The cytochrome P450 constitute a superfamily of heme-containing enzymes that occur in nearly all living organisms, from bacteria to mammals, These monooxygenases, which in animals are embedded in the endoplasmic reticulum membrane, catalyze reactions of the sort

                  RH + O₂ + 2 H⁺ + 2e⁻ → ROH + H₂O 

The electrons (e−) are supplied by NADPH, which passes them to cytochrome P450’s heme prosthetic group via the intermediacy of the enzyme NADPH P450 reductase. Here RH represents a wide variety of usually lipophilic compounds for which the different cytochromes P450 are specific. They include

a. polycyclic aromatic hydrocarbons 

b. polycyclic biphenyls

c. frequently carcinogenic compounds that are present in tobacco smoke, broiled meats, and other pyrolysis products

d. which were widely used in electrical insulators and as plasticizers and are also carcinogenic.

#Question id: 388

#Unit 1. Molecules and their Interaction Relevant to Biology

Calculate the pH of a solution prepared by mixing 2.0 mL of a strong acid solution of pH=3.0 and 3.0 mL of a strong base of pH=10.0.

#Question id: 389

#Unit 1. Molecules and their Interaction Relevant to Biology

A weak acid HA has a pKa of 5.0.  If 1.0 mol of this acid and 0.1 mol of NaOH were dissolved in one liter of water, what would the final pH be?

#Question id: 390

#Unit 1. Molecules and their Interaction Relevant to Biology

What are the properties arising due to varying concentrations of solute in a given solvent, irrespective of the nature of solute with respect to the solvent?

#Question id: 391

#Unit 1. Molecules and their Interaction Relevant to Biology

In a hospital laboratory, a 10.0 mL sample of gastric juice, obtained several hours after a meal, was titrated with 0.1 M NaOH to neutrality; 7.2 mL of NaOH was required. The patient’s stomach contained no ingested food or drink, thus assume that no buffers were present. What was the pH of the gastric juice?

#Question id: 392

#Unit 1. Molecules and their Interaction Relevant to Biology

When an ionic compound such as sodium chloride (NaCl) is placed in water, the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of solute particles (molecules or ions)?

#Question id: 393

#Unit 1. Molecules and their Interaction Relevant to Biology

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O ↔ H2CO3. Carbonic acid (H2CO3) is a weak acid. If CO2 is bubbled into a beaker containing pure, freshly distilled water, which of the following graphs correctly describes the results?