Question

Cells which are secretory in function have abundant (a) lysosomes (b) endoplasmic reticulum (c) dictyosomes (d) osteosomes.

Short answer

Secretory cells have abundant endoplasmic reticulum due to its role in protein synthesis and lipid production, which are essential for cell secretion.

Step-by-step solution

- Understanding secretory cells

To determine which organelles are abundant in cells with secretory function, one must first understand what a secretory cell does. Secretory cells specialize in producing and releasing (secreting) substances such as hormones, enzymes, and other important compounds.

- Identifying the function of each organelle

Lysosomes are involved in digestion and waste removal. The endoplasmic reticulum (ER) is involved in the synthesis and folding of proteins and the production of lipids. Dictyosomes refer to the Golgi apparatus, which modifies, sorts, and packages proteins and lipids for secretion. Osteosomes are not a recognized organelle in the context of cell biology.

- Associating the organelle to the secretory function

Since secretory cells are involved in producing and releasing substances, the organelle most associated with secretion is the endoplasmic reticulum. This is especially true for the rough endoplasmic reticulum, which has ribosomes on its surface and plays a crucial role in protein synthesis.

Key concepts

Endoplasmic Reticulum in Secretory Cells

The endoplasmic reticulum (ER) is a pivotal structure in the cells, especially for those with secretory functions. Imagine it as a factory where the assembly and initial modifications of proteins occur. In secretory cells, the ER is indeed abundant to meet the high demand for protein synthesis.

The ER exists in two forms: rough, with ribosomes dotting its surface, and smooth, which lacks ribosomes. Now, let's focus on the rough ER (RER), as it's directly involved in synthesizing proteins destined for secretion. The ribosomes on the RER are like workers on the production line, tirelessly creating proteins.

Process of Protein Synthesis in RER

Once a protein is synthesized by the ribosomes, it is threaded into the lumen of the RER where it may undergo a series of modifications. These may include folding into its three-dimensional shape or the addition of sugar molecules in a process called glycosylation. The proteins must be correctly assembled to function properly once they reach their destinations. Malfunctioning of the ER can lead to a range of diseases, due to improper protein formation.

• Protein folding
• Glycosylation
• Quality control and ER-associated degradation (ERAD)

After proteins are properly formed, they're packed into transport vesicles and sent to the Golgi apparatus for further processing.

Golgi Apparatus: The Secretory Cell's Post Office

The Golgi apparatus, often compared to a post office in the cell, follows the ER in the protein-secretion assembly line. It further processes, sorts, and packages proteins and lipids received from the ER. Think of it as the place where products are given a mailing address and are dispatched to their specific destinations.

Proteins arrive at the Golgi in vesicles, which fuse with the Golgi's membrane. The Golgi apparatus then takes on the role of modifying these proteins. Some modifications include:

• Adding or altering carbohydrate chains
• Phosphorylating proteins, which can alter their function or signaling
• Sulfation, which adds sulfate groups to molecules

Vesicle Formation and Secretion

After the proteins have been modified, they are packaged into vesicles once more. These are then directed to the appropriate part of the cell for use within the cell or sent to the cell membrane for secretion outside the cell. Without the Golgi apparatus, proteins and lipids would not be correctly sorted or modified, which is essential for the proper functioning of secretory cells.

Protein Synthesis: The Blueprint of Life in Action

Protein synthesis is a fundamental process that underpins how secretory cells function. At its core, it's the translation of genetic information into the functional molecules that cells need to carry out their roles.

It begins in the cell's nucleus, where genes are transcribed into messenger RNA (mRNA). This mRNA then travels out to the cytoplasm and to the ribosomes, which read the genetic code and translate it into the amino acid chains that will compose the proteins.

The Stages of Protein Synthesis

• Transcription: DNA is copied into mRNA.
• Translation: mRNA is decoded by the ribosome to build the protein chain.
• Post-Translational Modifications: The protein chain is folded and modified to become a functional protein.

Without this precise and highly regulated process, cells would be unable to produce the necessary proteins which are key for everything from enzymes catalyzing reactions to hormones signaling between cells. In secretory cells, the efficiency and fidelity of protein synthesis are especially crucial as they often produce large amounts of proteins for secretion.