Bio Exam 2
A cell that has neither a net gain of water nor net loss of water when it is immersed in a solution must be A) isotonic to its environment. B) hypotonic to its environment. C) hypertonic to its environment. D) metabolically inactive.
A)
Which of the following statements regarding thermodynamics is false? A) An automobile engine is a closed system because it does not exchange energy and matter with its surroundings. B) Thermodynamics is the study of energy transformations that occur in a collection of matter. C) An open system exchanges both energy and matter with its surroundings. D) A single cell or the planet Earth could be a thermodynamic system.
A) An automobile engine is a closed system because it does not exchange energy and matter with its surroundings.
What is the basic difference between exergonic and endergonic reactions? A) Exergonic reactions release energy; endergonic reactions absorb it. B) In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true. C) Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds. D) Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds.
A) Exergonic reactions release energy; endergonic reactions absorb it.
Which of the following is a typical feature of an ATP-driven active transport mechanism? A) The solute moves against the concentration gradient. B) The transport protein catalyzes the conversion of ADP to ATP. C) The transport protein must cross to the correct side of the membrane before the solute can bind to it. D) The transport protein is irreversibly phosphorylated as transport takes place.
A) The solute moves against the concentration gradient.
After the reverse osmosis system has been operating for 30 minutes, the solution in tank A would A) be hypertonic to tank B. B) move by passive transport to tank B. C) be isotonic to tank B. D) be hypotonic to tank B.
A) be hypertonic to tank B.
Heating inactivates enzymes by A) changing the enzyme's three-dimensional shape. B) removing phosphate groups from the enzyme. C) breaking the covalent bonds that hold the molecule together. D) causing enzyme molecules to stick together.
A) changing the enzyme's three-dimensional shape.
Inhibition of an enzyme is irreversible when A) covalent bonds form between inhibitor and enzyme. B) a noncompetitive inhibitor is involved. C) the shape of the enzyme is changed. D) a competitive inhibitor is involved.
A) covalent bonds form between inhibitor and enzyme.
Most of a cell's enzymes are A) proteins. B) lipids. C) amino acids. D) carbohydrates.
A) proteins.
Cells acquire low-density lipoproteins (LDLs) by A) receptor-mediated endocytosis. B) diffusion. C) pinocytosis. D) phagocytosis.
A) receptor-mediated endocytosis.
The active site of an enzyme is A) the region of an enzyme that attaches to a substrate. B) the region of a substrate that is changed by an enzyme. C) the region of a product that detaches from the enzyme. D) the highly changeable portion of an enzyme that adapts to fit the substrates of various reactions.
A) the region of an enzyme that attaches to a substrate.
If placed in tap water, an animal cell will undergo lysis, whereas a plant cell will not. What accounts for this difference? A) the relative inelasticity and strength of the plant cell wall B) the expulsion of water by the plant cell's central vacuole C) the fact that plant cells are isotonic to tap water D) the relative impermeability of the plant cell wall to water
A) the relative inelasticity and strength of the plant cell wall
A steer must eat at least 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates A) the second law of thermodynamics. B) the first law of thermodynamics. C) that some energy is destroyed in every energy conversion. D) that energy transformations are typically 100% efficient.
A) the second law of thermodynamics.
Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment A) is isotonic to the protozoan. B) is hypotonic to the protozoan. C) is hypertonic to the protozoan. D) contains a higher concentration of solutes than the protozoan.
B)
White blood cells (WBCs) are more resistant to lysis than red blood cells (RBCs). When looking at a sample of blood for WBCs, what could you do to reduce interference from RBCs? A) Mix the blood in a hypertonic solution, which will cause the RBCs to lyse. B) Mix the blood in a hypotonic solution, which will cause the RBCs to lyse. C) Mix the blood in an isotonic solution and allow the WBCs to float to the top. D) Mix the blood in a salty solution to cause the RBCs to lyse.
B) Mix the blood in a hypotonic solution, which will cause the RBCs to lyse.
A man with a dirty cut on his hand appears at the emergency department for treatment. In to clean the wound, the health-care provider should A) distilled water. B) a weak (low concentration) solution of salt water. C) a solution of very low pH to help kill any bacteria present. D) a solution of sterilized tap water.
B) a weak (low concentration) solution of salt water.
Which of the following substances could be a cofactor? A) a protein B) a zinc atom C) a polypeptide D) a ribosome
B) a zinc atom
Aquaporins A) allow water to cross the plasma membrane against its concentration gradient. B) allow water to cross the plasma membrane via facilitated diffusion. C) are found in all cells. D) allow for the active transport of water.
B) allow water to cross the plasma membrane via facilitated diffusion.
