Hello, in this video we will see the difference between primary active transport and secondary active transport. First with the analogy of hill and then across the cell membrane. Let's get started. Here is a hill, and there is a rock at it's base. We want to move the rock to the top of the hill. Obviously, we will need to put in some energy to move the rock uphill. Let's say we manually push it to the top. This movement is primary active transport. Active because we are actively moving the rock. And primary because we are putting our energy directly on the rock. Now at the base, there is another rock that we want to move up. Of course, we can move it manually, but with this rock already at the top, we have one more option. We can tie both the rocks with a rope and let the first rock slide down. This will move the other rock uphill. This is secondary active transport. It's secondary because we have first put the energy into this rock in form of the high altitude. And that energy is secondarily used to move the other rock up. This is the basic difference between primary and secondary active transport. When the ultimate source of energy is directly moving the object it's primary active transport. This transport gives potential energy to the object that has been moved. When that energy is secondarily used to move other objects, it's called secondary active transport. Now lets understand primary and secondary active transport across the cell membrane. Here active transport means moving molecules against electrochemical gradient. It is like uphill movement. In primary active transport energy comes directly from ATP or other high energy compounds. For example, movement of Na from inside to outside of the cell by Na-K ATPase pump. This pump takes energy directly from ATP and uses it to move Na against electrochemical gradient. So this is primary active transport. This transport establishes a concentration gradient for Na ions. It's like these Na ions are at the top of the hill with stored energy. And this energy can be secondarily used to move other ions uphill, for example Ca. All we need is a transporter that couples the movement of Na with movement of Ca. One such transporter is Na-Ca exchange transporter. Movement of Na down the concentration gradient, energizes this transporter. And that energy secondarily moves Ca against it's electrochemical gradient. Thus, this transport of Ca is secondary active transport, because energy from ATP was first stored in form of concentration gradient of Na. And that energy is secondarily used to move Ca. Quick summary. In primary active transport, energy comes directly from the ATP or other high energy compounds. This transport stores potential energy in the molecules that have been moved. When that energy is used secondarily to move other molecules it's called secondary active transport. So this is the fundamental difference between primary and secondary active transport. That's it for this video. If you feel this video will help your friends and colleagues, share it with them too. And don't forget to subscribe because lots more to come. At nonstop neuron, learning medical concepts is as easy as watching cartoons. Thanks for watching, see you in next video.