If a solution surrounding a cell is hypotonic relative to the inside of the cell, how will water move?
It will move into the cell via osmosis
If a solution surrounding a cell is hypertonic relative to the inside of the cell, how will the water move?
It will move out of the cell via osmosis
When does a concentration gradient exist?
When solute concentration differ on the two sides of a membrane
Which of the following must be true for osmosis to occur?
Solutions with different concentrations of solutes must be separated by a selectively permeable membrane
Why are the lipid bilayers in cells called "selectively preamble"?
They are permeable to some substance but not others.
Which of the following best describes a nuclear envelope?
It is continuous with the endomembrane system
Why is "receptor-mediated endocytosis" an appropriate term?
It starts when extracellular molecules bind t receptors
Which of the following is not true of secreted proteins?
They are transported from the Golgi apparatus to the ER
To find the nuclear localization signal in the protein nucleoplasmin, researchers separated the molecule's core and tail segments, labeled both with a radioactive atom, and injected them into the cytoplasm. Why did researchers conclude that the signal is in the tail region of the proteins?
Only the tail segments appeared in the nucleus
Molecular zip codes direct molecules to particular destinations in the cell. How are these signals read?
They bind to receptor proteins
Which of the following statements represents a fundamental difference between fibers found in the extracellular layers of plants and those of animals?
Animal fibers consist of proteins; plant fiber consist of polysaccharides instead.
In animals, where are most components of the extracellular material synthesized?
The rough ER and the Golgi Apparatus
Treating dissociated cells with certain antibodies make the cells unable to reaggregate. Why?
The antibodies bind to cell adhesion proteins called cadherins
What does it mean ti say that a signal is transduced?
the physical form of the signal changes between the outside of the cell and inside
Why are tight junctions found in only certain types of tissues, while desmosomes are found in a wide array of cells?
tight junctions are found only in epithelial cells that must be water tight
What physical event represents the receipt of an intercellular signal?
the binding of a hormone to a signal receptor, which changes confirmation in response
When does feedback inhibition occur?
when an enzyme that is active early in a metabolic pathway is inhibited by a product of the pathway.
What does the chemiosmotic hypothesis claim?
electron transport chains generate ATP indirectly, by the creation of a proton-motive force
What is the function of the reactions in a fermentation pathway?
to generate NAD+ from NADH, so glycolysis can continue
When do cells switch from cellular respiration to fermentation.
when electron acceptors required by the ETC are not available
Why are NADH and FADH2 said to have "reducing power"?
they donate electrons to components of the ETC, reducing those components
Why do the absorption spectrum for chlorophyll and the reaction spectrum for photosynthesis coincide?
wavelengths of light that are absorbed by chlorophyll trigger the light-capturing reactions
What happens when an excited electron is passed to an electron acceptor in a photosystem?
energy in the sunlight is transformed to chemical energy
What statement about daughter cells of mitosis is correct?
they are genetically identical to one another and to the parent cell
Progression through the cell cycle is regulated by oscillations in the concentration of which type of molecule?
What major events occur during anaphase of mitosis?
sister chromatids separate, forming independent chromosomes
What evidence suggests that during anaphase, kinetochore mictotubles shorten at the kinetochore and not at the base of the spindle apparatus?
when fluorescing microtubles are darkened in the middle, the darkened segment stays stationary as the fibers shorten near the kinetochore