Which of the following shows the abbreviation for an si unit of density? A. L/kg B. Ib/mL C. g/mL D. kg/m2

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many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.