Bio 201 exam 2
G-protein coupled receptors have ____ transmembrane domains
7
If it were injected directly into liver cells, cAMP would have the effect of:
Activating Protein Kinase A and, therefore, glycogen breakdown
The enzyme phosphofructokinase-1 (PFK-1) catalyzes the 3rd reaction in glycolysis. When AMP concentrations are very high, AMP binds to a location outside the active site PFK-1, which promotes catalysis. This is an example of:
Allosteric activation
Pyrimidines are synthesized through a long series of reactions beginning with the amino acid aspartate. The ribonucleotide CTP is the final compound in this pathway, and when there is enough CTP, it binds to and inhibits the enzyme that catalyzes the first reaction in the pathway, aspartate transcarbamoylase (ATCase). Because CTP is structurally and chemically different from the enzyme's natural substrates, this type of regulation must be:
Allosteric inhibition
As we learned in Lecture 15, protein phosphatases catalyze removal of phosphate groups from proteins. How would the activity of a protein phosphatase affect liver cell responses to epinephrine?
Decrease glucose production
Which of the following is a disadvantage of being multicellular?
Greater energy needs More difficult to absorb nutrients Reproduction more complicated
How does a compound that inhibits the GTPase activity of Gα affect liver cell responses to epinephrine?
It would increase glucose production.
Which of the following is NOT true of cell membranes?
Membranes consist of rigid patches of lipids arranged together in a mosaic like the tectonic plates.
Inhibition of which of the following would prevent indirect active transport of glucose into cells?
Na+/K+ ATPase
Imagine you walk into lab after spring break, and your TA hands you a beaker containing a solution of A, B, and C in water represented by the equilibrium shown below. If the solution has reached equilibrium, and the beaker is at pH 7.0, 25°C, and 1 atm pressure, what other information do you need to obtain in order to calculate ∆G°' for this reaction?
The concentrations of A, B, and C
If the graph below is a free energy diagram for a reaction, what is C?
The free energy of the products
Shown below are the results of two fluorescence recovery after photobleaching (FRAP) experiments. Which of the following could explain the difference between the data represented by the dashed line as compared to the data represented by the solid line?
The membrane of the cell indicated by the dashed line contains longer fatty acid chains in its phosopholipids.
Which of the following is true of steroid hormones but not a signaling molecule such as a ligand for G-protein coupled receptors?
Their receptors regulate gene transcription
Which of the following is true for all enzymes?
They alter the transition state.
A major function of the epithelium in animals is to prevent entry of pathogens and toxins from the environment. Which of the following is common to all epithelial cells?
They are held together by tight junctions.
Which of the following is never true of enzymes?
They lower ΔG of a reaction.
True or False: The concentration of Ca++ inside the cell is higher than it is outside.
false
The reaction below, phosphorylation of glucose, is exergonic because it is coupled to ATP hydrolysis. The enzyme hexokinase catalyzes this reaction. Which of the following best describes how an enzyme for this reaction works? glucose + ATP <=> glucose-6-P + ADP
the enzyme alters the mechanism of the reaction by altering the transition state.
Cell adhesion molecules are important components of:
tight junctions
True or False: The concentration of K+ inside the cell is higher than it is outside.
true
True or False: The concentration of Na+ outside the cell is higher than it is inside.
true
What is ∆G°' for the hydrolysis of ATP?
-7.3 kcal/mol
The protein:lipid ratio in a typical membrane (e.g. red blood cells) is approximately:
1:1
Cholesterol generally makes up what percentage of the lipid mass of the plasma membrane
25%
Cholesterol generally makes up what percentage of the lipid mass of the plasma membrane?
25%
The enzyme Succinate dehydrogenase (SDH) catalyzes the reaction succinate --> fumarate in the Citric Acid Cycle. The compound malonate, whose structure is just similar enough to succinate (structures shown below), can bind to the active site of SDH, preventing succinate from binding. This is an example of
Competitive inhibition
Which of the following is an enzyme?
