Biology Chapter5 Thinking Critically
Maria shakes the oil and vinegar dressing vigorously before pouring it on her salad. You, a student of biology, look at her salad and exclaim, SHOW HINT "Oh, look at all the little cells!" "Oh, look at all the little molecules!" "Oh, look at all those air bubbles!" "Oh, I love salads, too!"
"Oh, look at all the little cells!"
The process of a white blood cell engulfing a bacterium is osmosis .phagocytosis. receptor-mediated endocytosis. exocytosis.
.phagocytosis.
Most of our enzymes function best at a temperature of __________ and a pH of __________. What is the effect of higher temperatures on enzymes? SHOW HINT 35-40ºC; 6-8; speeding up their activity 35-40ºC; 2; denaturation 35-40ºF; 6-8; denaturation 35-40ºC; 6-8; denaturation
35-40ºC; 6-8; speeding up their activity
You're on a reality show called "The Transport Factor." The host hands you three different amino acids, four different sugars, and three oxygen molecules." Your question: "How many different transport proteins does the cell need to move this stuff across the plasma membrane using facilitated diffusion?" Quickly, you correctly respond: __________. SHOW HINT 1 3 7 10
7
What is meant by the term "enzyme specificity"? ANSWER An enzyme catalyzes only one type of reaction. An enzyme is present in only one cell type. An enzyme is specific for one temperature and pH range. An enzyme has only one active site. An enzyme is "used" only once.
An enzyme catalyzes only one type of reaction.
________ energy is the type of ________ energy used to power the work of the cell. ANSWER Chemical: potential Chemical: kinetic Heat: kinetic Thermal: kinetic Thermal: potential
Chemical: potential
Which of the following is a CORRECT statement about aquaporins? ANSWER Each aquaporin molecule allows billions of molecules of water to cross the plasma membrane each second. Each aquaporin molecule allows thousands of molecules of water to cross the plasma membrane each day. When injected into frog eggs in a hypotonic solution, aquaporin messenger RNA (mRNA) slows the rate of osmosis People whose kidney cells have too many aquaporin proteins have to urinate very often. Aquaporin proteins have been identified in animal cells, but not in plants or bacteria.
Each aquaporin molecule allows billions of molecules of water to cross the plasma membrane each second.
The pesticide malathion and some drugs used as anesthetics both block an enzyme that is critical for transmitting nerve impulses. Why don't patients die like insects when they undergo surgery? ANSWER Enzyme inhibition with malathion is irreversible but with anesthetics, reversible. Enzyme inhibition with malathion is reversible but with anesthetics, irreversible. The dose of enzyme inhibitor in malathion is much greater than in anesthetics. Insects are exposed to the enzyme for a long time, but most operations using these drugs are fairly brief. Enzyme inhibition with both drugs is irreversible but with anesthetics, "rescue" drugs are available.
Enzyme inhibition with malathion is irreversible but with anesthetics, reversible.
Imagine a U-shaped tube with a membrane at the bottom of the "U". The membrane is permeable to glucose, sucrose and water. You place a concentrated glucose solution on Side A and an equally concentrated sucrose solution on Side B. Describe the movement of each solute across the membrane during the first few hours. ANSWER Glucose will move into Side B down its concentration gradient, and sucrose will move into Side A down its concentration gradient. Glucose will move into Side B down its concentration gradient, and sucrose will remain on Side B until the movement of glucose has stopped. Sucrose will move into Side A down its concentration gradient, and glucose will remain on Side A until the movement of sucrose has stopped. "Free" water will move between Sides A and B through osmosis. Neither substance will cross the membrane because the concentrations on Sides A and B are the same.
Glucose will move into Side B down its concentration gradient, and sucrose will move into Side A down its concentration gradient.
What is one way of reducing the effectiveness of a competitive enzyme inhibitor? ANSWER Increase the concentration of the substrate. Increase the concentration of the enzyme. Increase the concentration of the competitive inhibitor. Decrease the concentration of the substrate. Decrease the concentration of the enzyme.
Increase the concentration of the substrate.
In an imaginary world where all things are possible, how could you increase the amount of energy that is stored in a molecule of ATP? SHOW HINT Increase the negative charge of each phosphate group. Alter the first and third phosphate groups to make them positive. Convert the middle phosphate group from a negative to a positive charge. Convert the negative charge of the phosphate groups to a positive charge
Increase the negative charge of each phosphate group
One model of the cell membrane is that it is a "fluid mosaic." What does this mean? ANSWER It consists of proteins suspended in a fluid phospholipid bilayer. It consists of phospholipids suspended in a bilayer of of proteins. It consists of ions and carbohydrates suspended in a bilayer of of proteins. It consists of small, nonpolar molecules suspended in a flud phospholipid bilayer. It consists of nucleotides, proteins and ions suspended in a flud phospholipid bilayer.
