The biosynthesis of chlorophylls and heme begins with the synthesis of δ‐aminolevulinic acid (ALA) from glutamic acid. 

Two molecules of ALA react to yield porphobilinogen (PBG). 

Four molecules of PBG form the ring structure of protoporphyrin IX, the common branch point for the synthesis of heme and chlorophyll. 

To make chlorophyll, a magnesium chelatase inserts Mg into the protoporphyrin IX ring

TLS Online TPP Program

#Id: 10341

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 10342

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 10343

#Unit 4. Cell Communication and Cell Signaling

The heavy chain is then expressed on the cell surface in combination with the surrogate light chain, which is made up of VpreB and λ5. 

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#Unit 4. Cell Communication and Cell Signaling

B- cell maturation

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#Unit 4. Cell Communication and Cell Signaling

T1 and T2 Transitional B Cells

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#Unit 4. Cell Communication and Cell Signaling

T1 cells are mIgMhi, mIgD -/lo, CD21-, CD23-, CD24+, and CD93+. 

T2 cells differ from T1 cells in having higher levels of mIgD and in expressing CD21 and CD23.