Unit 4

A chemical signal that binds to a receptor protein, triggering the cell signaling process

Signaling process when a cell releases a ligand that binds to a receptor on the same cell, starting the cell signaling process. the ligand-releasing cell and the target cell are the same cell. Ex. cancer cells, which release growth factors that stimulate the growth of their own cells

Signaling process where the ligand-releasing cells is in direct contact with the target cell that possesses the receptor for the ligand. Ex, the interaction between an antigen presenting cell and a helper T cell in the immune system

Signaling process where the ligand-releasing cell releases a ligand that has an effect on target cells that are near to the ligand-releasing cell. Ex, synaptic signaling between neurons

Signaling process were the ligand-releasing cell releases a ligand that travels long distances to target cells. Ex, effect of insulin on target cells far from the pancreatic cells that released the insulin

Protein embedded in the cell membrane that receive signals from ligands outside the cell. When cell membrane receptors bind to extracellular ligands, a shape change occurs in the cell membrane receptors, which starts the cell signaling process. Cell membrane receptors typically bind to hydrophilic ligands that cannot cross the cell membrane

Ligands involved in cell signaling that travel long distances from the ligand-releasing cell to the target cell

The process by which a cell responds to a ligand through a series of chemical reactions inside the cell, leading to a response in the cell

Cells containing the receptor for a specific ligand that can respond to the binding of the ligand to the receptor. Cells cannot respond to ligands for which they do not have the appropriate receptor

Proteins within the cell that bind to ligands. These cytoplasmic receptors typically bind to hydrophobic ligands that have crossed the membrane of the cell and entered the cytoplasm

A series of chemical reactions in which each molecule activates multiple molecules amplifying the cell’s response to a signal

Enzymes that add phosphate groups to other molecules, often activating those molecules

Enzymes that remove phosphate groups from other molecules, often deactivating those molecules

An enzyme that converts ATP into the secondary messenger cyclic AMP, cyclic AMP is an important secondary messenger in cell signaling

Intracellular signaling molecules that create chemical changes in a cell in response to the reception of chemical signals. Ex, cyclic AMp and the calcium ion (Ca2+)

Secondary messenger formed from ATP by the enzyme adenylyl cyclase

Occurs when a stimulus triggers a response that returns the system to homeostasis. Ex, an increase in body temperature in humans triggers sweating, which reduces the body temperature

Occurs when a stimulus triggers a response that increases the strength of the stimulus moving the system further form homeostasis. Ex, ethylene, which stimulates fruit ripening, ripening fruit releases more ethylene, which will stimulate even faster ripening

the stage of the cell cycle between cell divisions, which includes the G1, S, and G2 phases. the cell grows, replicates its chromosomes, and prepares for mitosis

The stage of the cell cycle in which replicated chromosomes are separated into two new nuclei. Mitosis consists of prophase, metaphase, anaphase, and telophase

Division of the cytoplasm at the end of mitosis or meiosis. In cells without a cell wall, a cleavage furrow forms to divide the cytoplasm. In cells with a cell well, a cell plate is formed, as well as a cleavage furrow

growth phase during interphase of the cell cycle, during which the cell grows and cellular organelles are replicated. Precedes the S phase

The phase of interphase in which the DNA is replicated. At the end, a cell contains twice the amount of DNA that is had at the beginning. Follows G1 and G2

the phase of interphase following the S phase, during which the cell continues to grow and prepare for mitosis

the phase of mitosis during which the chromatin condenses into visible chromosomes and the spindle fibers form in the nucleus. follows interphase and precedes metaphase

The phase of mitosis during which the chromosomes align along the center of the cell (also known as the metaphase plate) follows prophase and precedes anaphase.

The phase of mitosis during which the centromeres of the chromosomes split and the two chromatids separate and begin to move to opposite sides of the cell. At this point, each chromatid has its own centromere and is considered a separate chromosome. Follows metaphase and precedes telophase

The phase during which two nuclei are formed. After anaphase and usually precedes cytokinesis

The phase of the cell cycle during which a cell is not actively dividing. Fully differentiated cells are in it. Cellular signals may cause a cell to either enter or leave G0 depending on cellular conditions

Regulate the progression of the cell cycle. Occur at multiple points in the cell cycle and can stop the cell cycle if defects in components necessary for cell division are detected. May prevent mutated cells from dividing and causing tumors

Proteins whose levels vary throughout the cell cycle. Bind with cyclin-dependent kinases to form mitosis promoting (MPF) When levels of MPF are high enough, a cell will enter mitosis

Proteins which, when bonded to cyclins, form mitosis-promoting factor (MPF). When levels of MPF are high enough, a cell will enter mitosis. Levels of cyclin-dependent kinases are relatively constant during the cell cycle

Mitosis-promoting factor. This is a complex of cyclin-dependent kinases bound to cyclin proteins. High levels of mitosis-promoting factor will signal a cell to start mitosis

The process in normally dividing cells in which cells that exceed a particular density stop dividing. Stops uncontrolled cell division. Malignant cells do not exhibit this.

In some cell types cells must be attached to a surface to continue dividing. Malignant cells do not exhibit this

genes that stimulate normal rates of cell division. If it is mutated it may become an oncogene, which stimulates excessive rates of cell division. Are analogous to the accelerator on a car because they stimulate cell division

Cancer-causing genes that stimulate excessive rates of cell division

Genes that detect defects in DNA replication and will stop the cell cycle if mutations are detected. Are analogous to the brakes on a car because they stop cell division from proceeding

Programmed cell death. May occur if mutations are detected in a cell. also occurs

Checks that the original DNA is not damaged and cell has enough nutrients. If not passes, cell will enter G0 and maybe apoptosis

Checks that DNA has replicated correctly and cell is ready for mitosis. If not passes, cell will repair damage or apoptosis.

Checks that the spindles from the centrioles have correctly attached to kinetochores in the centromeres. If not pass cell will wait until microtubules attach correctly.