Membrane transport
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Membrane transport is the moving of biochemicals and other atomic or molecular substances across biological membranes.

Usually, two types are distinguished: Active transport requires chemical energy, while passive transport does not.

Membrane transport refers to carrying of substances across the cell membrane. It can be divided into two types:Membrane transport protein

1. Against concentration gradient and requiring energy for transport - called active transport

2. Along the concentration gradient and does not require energy for transport- called passive transport

Passive transport can be of two types:

1. Simple diffusion- crossing over of ions and other chemical substances across the cell membrane that is dependent on concentration gradient- substances diffuse across the cell membrane from higher concentration to lower concentration.

2. Facilitated transport- usually using a carrier that binds to the substance and carries it across the cell membrane without involving energy expenditure. For example, transport of iron by transferrin across the cell membrane.

Based on their specificity for carried substances, a number of transporters have been identified, like ATP-binding cassette transporter, Glutamate transporter, Neurotransmitter transporter, Glucose transporter, Dopamine transporters among others. These transporters can be grouped into two groups:(1) ATP Binding Cassette Transporter (ABC transporter) and (2) Solute Carrier Family.

Transporters are proteins that may be situated on the membrane surface of may be present in the cell cytoplasm. The later are activated by binding of the ligand to its receptors to reach the membrane surface for binding the substance to be transported. Glucose transporters.

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