Membrane transport

The model below shows how glucose, sodium ions ($\text{Na}^+$start text, N, a, end text, start superscript, plus, end superscript), and potassium ions ($\text{K}^+$start text, K, end text, start superscript, plus, end superscript) move between the intestinal lumen, an epithelial cell, and the blood in the small intestine. The relative concentrations of glucose, $\text{Na}^+$start text, N, a, end text, start superscript, plus, end superscript, and $\text{K}^+$start text, K, end text, start superscript, plus, end superscript inside and outside the epithelial cell are indicated.