Question

What's the difference between transporters and pumps in terms of selectivity, transport rate, and the specific mechanisms of transportation?

Answer 1

What's the difference between transporters and pumps in terms of selectivity, transport rate, and the specific mechanisms of transportation?

Answer:

Differences between transporters and pumps

1. In terms of selectivity :

Transporters- also called membrane transporters or carrier proteins. They allow the movement of certain ions, peptides, small molecules, lipids and macromolecules across the membrane of the cell.

It regulates the movement of these molecules through a biological membrane having the lipid bilayer and the proteins are embedded in it. There is selective membrane permeability that permits only to certain substances but not to others, this relies on the characteristics of the substance having specific chemical nature. The movement of molecules is accomplished with the help of membrane proteins or carrier proteins. The permeability of a substance varies as the cell membrane contains phospholipid bilayer gases like CO2, N2, O2 are permeable from the, membrane. Also, the small uncharged polar molecules are also either partially or completely permeable. But, the larger charged uncharged polar molecules and ions are not usually permeable to the cell membrane.

Pumps:

Are the active and uphill movement of molecules that hydrolyzes ATP for the transportation of ion and generates the electrochemical gradient membrane potential across membranes. It is a highly selective pathway, that is usually controlled by two gates in which one opens while the other remains closed and vice versa. One of the most common examples of a pump is Na and K pump.

In terms of transport rate:

1. Transporter: The membrane proteins also called carrier proteins can recognize only one substance at a time or one group having a similar chemical nature. Thus, this indicates a slower rate of transport. As the movement of each molecule requires the conformational change in the transporter, Transporters takes about ~ 10² -10⁴ molecules /second.
2. Ion pumps- the high coupling between the two transport molecules are able to gain energy that is stored in the electrochemical gradient of one ion to another. The free energy released becomes the source for another ion’s driving force. For example, sodium is one of the usual cotransporters and its electrochemical gradient energy drives large force for another molecule by active transport.

In terms of mechanism:

1: Transporter: there are various ways by which membrane transportation can take place.

1. Passive diffusion: in this, no expenditure of energy is required and the molecules are transported by simple diffusion.
2. Active diffusion: in this expenditure of energy is involved and the substances are usually transported against the concentration gradient. It also has secondary active transporters namely, symporters and antiporters.
3. Co transport: in which the two substances are transported by one protein which does not possess the ATPase activity. The ion pumps can be included under cotransporters as it is also one such type of transporter.

Pump: It possesses a protein that hydrolyzes ATP in order to transport the molecule across a membrane by generating an electrochemical gradient energy membrane potential.

This can be further simplified by the example of sodium and potassium pump:

• Firstly the three sodium ions bind to its active ion pump site.
• ATP is then hydrolysed and it phosphorylates the cytoplasm.
• There will be a structural change that will result in changing the position of sodium outer to exterior.
• This causes the low affinity of the sodium and subsequently as a result they are released.
• Sodium when released this stimulates the pump to bind two potassium ions towards the exterior side of membrane.
• This causes dephosphorylation of the pump and the original form is established again.
• That brings a high affinity for sodium than the potassium As a result two already bound potassium will now be released into the cytosol.
• And, the entire process repeats.