A uniport carrier is a membrane transport protein that moves only one kind of molecule. It does not generally require energy as it follows the concentration gradient of the molecule in question.
An example of a uniporter is the glucose transporter (GLUT) in found in erythrocytes (reffered to as GLUT1 to separate from other mamalian glucose transporters). This allows glucose to enter the cell via facilitated diffusion and it does so at approximately 50,000 times the rate that it would via simple diffusion. This process is not active (meaning it does not require an energy input). Once inside the cell the glucose is quickly phosphorylated to glucose-6-phosphate by the enzyme, hexokinase, to prevent it from diffusing out. This is also the first step in glycolysis.
Becker's World of the Cell, Eighth Edition (J. Hardin, G.Bertoni, L.J. Kleinsmith) 2012 San Fransisco:Pearson
Molecular Biology of the Cell, Fifth Edition (B. Alberts, A.Johnson, J.Lewis, M.Raff, K.Roberts, P.Walter) 2008 New York:Garland Science