A ribosome-associated protein called RelA receives the “alarm” and produces the “alarmone” ppGpp, which destabilizes open promoter complexes whose lifetimes are normally short, thus inhibiting Transcription.

TLS Online TPP Program

#Id: 5026

#Unit 3. Fundamental Processes

The rate of bacterial growth is assessed by the doubling time, the period required for the number of cells to double.

The shorter the doubling time, the faster the bacteria are growing.

Escherichia coli growth rates can range from doubling times as fast as 18 minutes to slower than 180 minutes.

TLS Online TPP Program

#Id: 9289

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 6361

#Unit 2. Cellular Organization

Repressors bind to specific sites on the DNA. In bacterial cells, such binding sites, called operators

Regulation by means of a repressor protein that blocks transcription is referred to as negative regulation. Activators provide a molecular counterpoint to repressors; they bind to DNA and enhance the activity of RNA polymerase at a promoter; this is positive regulation.Repressor binding to DNA is regulated by a molecular signal called effector

TLS Online TPP Program

#Id: 5796

#Unit 7. System Physiology – Animal

The major hormonal product of the coupling reaction is the molecule thyroxine (T4), which is formed when two molecules of DIT are joined together; the thyroxine then remains part of the thyroglobulin molecule.

TLS Online TPP Program

#Id: 5074

#Unit 6. System Physiology – Plant

Experiment on coleoptile phototropism