Explain why a cell may use facilitated diffusion rather than simple diffusion for transport
What will be an ideal response?
Simple diffusion involves the transport of nonpolar solutes (such as hydrocarbons and lipids, and gases such as O2 and CO2 ) that pass through the phospholipid bilayer without assistance from the membrane proteins. Facilitated diffusion involves the transport of charged or polar substances (such as ions and glucose) that cross the phospholipid bilayer with the help of a membrane protein.
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Which of the following does NOT correctly describe cardiac muscle cells?
A. They are much shorter than skeletal muscle fibers, and generally have a single nucleus. B. They can contract in the absence of external calcium. C. Their membranes are depolarized initially by the influx of sodium ions. D. They depolarize prior to contraction. E. They are arranged in layers surrounding hollow cavities in the heart.
Which feedback system structure provides input to the control center?
a) receptor b) muscle c) response d) effector e) efferent pathway
The increase in the number of motor units activated as a result of more intense
stimulation is called A) recruitment. B) latency. C) sustained contraction. D) threshold stimulation.
Which of the following is not true of a polar chemical bond?
A. It has no net electrical charge. B. It is ionized. C. It has opposite electrical charge at each end. D. It is covalent.