III. Vascular plants (pteridophyta)

EVOLUTION OF ROOTS

Instead of the rhizoids seen in bryophytes, roots evolved in the sporophytes of almost all vascular plants

TLS Online TPP Program

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#XL - T Zoology

The adhesiveness of cadherins depends on the presence of extracellular Ca2+

TLS Online TPP Program

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#XL - T Zoology

Two type of Cadherins:

1. Classical cadherin proteins

2. Nonclassical cadherin proteins

TLS Online TPP Program

#Id: 10066

#XL - T Zoology

Extracellular region of a classical cadherin contains five copies of the cadherin domain separated by flexible hinge regions

TLS Online TPP Program

#Id: 10067

#XL - T Zoology

Ca2+ ions bind to sites near each hinge and prevent it

from flexing, so that the whole string of cadherin domains behaves as a rigid and slightly curved rod to generate cell–cell adhesion

TLS Online TPP Program

#Id: 10069

#XL - T Zoology

Each classical cadherin molecule contains: 

A single TM domain

A short C-terminal cytosolic domain

Five extracellular “cadherin” domains (EC1–EC5)

TLS Online TPP Program

#Id: 10070

#XL - T Zoology

Three classes of classical cadherins: 

E-cadherin -present on epithelial cells

N-cadherin - present on nerve, muscle and lens cells

P-cadherin - present on cells in the placenta & epidermis