Which one of the following biological macromolecules is least likely to be a component of a biomembrane?
|E)||All of the choices are common components of biomembranes.|
A solute crossing a biomembrane from a region of low concentration to a region of high concentration with the aid of a transport protein and energy is most accurately referred to as
Which of the following is not a type of transport protein?
|E)||All of the choices are forms of membrane transport proteins.|
Which of the following is not an integral membrane protein?
|E)||All of the choices are integral membrane proteins.|
Under what conditions would a biomembrane be the most fluid at 37°C?
|A)||Long unsaturated fatty acyl tails plus cholesterol|
|B)||Short unsaturated fatty acyl tails and no cholesterol|
|C)||Short saturated fatty acyl tails and no cholesterol|
|D)||Short unsaturated fatty acyl tails plus cholesterol|
|E)||Long saturated fatty acyl tails plus cholesterol|
If the Frye and Edidin experiment was repeated using an incubation temperature of 30°C instead of 37°C, mouse H-2 protein would still be distributed evenly on both sides of the hybrid cell, but would take longer for the distribution to complete.
Which of the following statements does not represent a reason why integral membrane proteins might be restricted in their movements?
|A)||It is energetically unfavorable for the hydrophilic region of a membrane protein to cross the hydrophobic interior of the membrane.|
|B)||The cytosolic face of an integral membrane protein can be linked to the cell's cytoskeleton.|
|C)||Proteins are larger molecules than lipids and therefore move more slowly than lipids through a lipid bilayer.|
|D)||Integral membrane proteins can be attached to molecules in the extracellular space.|
|E)||All of the choices describe possible reasons for the restricted movement of integral membrane proteins.|
The technique most commonly used to study the interior of a biomembrane is known as
|A)||transmission electron microscopy.|
|C)||freeze-fracture electron microscopy.|
|D)||scanning electron microscopy.|
|E)||fluorescence recovery after photo bleaching.|
Arrange the following molecules in order from most likely to least likely to pass through a biomembrane.
- carbon dioxide
- K+ (Potassium ion)
|A)||iv > i > iii > ii|
|B)||iii > ii > i > iv|
|C)||ii > iii > iv > i|
|D)||iv > iii > i > ii|
|E)||ii > iii > i > iv|
True or False: The movement of water across a semipermeable membrane to balance solute concentrations is called osmosis and requires energy input.
A beaker of water is divided into two compartments, A and B, by an artificial lipid bilayer. The concentration of Na+ in compartment A is 1.0 M, while the concentration of Na+ in compartment B is 1.5 M. With regards to Na+ concentration, compartment A would be referred to as __________, while compartment B would be referred to as __________.
How does a freshwater organism like a paramecium maintain proper osmotic balance?
|A)||Paramecium have a rigid cell wall which prevents water loss.|
|B)||The cell membranes of paramecium contain special water pumps to move water into the cytoplasm.|
|C)||The cell membranes of paramecium contain special water pumps to move water out of the cytoplasm.|
|D)||Paramecium have contractile vacuoles which accumulate water, fuse with the plasma membrane, and discharge the water into the extracellular environment.|
|E)||No special mechanism is necessary because the cytoplasm is isotonic with the extracellular environment.|
A transmembrane channel that opens and closes in response to the direct binding of a molecule to the channel protein itself is referred to as a(n)
Carriers that bind two or more molecules or ions and transport them in opposite directions are called __________, while carriers that bind two or more molecules or ions and transport them in the same direction are called __________.
True or False: Existing proton (H+) gradients frequently provide the energy required to move nutrients against their concentration gradients.
Which one of the following statements about Na+/K+-ATPase pumps is incorrect?
|A)||Na+/K+-ATPase pumps are an example of an electrogenic pump.|
|B)||A typical animal cell utilizes thousands of Na+/K+-ATPase pumps to maintain ATPase gradients across the cell membranes.|
|C)||The Na+/K+-ATPase pump results in 2 K+ being released into the cytosol and 3 Na+ being released into the extracellular space.|
|D)||A Na+/K+-ATPase pumps alternates between two different conformations known as E1 and E2.|
|E)||Some animal cell types, like neurons, utilize a majority of their ATP to operate pumps like the Na+/K+-ATPase pump.|
Which of the following is not a function of an electrochemical gradient?
|A)||Export of waste products.|
|B)||Contraction of muscle fibers.|
|C)||Synthesis of ATP.|
|D)||Transmission of nerve impulses.|
Vesicles destined for exocytosis are typically derived from
|B)||smooth endoplasmic reticulum.|
|D)||the Golgi apparatus.|
Which one of the following statements about endocytosis is incorrect?
|A)||Endocytic vesicles can be formed when a receptor molecule binds a specific cargo molecule.|
|B)||All cell types are capable of phagocytosis, a form of endocytosis.|
|C)||Internalization of extracellular fluid is a form of endocytosis.|
|D)||Endocytosis is an invagination of the plasma membrane.|
|E)||All of these statements about endocytosis are correct.|
True or False: Bacteria invading a mammalian host are often removed when the host's immune system cells engulf the bacteria and fuse with lysosomes, which provide the energy for destruction of the bacteria.