It consists of proteins suspended in a fluid phospholipid bilayer.
Selective permeability of the cell membrane results in which of the following? SHOW HINT Only certain substances can enter or leave the cell. Only substances that use transport proteins may cross. Beneficial substances are allowed into the cell. Harmful substances are kept out of the cell.
Only certain substances can enter or leave the cell
In what way, if any, does osmosis differ from simple diffusion? ANSWER Polar water molecules cluster with hydrophilic molecules, so only free water diffuses down its concentration gradient. Polar water molecules avoid hydrophilic molecules, so only free water diffuses down its concentration gradient. Nonpolar water molecules cluster with hydrophilic molecules, so only free water diffuses down its concentration gradient. Polar water molecules cluster with hydrophilic molecules, and these are the only water molecules that cross the membrane. They are the same process: "osmosis" is used to distinguish the movement of water from that of other molecules.
Polar water molecules cluster with hydrophilic molecules, so only free water diffuses down its concentration gradient.
When you hear "Substance X is moved against its concentration gradient," what do you think of? ANSWER Substance X has moved from a region of lower to a region of higher concentration with the help of ATP. Substance X has moved from a region of higher to a region of lower concentration with the help of ATP. Substance X has moved from a region of lower to a region of higher concentration with the help of a transport protein. Substance X has moved from a region of higher to a region of lower concentration with the help of a transport protein. Substance X has moved from a region of higher to a region of lower concentration with the help of its concentration gradient.
Substance X has moved from a region of lower to a region of higher concentration with the help of ATP.
Imagine a metabolic pathway where: Molecule A → Molecule B → Molecule C → Molecule D → Product X. Enzyme 1 catalyzes the first reaction (Molecule A → Molecule B), Enzyme 2 catalyzes the second reaction (Molecule B → Molecule C), and so on. Product X exerts feedback inhibition on Enzyme 2. What is the consequence of this inhibition as Product X accumulates? ANSWER The concentration of Molecule B increases. The concentration of Molecule B decreases. The concentration of Molecule A increases. Molecule B is eliminated. The concentration of Molecule C increases.
The concentration of Molecule B increases.
Imagine a metabolic pathway where Product D, a hormone, is the result of three chemical reactions: Molecule A →Molecule B →Molecule C →Product D. Enzymes A, B, and C, respectively, catalyze the three reactions. The pathway is controlled by feedback inhibition of Product D on Enzyme A. What will happen if very high concentrations of Product D are produced? SHOW HINT The concentration of Molecule B will increase. The concentrations of Molecule A will fall. The concentration of Molecule A will rise. The concentrations of Molecule B will fall.
The concentrations of Molecule B will fall.
Two glucose solutions, A and B, are separated by a membrane that is permeable to water but impermeable to glucose. The glucose concentration in Solution A is much lower than in Solution B. Over time, which of the following occurs? SHOW HINT The concentrations of glucose in both solutions will become more equal. The concentration of glucose in solution A does not change. The concentration of glucose in Solution B will become higher. The concentration of water in solution B becomes lower.
The concentrations of glucose in both solutions will become more equal.
Which of the following is the best description of energy coupling in living things? SHOW HINT The energy released from endergonic reactions is used to drive exergonic reactions. An exergonic reaction releases energy, while an endergonic reaction does not. An endergonic reaction consumes energy, while an endergonic reaction does not. The energy released from exergonic reactions is used to drive endergonic reactions.
The energy released from exergonic reactions is used to drive endergonic reactions
Which of the following must be true before a small, nonpolar substance can diffuse across a membrane? SHOW HINT The membrane must contain the appropriate transport proteins. The membrane must be permeable to the substance. The membrane must be permeable to water. There must be equal concentrations of the substance on both sides of the membrane.
The membrane must be permeable to the substance.
What would happen if a careless health-care worker gave a patient a hypertonic intravenous solution? SHOW HINT The patient's cells would first shrivel, and then burst. The patient's cells would burst. The patient's cells would not change. The patient's cells would shrink.
The patient's cells would shrink.