G-alpha
Which of the following is least likely to diffuse through a cell's plasma membrane?
H+
Which of the following statements is NOT true?
The enthalpy of a closed system always increases.
For solutes that cannot diffuse through the membrane, water moves across the membrane from a region of ______ to a region of ______ solute concentration.
low to high
Consider the reaction: A + B <=> C + D. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, [B] = 0.1 M, [C] = 1.9 M, and [D] = 1.9 M; and the pH is 7.0. Keq for the reaction is _____ and the reaction is _____. (you do not need a calculator for this!)
361; exergonic
consider the reaction: A + B <=> C + D. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, [B] = 0.1 M, [C] = 1.9 M, and [D] = 1.9 M; and the pH is 7.0. Keq for the reaction is _____ and the reaction is _____. (you do not need a calculator for this!)
361; exergonic
Protein makes up what percentage of the mass of the plasma membrane in a typical cell (e.g. red blood cells)
50%
The enzyme phenylalanine hydroxylase (PAH) catalyzes the conversion of the amino acid phenylalanine to tyrosine. If for this reaction, Keq' = 18.1, ∆G°' is ____ and the reaction is ____.
<0; Exergonic
Collagen, an extremely important extracellular matrix protein, is constitutively secreted by fibroblast cells, a type of connective tissue cell. If you had a patient in which collagen is synthesized normally, but fails to be secreted into the extracellular matrix, which of the following would you examine as the likely cause of this problem?
A kinesin disorder
If you had a patient in which the lung epithelium was leaking fluids from the bloodstream into the lumen of the lung, which of the following is the most likely cause?
A mutation in a cell adhesion molecule
The active and inactive forms of a hypothetical enzyme are shown below. (The polypeptide is represented by the colored rectangles and grey lines holding them together.) The middle rectangle is the catalytic domain with the active site on the right. The reaction it is catalyzing is also shown on the right. The P in the red circle refers to a phosphate group. This enzyme is a/an _______ and it this form of enzyme regulation is _______.
ATPase; covalent modification
The last product in a reaction pathway often regulates the activity of the first enzyme in the branch of the pathway that is unique to its production when the concentration of the product gets very high. Because the structure of the product is very likely to differ substantially from that of the the enzyme's normal substrate, this type of regulation is most likely:
Allosteric inhibition
Which of the following is/are likely to elicit a rapid, reversible response?
An odorant that binds to a G protein-coupled receptor
Which adaptation specific to becoming multicellular compensates for the destabilizing effect of increased size? (Think carefully about answer choices!)
Both ECM and tight junctions
Which of the following is/are likely to elicit a slow, but long-lasting or even permanent cellular response?
Both growth factor signaling and steroid hormone signaling
The enzyme Succinate dehydrogenase (SDH) catalyzes the reaction succinate --> fumarate in the Citric Acid Cycle. The compound malonate, whose structure is just similar enough to succinate (structures shown below), can bind to the active site of SDH, preventing succinate from binding. This is an example of:
Competitive inhibition
Which of the following is NOT consistent with the fluid mosaic model of cell membranes
Different types of phospholipids are distributed equally between the inner and outer leaflets of the membrane.
Which of the following is NOT consistent with the fluid mosaic model of cell membranes?
Different types of phospholipids are distributed equally between the inner and outer leaflets of the membrane.
We learned in lecture that any reaction that breaks apart two phosphate groups, e.g. hydrolysis of a diphosphorylated molecule so that it becomes monophosphorylated, is:
Exergonic
Shown below are the results of two fluorescence recovery after photobleaching (FRAP) experiments. Which of the following could explain the difference between the data represented by the dashed line as compared to that represented by the solid line?
FRAP was performed on the same cell but at a lower temperature.
Which of the following statements is TRUE?
For any process to be energetically favorable, ΔG must be < 0.
