ap bio cell signaling

transcription factors

proteins that control the activity of a gene (turn on/off)

local regulators

ligands that only travel short distances

GPCR

g protein-coupled receptors - receptors that work w/ help of a g protein

RTKs

receptor tyrosine kinase - transfer phosphate groups from ATP to another protein

second messenger

small, non-protein, water-soluble molecules/ions that spread through a cell by diffusion

cAMP

cyclic AMP - second messenger, immediate effect is usually to activate protein kinase A

Ca2+

second messenger, a small change in ions represents a large percent change in concentration since its conc in cytosol is so much lower than outside the cell

conformer

internal condition changes w/ external changes

regulator

uses internal mechanisms to control internal change despite external changes

phosphorylation

transfer of a phosphate group to a protein from an ATP

dephosphorylation

removal of phosphates from proteins

transduction

conversion of signal to a response, usually involves amplification

local regulating signals

direct contact, gap junctions/plasmodesmata, free passage of substances through cytosol, short distances (paracrine signaling) and autocrine

evolutionary benefit

enables organisms to sense and respond to environment, coordinate functions,

types of reception

juxtacrine, endocrine, paracrine, autocrine

juxtacrine examples

signaling through plasmodesmata and gap junctions, interaction between T cells and ligands on APCs

endocrine examples

pancreas releasing insulin/glucagon, most hormones

paracrine examples

synapes/neurotransmitters, tissue repair (nearby cells release ligands to stimulate new blood vessel formation)

autocrine examples

cancer cells can secrete their own growth factors, liver cells also signal themselves to divide when the liver is injured to grow it back

protein vs steroid reception

protein: insoluble in fat, must bind to receptor on membrane which stimulates second messenger

steroid: fat soluble, can go through plasma membrane and bind to receptor inside of the cell (cytoplasm or nucleus)

protein reception examples

GPCRs (plasma membrane receptors that work w/ help of a g protein), ligand gated ion channels (receptor acts as a gate for ions when it changes shape, allows ions in through a channel in the receptor)

steroid reception examples

aldosterone binds to receptors in kidney cells, receptor enters nucleus and acts as transcription factor to activate genes that control water and Na2+ flow

testosterone enters cell, binds to androgen receptor in cytoplasm and changes its shape to release proteins, complex moves to nucleus and acts as a transcription factor

Ca2+ role, how/where is it stored

role: second messenger (regulates things like muscle contraction, nerve signaling)

storage: smooth ER, pathway to release involves IP3 and DAG as second messengers

vibrio cholera example

bacteria produces a toxin that modifies a G protein so that it is stuck in its active form, continually makes cAMP, causing intestinal cells to secrete salt into intestines, water follows by osmosis and can cause death from loss of water and salt

growth factors type of reception

paracrine signaling; stimulates nearby cells to grow and divide

role of phosphodiesterase

enzyme that breaks down cAMP and cGMP (second messengers) to control their levels and regulate processes in the body - controls intensity and duration of signals

blood sugar level effects of epinepherine and the liver

epinepherine stimulates breakdown of glycogen (stored glucose in liver), releasing sugar into bloodstream

signal transduction in cancer cells and possible treatment

abnormal functioning of RTKs associated w/ many types of cancer, which can trigger multiple signal transduction pathways at once. cancer cells ignore stop/apoptosis signals

treatments: kinase inhibitors, targeting ligands, antibodies that target specific receptors on a cancer cell’s and prevent ligands from binding to it

how can one signal cause multiple effects/target multiple types of cells

within a single cell: signal transduction pathways can branch out, allowing the signal to influence several different processes at once, production of second messengers can activate many different proteins

types of cells: different cell types might have receptors for the same ligand (ex epinephrine causes blood vessel (smooth muscle) cells to dilate and liver cells to release glucose)

negative feedback scenarios

regulating body temp, blood sugar, blood pressure

positive feedback scenarios

childbirth, blood clotting

epinephrine effect as a signal (liver, smooth muscle in blood vessels for skeletal muscle/intestines)

liver: breakdown of glycogen and release of glucose

smooth muscle that supplies skeletal muscle: makes cells relax, blood vessel dilates, more blood supplied to skeletal muscle

smooth muscle that supplies intestines: cells contract, decreasing blood flow to intestines

evolutionary significance of cell signaling and long term effects

evolutionary: enables multicellularity, allows cells to respond to external fatcors/changes, specialized functions (neurotransmission, immune response, regulating heart beat, etc)

long term effects: maintaining homeostasis, development of more complex signaling has allowed organisms to become more complex w/ specialized cells, can cause diseases when signaling malfunctions (cancer, autoimmune diseases)