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Chapter 5 Practice Problems
BIOL 1030: Donna W. Mastering Biology
Terms in this set (46)
Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements.
-Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane.
-The diverse proteins found in and attached to membranes perform many important functions.
-The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center.
Which of the following would be a factor that determines whether the molecule selectively enters the target cells?
the similarity of the drug molecule to other molecules that are transported into the target cells
When molecules move down their concentration gradient, they move from where they are ___ concentrated to where they are ___ concentrated
Diffusion across a biological membrane is called ___
In active transport,
molecules move across the plasma membrane against their concentration gradient.
A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of
Water crosses the plasma membrane
through facilitated diffusion or diffusion.
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
The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of
What name is given to the process by which water crosses a selectively permeable membrane?
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 ideal osmotic environment for an animal cell is a(n) __ environment
. An animal cell placed in a(n) ___ solution will gain water, swell, and possibly burst.
There is a net diffusion of water out of an animal cell when it is placed in a(n) ___ solution.
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 _____.
actively pump water back into their cells to counter its loss due to osmosis
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 _____.
B ... the diffusion gradient there is steeper
Facilitated diffusion is a type of _____.
Aquaporins are proteins that facilitate the transport of __________ across the membrane.
Which of the following is a difference between active transport and facilitated diffusion?
Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.
When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This molecule rapidly enters the cell regardless of whether its concentration is higher inside or outside the cell. Using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane?
Endocytosis moves materials _____ a cell via _____.
into ... membranous vesicles
You can recognize the process of pinocytosis when _____.
the cell is engulfing extracellular fluid
A white blood cell engulfing a bacterium is an example of _____.
A vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell.
A form of passive transport. Molecules move across the plasma membrane using a transport protein
the plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell
A form of passive transport. Molecules move across the plasma membrane using a transport protein.
Requires energy from the cell. Molecules move from 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 __________.
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.
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
Which of these are by-products of cellular respiration?
heat and water
Azidothymidine (AZT) is an antiretroviral drug used in the treatment of HIV. It shares a structural similarity to a nucleotide. What might be the mode of action for this drug?
An enzyme is considered a(n) __ because it speeds up a chemical reaction without being used up.
In a catalyzed reaction, a reactant is often called a(n)__ .
An enzyme is specific because the shape of its __ matches only particular reactants_.
An enzyme speeds up reactions by lowering the ___.
The ___ between an active site and its substrate often strains bonds and helps the reaction proceed
A(n) __ , which is often a vitamin, binds to an enzyme and plays a role in catalysis.
High temperatures or changes in pH can __ an enzyme, causing it to lose its shape and biological activity.
The synthesis of an amino acid follows this pathway: precursor A > intermediate B > amino acid C. Each reaction is catalyzed by a different enzyme. This metabolic pathway is controlled by feedback inhibition with amino acid C inhibiting the conversion of precursor A to intermediate B. Amino acid C acts as a _____ of the first enzyme in the pathway.
Why doesn't the antibiotic penicillin harm humans?
Human cells do not have cell walls.
Taq polymerase is an enzyme isolated from the organism Thermophilus 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?
the temperature should be raised
Lactase is essential for digesting lactose in milk. This enzyme is specific for this sugar. Why?
There is a precise compatibility between the active site and the lactose molecule.
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