BIO 201 Unit 2
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%
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
Consider the reaction: A <=> B. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, and [B] = 1.1 M. Keq' for this reaction is ____ and ∆G°' is _____. (You do not need a calculator for this.)
> 1; < 0
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? (Think very carefully before answering this question!)
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
Which of the following correctly describes a second messenger?
A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.
If it were injected directly into liver cells, cAMP would have the effect of:
Activating Protein Kinase A and, therefore, glycogen breakdown
Which of the following is an advantage of multicellularity?
All of the above
Which of the following is NOT TRUE of a second messenger in signal transduction?
All of the above are TRUE
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 is catalyzing is also shown. This form of enzyme regulation is
Allosteric activation
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
The enzyme phosphofructokinase-1 (PFK-1) catalyzes the reaction F6P + ATP --> F1,6BP + ADP during glycolysis. When ATP concentrations get very high, ATP also binds to a location on PFK-1 outside of the active site, preventing it from catalysis. This is an example of:
Allosteric inhibition
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 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
Which of the following is true for both GPCR signaling and steroid hormone signaling?
Both of the above
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
Which of the following is a DISADVANTAGE of endocrine signaling?
By the time it reaches the target cell, the ligand concentration is likely to be very low.
The reaction below shows the process by which the protease Chymotrypsin becomes activated. What is the zymogen?
Chymotrypsinogen
The enzyme Succinate dehydrogenase (SDH) catalyzes the reaction succinate --> fumarate in the Citric Acid Cycle (structures shown below). If fumarate binds to the active site of SDH, thereby preventing succinate from binding, this is an example of:
Competitive 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
As we learned in Lecture 15, protein phosphatases catalyze removal of phosphate groups from proteins. How would the activity of a protein phosphatase affect a cell's response to growth factors?
Decrease proliferation
Which of the following is a disadvantage of being a multicellular organism?
Decreased structural stability
Shown below is a free energy diagram for a chemical reaction. An enzyme that catalyzes this reaction acts by ________ the magnitude of__________
Decreasing; 2
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.
The H+ ATPase (a.k.a. "proton pump") creates electrochemical gradients across the membranes of many protists. This is an example of:
Direct active transport
"He was awakened in the middle of the night by a low growling that sounded as if it was coming from just outside his tent. In response, the cells of his adrenal medulla began to secrete epinephrine, causing his palms to sweat, his heart to race, and his hair to stand on end." Epinephrine is involved in what type of signaling as described in this passage?
Endocrine
Which of the following is a mechanism by which cells ensure a strong response to a small amount of ligand?
Enzyme cascades
ATP hydrolysis is highly _____ because it involves _____.
Exergonic; separation of negatively charged phosphate groups
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.
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
Diffusion of materials happen from low concentration to high concentration
False
True or False: The concentration of Ca++ in the cytoplasm is higher than it is in the smooth ER.
False
True or False: The concentration of Ca++ inside the cell is higher than it is outside.
False
True or False: The concentration of K+ outside the cell is higher than it is inside.
False
True or false: Only mutations that alter amino acid residues in the active sites of enzymes affect the function of the enzyme.
False
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 statements is TRUE?
For any process to be energetically favorable, ΔG must be < 0.
Which of the following is an advantage of multicellularity?
Greater mobility
Which of the following is least likely to diffuse through a cell's plasma membrane?
H+
ras, a small GTPase, hydrolyzes GTP slowly on its own, but its enzymatic activity is increased significantly in the presence of GTPase activating proteins (GAPs). Imagine you discovered a novel mutation that prevents GAP from binding to ras. This mutation would have the effect of:
Increasing cAMP production Increasing Protein Kinase A activity Increasing glucose production Increasing cell proliferation
Unlike in animals, in which the Na+ gradient is used, it is the H+ gradient in some other species that fuels transport of other compounds up their concentration gradients. This type of transport is:
Indirect active transport
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 an advantage of endocrine signaling?
It affects large numbers of cells.
Which of the following may be true for an enzyme?
It may chemically interact with its substrate.
Dr. Hutson really likes coffee. Despite that, this is not a question about caffeine. How does a compound that inhibits the GTPase activity of Gα affect liver cell responses to epinephrine?
It would increase glucose production.
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
Which of the following enzymes catalyzes phosphorylation of proteins using a phosphate group from ATP?
Kinases
Pertussis toxin is produced by Bordetella pertussis, a bacterium that causes whooping cough. Pertussis toxin catalyzes the addition of ADP-ribose (structure below) to Gα, which prevents Gα from binding to GPCRs thus "locking" it in the GDP-bound state. If you could observe liver cells treated with epinephrine in real time, how would one infected with pertussis compare to a control (i.e. one treated with epinephrine alone)?
Less glycogen breakdown
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
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.
Which of the following is a disadvantage of being a multicellular organism specifically as opposed to unicellular? (read and think carefully!)
More difficult to absorb nutrients
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
Inhibition of which of the following would prevent indirect active transport of glucose into cells?
Na+/K+ ATPase
Archeological evidence suggests that Neanderthals may have been aware of the medicinal properties of plants over 60,000 years ago. Imagine you are a modern-day ethnobotanist and have identified a compound from fossilized tree pollen that binds to the alpha subunit of the most common G-proteins. To test how the compound affects the activity of Gα, you treat liver cells with the compound and then epinephrine. You observe that the cells fail to produce glucose. Which of the following could be how the compound acts?
None of the above
What is the second messenger in the receptor tyrosine kinase signaling pathway?
None of the above
Which of the following correctly describes a second messenger?
None of the above
Which of the following is an advantage of paracrine signaling?
None of the above
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
"During embryonic development red blood cells begin to develop in patches called blood islands. The blood cells secrete growth factors that diffuse only to nearby cells, signaling differentiation into endothelial cells. The endothelial cells eventually form the linings of the blood vessels." The growth factor described in the passage is involved in what type of signaling?
Paracrine
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 2?
The activation energy
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? A + B <=> C
The concentrations of A, B, and C
Which of the following statements is NOT true?
The enthalpy of a closed system always increases.
If the graph below is a free energy diagram for a reaction, what is C?
The free energy of the products
If the graph below is a free energy diagram for a reaction, what is B?
The free energy of the reactants
If the graph below is a free energy diagram for a reaction, what is A?
The free energy of the transition state
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 true for all enzymes?
They increase the reaction rate.
Which of the following is never true of enzymes?
They lower ΔG of a reaction.
Which of the following is true of both GPCR signaling and steroid hormone signaling?
They may result from endocrine signals.
True or False: The concentration of Ca++ outside the cell is higher than it is inside.
True
True or False: The concentration of K+ inside the cell is higher than it is outside.
True
Water/solvent is the only thing that can move across the membrane in osmosis
True
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
Liver cells respond to epinephrine by breaking down glycogen. What is the second messenger in this patway?
cyclic AMP
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
∆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
Gain in oxygen atoms is
oxidation
Loss of electrons is
oxidation
Loss of hydrogen atom is
oxidation
Gain in hydrogen atoms is
reduction
Gain of electrons is
reduction
Cell adhesion molecules are important components of:
tight junctions