bio ch 5
Which of the following would tend to increase membrane fluidity?
A greater proportion of phospholipids with unsaturated hydrocarbon tails
The concentration of solutes in a particular cell is about 2%, but the cell contains almost no sucrose or urea. Sucrose cannot pass through the membrane of this cell, but water and urea can. Osmosis would cause this cell to shrink the most when immersed in which of the following solutions?
A hypertonic sucrose solution
Which of the following would be least likely to pass through a plasma membrane without the help of a transport protein?
A large polar molecule
Which of the following molecules is most likely to passively diffuse across the plasma membrane?
Carbon dioxide
In what way do the membranes of eukaryotic cells vary?
Certain proteins are unique to the membrane of each cell type.
Which of the following processes and organelle(s) account for the replacement of lipids and proteins lost from the plasma membrane?
Exocytosis and smooth and rough ER
Which of these statements describes some aspect of facilitated diffusion?
Facilitated diffusion of solutes may occur through transport proteins in the membrane.
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?
In the interior of the membrane
Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?
Membrane carbohydrates have a primary role in cell-cell recognition.
Steroid hormones enter a cell by simple diffusion. In doing so, these steroids __________.
None of the listed responses is correct.
Which of the following processes includes all the others?
Passive transport
Which of the following statements about passive transport is correct?
Passive transport involves movement of solute in both directions across a membrane, but with a net movement of solute down its concentration gradient.
Which of the following pairs correctly matches a membrane transport process to its primary function?
Pinocytosis; the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane
Which of the following enables a cell to concentrate and take in a specific kind of molecule?
Receptor-mediated endocytosis
The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true?
The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect.
Which of the following correctly describes a general property of all electrogenic pumps?
They create a voltage difference across a membrane
Testosterone, a lipid-soluble signaling molecule, crosses the membranes of cells throughout the body but affects only target cells because __________.
intracellular receptors for testosterone are present only in target cells
Nitric oxide is unusual among animal signal molecules in that it __________.
is a gas
Receptors for signal molecules __________.
may be found embedded in the plasma membrane, or found within the cytoplasm or nucleus
The general name for an enzyme that transfers phosphate groups from ATP to a protein is __________.
protein kinase
The molecule cAMP directly activates __________.
protein kinase A
Second messengers tend to be water-soluble and small. This accounts for their ability to __________.
rapidly move throughout the cell by diffusion
What event would activate a G protein?
replacement of GDP with GTP
Early work on signal transduction and glycogen metabolism by Sutherland indicated that __________.
the signal molecule did not interact directly with the cytosolic enzyme but required an intact plasma membrane before the enzyme could be activated
Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because __________.
they amplify the original signal manyfold
