expected to have
a _________________value. - CORRECT ANSWER✔✔- 1) protonation
2) low pKa
Which amino acid is NOT a target for kinases? - CORRECT ANSWER✔✔- Asp
A __________ inhibitor is a type of irreversible inhibitor. - CORRECT ANSWER✔✔-
covalent
Structure-based drug design strategies often devise competitive inhibitors that bind to certain
enzyme active sites. For example, saquinavir and indinavir are designed HIV protease
inhibitors that bind to the aspartate protease enzyme of HIV, which is required for the virus to
produce functional proteins for further HIV infection. Which of the following statements are
true about saquinavir and indinavir? - CORRECT ANSWER✔✔- -The removal of the phenyl
ring (six-membered carbon ring containing three double bonds and no attached functional
groups) on indinavir and saquinavir would likely affect their inhibitory activity.
,-D.Saquinavir and indinavir both have a component that mimics the natural Phe-Pro
dipeptide substrate of aspartate protease.
-Very high local concentrations of proteins with Phe-Pro or Tyr-Pro peptide bonds would
reduce the effectiveness of saquinavir and indinavir in limiting HIV's infectivity of new cells.
Which of the following is not a biochemical process affecting the bioavailability of enzymes?
- CORRECT ANSWER✔✔- binding of a competitive inhibitor
While glucagon (a peptide) and epinephrine (a tyrosine derivative) are very different agonists,
both signal through GPCR systems. Some of the components of the pathways are unique,
while other signaling components are shared between both systems. Place each item in the
appropriate category: glucagon and epinephrine shared, glucagon independent, or epinephrine
independent. - CORRECT ANSWER✔✔- shared:
-camp signaling pathways
-gsa activation
-adenylate cyclase activation
-net accumulation of glucose
glucagon:
-peptide binding to GPCR receptor
Epinephrine:
-Gqa activation
-activation of phospholipase C
-ligand binding to adrenergic receptor
Which of the following first messengers is unique because it is not water soluble and does not
bind directly to a membrane receptor? - CORRECT ANSWER✔✔- estradiol
Both epinephrine (a tyrosine derivative) and glucagon (a peptide hormone) increase glucose
export from the liver into the bloodstream. Each ligand binds a different receptor, but both
lead to an activation of PKA. How does this happen? - CORRECT ANSWER✔✔- Both
, receptors bind and activate the same Gα subunit, Gsα, which indirectly leadsto PKA
activation.
Choose the correct statements about the function and activity of arrestin. - CORRECT
ANSWER✔✔- A. PKA phosphorylation also modifies GPCR, leading to arrestin binding to
the receptor for endosomal transportD. Arrestin facilitates protein transport, which prevents a
receptor from reassociating with the G protein complex
Whether a G alpha subunit is active or inactive depends on which guanine nucleotide is
bound to it. Binding of GDP or GTP results in the protein switching between two
conformational states. Which of the following answers best describes the structural changes
that occur in a G alpha subunit due to guanine nucleotide binding? - CORRECT
ANSWER✔✔- Dissociation of GDP for GTP with the G alpha subunit structurally shifts the
switch II helix region, allowing for the association of G alpha with its effector proteins, such
as adenylate cyclase.
A ligand binds to a transmembrane protein. This causes a conformational change in the
protein that is detected by an intracellular protein. The intracellular protein is an enzyme that
adds phosphate groups to target proteins. The phosphorylated proteins cause a physiological
change within the cell. This is an example of - CORRECT ANSWER✔✔- a signal
transduction pathway
A plot of vo versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines. If the
line in the middle represents the enzyme activity in the absence of any allosteric effectors,
then the line to the __________ represents the enzyme in the __________ when bound to
__________. - CORRECT ANSWER✔✔- right; T state; CTP
Signal transduction is part of a cell's response to an external signal. Although signal
transduction pathways can differ in their details, there are some common elements.
Determine which of the statements below accurately describe signal transduction pathways.
Select the SIX correct statements. - CORRECT ANSWER✔✔- 1. A receptor changes
conformation upon binding, transmitting a signal across the cell membrane.
2. Signal transduction cascades, often involving protein kinases, amplify a signal
intracellularly.
4. A second messenger may carry a signal from the cell membrane to an organelle.
5. A ligand, such as a hormone, binds to a specific cell surface receptor on a target cell.
7. A receptor may pass on a signal by interacting with another protein or by acting as an
enzyme.
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