Introduction to Cell Signaling - Online Tutor, Practice Problems & Exam Prep

Cell signaling is essential for cellular communication, involving two key components: ligands and receptors. The process occurs in three steps: reception, where the ligand binds to the receptor; transduction, which converts the signal through a series of molecular interactions; and the cellular response, resulting in a physical or chemical change within the target cell. Various ligands, including amino acids, proteins, and hormones, initiate these pathways, highlighting the complexity and significance of cellular communication in biological systems.

Introduction to Cell Signaling

In this video, we're going to begin our introduction to cell signaling. Now, cell signaling is really just defined as the ability for all cells to produce, receive, and respond to external signals or conditions in the environment. And so, ultimately, cell signaling is going to allow for effective cellular communication, allowing for a cell to communicate with neighboring cells in its vicinity, but also communicate with distant cells that are further away as well. Now as we move forward in our course, we're going to talk a lot more about cellular communication and cell signaling. But what's important to note here is that cell signaling is going to require a minimum of 2 key components that we have numbered down below, number 1 and number 2. And so the very first key component of cell signaling is going to be the ligand itself. And so the ligand is defined as a small signaling molecule that is going to bind and form a complex with another biomolecule or a receptor. And this leads us to our second key component of cell signaling, and that is the receptor itself. And so the receptor is a biomolecule, typically a protein, that is going to change shape or change conformation upon ligand binding. And so when the ligand or the small signaling molecule binds to the receptor, it's going to cause a conformational change or change in shape of the receptor. And this conformational change is going to lead to a series of events within the cell, ultimately ending with a cellular response. And so let's take a look at our image down below to clear some of this up. And so notice that in this image, we have 2 cells. We have this cell over here on the left-hand side and we have this cell over here on the right-hand side. Now notice that this cell over here on the left-hand side is producing or generating this yellow circle here that we're calling the ligand. And again, the ligand is a small signaling molecule. And so because this cell here is producing the ligand, this cell over here on the left is going to be the signaling cell that is generating the signal or the ligand. And so this ligand that's produced by the signaling cell can diffuse over towards this other cell over here, which notice contains a receptor embedded in its cell membrane. And this receptor, again, is typically going to be a protein, and when the ligand actually comes and binds to the receptor, that is going to cause a confirmational change or a change in the shape of the receptor itself. And this conformational change in the receptor is going to lead to a series of events that's ultimately going to lead to the cellular response. And so, ultimately, this cell over here that has the receptor is going to be called the target cell because this is the cell that generates the cell target to the signal or the ligand created by the signaling cell. And so what's happening is this signaling cell over here is able to effectively communicate with this target cell over here. And so there are many different types of signaling pathways that lead to different types of cellular responses. And there are also many different types of ligands or many different types of signaling molecules. And over here on the left-hand side, we have this little table showing you some of the different types of ligands or signaling molecules that can lead to, a cell response. And so, the ligand or signaling molecule could be an amino acid, a protein, lipids or hormones, which we'll get to talk more about moving forward in our course, nucleotides, dissolved gases and neurotransmitters, which we'll also get to talk more about moving forward in our course. And this is just a small subset of the possibilities that of ligands or signaling molecules. And so this here concludes our brief introduction to cell signaling. And, again, we'll be able to talk more and more about cell signaling as we move forward in our course. So I'll see you all in our next video.

The cells of multicellular organisms use a variety of molecules as signals which are

a) Amino acids and proteins.

b) Nucleotides and lipids.

c) Dissolved gases like nitric oxide.

d) Only a and b.

e) a, b, and c.

• A. Amino acids and proteins.
• B. Nucleotides and lipids.
• C. Dissolved gases like nitric oxide.
• D. Only a and b.
• E. a, b, and c.

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

a) The receptor protein binds to the signal if it has a complementary shape.

b) If the signal is able to bind to the receptor it induces a change in the receptor protein's shape.

c) The change in the receptor protein's shape results in cellular action.

d) All of the above are correct.

• A. The receptor protein binds to the signal if it has a complementary shape.
• B. If the signal is able to bind to the receptor it induces a change in the receptor protein's shape.
• C. The change in the receptor protein's shape results in cellular action.
• D. All of the above are correct.

3 Steps of Cell Signaling

So now that we know from our last lesson video that cell signaling requires a minimum of 2 key components, the ligand or the signaling molecule and the receptor. In this video, we're going to focus on the 3 steps of cell signaling. And so cells receive external signals in a series of 3 steps that we have numbered down below, number 1, number 2, and number 3. And so the very first step of cell signaling is going to be reception or in other words, ligand binding. And so in this first step of reception, the ligand or the signaling molecule is going to bind to a very specific receptor causing the receptor to change its conformation or to change its shape. And so if we take a look at our image down below, what you'll notice is, here, this membrane represents the cell's plasma membrane that's separating the outside of the cell from the inside of the cell. And so over here on the left-hand side, what we have is the outside of the cell or the extracellular fluid. And over here on the right-hand side in the yellow background, what we have is the inside of the cell or the cytoplasm. And so notice that embedded here within the membrane is a receptor, and the signaling molecule or the ligand is here in red. And so in the very first step of cell signaling, which is again reception, what happens is the ligand or the signaling molecule here is going to bind to its receptor, like what we see here. The ligand is now bound to the receptor. And when the ligand binds to the receptor, it's going to cause a conformational change in the receptor, which will lead to step number 2 over here.

