Question

Some lymphocytes (white blood cells) synthesize and secrete defensive proteins known as antibodies. Which of the following represents the most likely path of these proteins from synthesis to secretion? a. endoplasmic reticulum-ribosomes - Golgi apparatusvesicles - plasma membrane b. ribosomes - Golgi apparatus-vesicles - endoplasmic reticulum-plasma membrane c. ribosomes - Golgi apparatus-lysosome- endoplasmic reticulum-plasma membrane d. ribosomes - endoplasmic reticulum-Golgi apparatusvesicles-plasma membrane e. ribosomes-lysosomes - endoplasmic reticulum-vesiclesGolgi apparatus

Short answer

d. ribosomes -> endoplasmic reticulum -> Golgi apparatus -> vesicles -> plasma membrane

Step-by-step solution

Understand the Question

Identify the path that defensive proteins, such as antibodies, follow from their synthesis within a cell to their secretion.

Recall Cellular Components and Their Functions

Ribosomes are responsible for protein synthesis. The endoplasmic reticulum (ER), especially the rough ER, aids in the folding and processing of proteins. The Golgi apparatus modifies, sorts, and packages proteins for secretion. Vesicles transport proteins to their destinations, and the plasma membrane is where secretion occurs.

Eliminate Incorrect Options

Eliminate options that list the cell organelles in an incorrect sequence for protein synthesis and secretion:Option a: Incorrect because ribosomes are not located within the ER.Option b: Incorrect because the Golgi apparatus occurs after the ER.Option c: Incorrect inclusion of lysosomes in the path.Option e: Incorrect sequence and inclusion of lysosomes.

Choose the Correct Path

Option d correctly represents the path: 'ribosomes -> endoplasmic reticulum -> Golgi apparatus -> vesicles -> plasma membrane'. Proteins are synthesized by ribosomes, then processed in the ER, followed by modification and packaging in the Golgi apparatus, then transported by vesicles, and finally secreted by fusing with the plasma membrane.

Key concepts

Lymphocytes

Lymphocytes are a type of white blood cell that play a crucial role in the immune system. They help the body fight off infections and diseases. There are two main types of lymphocytes: B cells and T cells.
B cells are responsible for the production of antibodies, which are proteins that target and neutralize foreign substances like bacteria and viruses. T cells, on the other hand, destroy infected cells and regulate the immune response.
Lymphocytes are produced in the bone marrow and then distributed to various parts of the body, including the lymph nodes, spleen, and bloodstream. They are constantly patrolling the body, ready to spring into action whenever they detect an invader.

Antibodies

Antibodies are specialized proteins that the immune system uses to identify and neutralize foreign invaders like bacteria and viruses. Each antibody is unique and specific to a particular antigen, the substance that stimulates the immune response.
When a B cell encounters an antigen, it becomes activated and starts producing antibodies. These antibodies bind to the antigens, marking them for destruction by other immune cells. This process is essential for the body’s ability to remember and respond more effectively to future infections by the same invader.
Antibodies are secreted into the bloodstream and distributed throughout the body, providing a first line of defense against infections. They also play a key role in vaccinations, which introduce a harmless form of an antigen to stimulate the production of antibodies and confer immunity.

Cell Organelles

Cell organelles are specialized structures within a cell that perform specific tasks, enabling the cell to function efficiently. Each organelle has a unique role:

• **Ribosomes**: Responsible for protein synthesis. They translate genetic information into proteins.
• **Endoplasmic Reticulum (ER)**: The rough ER is studded with ribosomes and assists in protein folding and processing, while the smooth ER is involved in lipid synthesis and detoxification.
• **Golgi Apparatus**: Modifies, sorts, and packages proteins for secretion. It acts as the cell's 'post office.'
• **Vesicles**: Small membrane-bound sacs that transport proteins and other molecules within the cell.
• **Plasma Membrane**: The outer boundary of the cell that regulates what enters and exits. It's crucial for protein secretion.

Together, these organelles coordinate to ensure proteins, like antibodies, are accurately made and sent to their required destinations.