How does a cell utilize a concentration gradient in accordance with the first law of thermodynamics?

Any ideas? I understand that energy can be transformed, transferred but not created or destroyed, but how does it relate to this? How does a cell utilize a concentration gradient in accordance with the first law of thermodynamics?
Man, this is a pretty broad question!! Here goes...





A cell must use ATP as a source of energy to transport nutrients against a concentration gradient. A cell can also diffuse nutrients across its gradient without having to use any energy (normal diffusion or facilitated diffusion). A cell prefers to limit the amount of energy it must use to transport nutrients. A mechanism such as the cotransport of glucose and sodium shows how this is utilized. In the endothelial cells of the intestinal tract, a sodium gradient is created by the Na-K-pump in the basolateral membrane. The potential energy created by this pump allows Na+ to move along it's gradient into the cell through the apical membrane, bringing glucose along with it (against it's gradient in most cases). This is called secondary active transport (doesn't draw immediate energy from ATP, but rather from a gradient). This mechanism shows how a cell utilizes a concentration gradient of one nutrient to move another nutrient across it's gradient. If this weren't the case, the cell wouldn't be able to access glucose unless the concentration inside the cell was lower than the concentration outside of the cell, which would severely limit almost every function in the body!!!





You can use this example to explain how the total energy in the system is conserved (no energy is destroyed or created, but rather transformed/transferred).