Unit 4: Cell Communication

What are the chemical signals called that cells use to communicate?

Ligands

What type of communication occurs through direct contact between cells?

Juxtacrine Communication

Give an example of juxtacrine communication.

Antigen presentation in immune cells.

What is paracrine communication?

Communication over short distances by releasing ligands that travel to nearby cells.

Provide an example of paracrine communication.

Neurons releasing neurotransmitter chemicals at a synapse.

What is quorum sensing in bacteria?

A process where bacteria use chemical messengers to regulate gene expression at a certain density.

How do morphogens function in embryonic development?

They are chemicals released at different locations in the embryo that turn developmental genes on or off based on local concentrations.

What is the primary immune response mechanism in plants?

Plants trigger apoptosis in nearby cells when a virus or bacteria is detected.

What is endocrine communication?

Communication over long distances by releasing ligands (hormones) that target specific cells.

What is an example of a hormone involved in endocrine communication?

Insulin or testosterone.

How does epinephrine function in the body?

It triggers different responses in specific tissues, such as breaking down glycogen in muscle cells.

What are signal transduction pathways?

Steps that a cell uses to relay a signal into a cellular response.

What are the three main parts of a signal transduction pathway?

Signal, transduction, and response.

Where are most receptors located in a cell?

On the cell's surface.

What type of receptors are ligand-gated ion channels?

Receptors that open or close in response to ligand binding.

What is the role of second messengers in signal transduction?

They relay a signal within the cell as part of transduction.

What is cyclic AMP (cAMP) derived from?

ATP.

What enzyme converts ATP to cAMP?

Adenylyl cyclase.

What is phosphorylation in the context of signal transduction?

A protein modification that is part of many signal transduction pathways.

What can mutations in receptor proteins affect?

They can alter the transduction of the signal, potentially inhibiting or upregulating it.

What is the difference between a wildtype receptor and a mutant receptor?

A wildtype receptor is non-mutated and normal, while a mutant receptor is altered and abnormal.

What is the role of kinases in cellular signaling?

Kinases are enzymes that add phosphate groups to target proteins, leading to their activation or inactivation.

What is the function of phosphatases?

Phosphatases remove phosphate groups from target proteins.

What is a phosphorylation cascade?

A series of events where one kinase activates one or more kinases, amplifying the signal.

How do second messengers contribute to signal amplification?

They work with phosphorylation cascades to convert a small input into a large cellular response.

What occurs when a ligand binds to a G-protein coupled receptor (GPCR)?

The GPCR is activated, leading to the exchange of GDP for GTP in the G protein.

What is the role of adenylyl cyclase (AC) in the signaling pathway?

Activated AC converts ATP to cAMP, which then activates protein kinase A (PKA).

What cellular responses can result from signaling pathways?

Responses may include changes in gene expression, cell division, apoptosis, and metabolic pathway regulation.

How does cholera toxin affect cellular signaling?

It activates a G protein, causing overproduction of cAMP, leading to prolonged open ion channels and severe diarrhea.

What is negative feedback in biological systems?

A mechanism that returns a system to its target set point after disruption, maintaining stability and homeostasis.

What is positive feedback in biological systems?

A mechanism that amplifies responses to produce a change or transformation, moving away from the set point.

How do insulin and glucagon maintain blood glucose levels?

They work together through signal transduction pathways to regulate blood glucose homeostasis.

What happens during the G1 phase of the cell cycle?

The cell grows and duplicates organelles while maintaining normal metabolic activities.

What occurs during the S phase of the cell cycle?

DNA is replicated, resulting in two sister chromatids connected at the centromere.

What is the purpose of mitosis?

To ensure the transfer of a complete genome from a parent cell to two genetically identical daughter cells.

What are the stages of mitosis?

Prophase, Metaphase, Anaphase, and Telophase (PMAT).

What is cytokinesis?

The process where the cytoplasm divides, resulting in two new daughter cells.

What role do cyclins play in the cell cycle?

Cyclins bind to and activate cyclin-dependent kinases (CDKs) to regulate cell cycle progression.

What is apoptosis?

The process of programmed cell death, important for development and removing damaged cells.

How can mutations in checkpoint proteins lead to cancer?

Mutations can disrupt the cell cycle, allowing uncontrolled cell division and tumor formation.

What is the significance of the G0 phase in the cell cycle?

Cells may exit the cycle and not divide, but can re-enter in response to appropriate signals.

What is the function of spindle fibers during mitosis?

They help align and separate chromosomes during cell division.

What happens during the prophase stage of mitosis?

Sister chromatids condense, the mitotic spindle begins to form, and the nuclear envelope disintegrates.

What is the role of the centromere in cell division?

It connects sister chromatids and organizes the spindle fibers during mitosis.

What is the effect of oxytocin during childbirth?

It stimulates contractions, and pressure from contractions leads to more oxytocin release, amplifying the response.

How do fruits use ethylene in ripening?

Fruits release ethylene to signal neighboring fruits to ripen, creating a positive feedback loop.