Question

Lactose is a source of ____ found covalently bound via
glycosidic bond to galactose
Select one or more:
a. sucrose
b. aspartic acid
c. fructose
d. glutamine
e. glucose​

Answer 1

Answer:

Protein glycosylation takes place inside the lumen of the endoplasmic reticulum (ER) and the Golgi complex, organelles that play central roles in protein trafficking (Figure 11.21). One such glycoprotein (depicted in Figure 11.20) is the proteolytic enzyme elastase (Section 9.1.4), which is secreted by the pancreas as a zymogen (Section 10.5). This protein is synthesized by ribosomes attached to the cytoplasmic face of the ER membrane, and the peptide chain is inserted into the lumen of the ER as it grows, guided by a signal sequence of 29 amino acids at the amino terminus. This signal sequence, which directs the protein through a channel in the ER membrane, is cleaved from the protein in the transport process into the ER (Figure 11.22). After the protein has entered the ER, the glycosylation process begins. The N-linked glycosylation begins in the ER and continues in the Golgi complex, whereas the O-linked glycosylation takes place exclusively in the Golgi complex.