Cell Biology MCQ | Advanced Level | Biology Olympiad Questions

1. A dichotomous key for a few cell components is given below. 1a. Found in cytosol…..go to 2 1b. Found in nucleus….A 2a. Membrane-bound structure….go to 3 2b. Structure is not membrane bound…B 3a. Flattened sheet-like structure….go to 4 3b. Spherical or elongated structure….go to 6 4a. Smooth exterior…..go to 5 4b. Rough exterior……C 5a. Involved in lipid metabolism…..D 5b. Several spherical vesicles found in vicinity…..E 6a. Bound by single membrane….got to 7 6b. Bound by double membrane………F 7a. Contains oxidative enzymes……..G 7b. Contains hydrolytic enzymes…….H E, F and G respectively most likely represent:

a) SER; Mitochondria and Lysosome b) Lysosome; Mitochondria and Peroxisome c) Golgi; Mitochondria and Peroxisome d) Golgi; Peroxisome and Lysosome

2. Which of the following sets of chemicals and/or instrument can be used to prepare sodium phosphate buffer of approximately pH 7.0?

 I. Na2HPO4 salt, NaH2PO4 salt and water. 

II. NaH2PO4 salt, NaOH solution and pH meter.

III. Na2HPO4 salt, water and pH meter. 

IV. Stocks of: NaH2PO4 solution, Na2HPO4 solution and water. (pKa values for phosphoric acid: 2.12, 7.21, 12.32) 

a) Only I

b)  Only IV

c) Only I, II and IV 

d)  I, II, III and IV

3.  One of the oxygen utilizing enzymes, cytochrome P450 catalyzes the following reaction:

R – H +NADPH + H⁺ + O2⇌ R – OH +NADP⁺ + H2O

 These enzymes are also found useful in detoxification of xenobiotics (chemicals foreign to an organism). Which of the following is the most likely mode of action of these enzymes?

 a. They create a non-reducing environment by utilizing NADPH, thus nullifying the effect of the xenobiotics. 

b. They create anaerobic conditions in the cell by utilizing oxygen and thus decreasing the effect of the xenobiotics.

 c. They convert the xenobiotics to its polar form, which is easy to be excreted. 

d. They promote oxidative phosphorylation to generate ATP for detoxification of the xenobiotics.

4. Absorption/transmission spectrum of a compound often provides information about its physical property such as color. Absorption spectra of three compounds are shown below.

I, II and III respectively represent: 

a. hemoglobin, oxyhemoglobin and water. 

b. oxyhemoglobin, hemoglobin and water. 

c. water, hemoglobin and oxyhemoglobin. 

d. oxyhemoglobin, water and hemoglobin

5. Biochemical purification of a protein from a cell extract often requires several purification steps involving various techniques. The purification process can be followed by gel electrophoresis of the starting protein mixture ie the cell homogenate and the fractions obtained from each subsequent purification step. Shown here are the schematic depictions of separation of proteins on a gel for the starting mixture of proteins (lane 1) and samples taken after each of the several purification steps

If lanes 1 and 2 indicate the separation of proteins from the crude cell homogenate and after salt fractionation respectively, then which of the techniques are represented in lanes 3, 4 and 5 respectively?

 a. Ion exchange chromatography; affinity chromatography and gel filtration chromatography

b. Gel filtration chromatography; ion exchange chromatography and affinity chromatography 

c. Affinity chromatography; ion exchange chromatography and gel filtration chromatography

 d. Ion exchange chromatography; gel filtration chromatography and affinity chromatography

Answers:

1.c) Golgi; Mitochondria and Peroxisome

2. c) Only I, II and IV 

3.  c. They convert the xenobiotics to its polar form, which is easy to be excreted. 

4. a. hemoglobin, oxyhemoglobin and water. 

5. d. Ion exchange chromatography; gel filtration chromatography and affinity chromatography