test 4

Paracrine signaling

A form of cell-to-cell communication where a cell produces a signal to induce changes in nearby cells, altering their behavior.

Endocrine signaling

A type of signaling where cells secrete hormones that travel long distances through the bloodstream to reach target cells.

Autocrine signaling

A form of signaling where a cell secretes a signaling molecule that binds to receptors on its own surface, affecting itself.

Contact-dependent signaling

Signaling that requires direct physical contact between cells through surface-bound molecules.

Reception

The first step in signal transduction where a signaling molecule binds to a specific receptor on or in the target cell.

Transduction

The process in signal transduction where the bound ligand activates a sequence of intracellular relay molecules.

Response

The specific cellular reaction triggered by the transduced signal in signal transduction.

Polar signaling molecules

Hydrophilic molecules that cannot easily pass through the lipid bilayer and have receptors on the cell surface.

Nonpolar signaling molecules

Hydrophobic molecules that can diffuse across the plasma membrane and have receptors located inside the cell.

Tissue

A group of similar cells and their extracellular matrix that work together to perform a specific function in an organism.

Microtubules

Hollow rods made of tubulin that maintain cell shape, facilitate motility, guide organelle movement, and form spindle fibers.

Microfilaments (Actin Filaments)

Solid rods made of actin involved in maintaining cell shape and facilitating muscle contraction and cell motility.

Intermediate Filaments

Fibrous proteins that maintain cell shape and anchor organelles, more permanent than microtubules and microfilaments.

Integrins

Transmembrane receptor proteins that mediate cell-ECM adhesion by connecting the ECM to the cytoskeleton.

Cadherins

Glycoproteins that mediate cell-to-cell adhesion in a calcium-dependent manner, binding to identical cadherins on adjacent cells.

Desmosomes

Cell junctions providing strong adhesion between cells, made of cadherin proteins linking to intermediate filaments.

Motor protein

Molecular motors that convert chemical energy into mechanical energy for movement, working with cytoskeletal filaments.

Gap junctions

Protein channels in animal cells allowing direct cytoplasmic communication and passage of small molecules between adjacent cells.

Plasmodesmata

Channels in plant cells that connect the cytoplasm of adjacent cells, allowing passage of water and solutes.

Prokaryotic genomes

Typically consist of a single, circular chromosome located in the nucleoid region, often with plasmids.

Eukaryotic genomes

Comprise multiple, linear chromosomes located within a nucleus, with DNA wrapped around histone proteins.

Prokaryotic replication

Occurs in the cytoplasm with a single origin of replication and bidirectional movement until forks meet.

Eukaryotic replication

Takes place in the nucleus with multiple origins of replication along linear chromosomes, regulated for DNA content.

Semi-Conservative DNA replication

A mechanism where each new DNA molecule consists of one original strand and one newly synthesized strand.

Primase

An enzyme that synthesizes a short RNA primer on the DNA template to provide a free 3' hydroxyl group for DNA polymerase.

Helicase

An enzyme that unwinds the DNA double helix at the replication fork by breaking hydrogen bonds.

Topoisomerase

An enzyme that prevents supercoiling by relieving strain during DNA unwinding.

DNA polymerase

The enzyme responsible for synthesizing new DNA strands by adding nucleotides to the 3' end.

Telomerase

An enzyme that extends telomeres in eukaryotic cells, adding repetitive DNA sequences to the end of chromosomes.

Telomeres

Repetitive nucleotide sequences at the ends of linear chromosomes that protect genetic information during replication.

Ligase

An enzyme that joins DNA fragments by forming phosphodiester bonds, such as in Okazaki fragments.