Selenocysteine is generated enzymatically from serine carried on a special tRNA that is charged by serine-tRNA synthetase. The Sec residues of selenoproteins are thought to participate in redox reactions such as those catalyzed by mammalian glutathione peroxidase and thioredoxin reductase

TLS Online TPP Program

#Id: 7019

#Unit 5. Developmental Biology

Once stem cells become positioned farther from the niche, signaling factors cannot reach them, and differentiation commences.

TLS Online TPP Program

#Id: 9645

#Unit 4. Cell Communication and Cell Signaling

Active Ras⋅GTP binds to the N-terminal autoinhibitory domain of Raf, altering its conformation and allowing the phosphate attached to this domain to be removed by cytosolic phosphatases, causing loss of 14-3-3 binding.

TLS Online TPP Program

#Id: 3025

#Unit 3. Fundamental Processes

A preformed RNA (often a tRNA) pairs with the template, allowing its 3'-0H end to be used to prime DNA synthesis.

TLS Online TPP Program

#Id: 5517

#Unit 10. Ecological Principles

Biotic potential / Intrinsic rate of natural increase (r) It is the inherent power of a population to grow and reproduce when environmental conditions are favorable, and resources are unlimited. 

TLS Online TPP Program

#Id: 6278

#Unit 3. Fundamental Processes

The complete enzyme or holoenzyme in E. coli has a molecular weight of ,460 kD. The holoenzyme (a2bbws) can be separated into two components: the core enzyme (a2bbw) and the sigma factor (the s polypeptide), which is concerned specifically with promoter recognition.