Paracrine/ Juxtacrine/ Endocrine

Paracrine Signaling

A secreted molecules diffuses locally and triggers a response in neighboring cells

Juxtacrine Signaling

A type of cell signaling between two cells that directly contact one another

Endocrine Signaling

A type of long-distance signaling in animals that utilizes hormones.

Synaptic Signaling

a nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell

allosteric acetylcholine receptor

Reception: binds to its respective receptor located in the membrane of the skeletal muscle. When its respective ligand binds it undergoes a conformational change

Transduction: allows the influx of Na+ to diffuse into the muscle cell

Response:causes the muscle cell to contract

Cytoplasmic Reception

Reception: small, nonpolar ligands diffused directly through the plasma membrane and into the cytoplasm where they bind with an intracellular receptor

Transduction: The receptor converts a molecular signal to a cellular response

Response: Can be a single step of a more complex signal transduction pathway

Steroids, Thyroids, Hormones, NO gas

hydrophobic chemical messengers who bind with a cytoplastmic (intracellular) receptor

gap junctions and plasmodesmata

allows direct communication between cells, the site of juxtacrine signaling

Kinetochore, Centromere, Sister Chromatids

Kinetochore

disk shaped protein that ataches chromatid to the mitotic spindle

Centromere

Specialized region that holds two sister chromatids together

Sister Chromatids

two strands of DNA; one is a replica of the other

Homologous chromosomes

Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis.

Cyclins and CDKs

control the timing of cell division

Cyclins

Synthesized in response to various molecular signals, including growth factors

G1 checkpoint

The restriction point, if not passed the cell goes into G0 phase

Prophase

The nuclear membrane disintegrates, strands of chromosomes condense and become visible, and the nucleolus disappears (Mitosis)

Metaphase

The chromosomes line up single file on a single plane, centrioles are at opposite ends of the cell, and spindle fibers run from centrioles to kinetochores (Mitosis)

Anaphase

Sister chromatids separate as spindle fibers pull them apart (Mitosis)

Telophase

Chromosomes cluster at opposite ends of the cell, the nuclear membrane reforms, and supercoiled chromosomes unravel and become invisible again (Mitosis)

Cytokinesis

The dividing of the cytoplasm

Prophase

Metaphase

Anaphase

Telophase

Contact Inhibition

-phenomenon in which cells cease dividing when they become crowded

-also called density-dependent inhibition

-a property of normal cells grown in culture

-cancer cells do not exhibit this characteristic; their growth is uncontrolled

Meiosis I

Synapsis and crossover occur, and homologous chromosomes seperate

Meiosis II

Sister chromatids seperate, uncoupling at the centromere, results in four total haploid cells

Crossing Over

Occurs during prophase I of meiosis, it is an exchange of genetic material between nonsister chromatids that increases variation in offspring, because it produces recombinant chromosomes consisting of combined gemes from two parents. Occurs following synapsis.

In mitosis, sister chromatids saperate; in meiosis I homologous pairs separate

The difference between metaphase of Mitosis and Meiosis