A plant cell in a hypotonic solution A) shrivels because of an outflow of water. B) becomes turgid because of an inflow of water. C) bursts because of an inflow of water. D) wilts because of an outflow of water.
B) becomes turgid because of an inflow of water.
In the lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. The solution in the balloon is ________ relative to the solution in the beaker. A) isotonic B) hypotonic C) hydrophilic D) hypertonic
B) hypotonic
Kinetic energy differs from chemical energy in that A) kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat. B) kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules. C) chemical energy is a particular form of kinetic energy. D) kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement
B) kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules.
The process of a white blood cell engulfing a bacterium is A) osmosis. B) phagocytosis. C) pinocytosis. D) receptor-mediated endocytosis.
B) phagocytosis.
The transfer of a phosphate group to a molecule or compound is called A) hydrogenation. B) phosphorylation. C) ionization. D) carboxylation.
B) phosphorylation.
In the reaction A → B + C + heat, A) there is a net input of energy. B) the potential energy of the products is less than that of the reactant. C) entropy has decreased. D) the potential energy of the products is greater than that of the reactant.
B) the potential energy of the products is less than that of the reactant.
Which of the following processes is endergonic? A) cellular respiration B) the synthesis of glucose from carbon dioxide and water C) the breakdown of glucose D) the burning of wood
B) the synthesis of glucose from carbon dioxide and water
Which of the following statements regarding active transport is false? _ A) Active transport requires the cell to expend energy. B) Active transport uses ATP as an energy source. C) Active transport is driven by the concentration gradient. D) Active transport can move a solute against its concentration gradient.
C) Active transport is driven by the concentration gradient.
How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a noncompetitive inhibitor? A) Competitive inhibitors change the enzyme's tertiary structure; noncompetitive inhibitors cause polypeptide subunits to dissociate. B) Competitive inhibitors interfere with the enzyme; noncompetitive inhibitors interfere with the reactants. C) Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site. D) Competitive inhibitors bind to the enzyme reversibly; noncompetitive inhibitors bind to it irreversibly.
C) Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site.
A group of single cell organisms collected from the ocean was brought into the lab for examination. The lab assistant was concerned that the water had become full of toxic waste products and so added clean water to the culture. All of the organisms died, and when she looked at them under the microscope, all she could see were bits and pieces of them scattered throughout the water. What likely happened? A) She added sea water to which she had added too much salt, and they ruptured. B) She added too little salt to the sea water she added, and the organisms all lost too much water and shriveled up. C) She added water that was hypotonic to the culture of organisms, and they ruptured. D) She added water isotonic to the organisms, causing too much water to move in and out of the organism, and they ruptured.
C) She added water that was hypotonic to the culture of organisms, and they ruptured.
The energy required to initiate an exergonic reaction is called A) exergonic energy. B) endergonic energy. C) activation energy. D) input energy.
C) activation energy.
Living systems A) are examples of a closed system. B) violate the second law of thermodynamics. C) decrease their entropy while increasing the entropy of the universe. D) violate the first law of thermodynamics.
C) decrease their entropy while increasing the entropy of the universe.
Which of the following direct energy transfers is impossible in living systems? A) chemical energy to kinetic energy B) light energy to potential energy C) heat to light energy D) light energy to chemical energy
C) heat to light energy
In a hypotonic solution, an animal cell will A) neither gain nor lose water. B) experience turgor. C) lyse. D) shrivel.
C) lyse.
According to ________, energy cannot be created or destroyed. A) the second law of thermodynamics B) the third law of thermodynamics C) the first law of thermodynamics D) Aristotle's first principle
C) the first law of thermodynamics
Facilitated diffusion across a biological membrane requires ________ and moves a substance ________ its concentration gradient. A) energy and transport proteins; against B) energy and transport proteins; down C) transport proteins; down D) transport proteins; against
C) transport proteins; down
Which of the following is a coenzyme? A) iodine B) zinc C) vitamin B6 D) iron
C) vitamin B6
In the lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur? A) Water will enter the balloon. B) Sucrose will leave the balloon. C) Sucrose will enter the balloon. D) Water will leave the balloon.
D)
When two aqueous solutions that differ in solute concentration are placed on either side of a semipermeable membrane and osmosis is allowed to take place, the water will _____ A) exhibit a net movement to the side with lower solute concentration. B) exhibit a net movement to the side with higher free water concentration. C) exhibit an equal movement in both directions across the membrane. D) exhibit a net movement to the side with lower free water concentration.
D)
Which of the following statements regarding enzyme function is false? A) Enzymes emerge unchanged from the reactions they catalyze. B) An enzyme's function depends on its three-dimensional shape. C) Enzymes are very specific for certain substrates. D) Enzymes are used up when they catalyze a chemical reaction so must be synthesized for each new chemical reaction.
