82 terms

Bio 203 MT3

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
cellular respiration
Which of these is exhibiting kinetic energy?
a space station orbiting Earth
"Conservation of energy" refers to the fact that _____.
energy cannot be created or destroyed but can be converted from one form to another
Chemical energy is a form of _____ energy.
The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of _____.
a catabolic pathway
Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy?
the covalent bonds of a sugar molecule: potential energy
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
Which of the following is (are) true for anabolic pathways?
They 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
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.
Whenever energy is transformed, there is always an increase in the
entropy of the universe
Which of the following statements is representative of the second law of thermodynamics?
Cells require a continuous input of energy to maintain their high level of organization.
Which of the following is an example of potential rather than kinetic energy?
a molecule of glucose
Which of the following statements about equilibrium of chemical reactions is correct?
A reaction that is at equilibrium is not capable of doing any work.
The mathematical expression for the change in free energy of a system is ΔG =ΔH - TΔS. Which of the following is (are) correct?
ΔG is the change in free energy.
A system at chemical equilibrium
can do no work
A chemical reaction that has a positive ΔG is best described as
For the hydrolysis of ATP to ADP + i, the free energy change is -7.3 kcal/mol under standard conditions (1 M concentration of both reactants and products). In the cellular environment, however, the free energy change is about -13 kcal/mol. What can we conclude about the free energy change for the formation of ATP from ADP and i under cellular conditions?
it is about +13 kcal/mol
The reaction A --> B + C + heat is released in a(n) _____ reaction.
A(n) _____ reaction occurs spontaneously.
Which of these reactions requires a net input of energy from its surroundings?
In cells, what is usually the immediate source of energy for an endergonic reaction?
The reaction ADP + P --> ATP is a(n) _____ reaction.
The energy for an endergonic reaction comes from a(n) _____ reaction.
Select the INCORRECT association.
What is energy coupling?
the use of energy released from an exergonic reaction to drive an endergonic reaction
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?
gamma-phosphate (the terminal phosphate)
A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they don't 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.
is a molecule that acts as an intermediary to store energy for cellular work.
In general, enzymes are what kinds of molecules?
Enzymes work by _____.
reducing EA
An enzyme _____.
is an organic catalyst
What name is given to the reactants in an enzymatically catalyzed reaction?
As a result of its involvement in a reaction, an enzyme _____.
is unchanged
Enzymes are described as catalysts, which means that they _____.
increase the rate of a reaction without being consumed by the reaction
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes?
The active site can provide heat from the environment that raises the energy content of the substrate.
The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation?
The compound is a competitive inhibitor.
Which of the following statements is true about enzyme-catalyzed reactions?
The reaction is faster than the same reaction in the absence of the enzyme.
A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because
the activation energy barrier for this reaction cannot easily be surmounted at room temperature.
Which of the following statements regarding enzymes is true?
Enzymes increase the rate of a reaction by lowering the activation energy barrier.
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?
-20 kcal/mol
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(n)
cofactor necessary for enzyme activity
How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
by changing the shape of the enzyme's active site
For the enzyme-catalyzed reaction shown in the figure, which of these treatments will cause the greatest increase in the rate of the reaction, if the initial reactant concentration is 1.0 micromolar?
doubling the enzyme concentration
Most enzyme molecules...
are occupied by substrate at high reactant concentrations.
Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid.

What is malonic acid's role with respect to succinate dehydrogenase?
it is a competitive inhibitor
Consider a situation in which the enzyme is operating at optimum temperature and , and has been saturated with substrate. What is your best option for increasing the rate of the reaction?
Increase the enzyme concentration.
A(n) _____ inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate.
A(n) _____ inhibitor binds to a site on the enzyme that is not the active site.
Usually, a(n) _____ inhibitor forms a covalent bond with an amino acid side group within the active site, which prevents the substrate from entering the active site or prevents catalytic activity.
The competitive inhibitor competes with the substrate for the _____ on the enzyme
active site
When the noncompetitive inhibitor is bonded to the enzyme, the shape of the _____ is distorted.
Enzyme inhibitors disrupt normal interactions between an enzyme and its _____.
You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely.
The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.
You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down.
What can you do to speed the reaction up again?
Add more substrate; it will outcompete the inhibitor and increase the reaction rate.
Which of the following statements about feedback regulation of a metabolic pathway is correct?
The final product of a metabolic pathway is usually the compound that regulates the pathway.
Which of the following statements describes enzyme cooperativity?
A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits.
A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.

With respect to the enzyme that converts X to Y, substance A functions as
an allosteric inhibitor
The permeability of a biological membrane to a specific polar solute may depend on which of the following?
the types of transport proteins in the membrane
What kinds of molecules pass through a cell membrane most easily
small and hydrophobic
Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
It exhibits a specificity for a particular type of molecule.
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
Which of the following statements is correct about diffusion?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
The movement of the hydrophobic gas, nitrous oxide () (laughing gas) into a cell is an example of
diffusion across the lipid bilayer
In facilitated diffusion, what is the role of the transport protein?
Transport proteins provide a hydrophilic route for the solute to cross the membrane.
Mammalian blood contains the equivalent of 0.15 M NaCl . Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?
Water will leave the cells, causing them to shrivel and collapse.
Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?
The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.
When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?
The cell will become turgid.
A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water-equal to the volume of blood lost-is transferred directly into one of his veins. What will be the most probable result of this transfusion?
The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.
You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?
similarity of the drug molecule to other molecules transported by the target cells
What distinguishes facilitated diffusion from simple diffusion?
Membrane proteins help move molecules across the membrane.
Which of the following transporters does not use passive transport to move molecules across a membrane?
Sodium-potassium pump
True or false? Active transport differs from passive transport in that active transport does not require an input of energy.
Which membrane protein would be used to move glucose across a membrane from a region of higher concentration to a region of lower concentration?
Lactose transport by membrane proteins occurs under conditions in which the concentration of lactose inside the cell is higher than the concentration outside the cell. What type of transport is used to move lactose into the cell?
active transport
The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following?
cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis
Active and passive transport of solutes across a membrane typically differ in which of the following ways?
Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy.
What is the voltage across a membrane called?
membrane potential
The sodium-potassium pump is called an electrogenic pump because it
contributes to the membrane potential.
Ions diffuse across membranes through specific ion channels
down their electrochemical gradients
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in