Cell Signalling

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Questions and Answers

What is the primary function of ligands in intercellular signaling?

To communicate information within a cell

To maintain the structural integrity of cells

To bind to specific receptors in target cells (correct)

To release neurotransmitters between nerve cells

Which type of signaling primarily involves chemical signals that move by diffusion through the extracellular matrix?

Endocrine signaling

Autocrine signaling

Paracrine signaling (correct)

Direct signaling

Which example correctly represents endocrine signaling?

Neurotransmitters crossing synapses

Chemical signals acting locally between adjacent cells

Insulin regulating blood sugar levels (correct)

Cells responding to their own released ligands

In which type of signaling do the signaling cells also bind to the released ligands?

Autocrine signaling Signup and view all the answers

How does paracrine signaling differ from endocrine signaling?

Paracrine signaling acts over short distances, while endocrine signals operate over long distances. Signup and view all the answers

What role do gap junctions play in intercellular communication?

They allow direct transport of signaling molecules between cells. Signup and view all the answers

Which of the following statements regarding neurotransmitters is accurate?

They enable quick signal transmission across synapses. Signup and view all the answers

What typically happens to paracrine ligands after their release?

They are degraded quickly to maintain response localization. Signup and view all the answers

What distinguishes synaptic signaling from other forms of intercellular signaling?

Synaptic signaling relies on neurotransmitters to transmit signals over small distances. Signup and view all the answers

What is the primary function of autocrine signaling in early organism development?

To ensure cells develop into appropriate tissues and functions Signup and view all the answers

Which type of receptor binds to hydrophobic ligand molecules within the cytoplasm?

Internal receptors Signup and view all the answers

What type of receptors are primarily involved in ion passage through the plasma membrane?

Ion channel-linked receptors Signup and view all the answers

Which mechanism explains how viruses adapt to infect new host species?

Evolving viral proteins that bind to new cell-surface receptors Signup and view all the answers

What role does the intracellular domain of an enzyme-linked receptor play?

It has a direct association with an enzyme for intracellular activity Signup and view all the answers

What happens upon the activation of cell-surface receptors in multicellular organisms?

They trigger complex signaling pathways that lead to specific responses Signup and view all the answers

Which of the following conditions can lead to insulin resistance?

Insensitivity of receptors to insulin Signup and view all the answers

Which type of receptor is often linked to various diseases, including hypertension and cancer?

Cell-surface receptors Signup and view all the answers

What is the role of calcium ions in gap junctions?

They facilitate communication between neighboring cells Signup and view all the answers

What is a characteristic feature of G-protein-linked receptors?

They can release toxins that disrupt signaling in host cells Signup and view all the answers

Study Notes

Intercellular Signaling

Cells communicate via intercellular signaling (between cells) and intracellular signaling (within a cell).
Signaling cells release ligands, chemical signals that bind to receptors on target cells.
Ligands and receptors have specificity—a particular ligand typically binds only to its specific receptor.

Types of Signaling

Paracrine signaling: Signals diffuse locally through the extracellular matrix, eliciting rapid, short-lived responses. Examples include synaptic signals and neurotransmitters. Signals are quickly degraded to keep the response localized, allowing for the response to quickly change if the signal is released again. A synapse is the junction between nerve cells.
Endocrine signaling: Long-distance signaling from endocrine cells producing hormones, which have a slower, longer-lasting effect. Hormones travel in the bloodstream.
Autocrine signaling: Signaling cells can also bind to released ligands, where the signaling cell and target cell can be the same or similar. Crucial in development and regulates processes like pain and inflammation.
Direct signaling across gap junctions: Intracellular mediators allow small signaling molecules to move between cells through fluid-filled channels in plasma membranes.

Receptors

Internal receptors: Located in the cytoplasm, bind hydrophobic ligands that cross the plasma membrane. These changes trigger the exposure of a DNA-binding site, influencing gene expression.
Cell-surface (transmembrane) receptors: Membrane-anchored proteins with three components: an extracellular domain (binding site), a transmembrane domain, and an intracellular domain. Cell-surface receptors are crucial in multicellular organisms and exhibit specificity. Errors in receptors can contribute to health issues like hypertension, asthma, and cancer. Three categories of cell-surface receptors include ion channel-linked, G-protein-linked, and enzyme-linked receptors.

Ion Channel-Linked Receptors

These receptors bind ligands, opening channels that allow specific ions to pass through cell membranes. Hydrophobic amino acids form the membrane-spanning region of the channel while hydrophilic amino acids line the channel's interior to facilitate ion passage. Ligand binding triggers conformational changes, affecting ion flow.

G-Protein-Linked Receptors

Involved in various cellular processes and are susceptible to interference by pathogenic bacteria like those causing pertussis, botulism, and cholera.

Enzyme-Linked Receptors

These receptors have intracellular domains associated with enzymes. The enzymatic activity is triggered by ligand binding, initiating intracellular signaling cascades. Examples include tyrosine kinase receptors like HER2, a receptor involved in cancer. Drugs like lapatinib can reduce tumor growth by inhibiting HER2 receptor activation. Insulin also interacts with an enzyme linked receptor and triggers responses like glycogen synthesis and glucose uptake.

Ligands and Signal Transmission in Multicellular Organisms

Small Hydrophobic Ligands: Directly pass through the plasma membrane and interact with internal receptors. Examples include steroids (estradiol, testosterone, cholesterol), thyroid hormones, and vitamin D.
Water-soluble Ligands: Cannot pass through the membrane due to polarity or size and bind to cell-surface receptors.
Other Ligands: Nitric oxide diffuses directly through the plasma membrane and interacts with receptors in smooth muscle, inducing tissue relaxation.

Receptor Involvement in Health

Receptor-related problems like downregulation of insulin receptors or a loss of receptor sensitivity, can lead to issues like insulin resistance.

Viral Interactions with Host Cells

Viruses rely on host cells to reproduce and often target cell-surface receptors to enter. Differences in receptor types across species can limit viral spread between animal species. Viral mutations allow viruses to bind to receptors in new hosts, enabling rapid spread.

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Description

Test your knowledge on intercellular signaling methods and their mechanisms. This quiz covers various types of signaling, including paracrine, endocrine, and autocrine signaling. Dive into the specificity of ligands and receptors and their roles in cellular communication.