Cell Communication: Surface Receptors & Adhesion Molecules: Videos & Practice Problems

Cell communication is vital for immune responses, involving surface receptors and adhesion molecules. Surface receptors, which span the cytoplasmic membrane, bind specific ligands, triggering internal cellular responses. Adhesion molecules facilitate the binding of immune cells to endothelial cells in blood vessels, enabling their migration to infected tissues. This process is crucial for effective cellular immunity, allowing immune cells to respond to pathogens and initiate defense mechanisms. Understanding these interactions enhances our knowledge of immune system functionality and disease response.

Cell Surface Receptors

Cell communication is a vital process in the immune system, primarily facilitated by surface receptors and adhesion molecules. These components are crucial for signaling during infections, enabling immune cells to detect and migrate to affected areas in the body.

Surface receptors are specialized proteins located on the cell membrane that allow cells to sense and respond to external signals, known as ligands. Each surface receptor is designed to bind to a specific ligand, which triggers a response within the cell. This interaction is essential for the cell to react appropriately to environmental changes. The binding of a ligand to its corresponding receptor initiates a cascade of intracellular events, leading to various cellular responses that are critical for effective immune function.

Cells possess the ability to modify the number and types of surface receptors they express. This adaptability enables them to adjust their sensitivity and response rates to specific ligands, enhancing their ability to communicate and respond to external stimuli. For instance, when a signaling cell releases a ligand, only those recipient cells equipped with the appropriate surface receptors can respond, highlighting the specificity of this communication process.

In summary, surface receptors play a pivotal role in cell communication, particularly in the context of immune responses. Understanding how these receptors function and interact with ligands is fundamental to grasping the complexities of cellular signaling and the immune system's operation.

Which of the following is likely to be a response by a receptor protein to an approaching signal molecule?

• A. Recognize the receptor protein having the correct 3-D shape.
• B. Receptor protein binds to signal if having complementary shape.
• C. Once a signal binds to a receptor protein it induces a change in the receptor protein's shape.
• D. Change in the receptor protein's shape results in a cellular response to the signal.
• E. All of the above are correct.

Answer: (E)

Which of the following statements about cell surface receptors is incorrect?

• A. Cell surface receptors can span the entire plasma membrane connecting the exterior and interior cell environments.
• B. Once differentiated, cells cannot change the number or type of cell surface receptors that they possess.
• C. A cell has a wide range of surface receptors to allow it to respond to varying types of signals.
• D. The immune system uses ligands and cell surface receptors to provide immune support for infected tissues.

Answer: (B)

Adhesion Molecules

Adhesion molecules are essential cell surface proteins that facilitate the binding of cells to one another, playing a crucial role in cell communication. These molecules are particularly important in the immune response, as they enable immune system cells to adhere to the endothelial cells lining blood vessels. This adhesion is vital for allowing immune cells to migrate into tissues that are infected with pathogens, such as bacteria.

When a tissue is infected, endothelial cells respond by producing adhesion molecules. This process creates a binding event where adhesion molecules on immune cells interact with those on endothelial cells. This interaction is a key step in the immune response, as it allows immune cells to exit the bloodstream and enter the affected tissue, where they can mount an attack against the invading microbes.

In summary, adhesion molecules are integral to cellular immunity, facilitating the migration of immune cells to sites of infection. Understanding their function enhances our knowledge of how the immune system operates and sets the stage for further exploration of related concepts, such as cytokines, which are signaling molecules that also play a significant role in immune responses.

Why are adhesion molecules considered a form of cell communication in immune responses?

• A. Adhesion molecules allow immune cells to attach to infected cells & signal immune responses.
• B. Adhesion molecules allow immune cells to attach to endothelial cells & trigger immune cell entry into tissues.
• C. Adhesion molecules act as channels that allow signals to travel between two neighboring cells.
• D. Adhesion molecules are signals sent from immune cells to infected cells to trigger apoptosis.
• E. A and B.
• F. C and D.
• G. All of the above.

Answer: (E)

If the endothelial cells of the blood vessels in the body did not possess adhesion molecules, which of the following would occur?

• A. The immune cells which respond to infection or injury would not be able to leave the blood stream.
• B. The immune cells would not be able to detect where the infection is in the body.
• C. The immune cells would not be able to phagocytose the infecting microbes and damaged tissue.
• D. The blood vessels would adhere to the immune cells allowing them entry to infected regions of the body.

Answer: (A)

Here’s what students ask on this topic:

What are cell surface receptors and how do they function in cell communication?

Cell surface receptors are proteins located on the cell membrane that play a crucial role in cell communication. These receptors span the entire cytoplasmic membrane, connecting the outside of the cell to the inside. They function by binding to specific molecules known as ligands. When a ligand binds to its corresponding receptor, it triggers a cascade of events inside the cell, leading to a specific cellular response. This process allows the cell to sense and respond to external signals, which is vital for various physiological processes, including immune responses. Cells can also alter the number and types of surface receptors they express, thereby modulating their sensitivity and response to different ligands.

What role do adhesion molecules play in the immune system?

Adhesion molecules are cell surface proteins that facilitate the binding of immune cells to other cells, such as endothelial cells lining blood vessels. This binding is essential for immune responses, as it allows immune cells to migrate from the bloodstream into infected tissues. Once in the tissues, these immune cells can attack pathogens and generate immune responses. Adhesion molecules also enable direct cell-to-cell communication by allowing cells to deliver signaling molecules to each other. This process is crucial for coordinating the immune response and ensuring that immune cells reach the site of infection to combat pathogens effectively.

How do ligands and surface receptors interact to trigger a cellular response?

Ligands are specific molecules that bind to cell surface receptors, which are proteins on the cell membrane. When a ligand binds to its corresponding receptor, it induces a conformational change in the receptor. This change triggers a series of intracellular signaling pathways, often referred to as a signaling cascade. These pathways involve various molecules and enzymes that amplify the signal and ultimately lead to a specific cellular response. This response can include changes in gene expression, enzyme activity, or cellular behavior, allowing the cell to adapt to external signals and maintain homeostasis.

Why is the ability of cells to alter the number and types of surface receptors important?

The ability of cells to alter the number and types of surface receptors is crucial for modulating their sensitivity and response to different ligands. This adaptability allows cells to fine-tune their responses to changing environmental conditions and external signals. For example, during an immune response, cells may increase the expression of specific receptors to enhance their ability to detect and respond to pathogens. Conversely, cells can downregulate receptors to reduce sensitivity and prevent overactivation, which could lead to inflammation or autoimmune disorders. This dynamic regulation ensures that cells can respond appropriately to various physiological and pathological stimuli.

How do adhesion molecules facilitate the migration of immune cells to infected tissues?

Adhesion molecules facilitate the migration of immune cells to infected tissues by enabling these cells to bind to endothelial cells lining the blood vessels. When a tissue is infected, endothelial cells express specific adhesion molecules on their surface. Immune cells circulating in the bloodstream have complementary adhesion molecules that can bind to these endothelial adhesion molecules. This binding event allows immune cells to adhere to the blood vessel walls and migrate through the vessel lining into the infected tissue. Once in the tissue, immune cells can target and eliminate pathogens, thereby contributing to the immune response.