Researchers used frog eggs to learn more about aquaporins. What characteristic of normal frog eggs was essential in these studies? ANSWER They are largely impermeable to water. They are highly permeable to water. They are surrounded by a hypertonic solution. They contain high levels of aquaporins. They can translate mRNA into protein.
They are largely impermeable to water.
Which of the following statements about coenzymes is correct? ANSWER They are organic cofactors with enzymes in reactions. They are organic and inorganic cofactors with enzymes in reactions. They speed up reactions faster than enzymes. They are specific for a particular enzyme. They are inorganic cofactors with enzymes in reactions.
They are organic cofactors with enzymes in reactions.
What happens to people with defective aquaporins? SHOW HINT They cannot reabsorb water, and they urinate very often. They cannot reabsorb water, and they urinate rarely. They reabsorb too much water, and they urinate rarely. They reabsorb too much water, and they urinate very often.
They cannot reabsorb water, and they urinate very often.
In what sense are living cells more efficient than internal combustion engines? ANSWER They convert a greater proportion of fuel to useful energy. They convert a smaller proportion of fuel to useful energy. They use less fuel overall. They create more entropy. They are much smaller.
They convert a greater proportion of fuel to useful energy.
What is one reason that penicillin, an enzyme inhibitor, is not used to treat viral infections such as HIV? SHOW HINT Penicillin makes it impossible for enzymes to function. Many people are allergic to penicillin. Penicillin is specific for one bacterial enzyme. Penicillin and other antibiotics enhance viral function.
They make it impossible for the substrate to bind to the active site.
A plant cell placed into an isotonic solution _______. An animal cell placed into an isotonic solution _______. ANSWER becomes flaccid: neither swells nor shrivels neither swells nor shrivels: neither swells nor shrivels remains turgid: shrivels becomes flaccid: shrivels remains turgid: bursts
becomes flaccid: neither swells nor shrivels
A plant cell in a hypotonic solution bursts because of an inflow of water. shrivels because of an outflow of water. wilts because of an outflow of water. becomes turgid because of an inflow of water.
becomes turgid because of an inflow of water.
A transport protein that provides a passageway across a membrane is a (an) __________. A transport protein that binds, then releases, its passenger is a (an) __________. SHOW HINT aquaporin; channel channel; carrier carrier; channel aquaporin; carrier
channel; carrier
Receptor-mediated endocytosis relies on which of the following? SHOW HINT insulin coated pits vacuoles the Golgi apparatus
coated pits
Before refrigeration, meat was preserved by adding ________. What effect did this have on any contaminating bacteria or fungi? ANSWER concentrated salt solutions: plasmolysis dilute salt solutions: swelling and bursting concentrated salt solutions: swelling and bursting concentrated sugar solutions: plasmolysis dilute sugar solutions: swelling and bursting
concentrated salt solutions: plasmolysis
Building a molecule of ATP is an ________process. Hydrolyzing a molecule of ATP is an _______ process. This cycle is an example of _________. ANSWER endergonic: exergonic: energy coupling exergonic: endergonic: energy coupling exergonic: exergonic: metabolism endergonic: endergonic: energy coupling endergonic: exergonic: metabolism
endergonic: exergonic: energy coupling
Photosynthesis is an _______ process. Energy from ______ allows the production of products with ________. ANSWER endergonic: the sun: higher potential energy than the reactants endergonic: the sun: lower potential energy than the reactants exergonic: the sun: higher potential energy than the reactants exergonic: metabolism: lower potential energy than the reactants endergonic: mitochondria: about the same potential energy as the reactants
endergonic: the sun: higher potential energy than the reactants
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 feedback inhibition. noncompetitive inhibition .irreversible inhibition .competitive inhibition.
feedback inhibition.
At what stage of active transport is ATP needed? ANSWER for the transport protein to change its shape attachment of the solute to its transport protein release of the solute from its transport protein return of the transport protein to its original shape in all the listed steps
for the transport protein to change its shape
What is the function of junction proteins? SHOW HINT transport substances across the membrane form channels between adjacent cells support the membrane relay messages across the membrane
form channels between adjacent cells
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. hypotonic isotonic hypertonic
hypotonic
When you water a plant, you are giving it a(an) __________ solution. What effect does this have on the plant? SHOW HINT hypotonic; It remains standing upright. hypotonic; The plant wilts. hypertonic; The plant plasmolyzes. isotonic; It remains standing upright
hypotonic; It remains standing upright.