A mutation that causes a decrease in the GTPase activity of G-alpha in liver cells would have the effect of:
Increasing the activity of Protein Kinase A Increasing the production of glucose Increasing the activity of Glycogen phosphorylase
Cells shrink when you place them in a solution with a high concentration of the amino acid glycine. This indicates that the cell membrane:
Is NOT permeable to glycine but IS permeable to water
Which of the following is a DISadvantage of paracrine signaling?
It affects only a small number of cells.
Which of the following is NOT TRUE of a second messenger in signal transduction?
It is diffusible It is produced when the "first messenger" binds to its receptor It may activate enzymes
Which of the following may be true for an enzyme?
It may chemically interact with its substrate.
Chloride ion (Cl-) concentrations must be maintained much higher outside of cells than inside of cells. How this gradient is maintained is complex, but a key transporter co-transports Cl- along with K+ ions. The name of this transport protein could be ____ and its mode of transport would be ____
K+/Cl- symporter; indirect active transport
Chloride ion (Cl-) concentrations must be maintained much higher outside of cells than inside of cells. How this gradient is maintained is complex, but a key transporter co-transports Cl- along with K+ ions. The name of this transport protein could be ____ and its mode of transport would be ____.
K+/Cl- symporter; indirect active transport
Chloride ion (Cl-) concentrations are approximately 10x higher outside of cells than inside. Imagine you discovered a novel protein that is required in liver cells for transporting Cl- out of the cell up its concentration gradient, and further found that this protein only functions if the Na+/K+ ATPase is active. This suggests that the Cl- transport protein is a
Na+/Cl- antiporter
Which of the following can diffuse most easily through the cell membrane?
O2
Which of the following should be able to diffuse most easily through a cell's plasma membrane?
O2
Which of the following reactions can we say is definitely energetically favorable, i.e. it can go without an input of energy
One in which ΔG < 0
Which of the following enzymes catalyzes phosphorylation of proteins using inorganic phosphate, i.e. the phosphate buffering the cell?
Phosphorylases
Extracellular chloride ion (Cl-) concentrations are much higher than intracellular. This gradient is maintained in part by co-transport of K+ and Cl- out of the cell using indirect active transport. Maintenance of the Cl- concentration gradient using this mechanism is therefore dependent on:
The Na+/K+ ATPase
If the graph below is a free energy diagram for a reaction, what is number
The activation energy
If the graph below is a free energy diagram for a reaction, what is B?
The free energy of the reactants
The active and inactive forms of a hypothetical enzyme are shown below. (The polypeptide is represented by the colored rectangles and grey lines holding them together.) The middle rectangle is the catalytic domain and the reaction it catalyzes is also shown. This form of enzyme regulation is _______.
Zymogen activation
Consuming very large amounts of certain foods/drinks can affect the digestive system in profound ways. Which of the following would LEAST likely cause some sort of osmotic shock to your stomach and intestinal cells if you consumed a very large amount of it in a short period of time?
butter
After you eat, insulin is secreted by pancreatic Beta cells into the bloodstream, where it diffuses throughout the body to bind to receptors on target cells, telling them to take up glucose. This mode of signaling is referred to as:
endocrine
The hormone glucagon is secreted by the pancreas in response to low blood sugar. Liver cells respond to glucagon by breaking down glycogen to form glucose, which is then release into the bloodstream for the other tissues. Based on this information, what mechanism is most likely used to transport glucose out of the cell into the bloodstream?
facilitated diffusion
True or false: if entropy increases, the reaction is definitely exergonic.
false
True or false: if ΔH < 0, the reaction is definitely exergonic.
false
True or false: if ΔS > 0, the reaction is definitely exergonic.
false
Which of the following is an advantage of juxtacrine signaling?
fast
Which of the following is an advantage of multicellularity?
greater mobility
∆G°' for the hydrolysis of ATP is considered to be
highly exergonic
Factors that increase membrane fluidity have the effect of _______ membrane permeability:
increasing
Which of the following never uses simple diffusion to pass through the cell membrane?
ions
Which of the following enzymes catalyzes phosphorylation of proteins using a phosphate group from ATP?
kinases
