Hint: Every particle has its density or a different sediment rate at which it can be separated from the higher and lower density particles. It needs a fast-rotating machine whose speed can be controlled. The rpm (revolution per minute) is the unit of a centrifuge. The cell can be studied after separating all its cell organelles.
Complete answer: What is centrifugation? The technique of applying the centrifugal force to separate the particles from the solution based on their size, shape, density, rotor speed etc., this is called centrifugation. There are various types of centrifugations.
What is isopycnic centrifugation? When the particles are separated from the liquid-based on their density, that is isopycnic centrifugation. The particles move until their density is the same as the gradient in the surrounding medium.
> Option A: Density gradient centrifugation: The separation of the components of the sample based on the density solely is called the density gradient centrifugation. It is used to separate bacteria from the food matrices.
> Option B: Zonal centrifugation: When the particles are separated on the basis of their size, it is called zonal centrifugation. A lower density gradient is used to separate the particles.
> Option C: Differential centrifugation: It is also called Differential velocity centrifugation. This separates the particles based on their sedimentation rate. It is used in biology to separate the cell organelles.
Hence, The correct answer is option (A).
Note: Centrifuge is a fast rotating machine that applies centrifugal force to its contents. There is a rotor in the machine. The cells are homogenized in the machine to break their membranes and walls. The supernatant can be centrifuged again to get the other less dense particles. To avoid the disruption of the enzymes, an ice-cold isotonic solution is added.