phospholipids are well suited to be the main structural components of membranes because they ___
form a selectively permeable structure.
the lipids in a cell membrane are arranged ___
so that the nonpolar parts of two lipids point toward each other.
phospholipids are well suited to serve as the major component of the plasma membrane because they ____
have a water soluble part and a water insoluble part.
which of the following describes the general structure of a cell membrane?
proteins embedded in two layers of phospholipids.
the membrane is referred to as "fluid mosaic" structure. which of the following statements is true?
the fluid is phospholid, and the mosaic is protein.
as shown below, proteins perform a number of functions within membraines. which of the following statements is true about membrane proteins?
proteins can bind other molecules, which may trigger specific cellular functions.
which of the following statements is true about passive trabsport?
passive transport requires no expenditure of cellular energy.
the movement of atoms, ions, or molecules from a region of higher concentration to regions of lower concentration is called ____
cells A and B are the same size and shape, but cell A is metabolically quite and cell B is actively consuming oxygen. oxygen will diffuse more quickly into cell ____ because ____
B--- the diffusion gradient there is steeper.
how does passive transport functions?
passive transport transports molecules without the assistance of proteins from an area of high concentration to an area of lower concentration.
the concentration of solutes in a red blood cell is about 2%. sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immmersed in which of the following solutions?
a hypertonic sucrose solution
green olives may be preserved in brine, which is a 20-30% salt solution. how does this method prevent contamination by microorganisms?
bacteria can't survive in a hypertonic solution because they lose water.
seawater is dangerous to drink because ______
sea water is hypertonic to your body tissues and drinking it will cause you to lose water by osmosis.
which of these situations accurately represents osmoregulation in organisms?
plant cells need a hypotonic environment in order to stay turgid.
if the volume of a cell increases when it is placed in a aqueous solution, that solution is said to be ____ to the cell
which of these statements describes what occurs in facilitated diffusion?
facilitated diffusion of solutes occurs through protein pores in the membrane.
which of the following is a difference between active transport and facilitated diffusion?
active transport requires the expenditure of celullar energy, and facilitated diffusion does not.
when in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. this occurs regardless of whether the concentration of this molecule is higher inside or outside the cell. using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane?
the transport of molecules of a particular solute from inside an animal cell across the cell membrane to the extracellular fluid always requires energy when ____
the concentration of the solute is lower inside the cell than outside it.
which of the following statements about cell membrane transport is true?
active transport works with the assistance of proteins to move molecules from areas of low concentration to areas of high concentration.
which of the following enables a cell to pick up and concentrate a specific kind of molecule?
a nursing infant is able to obtain disease fighting antibodies, which are large protein molecules, from its mother's milk. these molecules probably enter the cell lining the baby's digestive tract via ____
which one of the following terms specifically refers to the intake of very large particles by cells?
which statement best describes phagocytosis?
a cell engulfs a particle by wrapping pseudopodia around it and packaging it within a vacuole.
the secretion of neurotransmitters out of the nerve cell, from small vesicles at the end of the axon, can be considered an example of ____