Which of the following organisms is likely to contain biomembranes?
All living organisms contain biomembranes
Cellular membranes are
Which of the following is the major lipid found in membranes?
Which of the following is NOT true of the plasma membrane?
The extracellular and intracellular layers or leaflets are highly symmetrical.
Which of the following statements about plasma membranes is INCORRECT?
They have both integral and peripheral proteins.
Scientists unearth a Wooly Mammoth from the Siberian Ice Sheath and discover that a eukaryotic "amoeba"-like cell is still alive. Which component of the cell membrane might contribute to maintaining the fluidity of plasma membranes under freezing conditions?
high levels of unsaturated fatty acyl tails within the lipid bilayer
Which of the following statements is CORRECT about biomembranes?
Membrane proteins are globular, and some span the phospholipid bilayer and project from both sides of the membrane.
A scientist produces an artificial membrane from phospholipids and notices that oxygen, but not glucose readily moves through the membrane. What might account for the inability of glucose to move through the artificial membrane?
The artificial membrane lacked a protein needed for glucose transport.
Which of the following is NOT a component of plasma membranes?
glycosylated nucleic acids
Around what percentage of all genes encode membrane proteins?
Which of the following is NOT a function of cellular membranes?
maintenance of cell shape
Which of the following statements is TRUE of membrane phospholipids?
They freely move laterally within the membrane.
Phospholipids and ________ are the major components of cell membranes.
Cell surface molecules are labeled with a fluorescent tag and then a portion of them are bleached with a laser beam. What would one observe after the cell is incubated for a few minutes?
The bleached molecules would diffuse laterally through the membrane and intermix with unbleached molecules.
The following affect membrane fluidity EXCEPT
the relative amounts of phospholipids containing saturated or unsaturated fatty acyl tails.
Which of the following is TRUE of phospholipids that flip-flop across the lipid bilayer?
The process requires energy and the flippase enzyme.
Cellular membranes are mosaic and
How might a plant cell compensate for the excessive membrane fluidity that occurs during prolonged exposures to elevated temperature?
Alter the lipid composition to have longer fatty acyl tails and fewer double bonds.
Glycosylated proteins and lipids within the plasma membrane are important for
cell recognition and protection.
Which of the following is important for allowing large, charged molecules to pass through the membrane?
Placing celery sticks in fresh water will make them more turgid and harder. This is because
the celery is hypertonic to fresh water.
Of the following molecules, which passes through a lipid bilayer most readily?
Which of the following molecules would you predict moves through a lipid bilayer most rapidly?
Animal cells are permeable to water and urea but NOT to sucrose. The inside of a cell contains 1 M sucrose and 1 M urea and the outside 1 M sucrose and 2 M urea. The solution inside with respect to outside the cell is
Animal cells are permeable to water and urea but NOT to sucrose. Initially, the inside of a cell contains 1 M sucrose and 1 M urea and the outside 1 M sucrose and 2 M urea. After the system reaches equilibrium, what changes are observed?
The molarity of sucrose would be similar inside and outside the cell and water would move out of the cell causing the cell to shrivel.
Which of the following statements is CORRECT about active transport?
A. It requires energy.
B. It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
C. It requires integral proteins.
D. It is necessary to maintain solute gradients across a membrane.
Which of the following is NOT true of passive diffusion?
Passive diffusion requires the presence of a transmembrane protein.
Following a meal glucose must move from the gut lumen where there is a high glucose concentration into the intestinal cell where there is a relatively low level of glucose. This movement is called
The pressure required to stop water from moving across the membrane by osmosis is called
Water diffuses through certain organs such as the kidneys and bladder much faster than would occur by passive diffusion through a lipid bilayer alone. What accounts for this more rapid rate of water transport in these organs?
Presence of aquaporin channels for facilitated diffusion of water.
The movement of sucrose and H+ into the cell by a common membrane protein reflects transport through a
The statements about transport of Ca2+ from the cytosol (low Ca2+ concentration) into the endoplasmic reticulum (high Ca2+ concentration) are true EXCEPT which of the following?
Calcium movement occurs by facilitated diffusion using a transporter protein.
Acetylcholine binds this membrane protein, which subsequently opens to allow sodium to enter the cell. Acetylcholine exerts its effect on what type of transport protein?
Sodium concentrations are higher outside and glucose concentrations are higher inside the cell. Using the same membrane protein for Na+ and glucose transport, what is it called when a Na+ electrochemical gradient is used to drive glucose transport into the cell against its concentration gradient?
secondary active transport
________ bind two or more ions or molecules and transport them in opposite directions across a membrane.
Which of the following statement about the plasma membrane Na+/K+-ATPase pump is INCORRECT?
It is a pump for active transport of K+ out of the cell and Na+ into the cell.
The release of insulin from pancreatic cells occurs by
Which of the following best describes the selective uptake of a specific cargo molecule into the cell through receptor binding and aggregation?