For example, glucose attaches to a glucose transporter protein on the outside
surface of the cell membrane, the protein changes shape and the glucose passes through the membrane and is released into the cell (Tortora and Derrickson 2009a). Some membrane proteins are involved in catalysing specifi c chemical reactions inside or outside the cell. In addition, membrane proteins can act as receptors. These proteins are involved
in recognising and binding to substances such as
hormones (Tortora and Derrickson 2009a).