Membrane transport protein

If the process uses chemical energy, such as adenosine triphosphate (ATP), it is called primary active transport.

Membrane transport proteins that are driven directly by the hydrolysis of ATP are referred to as ATPase pumps.

[9] These types of pumps directly the exergonic hydrolysis of ATP to the unfavorable movement of molecules against their concentration gradient.

[citation needed] Secondary active transport involves the use of an electrochemical gradient, and does not use energy produced in the cell.

[10] Secondary active transport commonly uses types of carrier proteins, typically symporters and antiporters.

[citation needed] Facilitated diffusion is the passage of molecules or ions across a biological membrane through specific transport proteins and requires no energy input.

Osmosis is important in regulating the balance of water and salt within cells, thus it plays a critical role in maintaining homeostasis.

[17][18] (Grouped by Transporter Classification database categories) Facilitated diffusion occurs in and out of the cell membrane via channels/pores and carriers/porters.

GLUT1 is a named carrier protein found in almost all animal cell membranes that transports glucose across the bilayer.

As GLUT 1 is a type of carrier protein, it will undergo a conformational change to allow glucose to enter the other side of the plasma membrane.

These channels are commonly associated with excitable neurons, as an influx of sodium can trigger depolarization, which in turn propagates an action potential.

[citation needed] Other specific carrier proteins also help the body function in important ways.

[10] A number of inherited diseases involve defects in carrier proteins in a particular substance or group of cells.

This transport system normally removes cysteine from the fluid destined to become urine and returns this essential amino acid to the blood.

For example, levels of riboflavin carrier protein (RCP) have been shown to be significantly elevated in people with breast cancer.

The sodium–potassium pump (a type of P-type ATPase ) is found in many cell (plasma) membranes and is an example of primary active transport. Powered by ATP, the pump moves sodium and potassium ions in opposite directions, each against its concentration gradient. In a single cycle of the pump, three sodium ions are extruded from and two potassium ions are imported into the cell.
Facilitated diffusion in the cell membrane, showing ion channels (left) and carrier proteins (three on the right).
This picture represents symport. The yellow triangle shows the concentration gradient for the yellow circles while the green triangle shows the concentration gradient for the green circles and the purple rods are the transport protein bundle. The green circles are moving against their concentration gradient through a transport protein which requires energy while the yellow circles move down their concentration gradient which releases energy. The yellow circles produce more energy through chemiosmosis than what is required to move the green circles so the movement is coupled and some energy is cancelled out. One example is the lactose permease which allows protons to go down its concentration gradient into the cell while also pumping lactose into the cell.
The picture represents uniport. The yellow triangle shows the concentration gradient for the yellow circles and the purple rods are the transport protein bundle. Since they move down their concentration gradient through a transport protein, they can release energy as a result of chemiosmosis . One example is GLUT1 which moves glucose down its concentration gradient into the cell.
This picture represents antiport. The yellow triangle shows the concentration gradient for the yellow circles while the blue triangle shows the concentration gradient for the blue circles and the purple rods are the transport protein bundle. The blue circles are moving against their concentration gradient through a transport protein which requires energy while the yellow circles move down their concentration gradient which releases energy. The yellow circles produce more energy through chemiosmosis than what is required to move the blue circles so the movement is coupled and some energy is cancelled out. One example is the sodium-proton exchanger which allows protons to go down their concentration gradient into the cell while pumping sodium out of the cell.