mastering biology ch 5
Which of the following is an accurate comparison of active transport and facilitated diffusion? Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient. In both types of movement, phosphate groups alter the shape of transport proteins. Facilitated diffusion requires the use of ATP; active transport does not require ATP. Active transport requires membrane proteins; facilitated diffusion does not require membrane proteins.
Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient.
Which statement regarding enzyme function is true? Enzymes cannot function at a pH lower than 6. Excessive salt ions can cause an enzyme to denature. Higher temperatures allow greater contact between enzymes and substrates; therefore, the higher the temperature the better the enzyme will function. Most coenzymes are inorganic substances such as ions of iron or potassium.
Excessive salt ions can cause an enzyme to denature.
The hydrolysis of DNA into nucleotides constitutes an exergonic reaction. Yet, DNA is quite stable. Why is this the case? The activation energy required to initiate this reaction is seldom reached. DNA synthesis occurs at the same rate as DNA hydrolysis, so DNA only appears stable. No enzymes exist to facilitate DNA hydrolysis. Only endergonic reactions proceed rapidly.
The activation energy required to initiate this reaction is seldom reached.
In a theoretical world where all things are possible, how could you increase the amount of energy that could be stored in a molecule of ATP? a)Increase the negative charge of each phosphate group. b)Alter the first and third groups to make them positive. c)Change the middle phosphate group from a negative to a positive charge. d)Convert the negative charge of the phosphate groups to a positive charge.
a)Increase the negative charge of each phosphate group.
Taq polymerase is an enzyme isolated from the organism Thermus aquaticus. This organism has been found living in the hot springs of Yellowstone National Park. This enzyme is used to copy human DNA from crime scenes. Most reactions are performed at ranges similar to those of the human body; however, what considerations should be made for optimum use of this enzyme? a)The temperature should be raised. b)The enzyme will not work on human DNA. c)Nothing should be altered. d)The pH should be decreased.
a)The temperature should be raised.
In an oil-based, nonpolar environment, phospholipids would arrange themselves so that they __________. a) would not pack together at all b) would stay together but in a reverse orientation, with their tails projecting outward c) would never associate but instead would remain as individual molecules completely dissolved in the oil d) would pack more tightly together than they would in a watery environment
b) would stay together but in a reverse orientation, with their tails projecting outward
New drugs are being developed to lower levels of circulating cholesterol. A successful drug would be one that _____. a)blocks the synthesis of LDL receptors b)increases the rate of LDL receptor-mediated endocytosis c)increases exocytosis in cells that line blood vessels, especially those of the heart d)binds to the LDL receptor and blocks receptor-mediated endocytosis
b)increases the rate of LDL receptor-mediated endocytosis
An enzyme is considered a(n) _______ because it speeds up a chemical reaction without being used up.
catalyst
A(n)________, which is often a vitamin, binds to an enzyme and plays a role in catalysis
coenzyme
A specific ______ speeds up each of a cell's chemical reactions
enzyme
Through energy coupling, cells use___________ , or energy-releasing, reactions to drive _____________ or energy-requiring, reactions. The molecule ______ is the energy shuttle between these two types of reactions.
exergonic, endergonic,ATP
Mechanisms such as ___________________enable precise control over a cell's __________ -- all of its chemical reactions
feedback inhibition, metabolism
There is a net diffusion of water out of an animal cell when it is placed in a(n)___________solution
hypertonic
A plant cell placed in a(n) ___________ ___________will lose water and plasmolyze
hypertonic solution
An animal cell placed in a(n) _________ solution will gain water, swell, and possibly burst.
hypotonic
The________ ______between an active site and its substrate often strains bonds and helps the reaction proceed
induced fit
You're on the pilot episode of a new reality show called "The Transport Factor." The host hands you three different amino acids, four different sugars, and two different ions. Then the host shouts, "How many different proteins does the cell need to move these molecules across the plasma membrane using facilitated transport?" Quickly, you correctly respond: _____. nine five three one
nine
There are three main types of cellular work: chemical, transport, and movement. Most of this work is powered by the transfer of a phosphate group from one molecule to another in a process known as___________________
phosphorylation
In a catalyzed reaction, a reactant is often called a(n) __________ .
substrate
What controls the direction of a molecule, such as oxygen, involved in passive transport? the size of the oxygen molecule the direction of the oxygen concentration gradient the type of cell to or from which the oxygen molecule is moving the amount of energy available to transport oxygen
the direction of the oxygen concentration gradient
Frequently, transplanted organs are rejected by the recipient's body. How is this reaction related to plasma membranes? The phospholipid bilayers become disrupted during transplant and may never re-form, causing the tissues to lose their function. Everyone's organs contain different amounts of cholesterol. The fibers of the extracellular matrix differ from individual to individual. Each person has a unique set of carbohydrate chains attached to his or her plasma membranes.
Each person has a unique set of carbohydrate chains attached to his or her plasma membranes
Kinetic energy is energy in motion. Potential energy is _____ energy. a)stored b)electromagnetic c)heat d)solar
a)stored
An enzyme speeds up reactions by lowering the _______ ________
activation energy
An enzyme is specific because the shape of its _______ ______matches only particular reactants
active site
Utah's Great Salt Lake has an average salinity seven times higher than that of the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____. a)synthesize membranes that are impermeable to substances that upset osmotic balance b)actively pump water back into their cells to counter its loss due to osmosis c)actively pump water back out of their cells to counter its inflow due to osmosis d)actively pump salt back out of their cells to counter its inflow due to osmosis
b)actively pump water back into their cells to counter its loss due to osmosis
In active transport, a)no energy input is required from the cell. b)molecules move across the plasma membrane against their concentration gradient. c)the plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. d)molecules move across the plasma membrane by crossing the lipid bilayer directly, rather than by using a transport protein. e)a vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell.
b)molecules move across the plasma membrane against their concentration gradient.
