This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Chemical Basis of Life – Acids, Bases and Buffers”.
1. Which of the following is released when a Hydrogen atom loses an electron?
Explanation: Whenever a hydrogen atom releases a shared electron in solution, a proton is also released. For example, acetic acid undergoes dissociation reaction to release acetate ion and a proton.
2. Which of the following is an example of amphoteric molecule?
a) Acetic acid
b) Malic acid
Explanation: Water is an example of both an acid and a base, and is therefore an amphoteric molecule. It can accept a proton thereby acting as a base and can also donate a proton acting as an acid.
3. Acids that lose a proton easily are weak acids.
Explanation: The strength of an acid is measured by the relative ease by which it loses a proton. The more readily the proton is lost, more strong is the acid. An example of a strong acid is Hydrogen Chloride which readily transfers its protons to water.
4. What is the full form of pH?
a) Positive hydrogen
b) Potential Hydrogen
d) Proton of hydrogen
Explanation: The acidity of a compound is measured by the concentration of hydrogen ions and is expressed in terms of pH- potential hydrogen. pH equals negative logarithmic concentration of protons.
5. A solution having a pH of 6 has a proton concentration of _______
a) 10-6 M
b) 106 M
c) 6 M
d) 0.6 M
Explanation: pH equals negative logarithmic concentration of protons. Since the pH scale is logarithmic, an increase of one pH unit corresponds to ten-fold decrease in hydrogen ion/ proton concentration.
6. What is the concentration of pure water?
a) 55.51 M
b) 25.51 M
c) 55 M
d) 25 M
Explanation: The concentration of pure water is always 55.51 Molar. On the basis of this universal value ion-product constant Kw for water is calculated, which is a constant value at 25℃.
7. In presence of an acid, amino group can be ____________
b) Washed away
Explanation: In presence of an acid, amino group can be Protonated because an acid release proton, thereby increasing the hydrogen ion concentration in its vicinity and this can result in disruption of the protein activity to which amine group is attached.
8. Buffers react with _______________ ions.
a) hydrogen, hydroxyl
b) magnesium, calcium
Explanation: Buffers react with free hydrogen and free hydroxyl ions resisting changes in the pH and protecting cells and solutions from destroying. Buffers are also routinely used in laboratories.
9. Buffers usually contain ________________ with its conjugate ____________
a) weak base, base
b) strong base, acid
c) weak acid, base
d) weak acid, acid
Explanation: Buffers are solutions that resists change in pH. They can be made up of a weak acid and its conjugate base or a weak base and its conjugate acid. An example of a buffer is a solution of acetic acid(weak acid) and sodium acetate(conjugate base).
10. Carbonic acid and bicarbonate ions buffer which of the following?
Explanation: Carbonic acid and bicarbonate ions buffer the blood and hold its pH at 7.4. Carbonic acid is a weak acid and bicarbonate ions are basic in nature. A change in pH of the blood can lead to abnormalities.
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