Here are the essential concepts you must grasp in order to answer the question correctly.
Active Transport
Active transport is a cellular process that moves ions or molecules against their concentration gradient, from an area of lower concentration to an area of higher concentration. This process requires energy, typically in the form of ATP, because it is working against the natural tendency of substances to move from high to low concentration. In the context of sodium movement, active transport is essential for maintaining the necessary sodium levels within the cell.
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Concentration Gradient
A concentration gradient refers to the difference in the concentration of a substance across a space or membrane. In this scenario, the sodium concentration inside the cell is significantly lower than outside, creating a gradient that drives sodium ions to move into the cell. Understanding this gradient is crucial for determining how substances can move across cell membranes, either passively or actively.
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Concentration Gradients and Diffusion
Passive Transport
Passive transport is the movement of substances across a cell membrane without the use of energy, relying instead on the natural kinetic energy of molecules. This process occurs along the concentration gradient, meaning substances move from areas of higher concentration to lower concentration. While passive transport is important for many cellular functions, it cannot be used to move sodium out of the cell against its concentration gradient, which is why active transport is necessary in this case.
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Passive vs. Active Transport