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via _____. a)osmosis b)active transport c)endocytosis d)passive transport
c)endocytosis
The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of a)exocytosis. b)active transport. c)endocytosis. d)diffusion. e)passive transport.
c)endocytosis.
In cellular respiration, most energy is released and transferred to ATP when _____. a)high-energy C-C and C-H bonds in glucose are broken b)low-energy C-H bonds in glucose are broken c)high-energy electrons "fall" to lower energy levels d)low-energy electrons are "raised" to higher energy levels
c)high-energy electrons "fall" to lower energy levels
A pharmaceutical company wishes to focus on an enzyme to develop new medications. What type of study would be of the greatest benefit? a)Knowing the structure of enzymes may make it possible to design enzymes that raise the activation energy above that of the spontaneous reaction to allow more efficient drug synthesis. b)Studying the structure of an enzyme would help pharmaceutical companies determine the enzyme's substrate. c)Studying the structure would help pharmaceutical companies create enzymes that are not destroyed during reactions. d)Understanding the enzyme's structure would help pharmaceutical companies design molecules that fit to the binding site and alter activity.
d)Understanding the enzyme's structure would help pharmaceutical companies design molecules that fit to the binding site and alter activity.
The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of a)diffusion. b)facilitated diffusion. c)passive transport. d)active transport. e)exocytosis
d)active transport.
The ideal osmotic environment for an animal cell is a(n) ________ environment
isotonic
A plant cell surrounded by a(n)___________ ________will be flaccid (limp).
isotonic solution
Which of the following is highest in chemical energy? one molecule of glucose one molecule of ATP one molecule of H2 one molecule of CO2
one molecule of glucose
Succinylcholine is structurally almost identical to acetylcholine, but if combined with the enzyme that normally hydrolyzes acetylcholine, the enzyme is no longer able to hydrolyze acetylcholine. This suggests that _____. a)succinylcholine must be a competitive inhibitor of acetylcholine b)the active site must have the wrong configuration to permit succinylcholine binding c)succinylcholine must be a noncompetitive inhibitor d)succinylcholine must regulate the activity of this enzyme by negative feedback
a)succinylcholine must be a competitive inhibitor of acetylcholine
Which of the following is a difference between active transport and facilitated diffusion? a)Facilitated diffusion involves transport proteins, and active transport does not. b)Active transport requires the expenditure of cellular energy, and facilitated diffusion does not. c)Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. d)Active transport involves transport proteins, and facilitated diffusion does not.
b)Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.
Cells A and B are the same size and shape, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____. a)A ... its membrane transport proteins will not be saturated b)B ... the oxygen molecules inside cell B have a higher kinetic energy c)B ... the diffusion gradient there is steeper d)A ... the diffusion gradient there is shallower
c)B ... the diffusion gradient there is steeper
Green olives may be preserved in brine, which is a 20-30% salt solution. How does this method prevent contamination by microorganisms? a)High salt concentrations lower the pH, thus inhibiting the process of glycolysis. b)High salt concentrations raise the pH, thus inhibiting the process of glycolysis. c)Bacteria can't survive in a hypertonic solution because they lose water. d)Bacterial cell walls are shriveled up by salt, causing the cell to burst
c)Bacteria can't survive in a hypertonic solution because they lose water.
A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of a)endocytosis. b)active transport. c)facilitated diffusion. d)exocytosis. e)diffusion.
c)facilitated diffusion.
What condition might result from an excess of aquaporins? What condition might result from an excess of aquaporins? a)malaria b)hereditary diabetes insipidus c)fluid retention in pregnant women d)dehydration
c)fluid retention in pregnant women
In plant cells, carbon dioxide and water are joined to form carbohydrates. Plant cells can also break down carbohydrates such as glucose, releasing carbon dioxide, water, and energy. No one has ever observed such reactions between water and carbon dioxide outside of living cells. What allows simple molecules to assemble into more complex molecules, and also disassemble, in cells but not in other, nonbiological environments? a)Cells are far more efficient in energy transactions than are nonliving substances. b)Cells are subject to only the first law, not the second law, of thermodynamics. c)Cells possess properties not seen in nonliving things, which allow them to run physical processes in reverse. d)Cells couple energy-releasing reactions to energy-requiring reactions.
d)Cells couple energy-releasing reactions to energy-requiring reactions.
Water crosses the plasma membrane a)through cotransport. b)using a process that requires energy from the cell. c)through active transport. d)through facilitated diffusion or diffusion. e)against its concentration gradient.
d)through facilitated diffusion or diffusion.
Energy is conserved. This means that in any system, _____. a)energy is constantly recycled b)high-quality energy input equals high-quality energy output c)light energy is released to replace the original input of solar energy d)total energy input equals total energy output
d)total energy input equals total energy output
High temperatures or changes in pH can______an enzyme, causing it to lose its shape and biological activity
denature
The ideal osmotic environment for a plant cell is a(n) _______________ ____________________
hypotonic environment
Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. What really drives osmosis? the difference in water concentration across a selectively permeable membrane the first law of thermodynamics the difference in the height of water columns on either side of a selectively permeable membrane the difference in sugar or ion concentration across a selectively permeable membrane
the difference in water concentration across a selectively permeable membrane
Macrophages are white blood cells that roam the body searching for invading microbes. Inside macrophage vacuoles these invaders are destroyed. How do the microbes get inside the macrophages? The invaders cross the membranes via active transport through specific transport proteins. Microbes are engulfed into the macrophage via phagocytosis. They are taken in by the form of exocytosis known as pinocytosis. The invaders cross the membranes via facilitated transport through specific transport proteins
Microbes are engulfed into the macrophage via phagocytosis.
