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

#Id: 7931

#XL - Q Biochemistry

Microsomes

when cells are homogenized, the rough ER breaks up into small closed vesicles with ribosomes on the outside

TLS Online TPP Program

#Id: 7930

#XL - Q Biochemistry

Secretory pathway

pathway of protein trafficking that flows through the ER

TLS Online TPP Program

#Id: 7929

#XL - Q Biochemistry

The ER captures selected proteins from the cytosol as they are being synthesized. These are of two types:

Transmembrane proteins

Water-soluble proteins

TLS Online TPP Program

#Id: 7928

#XL - Q Biochemistry

Muscle cells have an abundant, modified smooth ER called the sarcoplasmic reticulum.

The release and reuptake of Ca2+ by the sarcoplasmic reticulum trigger myofibril contraction and relaxation, respectively

TLS Online TPP Program

#Id: 7927

#XL - Q Biochemistry

Function of the ER:

most eukaryotic cells is to sequester Ca2+ from the cytosol (High concentration of Ca2+-binding proteins in the ER facilitates Ca2+ storage)

TLS Online TPP Program

#Id: 7926

#XL - Q Biochemistry

Rough ER, which is associated with ribosomes, functions in the synthesis and processing of secreted and membrane proteins

Smooth ER, which lacks ribosomes, functions in lipid synthesis.