The Birth of a Gene - Duplication is the most common way that new genes arise in eukaryotes. 

TLS Online TPP Program

#Id: 7930

#Section 3: Genetics, Cellular and Molecular Biology

Secretory pathway

pathway of protein trafficking that flows through the ER

TLS Online TPP Program

#Id: 7929

#Section 3: Genetics, Cellular and Molecular Biology

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

#Section 3: Genetics, Cellular and Molecular Biology

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

#Section 3: Genetics, Cellular and Molecular Biology

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

#Section 3: Genetics, Cellular and Molecular Biology

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.

TLS Online TPP Program

#Id: 7925

#Section 3: Genetics, Cellular and Molecular Biology

Endoplasmic reticulum

Network of interconnected membranous structures within the cytoplasm of eukaryotic cells contiguous with the outer nuclear envelope.