Question

Which of the following does not describe a typical cellular response to signaling molecules? a. activation of enzymes within the cell b. change in the function of structural proteins, which determine cell shape c. alteration of levels of certain proteins in the cell by changing the level of gene expression d. change in a gene sequence that encodes a particular protein e. all of the above are examples of cellular responses.

Short answer

The correct answer is d. A change in a gene sequence that encodes a protein is not a typical cellular response to signaling molecules.

Step-by-step solution

Understand Cell Signaling

Cell signaling is the process by which cells communicate with one another using signal molecules. It can trigger various responses including activation of enzymes, change in protein function, and alteration of protein levels by modifying gene expression.

Identify Typical Cellular Response

Review all the options, most options a, b and c describe changes in cell functioning - like enzyme activation, structural protein function changes and protein level alteration through gene expression modification. These are all typical cellular responses to signaling molecules.

Identify Atypical Cellular Response

Option d discusses changes in gene sequences that encode proteins. This does not typically occur as a result of interaction with signaling molecules. Signaling molecules affect cell function and activities, not the genetic sequence itself. Thus, this is the correct answer.

Verify All Options

Option e suggests all given options are typical. Given that d is not typical, this option is also invalid.

Key concepts

Signal Molecules

Signal molecules are essential for communication between cells. They function like messengers carrying instructions for various cellular actions. These molecules can take different forms, such as proteins, lipids, or gases. Each of them is designed to bind specifically to particular proteins, called receptors, located either on the cell surface or within the cell.

When a signal molecule binds to its receptor, it sets off a chain of events inside the cell referred to as a signaling pathway. This binding typically causes the receptor to change its shape slightly, a phenomenon called conformational change. It is this change that triggers subsequent reactions within the cell that leads to a cellular response.

Examples of common signal molecules include hormones like insulin or growth factors like epidermal growth factor (EGF). Each specific signal molecule has a distinct function. For instance, insulin helps in regulating glucose levels in the body. Understanding the role of these molecules helps in grasping how cells interpret and respond to their environment effectively.

Cellular Responses

Cellular responses are the various outcomes produced as a result of cell signaling. After a signal molecule interacts with its receptor, the cell undergoes one or more changes depending on the signal received.

Typical cellular responses include:

• Activation of enzymes, which speed up or catalyze chemical reactions necessary for the cell's survival and function.
• Modification of structural proteins, which can cause changes in the cell's shape or volume.
• Alteration of cell surface characteristics, affecting how cells interact with one another.
• Regulation of the cell cycle, impacting cell division and growth.

These responses allow the cell to adapt to new signals rapidly and efficiently. They can range from simple and short-term responses such as opening or closing of an ion channel, to more complex and long-term ones like changes in gene expression.

Gene Expression

Gene expression is a critical aspect of cell signaling. It involves turning a gene's encoded information into a functional product, typically a protein.

When a cell receives a signal to change gene expression, it often involves altering the rate at which a particular gene is transcribed into messenger RNA (mRNA). Once transcribed, the mRNA is translated into a protein, which then performs specific functions within the cell.

One of the primary ways signaling molecules affect gene expression is through transcription factors. These are proteins that help turn certain genes on or off by binding to nearby DNA.

• This can lead to increased production of proteins, influencing various cellular activities and responses. For example, in response to a growth factor, cells might produce more proteins necessary for cell division, contributing to growth or repair.
• Lack of proper gene expression, however, can result in diseases or dysfunctional cell processes.

Therefore, understanding how gene expression is regulated by signals is crucial to comprehending cell behavior and function.