Which of the following types of molecules are the major structural components of the cell membrane?
nucleic acids and proteins
*phospholipids and proteins
phospholipids and cellulose
proteins and cellulose
glycoproteins and cholesterol
According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
They are free to depart from the membrane and dissolve in the surrounding solution.
They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
They frequently flip-flop from one side of the membrane to the other.
They have hydrophilic tails in the interior of the membrane.
*They can move laterally along the plane of the membrane.
Which of the following statements is correct about diffusion?
It requires integral proteins in the cell membrane.
It is very rapid over long distances.
*It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
It requires an expenditure of energy by the cell.
Mammalian blood contains the equivalent of 0.15 M . Seawater contains the equivalent of 0.45 M . What will happen if red blood cells are transferred to seawater?
The blood cells will expend ATP for active transport of into the cytoplasm.
NaCl will be exported from the red blood cells by facilitated diffusion.
The blood cells will take up water, swell, and eventually burst.
NaCl will passively diffuse into the red blood cells.
*Water will leave the cells, causing them to shrivel and collapse.
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in?
White blood cells engulf bacteria through what process?
Which of the following molecular movements is due to diffusion or osmosis?
The sodium-potassium pump pumps three sodium ions out of a neuron for every two potassium ions it pumps in.
Ten minutes after a perfume bottle is dropped in a room, perfume can be smelled in the opposite corner of the room.
*When a plant cell is placed in salt water, water moves out of the central vacuole of the cell.
Select the correct statement about osmosis.
Osmotic equilibrium cannot be reached unless solute concentrations equalize across the membrane.
If a dead cell is placed in a solution hypotonic to the cell contents, osmosis will not occur.
*Osmosis is the diffusion of water molecules across a selectively permeable membrane
What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?
Water molecules no longer move between the solutions.
Water molecules continue to move from the hypotonic solution to the hypertonic solution.
*Water molecules move between the two solutions, but there is no net movement of water across the membrane.