Describe the main functions of the plasma membrane
What will be an ideal response?
Besides acting as a mechanical barrier that traps needed molecules within the cell, the plasma membrane helps determine the cell's composition by selectively permitting specific substances to pass between the cell and its environment. The plasma membrane controls the entry of nutrient molecules and the exit of secretory and waste products. In addition, it maintains differences in ion concentrations inside and outside the cell, which are important in the membrane's electrical activity. The plasma membrane also participates in the joining of cells to form tissues and organs. Finally, it plays a key role in enabling a cell to respond to signals from chemical messengers in the cell's environment; this ability is important in communication among cells.
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Lymphatic capillaries are present in ________
A) digestive organs B) CNS C) bones and teeth D) bone marrow
As the charge on the membrane of a typical neuron approaches 0 from -70 mV, the cell is
A) only depolarizing. B) only becoming more difficult to stimulate. C) hyperpolarizing and becoming more difficult to stimulate D) only repolarizing. E) only hyperpolarizing.
A cell that contains 23 pairs of chromosomes is
A. haploid. B. monoid. C. diploid. D. polyploid.
What do skeletal and cardiac muscle cells share in common?
A) multinucleate cells B) branched cells C) intercalated discs situated between cells D) striations