Some molecules need help to move through the cell membrane in the form of energy because transport occurs against the concentration gradient and, therefore, the molecules require an energy supply.
The transport in cells is carried out through their membrane by different mechanisms, in order to enter nutrients and eliminate waste.
Many molecules can pass through the membrane without difficulty, but there are others that, due to their composition, it is not easy to do so and therefore require an energy supply.
For this there is the active transport of molecules, it requires energy to be carried out, since it is a type of movement where molecules go against the concentration gradient (from a place of lower concentration to one of higher concentration) and it is carried out by means of pumps, a clear example is the pump that transports sodium and potassium.
If the cells were unable to carry out this transport, the organism would not carry out its vital activities.
Therefore, we can conclude that some molecules need energy to move across a cell membrane because they go against the concentration gradient.
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