Question

A membrane receptor is most likely to be a(n): (A) \(\quad\) embedded protein with catalytic activity. (B) \(\quad\) transmembrane protein with sequestration activity. (C) \(\quad\) membrane-associated protein with sequestration activity. (D) \(\quad\) transmembrane protein with catalytic activity.

Short answer

D

Step-by-step solution

- Understand the Question

Determine what a membrane receptor is likely to be. A membrane receptor generally spans across the membrane and participates in signal transduction.

- Analyze the Options

Examine the given choices: (A) embedded protein with catalytic activity, (B) transmembrane protein with sequestration activity, (C) membrane-associated protein with sequestration activity, (D) transmembrane protein with catalytic activity.

- Evaluate Correct Characteristics

A typical membrane receptor spans the entire membrane, meaning it is a transmembrane protein. Additionally, these receptors often exhibit catalytic activity rather than sequestration activity.

- Eliminate Incorrect Options

Discard options (B) and (C) because they mention sequestration activity. Discard option (A) because the receptor must be transmembrane rather than embedded.

- Identify the Correct Answer

The correct description of a membrane receptor is: transmembrane protein with catalytic activity, which corresponds to option (D).

Key concepts

Signal Transduction

Signal transduction is a vital process in biology that involves the transmission of a signal from outside the cell to its interior. It begins when a signaling molecule binds to a specific receptor on the cell membrane. This receptor then undergoes a conformational change, setting off a cascade of events inside the cell.

Think of signal transduction as a relay race. The signaling molecule is the baton handed off first to the membrane receptor. The receptor, acting as the first relay runner, passes the signal to various intracellular molecules. These molecules, in turn, continue to propagate and amplify the signal until the cell responds appropriately.

• Membrane receptors are crucial for this process.
• They are often transmembrane proteins that can transmit the signal across the cell membrane.
• After receiving the signal, receptors often activate proteins inside the cell, initiating various cellular functions.

This process ensures that cells respond accurately and efficiently to their environment, whether it's triggering cell growth, immune responses, or other cellular activities.

Transmembrane Proteins

Transmembrane proteins are integral to the structure and function of cell membranes. These proteins span the entire lipid bilayer, with parts exposed on both the outside and inside of the cell.

Transmembrane proteins can perform various functions. However, when we talk about membrane receptors, their primary role is in signal transduction. They detect extracellular signals and convey them into the cell:

• They have hydrophobic regions that interact with the lipid bilayer, anchoring them firmly in place.
• Their hydrophilic regions protrude into the aqueous environments inside and outside the cell, making them accessible to signaling molecules.
• Their ability to undergo conformational changes allows them to transmit signals across the cell membrane.

Transmembrane proteins are essential for many cellular processes, making them crucial targets for therapeutic interventions in various diseases.

Catalytic Activity

Catalytic activity in membrane receptors refers to their ability to facilitate and accelerate biochemical reactions upon receiving a signal. This activity is often part of the cell's response to external stimuli.

Membrane receptors with catalytic activity typically have an intrinsic enzyme function or are directly associated with enzymes. Upon activation by a signaling molecule, these enzymes catalyze specific biochemical reactions inside the cell.

• One common type of catalytically active receptor is the receptor tyrosine kinase (RTK).
• RTKs phosphorylate tyrosine residues on specific proteins, which can trigger a variety of cellular processes.
• These receptors significantly impact cell growth, proliferation, and differentiation.

The catalytic activity of membrane receptors underscores their importance in precisely modulating cellular responses, ensuring that the appropriate action is taken in response to specific signals.