And so in step 2, what we have is transduction. So after the ligand binds to the receptor and causes a conformational change in the receptor, this is going to lead to a pathway of interactions in the cell that ultimately is going to transduce as implied by transduction, or, in other words, convert transduce or convert the signal, to change to a change within the cell. And so in the process of transduction, there's really just gonna be a series of interactions, and this series of interactions is ultimately going to convert that external signal or that external ligand, into a change within the cell. So let's take a look at step number 2 down below right here. And so notice step number 2 is transduction. And so with transduction, there's a series of events. Notice that we have, a, b, and c here within step number 2. And so in transduction, what happens is the conformational change within the receptor from step number 1 is gonna lead to, a series of events where, some molecule is going to become activated, which could lead to the activation of another molecule, which could lead to the activation of another molecule, and so on. And ultimately, the transduction step here is going to vary significantly between different pathways. But ultimately with transduction, there's gonna be a series of events, and at the end of transduction, it leads to the last step, which is the cellular response. And so that is our step number 3 of cell signaling. And so the cellular response is going to be the end result of the cell signaling pathway that is going to end up causing a physical or chemical change in response to the extracellular ligand that originated. And so the signaling molecule or the the ligand ultimately is going to be triggering this cellular response. And so the cell response is generated, in response to the extracellular signaling molecule or the ligand. And so, really this here concludes our introduction to the 3 steps of cell signaling. And, again, as we move forward in our course, we'll be able to talk more and more about cell signaling. So I'll see you all in our next video.

Signal transduction pathways:

a) Are necessary for signals to cross the membrane.

b) Include the intracellular events caused by a signal binding to a receptor.

c) Include the extracellular events caused by a signal binding to a receptor.

d) Carry a signaling molecule to the nucleus of a cell.

• A. Are necessary for signals to cross the membrane.
• B. Include the intracellular events caused by a signal binding to a receptor.
• C. Include the extracellular events caused by a signal binding to a receptor.
• D. Carry a signaling molecule to the nucleus of a cell.

What does it mean to say that a signal is transduced?

a) The signal enters the cell directly and binds to a receptor inside.

b) The physical form of the signal changes as it passes from the cell membrane to the intracellular target.

c) The signal is amplified, such that even one signal molecule evokes a large response.

d) The signal triggers a sequence of phosphorylation events inside the cell.

• A. The signal enters the cell directly and binds to a receptor inside.
• B. The physical form of the signal changes as it passes from the cell membrane to the intracellular target.
• C. The signal is amplified, such that even one signal molecule evokes a large response.
• D. The signal triggers a sequence of phosphorylation events inside the cell.

Here’s what students ask on this topic:

What are the key components of cell signaling?

The key components of cell signaling are ligands and receptors. Ligands are small signaling molecules that bind to receptors, which are typically proteins. This binding causes a conformational change in the receptor, initiating a series of events within the cell that lead to a cellular response. Ligands can be various types of molecules, including amino acids, proteins, lipids, hormones, nucleotides, dissolved gases, and neurotransmitters. Understanding these components is crucial for grasping how cells communicate with each other and respond to their environment.

What are the three steps of cell signaling?

The three steps of cell signaling are reception, transduction, and response. In the reception step, the ligand binds to a specific receptor, causing a conformational change. During transduction, this change triggers a series of interactions within the cell, converting the external signal into an internal one. Finally, the response step results in a physical or chemical change within the cell, such as gene expression or enzyme activation, in response to the original extracellular signal.

How do ligands and receptors interact in cell signaling?

In cell signaling, ligands and receptors interact through a binding process. The ligand, a small signaling molecule, binds to a specific receptor, usually a protein, on the target cell's surface. This binding causes the receptor to undergo a conformational change, which initiates a series of intracellular events. These events ultimately lead to a cellular response, allowing the cell to react to external signals. This interaction is crucial for effective cellular communication and response to environmental changes.

What types of molecules can act as ligands in cell signaling?

Various types of molecules can act as ligands in cell signaling. These include amino acids, proteins, lipids, hormones, nucleotides, dissolved gases, and neurotransmitters. Each type of ligand can bind to specific receptors, triggering different cellular responses. Understanding the diversity of ligands is essential for comprehending the complexity of cell signaling pathways and how cells communicate and respond to their environment.

What is the role of transduction in cell signaling?

Transduction is the second step in cell signaling, following ligand binding to the receptor. During transduction, the conformational change in the receptor triggers a series of intracellular interactions. These interactions convert the external signal into an internal one, leading to a specific cellular response. The transduction process often involves multiple molecules and pathways, ensuring that the signal is accurately relayed and amplified within the cell. This step is crucial for translating external signals into meaningful cellular actions.