Cell Communication

Why is cell-to-cell communication essential for multicellular organisms?

It allows for coordinated responses and regulation of cellular activities.

What are the universal mechanisms discovered in cellular regulation?

Combined effects of multiple signals determine cell response.

What is a signal transduction pathway?

A series of steps by which a signal on a cell's surface is converted into a specific cellular response.

How do yeast cells find and identify potential mates?

Through signal transduction pathways.

What is the role of autoinducers in bacterial communication?

They allow bacteria to detect population density through a process called quorum sensing.

What are gap junctions?

Cell junctions that directly connect the cytoplasm of adjacent animal cells.

What are plasmodesmata?

Cell junctions that connect the cytoplasm of adjacent plant cells.

What is paracrine signaling?

A type of local signaling where messenger molecules travel only short distances to stimulate nearby cells.

What is synaptic signaling?

A specialized type of local signaling in the nervous system where neurotransmitters diffuse across a synapse.

What is endocrine signaling?

A form of long-distance signaling where hormones are released into the bloodstream to target cells.

What are the three stages of cell signaling proposed by Earl W. Sutherland?

Reception, Transduction, and Response.

What happens during the reception stage of cell signaling?

A target cell receives a signal molecule that binds to a receptor protein.

What occurs during the transduction stage of cell signaling?

The signal molecule changes the receptor protein, initiating a series of chemical reactions inside the cell.

What is the response stage in cell signaling?

Changes in the cell that may involve regulation of cytoplasmic activities or transcription of DNA.

How does epinephrine affect the body during the fight or flight response?

It redirects blood away from skin and digestive organs to muscles and heart, and signals the liver to release glucose.

Why is cell signaling considered complicated?

It ensures proper timing of communication and activities occur in the right cells at the right time.

What is the significance of the conservation of signaling processes across species?

It indicates that fundamental mechanisms of communication have been maintained throughout evolution.

What is the role of growth factors in local signaling?

They stimulate nearby cells to grow and divide.

What is the function of neurotransmitters in synaptic signaling?

They trigger a response in the target cell after diffusing across the synapse.

How do hormones vary in endocrine signaling?

Hormones vary widely in size and shape, affecting their function and target specificity.

What is quorum sensing?

A process by which bacteria communicate and coordinate their behavior based on population density.

What is the first step in a signal transduction pathway?

The arrival of a signal on a cell surface.

What allows cells in a multicellular organism to communicate over long distances?

Hormones traveling through the circulatory system.

What is the outcome of successful cell communication?

Coordinated activities that allow organisms to function as a cohesive unit.

How did the study of yeast cells contribute to our understanding of cell signaling?

It provided insights into the mechanisms of signal transduction and mating behaviors.

What occurs when a signal molecule binds to a receptor protein?

The receptor protein changes shape.

What is a ligand?

A signal molecule that binds to a receptor.

What type of receptors are most signal receptors?

Plasma membrane proteins.

What are the three main types of membrane receptors?

G protein-coupled receptors, Receptor Tyrosine Kinases, Ligand-gated Ion channel receptors.

How do G protein-coupled receptors function?

They work with the help of a G protein that acts as an on/off switch.

What molecule do G proteins bind to?

The energy-rich molecule GTP.

What happens when GDP is bound to a G protein?

The G protein is inactive.

What is the role of the G protein in signal transduction?

It activates an enzyme after being activated by a receptor.

What happens to GTP after the G protein is activated?

It is hydrolyzed to GDP, making the G protein inactive again.

What is the function of receptor tyrosine kinases?

They form dimers, attach phosphates to tyrosines, and activate relay proteins.

What occurs when a signal molecule binds to receptor tyrosine kinases?

Two receptor polypeptides associate to form a dimer.

What is the result of dimerization in receptor tyrosine kinases?

It activates the tyrosine-kinase regions, which add phosphates from ATP.

What do ligand-gated ion channels do?

They open to allow specific ions to flow through when a ligand binds.

What is the effect of ion channel receptors on membrane potential?

They can rapidly change the concentration of ions inside the cell.

Where are intracellular receptors found?

In the cytoplasm or nucleus of target cells.

What types of chemical messengers can activate intracellular receptors?

Small or hydrophobic chemical messengers, such as steroid hormones.

What role does the hormone-receptor complex play in gene expression?

