Respuesta :
Answer:
D
Explanation:
The correct option here would be D.
The endomembrane system refers to a group of membrane-based organelles whose primary function is to synergistically work together to modify, package, and transport lipids and proteins. The system includes organelles such as the lysosome, the nuclear envelope, the endoplasmic reticulum, and the Golgi apparatus.
For an endomembrane system function involving a protein, the protein would first of all need to be synthesized by the ribosome - the free ones or the ones attached to the rough endoplasmic reticulum. Thereafter, the synthesized protein would then be folded or packaged into transportable vesicles. The vesicles are then received by the Golgi apparatus which further modifies the proteins before transporting them accordingly.
Hence, the correct order of a typical endomembrane system function would be:
- Ribosomes on the RER synthesize proteins.
- Proteins are packaged into transport vesicles.
- Golgi apparatus receives transport vesicles from the RER.
- Proteins are modified by the Golgi apparatus.
- Modified proteins may be secreted from the cell by exocytosis.
Protein synthesis involves transcription and translation. Once the protein is synthesized, it suffers a few modifications in the RER and the Golgi complex, before leaving to its final destiny. The correct option is D. ⇒ 2, 3, 1, 5, 4
Protein synthesis and modification
Transcription ⇒ mRNA syntheis
The first step before protein synthesis begins is to synthesize messenger RNA, mRNA.
This is the coping process of the DNA section for the desired protein, and it happens in the nucleus.
Translation:
- Cytoplasm stage
Translation takes place when the formed mRNA moves to the cytoplasm through the nucleus membrane pores, and meets a ribosome.
Ribosomes are organelles composed by the association of proteins with rRNA and tRNA. They can be found in the rough endoplasmic reticulum or floating in the cytosol.
While the ribosome reads mRNA strain from its 5´ extreme to 3´, tRNA adds the correct amino acids to build the polypeptide.
- Endoplasmic Reticulum Stage
Some proteins are destined for membrane or exportation. Their synthesis starts in the cytoplasm but finishes in the Rough endoplasmic reticulum.
When the ribosome and the growing molecule reach the RER, the synthesizing protein keeps enlarging forward the reticulum lumen.
When the new polypeptide synthesis is complete, it is released into the reticulum lumen.
The endoplasmic reticulum is in charge of protein folding, maturation, and transport, especially those destined for secretion. It produces the latest protein modifications after transduction and initiates the glycosylation process.
The new proteins get packaged into vesicles that carry them to the Golgi complex.
- Golgi complex stage
Once the protein synthesis in the endoplasmic reticulum is over, these molecules are packaged into vesicles and sent to the Golgi complex.
In the Golgi complex, proteins suffer their final association with carbohydrates and lipids to originate glycoproteins and glycolipids.
- Destiny stage
Glycoproteins and glycolipids are packaged again into new vesicles that drive them to their final destiny.
Proteins destined for exportation are packaged and sent from the Golgi complex to the cell membrane into vesicles.
When the secretory vesicle reaches the target, its membrane fuses with the cell membrane, releasing its content to the extracellular space. This secreting process is known as exocytosis.
According to this resume about protein synthesis, we can say that the correct order is option D. ⇒ 2, 3, 1, 5, 4
2. Ribosomes on the RER synthesize proteins.
3. Proteins are packaged into transport vesicles.
1. Golgi apparatus receives transport vesicles from the RER.
5. Proteins are modified by the Golgi apparatus.
4. Modified proteins may be secreted from the cell by exocytosis.
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