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Bio 1113 Practice Test Questions
Terms in this set (66)
What is true of metabolism and its entirety in all organisms
it consists of all the energy transformation reactions in an organism
Which of the following is an example of potential rather than kinetic energy
a molecule of glucose
Most cells cannot harness heat to perform work because
temperature is usually uniform throughout the cell
Which of the following involves a decrease in entropy
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones
catabolism (catabolic pathways)
consume energy to build up polymers from monomers
Which of the following is a statement of the first law of thermodynamics
energy cannot be created or destroyed
For living organisms, which of the following is an important consequence of the first law of thermodynamics
the organism ultimately must obtain all of the necessary energy for life from its environment
Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics
as a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
Which of the following statements is a logical consequence of the second law of thermodynamics?
every chemical reaction must increase the total entropy of the universe.
Which of the following statements is representative of the second law of thermodynamics?
Cells require a constant input of energy to maintain their high level of organization
Which of the following types of reactions would decrease the entropy within a cell?
Biological evolution of life on Earth, from simple prokaryote-like cells to large, multicellular eukaryotic organisms
has occurred in accordance with the law of thermodynamics
The mathematical expression for the change in free energy of a system is ^G=^H-T^S
What is correct about this
^G is the change in free energy
A system at chemical equilibrium
can do no work
Which of the following is true for all exergonic reactions
the reaction proceeds with a net release of free energy
A chemical reaction that has a positive ^G is best described as
Chemical equilibrium is relatively rare in living cells. An example of a reaction at chemical equilibrium in a cell would be
a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell
In solution, why do hydrolysis reactions occur more readily than condensation reactions?
Hydrolysis increases entropy and is exergonic
Why is ATP an important molecule in metabolism
it provides energy coupling between exergonic and endergonic reactions
When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about half as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation.
Reactant and product concentrations in the test tube are different from those in the cell
Which of the following is most similar in structure to ATP
a RNA nucleotide
supply energy, primarily in the form of ATP, for the cell's work
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
it is lost to the environment
When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell?
it may be used to form a phosphorylated intermediate
number of systems for pumping ions across membranes are powered by ATP. Such ATP- powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion
concentration of 10-7 while the concentration in the SR is 10-2, then how is the ATPase acting?
ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
Which of the following is true of enzymes?
Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
Which of the following is true when comparing an uncatalyzed reaction to the same reaction with a catalyst?
The catalyzed reaction will have the same ∆G.
The lock-and-key analogy for enzymes applies to the specificity of enzymes _____.
Binding to their substrate
You have discovered an enzyme that can catalyze two different chemical reactions. Which of the following is most likely to be correct?
Either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's _____.
During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction?
The active site of an enzyme is the region that _____.
is involved in the catalytic reaction of the enzyme
According to the induced fit hypothesis of enzyme catalysis, _____.
the binding of the substrate changes the shape of the enzyme's active site
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as _____.
a cofactor necessary for enzyme activity
A noncompetitive inhibitor decreases the rate of an enzyme reaction by _____.
changing the shape of the enzyme's active site
How might a change of one amino acid at a site, distant from the active site of an enzyme, alter an enzyme's substrate specificity?
by changing the shape of an enzyme
For the enzyme- catalyzed reaction shown in the figure, if the initial reactant concentration is 1.0 micromolar, which of these treatments will cause the greatest increase in the rate of the reaction?
doubling the enzyme concentration
Allosteric enzyme regulation is usually associated with _____.
an enzyme with more than one subunit
Which of the following is an example of cooperativity?
a molecule binding at one unit of a tetramer, allowing faster binding at each of the other three
Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?
localization of enzymes into specific organelles or membranes
Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization?
They can more readily encounter and phosphorylate other membrane proteins.
Biological systems use free energy based on empirical data that all organisms require a constant energy input. The first law of thermodynamics states that energy can be neither created nor destroyed. For living organisms, which of the following statements is an important consequence of this first law?
The organism must ultimately obtain all the necessary energy for life from its environment.
In a biological reaction, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the amount of succinate molecules to those of malonic acid reduces the inhibitory effect if malonic acid. Select the correct identification of the molecules described in the reaction.
Succinate is the substrate, and fumarate is the product in the reaction.
Substrate-level phosphorylation occurs
in both glycolysis and the citric acid cycle
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation reduction reaction
loses electrons and loses potential energy
When electrons move closer to a more electronegative atom, what happens? The more electronegative atom is
reduced, and energy is released
Which of the listed statements describes the results of the following reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced.
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes _____.
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes _____.
Which of the following statements about NAD+ is true?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
The oxygen consumed during cellular respiration is involved directly in which process or event?
accepting electrons at the end of the electron transport chain
Carbohydrates and fats are considered high-energy foods because they _____.
have a lot of electrons associated with hydrogen.
A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?
Catabolic processes are activated that generate more ATP.
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mol and the free
energy for the reduction of NAD+ to NADH is +53 kcal/mol. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?
Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.
Starting with one molecule of glucose, the energy-containing products of glycolysis are _____.
2 NADH, 2 pyruvate, and 2 ATP
In glycolysis, for each molecule of glucose oxidized to pyruvate _____.
two molecules of ATP are used and four molecules of ATP are produced.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
Most of the CO2 from the catabolism of glucose is released during _____.
the citric acid cycle
Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with
some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of _____.
Which electron carrier(s) function in the citric acid cycle?
NADH and FADH2
If you were to add one of the eight citric acid cycle intermediates to the culture medium of yeast growing in the laboratory, what do you think would happen to the rates of ATP and carbon dioxide production?
The rates of ATP production and carbon dioxide production would both increase.
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?
oxidation of pyruvate to acetyl CoA and the citric acid cycle
If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle?
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