Nicotiana tabacum cells are cultured to high density for production of polysaccharide gum. The reactor used is a stirred tank, containing initially 100 litres medium. The maximum specific growth rate of the culture is 0.18 d^-1 and the yield of biomass from substrate is 0.5 g g^-l. The concentration of growth-limiting substrate in the medium is 3% (w/v). The reactor is inoculated with 1.5 g l^{- 1} cells and operated in batch until the substrate is virtually exhausted; medium flow is then started at a rate of 4 l d^-1. Fed-batch operation occurs under quasi-steady-state conditions. Fed-batch operation is carried out for 40 d. What is the final mass of cells in the reactor?

                               _____________________

#Question id: 398

#Section 4: Fundamentals of Biological Engineering

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). (See figure.)

If the pH of blood drops, one would expect ________.

#Question id: 399

#Section 4: Fundamentals of Biological Engineering

Calculate the pH of a 1 L solution containing 0.100 M formic acid and 0.100 M sodium formate before and after the addition of 1.00 mL of 5.00 M NaOH. How much would the pH change if the NaOH were added to 1.00 L of pure water? (pKa for formic acid is 3.75)

#Question id: 400

#Section 4: Fundamentals of Biological Engineering

Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that ________.

#Question id: 401

#Section 4: Fundamentals of Biological Engineering

.Which of the following graphs describes the relationship between [H3O+] and pH?

#Question id: 402

#Section 2: General Biology

If the DG'° of the reaction A -> B is –40 kJ/mol, under standard conditions the reaction:

#Question id: 402

#Section 4: Fundamentals of Biological Engineering

If the DG'° of the reaction A -> B is –40 kJ/mol, under standard conditions the reaction: