Does active transport requires a semi-permeable membrane ?
Recently I came to a question in my mid-year examination and my head went all blank when I saw a question in my biology paper.
The question asked "Which of the following stement is correct about active transport ?" Here are the choices : (i) requires energy (ii)requires transport protein (iii)follows concentration gradient (iv)requires a semi-permaeble membrane.
What is the answer ? Plz help !
Active transport is transport from low to high concentration. Whenever this situation occurs, energy is needed to facilitate transport. An example in the body are the nephrons in the kidneys filtering urea from the circulating blood. There will always be a higher concentration of urea in the nephrons relative to the urea dissolved in the blood. In order for filtration to proceed from low concentration to high, the cells of the nephrons must expend energy to do this. Active transport is exactly what the term active implies--think of energy use.
Active transport is the process which involves energy from cellular respiration for the movement of substances against the concentration gradient that is from a region of higher concentration to a region of lower concentration. Thus, the provision of a semi-permeable membrane is not a compulsion.
The answer is the first one
Active transport is from higher to lower concentration gradient. It is a law of nature that in this case energy will be required. So I think option "A" is correct.
Carrier proteins are some proteins (like fibers) which grab the material and transport it. This phenomenon occurs in diffusion, osmosis as well as active transport but not always. I mean that it is not a hard and fast rule that they will always be required for active transport.
Active transport does not folow concentration gradient i.e form higher to lower. In fact ti is the exact opposite.
When a membrane comes in between the process is known as osmosis. Active transport does not require a membrane.
The answer is 'requires energy'
The opposite to active transport is passive transport- passive transport requires a semi-permeable membrane because the cell isn't using any energy- so it needs to get in somehow. For a cell to use active transport, it needs to activiely pull in particular proteins, nutrients, etc, therefore it needs energy to actually obtain the subctances that it needs.
Think of it as this analogy: You're on a boat on a river and the engine is not on and you're following the current of the river. It requires no energy and is known as passive transport.
Now, you wish to move the boat against the current. For the boat to move up stream, you must turn on the engine and use thrust power, thus using energy. Hence, active transport.