Asked Jun 6, 2019

Can you explain ACTIVE transport - more specifically how transport is facilitated by proteins (carriers or pumps) OR bulk transport of molecules. 


Expert Answer

Step 1

Movements of ions and molecules in and across the cell membrane are regulated by a set of transport mechanism that is collectively termed as membrane transport mechanisms. The transport mechanisms include simple diffusion, facilitated diffusion, osmosis, and active transport.

Step 2

Active transport is a type of energy-dependent membrane transport mechanism in which the molecules and ions can move across the membranes against their concentration gradient (from lower concentration to the higher concentrated area). This action is accompanied by the breakdown of ATP molecules. There are two types of active transport mechanisms namely-

  • Direct active transport-ATP is directly used for pumping molecules against the concentration gradient.
  • Indirect active transport or cotransport-Here, the ATP is used indirectly. Movement of one molecule across the gradient usually provides energy for the transportation of some other molecules against its concentration gradient.
Step 3

Active transport requires energy expenditure, as it transfers the molecules against their concentration gradient. Movement of molecules through active transport is facilitated by certain proteins. Major types of proteins that facilitate active transport are as follows:

1. Membrane proteins as carrier protein: Carrier proteins are present within the cell membrane that transports the molecule by changing their shape, o...

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