New drugs are being developed to lower levels of circulating cholesterol. A successful drug would be one that __________. SHOW HINT blocks the synthesis of LDL receptors increases exocytosis in cells that line blood vessels increases the rate of LDL receptor-mediated endocytosis reduces the rate of LDL receptor-mediated endocytosis
increases the rate of LDL receptor-mediated endocytosis
Why are a cell's high-energy complex molecules (DNA, proteins, carbohydrates, lipids) so stable? SHOW HINT The activation energy required to break them down spontaneously is too high. The activation energy required to break them down spontaneously is too low. No enzymes exist to facilitate the hydrolysis of these molecules. The bonds within these molecules are hard to break.
induced fit; catalysis
Light and thermal energy are types of __________ energy. __________ energy is the potential energy that may be released in a chemical reaction. SHOW HINT potential; kinetic kinetic; chemical heat; chemical heat; light
kinetic; chemical
Enzymes ______ the activation energy of a reaction. The energy change between products and reactants is _______ for a reaction that is catalyzed versus one that is not. ANSWER lower: the same lower: greater raise: greater raise: the same lower: less
lower: the same
Which of the following does active transport allow a cell to do, that diffusion does not allow? SHOW HINT maintain the same internal and external concentrations of substances maintain higher concentrations of most substances inside cells maintain different internal and external concentrations of substances move small nonpolar molecules into or out of the cell
maintain different internal and external concentrations of substances
Which of the following prevents the cells of a freshwater fish from becoming hypotonic and bursting? ANSWER osmoregulation osmosis tonicity aquaporins passive diffusion
osmoregulation
Both a living cell and an automobile convert fuel and ______ to the waste products ___________. In the process, ______ is produced, which represents the entropy of the reaction. ANSWER oxygen: CO2 and water: heat oxygen: CO2 and water: energy CO2: oxygen and water: heat oxygen: energy and water: CO2 energy: CO2 and oxygen: heat
oxygen: CO2 and water: heat
Many people take the drug ibuprofen to reduce pain and inflammation. Ibuprofen reduces the concentration of __________ in the body. It works as a (an) __________. SHOW HINT bacteria; antibiotic bacteria; enzyme inhibitor prostaglandins; enzyme inhibitor prostaglandins; competitive inhibitor
prostaglandins; enzyme inhibitor
What is the function of the sodium-potassium pump in nerve cells? ANSWER pump Na+ out of the cell and K+ into the cell pump K+ out of the cell and Na+ into the cell pump Na+ and CO2 out of the cell and K+ into the cell pump K+ and CO2 out of the cell and Na+ into the cell pump K+ and CO2 out of the cell and Na+ and O2 into the cell
pump Na+ out of the cell and K+ into the cell
Researchers used frog eggs in the initial studies of aquaporin. These eggs are usually impermeable to water. What process did they observe in eggs that had been treated with aquaporin mRNA, but not in control eggs, when placed in a hypotonic solution? SHOW HINT rapid rupture longer survival slow swelling shrinkage and shriveling
rapid rupture
Which method of transport uses coated pits? ANSWER receptor-mediated endocytosis vacuole-mediated endocytosis phagocytosis facilitated diffusion exocytosis
receptor-mediated endocytosis
Cells acquire low-density lipoproteins (LDLs) by diffusion. phagocytosis. receptor-mediated endocytosis. exocytosis.
receptor-mediated endocytosis.
Endergonic reactions _______ energy and result in products that have _____ potential energy than the reactants. ANSWER require: higher require: lower release: higher release: lower release: variable levels of
require: higher
Anything that prevents ATP formation will most likely force the cell to rely on lipids for energy. force the cell to rely on ADP for energy .have no effect on the cell. result in cell death.
result in cell death.
Which is the most inclusive and correct list of substances that use facilitated diffusion to cross cell membranes? ANSWER sugars, amino acids, ions, water sugars, amino acids, ions amno acids, ions, water, nonpolar molecules sugars, amino acids, ions, water, oxygen sugars, ions, water, some proteins
sugars, amino acids, ions, water
Let's compare your favorite car and your favorite cell, perhaps a liver cell. Which is more efficient at generating energy for work? What form does the energy take that is not used for work? SHOW HINT the cell; as heat the car; as light the car; as heat the cell; as light
the cell; as heat
What determines the direction of diffusion of a small, nonpolar molecule, such as oxygen, across a membrane? SHOW HINT the size of the oxygen molecules the availability of a transport protein the oxygen concentration gradient the amount of energy available to transport oxygen
the oxygen concentration gradient
