Cell Signaling and Division

Flashcards covering key concepts in cellular signaling and mechanisms of cell division, focusing on definitions and mechanisms.

Endocrine signaling

Release of hormones into the bloodstream to produce systematic effects.

Paracrine signaling

Signaling mechanism where a ligand is released and diffuses to a receptor on a neighboring cell.

Autocrine signaling

When ligands are released and interact with receptors on the same cell that released them.

Gap Junctions

Channels that allow ions and small molecules to move between cells.

Internal receptors

Receptors that bind hydrophobic ligands like steroid hormones which move across the cell membrane.

Cell-surface receptors

Receptors that interact with water soluble ligands and require transmembrane proteins.

Signal transduction

The process by which a receptor-ligand interaction brings about a cellular response.

Ligand-gated ion channels

Receptors that open channels to allow ions to move down their electrochemical gradient upon ligand binding.

G-protein coupled receptors

Receptors that use GTPases to transmit signals within cells, cycling between inactive and active states.

Enzyme-linked receptors

Receptors that have enzymatic activity and activate downstream signaling proteins.

Phosphorylation

The addition of a phosphate group to an amino acid by kinases that transmits intracellular signals.

Second messengers

Small molecules that propagate the signal from a receptor to target proteins inside the cell.

EGF signaling

A pathway where EGF ligands activate EGFR, triggering a cascade that regulates protein synthesis.

Quorum sensing

A bacterial signaling mechanism that indicates population density, affecting gene expression.

Binary fission

A process of asexual reproduction in prokaryotes where a single cell divides into two identical cells.

Mitosis

The process of cell division that results in two genetically identical daughter cells.

Meiosis

A process of cell division that reduces ploidy from diploid to haploid, creating genetically unique gametes.

Crossing over

The exchange of genetic material between homologous chromosomes during Prophase I of meiosis.

Mendel's law of segregation

States that each organism inherits two alleles for a gene, which separate during gamete formation.

Epistasis

Occurs when one gene's expression is influenced or masked by another gene.

What are the four types of signaling mechanisms in multicellular organisms?

1. Endocrine - Hormones are released into the bloodstream for systematic effects. 2. Paracrine - Ligands diffuse to neighboring cell receptors. 3. Autocrine - Ligands interact with receptors on the signaling cell itself (self-signaling). 4. Gap Junctions - Ions and small molecules pass between connected cells (e.g., in cardiomyocytes).

Compare internal receptors and cell-surface receptors.

Internal receptors bind hydrophobic ligands (e.g., steroid hormones) and often act as transcription factors in the cytoplasm. Cell-surface receptors bind water-soluble ligands requiring transmembrane receptors with external binding and intracellular domains.

How do ligands' structures relate to their mechanism of action?

Hydrophobic ligands can cross the plasma membrane and bind to internal receptors. Water-soluble ligands need transmembrane receptors with specific domains to facilitate binding and signaling.

How does ligand binding initiate signal transduction?

Ligand binding induces conformational changes in receptors (e.g., ligand-gated ion channels open), allowing ions to flow down their electrochemical gradient, initiating the signal transduction process within the cell.

What role do G-proteins play in signal transduction?

G-proteins, when activated by ligand binding, exchange GDP for GTP, which activates them to influence downstream signaling proteins, usually through phosphorylation.

Describe the function of enzyme-linked receptors in signaling.

Enzyme-linked receptors possess enzymatic activity; for instance, tyrosine receptor kinases dimerize upon ligand binding, phosphorylating their intracellular domains to activate downstream signaling proteins.

What is the significance of second messengers in signal transmission?

Second messengers are molecules (e.g., cAMP, IP3, DAG) that propagate signals initiated by receptor activation, influencing various downstream cellular activities and responses.

Explain the role of phosphorylation in intracellular signal transmission.

Phosphorylation involves adding phosphate groups to proteins by kinases, which can activate or deactivate signaling pathways and are crucial for transmitting signals within the cell.

How do signaling pathways influence cellular responses such as metabolism and growth?

Signaling pathways activate cascades leading to changes in protein expression, metabolism (e.g., glucose uptake via adrenaline), and cell growth (e.g., EGF signaling activating the MAP kinase pathway).

What is quorum sensing in bacteria?

Quorum sensing is a process where bacteria communicate via signaling molecules, such as autoinducers, to sense their population density and coordinate behavior, such as biofilm formation, based on density changes.

Describe binary fission in prokaryotes.

Binary fission involves the replication of circular DNA from the origin, followed by the movement of FtsZ proteins to the cell center, facilitating the separation and formation of two daughter cells.

How does meiosis differ from mitosis?

Meiosis includes two rounds of division (Meiosis I and II), leads to genetic variation through recombination, and reduces chromosome number (from diploid to haploid), while mitosis is a single division producing identical cells.

What are the implications of Mendel's laws of segregation and independent assortment?

Mendel's law of segregation states that alleles separate during gamete formation, while independent assortment indicates that genes on different chromosomes segregate independently,