In order for a muscle cell to contract, sodium ions (Na+) must be removed from the cell and potassium ions (K+) must enter the cell. Both of these lons travel
against the cell's concentration gradient. This process is most likely achieved
througn-
A. Simole diffusion across the cell membrane using no energy
b. A channel protein using no eneray
C. A protein pump using energy
d. A channel protein using energy

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Some technological solutions to problems like global warming meet the specific needs and situations of local communities. an example from india involves converting the solid waste from cattle into clean-burning fuel for cooking. this reduces the amount of greenhouse gases, specifically methane and carbon dioxide, released into the environment from wood fires. when evaluating the feasibility of implementing this solution, computer models are used to weigh costs against benefits. what factor is least likely to impact the decision on adopting this technology?

What causes darkening of the skin as melanin production increases

Which of these is true for bacteria because they are prokaryotic cells? a. they can engulf body cells in order to make memory cells. b. they must invade viruses in order to reproduce. c. they are much larger than eukaryotic body cells. d. they can reproduce on their own outside of other cells.