Module 5 Assessment: Protein Synthesis and its Transportation

This assignment explores the process of protein synthesis and its subsequent transport within a cell. It begins by describing the endoplasmic reticulum (ER), differentiating between its smooth and rough forms, and highlighting its crucial role in protein synthesis, processing, and trafficking. The assignment then details the pathway of secreted proteins, starting from their synthesis in the pancreas and moving through the rough ER and Golgi apparatus before being secreted from the cell. The role of vesicles in transporting proteins is also explained. Furthermore, the assignment discusses the importance of targeting signals in directing proteins to their correct destinations, including the lysosomes. Finally, the assignment describes the function of lysosomes in cellular digestion and the consequences of lysosomal storage diseases. References to relevant research articles and books are also provided.

Module 5 Assessment

Protein Synthesis and its transportation
Endoplasmic reticulum refers to a network of membrane flattened saccules or cisternae,
tubules and nuclear envelope which together extend throughout the cell. It is considered as an
intracellular organelle which conduct several functions including protein synthesis, processing
(folding, gltcosylation, quality control), trafficking, calcium homeostasis, intracellular signaling
and lipid & xenobiotic metabolism. Moreover, ER is divided into Smooth (SER) and rough
(RER) on basis of absence or presence of lysosomes at external surface. However, pancreas is
primary organ which is responsible for digestion of food and pancreatic acinar cells synthesize
new proteins that secret digestive enzymes into small intestine (Yao and et. al., 2011).
Meanwhile, after a brief exposure of pancreatic cells to radioactive amino acids, the newly
formed proteins were detected in rough ER but non- radioactive amino acids directs them
towards Golgi apparatus. Thus, cytosolic surface of membranes have attached ribosomes that are
synthesizing proteins for import into the ER.
Pathway of secreted protein
 Initially, Newly synthesize in pancreas
 Meanwhile, Rough Endoplasmic Reticulum
 Moreover, Golgi Apparatus
 Additionally, Secretory vesicles
 At last, Cell exterior
The protein are imported into ER through cytosolic surface of RER membrane with
attached ribosomes which synthesize protein in proper manner. Meanwhile, the final destination
of proteins is ER lumen or membrane and finally received by Golgi Complex to be processed
further as well as sorted for transporting to eventual destinations including lysosomes, plasma
membrane or secretions.
There are several molecules including proteins in body which are too for directly passing
through membranes (Gilbert, 2012). Meanwhile, theses large molecules are loaded into small
membrane wrapped containers which are known as vesicles. Additionally, the formation of
vesicles takes place in plasma membrane, Endoplasmic reticulum or Golgi complex. In case of
most of the proteins, they get transported to the Golgi apparatus for the synthesis of vesicles and
then transported to appropriate destinations such as inner space of organelle, different
intracellular membranes, plasma membrane or to the exterior of cell through secretion. The
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delivery procedure of conducted on basis of information carried by each protein molecule.
Moreover, targeting signals is a kind of mechanism which is helpful in transportation of proteins
to different specified locations which is called as protein targeting or sorting. Additionally,
targeting signals are known as pieces of information which are responsible for transport of
proteins to at correct sites.
The lysosomes are composed of soluble and trans membrane proteins which are targeted
to lysosomes in a signal dependent manner. It is a membrane enclosed organelles that contains
different types of enzymes which are bale to break down overall polymers such as proteins,
nucleic acids, carbohydrates and lipids (Zhang and et. al., 2012). The function of lysosomes is in
digestive system of cell for both perspectives including degrading material outside and digest
obsolete components inside the cell. Additionally, mutations in genes are responsible for more
than 30 different genetic diseases in human beings which are known as Lysosomal Storage
Disease. The defect in mechanism was that the undigested material accumulates within the
lysosomes of affected individuals and it happen due to deficiency in single lysosomal enzymes.
REFERENCES
Books and journals
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Yao, Y. X. and et. al., 2011. Isolation and characterization of an apple cytosolic malate
dehydrogenase gene reveal its function in malate synthesis. Journal of plant physiology.
168(5). pp.474-480.
Gilbert, L. ed., 2012. The juvenile hormones. Springer Science & Business Media.
Zhang, Y. and et. al., 2012. The synthesis, transportation and degradation of BmLP3 and
BmLP7, two highly homologous Bombyx mori 30K proteins. Insect biochemistry and
molecular biology. 42(11). pp.827-834.
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