The bacterial chromosome is a single replicon; thus, the frequency of replication cycles is controlled by the number of Initiation events at the single origin.

TLS Online TPP Program

#Id: 1716

#Unit 4. Cell Communication and Cell Signaling

The serum half-life of IgE is quite short (only 2 to 3 days). However, when bound to its receptor on an innate immune cell, IgE is stable for weeks.

TLS Online TPP Program

#Id: 1717

#Unit 4. Cell Communication and Cell Signaling

IgE binds two different receptors, the high-affinity FcεRI, which is responsible for most of the symptoms we associate with allergy, and the lower-affinity FcεRII, which regulates the production of IgE by B cells, as well as its transport across cells.

TLS Online TPP Program

#Id: 1718

#Unit 4. Cell Communication and Cell Signaling

FcεRI, which binds IgE with an exceptionally high-affinity constant of 10^10 M^-1 .

TLS Online TPP Program

#Id: 1719

#Unit 4. Cell Communication and Cell Signaling

The other IgE receptor, designated FcεRII, or CD23, has a much lower affinity for IgE (Kd of 1 * 10 6 M -1 )

TLS Online TPP Program

#Id: 1720

#Unit 4. Cell Communication and Cell Signaling

Most cells express a tetrameric form of FcεRI, which includes an α and β chain and two identical disulfide-linked γ chains.

TLS Online TPP Program

#Id: 1721

#Unit 4. Cell Communication and Cell Signaling

Monocytes and platelets express an alternative form lacking the β chain.