It acts as a transcription factor to turn on specific genes.

What is the main role of aldosterone?

To regulate salt and water in the body, affecting blood pressure.

What is signal transduction?

A series of molecular interactions that relay signals from receptors to target molecules in the cell.

What is a key characteristic of G protein-coupled receptors?

They can trigger multiple signaling pathways.

What happens when a ligand dissociates from a ligand-gated ion channel?

The gate closes and ions can no longer enter the cell.

What is the significance of G proteins in medicine?

60% of all medicines influence G-proteins.

What is the function of activated relay proteins in receptor tyrosine kinases?

They trigger transduction pathways leading to cellular responses.

What does the activation of a G protein lead to?

It alters the activity of an enzyme, triggering a cellular response.

What is the role of the cytoplasmic side of a G protein-coupled receptor?

It binds to an inactive G protein after the receptor is activated.

What is the outcome of the binding of a signal molecule to a receptor?

It leads to a change in the receptor's shape and initiates a signaling cascade.

What happens to the G protein after it activates an enzyme?

It dissociates from the receptor and returns to its inactive state.

What is the purpose of multistep pathways in signal transduction?

They amplify a signal and provide opportunities for coordination and regulation of the cellular response.

What does the term 'transduce' mean in the context of cell signaling?

To convert a message into another form.

What are the primary molecules that relay a signal from receptor to response?

Mostly proteins.

How does a receptor activate a signal transduction pathway?

Like falling dominoes, the receptor activates another protein, which activates another, until the response-producing protein is activated.

What is phosphorylation?

The process where protein kinases transfer phosphates from ATP to proteins, causing them to change shape and become activated.

What is a phosphorylation cascade?

A signaling pathway involving a series of protein phosphorylations.

What role do protein phosphatases play in cell signaling?

They remove phosphates from proteins, making them inactive and available for reuse.

What are second messengers in cell signaling?

Small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion.

What is the first messenger in a signaling pathway?

The extracellular signal molecule (ligand) that binds to the receptor.

What is cyclic AMP (cAMP) and its role in signaling?

A widely used second messenger that activates protein kinase A, which then phosphorylates other proteins.

What is the function of adenylyl cyclase?

It converts ATP to cAMP in response to an extracellular signal.

What happens to cAMP when the signaling is complete?

Phosphodiesterase breaks down cAMP into AMP.

What is the output response of a cell to an extracellular signal?

Regulation of transcription or cytoplasmic activities.

Where can cellular responses occur in relation to signal transduction?

In the cytoplasm or involve action in the nucleus.

What is a transcription factor?

A molecule that functions to regulate the synthesis of enzymes or other proteins by turning genes on or off in the nucleus.

What is the significance of signal amplification in cell signaling?

Enzyme cascades amplify the cell's response, with each step producing a greater number of activated products.

How do different cells respond to the same signal?

Different cells have different collections of proteins that allow them to detect and respond to signals in unique ways.

What are scaffolding proteins?

Large relay proteins that increase signal transduction efficiency by grouping together different proteins involved in the same pathway.

What is the role of inactivation mechanisms in cell signaling?

They ensure that when signal molecules leave the receptor, the receptor reverts to its inactive state.

What is the role of relay molecules in a signal transduction pathway?

They help transmit the signal from the receptor to the response.

What is the effect of epinephrine on liver cells?

It stimulates glycogen breakdown through a signaling pathway.

What is the relationship between protein kinases and ATP in signaling pathways?

Protein kinases transfer phosphates from ATP to proteins, activating them.

What is the significance of pathway branching in cell signaling?

It allows for multiple responses to a single signal, enhancing the specificity of the response.

What is cross-talk in cell signaling?

Interactions between different signaling pathways that help coordinate cellular responses.

What happens during the activation of a transcription factor?

It leads to the regulation of gene expression, affecting cellular activities.

How does the specificity of cell signaling contribute to cellular function?

Different proteins in different cells allow for varied responses to the same signal.

What is the role of calcium ions in signal transduction?

They act as common second messengers that participate in various signaling pathways.

What is the immediate effect of cAMP in a signaling pathway?

Usually the activation of protein kinase A.

What is the function of phosphodiesterase in relation to cAMP?

It breaks down cAMP into AMP, terminating the signaling effect.