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: 10091

#Unit 4. Cell Communication and Cell Signaling

Outside-in signaling

Binding of integrins to their ligands induces conformational changes in their cytoplasmic domains, directly or indirectly altering their interactions with cytoplasmic proteins

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#Id: 10092

#Unit 4. Cell Communication and Cell Signaling

Inside-out signaling

intracellular signaling pathways can, via adapter proteins, modify the ability of integrins to bind

to their extracellular ligands

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#Id: 10093

#Unit 4. Cell Communication and Cell Signaling

Integrin exist in two conformations: 

Inactive, low-affinity, “bent” conformation  

Active, high-affinity, “extended” conformation

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#Id: 10094

#Unit 4. Cell Communication and Cell Signaling

Activation of integrins involves:

Conformational changes near the propeller and 

 βA domains

Separation of the transmembrane and cytoplasmic domains

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#Id: 10095

#Unit 4. Cell Communication and Cell Signaling

Hemidesmosomes are integrin-containing anchoring junctions that attach cells to elements of the underlying extracellular matrix.

TLS Online TPP Program

#Id: 10096

#Unit 4. Cell Communication and Cell Signaling

Integrins have an important function in neuroregeneration after injury of the peripheral nervous system.