Question 1

Which of the following is the primary buffer system used in the preparation of Tris-HCl buffer for biochemical experiments?

Accepted Answer

Tris-HCl buffer system

Question 2

A student is preparing a 1 M Tris-HCl buffer. If the molecular weight of Tris base is 121.14 g/mol, how many grams are needed to make 1 L of 1 M solution?

Accepted Answer

$$121.14 g$$

Question 3

Why is it important to adjust the pH of a Tris buffer at the temperature at which it will be used?

Accepted Answer

The pH of Tris buffer decreases with increasing temperature

Question 4

A protocol requires you to add 5 mL of 1 M Tris-HCl to a solution. What is the final amount of Tris-HCl (in moles) added?

Accepted Answer

$$0.005$$ \, 	ext{mol}$

Question 5

Which of the following best explains why EDTA is included in many biochemical buffer solutions?

Accepted Answer

To chelate divalent metal ions and inhibit metal-dependent enzymes

Question 6

You are instructed to add 1 mL of 0.5 M EDTA to your buffer. How many millimoles of EDTA are you adding?

Accepted Answer

$$0.5$$ \, 	ext{mmol}$

Question 7

A buffer recipe calls for the addition of 1 mL of 1 M NaCl. What is the final concentration of NaCl if the total buffer volume is 100 mL?

Accepted Answer

$$0.01$$ \, 	ext{M}$

Question 8

Which of the following is the most likely reason for adding glycerol to a biochemical buffer?

Accepted Answer

To increase the viscosity and stabilize proteins

Question 9

If you need to prepare 20 mL of buffer and your protocol specifies adding 1 mL of 1 M Tris-HCl, what is the final concentration of Tris-HCl in the buffer?

Accepted Answer

$$0.05$$ \, 	ext{M}$

Question 10

A buffer solution contains 1 mL of 1 M Tris-HCl, 1 mL of 0.5 M EDTA, and 1 mL of 1 M NaCl, made up to 20 mL with water. Which component is present at the lowest final concentration?

Accepted Answer

EDTA

Question 11

Which of the following steps is essential to ensure the buffer is at the correct pH for use in enzyme assays?

Accepted Answer

Adjust the pH after adding all components and before making up to final volume

Question 12

If you mistakenly add 10 mL of 1 M NaCl instead of 1 mL to your buffer, what is the most likely effect on your biochemical experiment?

Accepted Answer

The buffer will have increased ionic strength, possibly denaturing proteins or inhibiting enzyme activity

Question 13

Which of the following best describes the role of water in the preparation of biochemical buffers?

Accepted Answer

Serves as the solvent to dissolve all buffer components and bring the solution to final volume

Question 14

A buffer is prepared by mixing 1 mL of 1 M Tris-HCl, 1 mL of 0.5 M EDTA, and 1 mL of 1 M NaCl, then adding water to a final volume of 20 mL. What is the final concentration of EDTA in the buffer?

Accepted Answer

$$0.025$$ \, 	ext{M}$

Question 15

Which of the following is a potential consequence of not adding EDTA to a buffer used for DNA extraction?

Accepted Answer

Increased risk of DNA degradation by DNases

Enzyme Kinetics: Michaelis-Menten and Inhibitor Effects

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