D) Enzymes are used up when they catalyze a chemical reaction so must be synthesized for each new chemical reaction.
Which of the following statements regarding enzymes is true? A) All enzymes depend on protein cofactors to function. B) An enzyme's function is unaffected by changes in pH. C) Enzymes are inorganic. D) Enzymes catalyze specific reactions.
D) Enzymes catalyze specific reactions.
Which of the following statements about the ATP molecule is true? A) Extremely stable bonds link the second and third phosphate groups. B) It contains the sugar glucose. C) It contains five phosphate groups. D) It releases energy when one phosphate group leaves ATP.
D) It releases energy when one phosphate group leaves ATP.
Which of the following statements is true for all types of passive transport? A) Proteins are needed to transport molecules across the membrane. B) Ions never cross the plasma membrane by passive transport. C) Only small polar molecules are able to cross the plasma membrane. D) The concentration gradient is the driving force.
D) The concentration gradient is the driving force.
Substrates bind to an enzyme's ________ site. A) inhibitory B) allosteric C) phosphate D) active
D) active
Which of the following processes can move a solute against its concentration gradient? A) osmosis B) facilitated diffusion C) passive transport D) active transport
D) active transport
Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing A) chemical energy into potential energy. B) kinetic energy into thermal energy. C) kinetic energy into potential energy. D) chemical energy into kinetic energy.
D) chemical energy into kinetic energy.
Phagocytosis is to eating as pinocytosis is to A) osmosis. B) chewing. C) lysis. D) drinking.
D) drinking.
ATP can be used as the cell's energy exchange mechanism because A) ATP is a disposable form of chemical energy, used once and then discarded by the cell. B) ATP is the most energy-rich small molecule in the cell. C) endergonic reactions can be fueled by coupling them with the formation of ATP from ADP. D) endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP.
D) endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP.
When a cell uses chemical energy to perform work, it uses the energy released from a/an ________ reaction to drive a/an ________ reaction. A) spontaneous; exergonic B) exergonic; spontaneous C) endergonic; exergonic D) exergonic; endergonic
D) exergonic; endergonic
Certain cells that line the stomach synthesize a digestive enzyme and secrete it into the stomach. This enzyme is a protein. Which of the following processes could be responsible for its secretion? A) pinocytosis B) diffusion C) endocytosis D) exocytosis
D) exocytosis
Bacterial production of the enzymes needed for the synthesis of the amino acid tryptophan declines with increasing levels of tryptophan and increases as tryptophan levels decline. This is an example of A) irreversible inhibition. B) competitive inhibition. C) noncompetitive inhibition. D) feedback inhibition.
D) feedback inhibition.
When an enzyme catalyzes a reaction, A) it acts as a reactant. B) it is used once and discarded. C) it raises the activation energy of the reaction. D) it lowers the activation energy of the reaction.
D) it lowers the activation energy of the reaction.
An energy barrier A) is the amount of energy that must be produced by the reactants to end a chemical reaction. B) can only be overcome with the use of enzymes. C) is higher than the activation energy of a reaction. D) prevents the spontaneous breakdown of molecules in the cell.
D) prevents the spontaneous breakdown of molecules in the cell.
Which of the following processes is classified as a metabolic pathway? A) passive diffusion B) osmosis C) cell lysis D) protein synthesis
D) protein synthesis
The molecules responsible for membrane transport are A) carbohydrates. B) steroids. C) phospholipids. D) proteins.
D) proteins.
Anything that prevents ATP formation will most likely A) force the cell to rely on lipids for energy. B) force the cell to rely on ADP for energy. C) have no effect on the cell. D) result in cell death.
D) result in cell death.
If you shut off the system and pressure was no longer applied to tank A, you would expect A) the water to flow in equal amounts in both directions. B) the water to flow from tank A to tank B. C) the water to flow against the concentration gradient. D) the water to reverse flow from tank B to tank A.
D) the water to reverse flow from tank B to tank A.
You are adrift in the Atlantic Ocean and, being thirsty, drink the surrounding seawater. As a result, A) you quench your thirst. B) your cells become turgid. C) your cells lyse from excessive water intake. D) you dehydrate yourself.
D) you dehydrate yourself.
A child is brought to the hospital with a fever of 107°F. Doctors immediately order an ice bath to lower the child's temperature. Which of the following statements offers the most logical explanation for this action? A) Elevated body temperatures cause molecules to vibrate more quickly and prevent enzymes from easily attaching to reactants. This would slow vital body reactions. B) Elevated body temperature will increase reaction rates in the child's cells and overload the limited number of enzymes found in the cell. C) Elevated body temperatures will increase the energy of activation needed to start various chemical reactions in the body. This will interfere with the ability of enzymes to catalyze vital chemical reactions. D) Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.
Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.
