Biological Techniques MCQs ||| ZOO101 MCQs ||| Set 1

MCQs (Multiple Choice Questions )

1)  Centrifugal force is experienced by a particle in ----------- motion.

    a)        Random motion

    b)        Circular motion

    c)        Both of these

Correct Answer:

The correct answer is  'b'.

Explanation:

Centrifugal force is not a true force in the traditional sense, but rather an apparent or fictitious force that arises due to the inertia of the particle. It is a result of the particle's tendency to continue moving in a straight line due to its inertia while constrained to move in a circular path.

As the particle moves in a circle, it constantly changes its direction. In order to maintain this curved path, there must be a force acting on the particle toward the center of the circle. This force, called the centripetal force, keeps the particle in circular motion by continuously changing its velocity vector.

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. In the case of circular motion, the reaction to the centripetal force is the centrifugal force, which appears to act outward from the center of the circle. This apparent force is experienced by the particle, giving the sensation of being pushed away from the center.

It is important to note that centrifugal force does not exist in an inertial reference frame but is rather a result of observing the motion from a non-inertial frame, which is moving with the particle. From an inertial frame of reference, only the centripetal force is considered, and there is no outward force acting on the particle.

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2) Red cells separated from the plasma of cells create a centrifugal force upto_______.

    a)        800,000 x g

    b)        700,000 x g 

    c)        900,000 x g

Correct Answer: 

The correct answer is  'c'.

Explanation:

In a centrifuge, red blood cells can be separated from the plasma by subjecting the blood sample to a centrifugal force. This force is generated by the rapid spinning of the centrifuge, causing the denser red blood cells to move toward the bottom of the tube while the less dense plasma moves toward the top.

The "g" in the value represents the acceleration due to gravity, which is a measure of the force applied. When we say "900,000 x g," it means that the centrifuge is generating a force 900,000 times stronger than the force of gravity on Earth.

By applying such a high centrifugal force, red blood cells, which are denser and heavier than plasma, can be effectively separated from the plasma. The specific force required may vary depending on the type of centrifuge and the desired level of separation.

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3) The rotational speed of red cells that are separated from plasma cell is______.

    a)        170,000 rpm

    b)        150,000 rpm

    c)        120,000 rpm

Correct Answer:  

The correct answer is  'b'.

Explanation:

The rotational speed mentioned (150,000 rpm) refers to the number of revolutions the centrifuge performs per minute. When a blood sample is placed in the centrifuge and spun at this speed, it generates a centrifugal force that separates the components of the blood based on their density.

As the centrifuge spins rapidly, the denser red blood cells are forced to move toward the bottom of the tube due to the higher centrifugal force acting on them. At the same time, the less dense plasma moves toward the top. This process effectively separates the red blood cells from the plasma.

The specific speed of 150,000 rpm is chosen to optimize the separation process, ensuring a reliable and efficient separation of the blood components. Different centrifuges might have various speeds depending on the desired application and the properties of the substances being separated. In this case, it is the speed required to separate red cells from plasma
effectively.

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4) Centrifugal force is ________.

    a)        F = r * W^2 * M

    b)        F = W^2  * r * m

    c)        F = M * W^2 *r

Correct Answer: 

The correct answer is  'c'.

Explanation:

The correct equation for centrifugal force is:

F = M * w^2 * r

Where:

F is the centrifugal force,

M is the mass of the object being rotated, w is the angular velocity (rotation rate) of the object in radians per second, r is the distance from the center of rotation to the object.

In this equation, the centrifugal force is proportional to the mass of the object, the square of its angular velocity, and the distance from the center of rotation. As the rotational speed or the distance from the center increases, the centrifugal force also increases. This principle is used in centrifuges to separate substances of different densities based on their response to centrifugal force.

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5) In the formula F= M *w^2 *r , w represents:

    a)        Average angular velocity

    b)        Stem and leaf plot

    c)        Radius of rotation

Correct Answer: 

The correct answer is  'a'.

Explanation:

In the formula F = M * w^2 * r, "w" represents the angular velocity of the object in radians per second.

Angular velocity (w) is a measure of how fast an object is rotating or revolving around a fixed point. It indicates the rate of change of angular displacement with respect to time. The unit of angular velocity is radians per second (rad/s). The symbol "w" is often used to represent angular velocity in mathematical equations.

In the context of the formula, angular velocity (w) plays a crucial role in determining the centrifugal force (F) acting on an object with mass (M) that is rotating at a distance (r) from the center of rotation. The greater the angular velocity and the distance from the center of rotation, the larger the centrifugal force experienced by the object. This relationship is used
in various applications, including centrifuges used to separate substances based on their densities.

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6) Angular velocity is:

    a)        Force experienced by a particle in circular motion

    b)        Rate of rotation around an axis

    c)        None of these

Correct Answer: 

The correct answer is  'b'.

Explanation:

Angular velocity refers to the rate at which an object rotates or revolves around a fixed axis. It is the change in angular displacement per unit of time, and it is usually measured in radians per second (rad/s). The angular velocity describes how fast an object is spinning or moving in a circular path around a central point or axis. It is a fundamental concept in
rotational motion and is used to quantify the rotational speed of objects.

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7) Formula for Angular velocity is:

    a)        G = r * w ^2

    b)        F = M * w^2 * r

    c)        W = 2 * `\pi` * rev`min^{-1}/60

Correct Answer: 

The correct answer is  'c'.

Explanation:

In this formula, "W" represents the angular velocity, and it is given in revolutions per minute (rev/60). The symbol π (pi) is a mathematical constant representing the ratio of a circle's circumference to its diameter, approximately equal to 3.14159. This formula provides a way to convert angular velocity from revolutions per minute to radians per second, which is another common unit of angular velocity used in physics and engineering calculations.

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8) Rate of sedimentation is:

    a)        S= dr/dt (1/w^2r)

    b)        S= w^2r(1-`v_p`)

    c)        dr/dt= M(1-`v_p`)/NA fw^2r

Correct Answer: 

The correct answer is  'b'.

Explanation:

S = w^2 * r * (1 - v_p)

In this formula:

S represents the rate of sedimentation,

w is the angular velocity of the rotating object (in radians per second), r is the distance from the center of rotation to the particle, v_p is the partial specific volume of the particle (a property related to its density and volume).

This equation describes the rate at which particles in a liquid mixture settle or sediment under the influence of centrifugal force in a centrifuge. The rate of sedimentation depends on the angular velocity of the centrifuge, the distance from the center of rotation, and the properties of the particles, specifically their partial specific volume.

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9) The aim of preparative ultracentrifugation is:

    a)        To isolate and purify specific particles

    b)        To study molecular interaction

    c)        To separate particles

Correct Answer: 

The correct answer is  'a'.

Explanation:

Preparative ultracentrifugation is a technique used to separate and purify specific particles, such as proteins, nucleic acids, and subcellular organelles, from complex mixtures. By subjecting the mixture to high centrifugal forces and carefully controlling the centrifugation parameters, the particles of interest can be separated based on their density, size, or
molecular weight. This technique is commonly used in biochemistry, molecular biology, and other scientific fields to obtain highly purified samples for further analysis and study.

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10) How many types of isotope fractionation:

    a)        3

    b)        2

    c)        4

Correct Answer: 

The correct answer is  'c'.

Explanation:

There are four types of isotope fractionation (of which the first two are normally most important): equilibrium fractionation, kinetic fractionation, mass-independent fractionation (or non-mass-dependent fractionation), and transient kinetic isotope fractionation.

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