The 3D structure of the complete Escherichia coli ribosome with bound mRNA and tRNAs revealed that the very amino terminus of one protein (L27) does reach into the active site. This finding suggested a role for this protein in catalysis. To test this possibility, the nine amino acids at the L27 amino terminus that were in close proximity to the active site were eliminated by mutation. The following possible outcomes were found to be correct as

A. The resulting cells produced ribosomes with reduced but detectable peptidyl transferase activity

B. Region of the L27 protein contributes to peptidyl transferase activity

C. The mutant ribosomes, didn’t synthesised wildtype levels of cells

D. Vast majority of this increase in peptide bond formation is retained, even without the presence of L27 in the active site

E. The most likely role for L27 is to correctly position one or more of the RNA components of the active site

#Question id: 3049

#Unit 2. Cellular Organization

E. coli cells typically make most of their ATP by metabolizing glucose. Under the conditions of this experiment, what should be true of E. coliʹs generation time

#Question id: 3050

#Unit 2. Cellular Organization

Agar is well suited as a solidifying agent because

A. it has been melted in boiling water

B. it can be cooled to about 40 to 42°C before hardening

C. it will not melt again until the temperature rises to about 80 to 90°C.

D. most microorganisms cannot degrade it.

#Question id: 3051

#Unit 2. Cellular Organization

You have 10^10 cell/L of bacterial stock solution. To prepare 1 liter of growth medium containing 1000 bacteria, the volume in microlitre of this stock solution that should be added is

#Question id: 3052

#Unit 2. Cellular Organization

How many average CFU will form on petriplate if 0.1ml sample plating from 104 diluted sample (original sample contain 3x10^7 bacteria per ml)

#Question id: 3053

#Unit 2. Cellular Organization

Bacterial culture contains 1000/ mL in the exponential growth phase. If you consider a generation time of 20 minutes, the total number of organisms / mL 60 minute will be

#Question id: 3054

#Unit 2. Cellular Organization

A pure culture in exponential growth phase has a bacterial concentration of 6.4 x 10^8 cells/ml. If the bacterium has a generation time of 1 h, how long ago was the cell concentration 8.0 x 10^7 cells/ml?