Biology - Chapter 9

what happens at the signal transduction step

the process in which an extracellular molecule acts as a signal to activate a receptor which transmit information through the cytoplasm.

what is the responsibility of receptor kinase signaling

-formation of elongation of limb buds(arm and legs) -wound healing: triggers cell division to repair wound gene expression: allow cells to grow and divide, etc..

what are the four essential elements for communication

-signaling cell -signaling molecule -receptor molecule -receptor cell

what happens in the termination of a G protein coupled signal

1. activated G protein deactivates itself by converting GTP to GDP 2. enzymes in cytosol degrade cAMP white stops phosphorylation and activation of target protein 3. phosphatase remove phosphate groups from proteins causing them to be inactive 4.signal molecule detaches from the receptor over time, which inactivates the receptor.

what are the step of cell signaling

1. receptor activation 2. signal transduction 3. response 4. termination

Many diseases are the result of a problem with cell signaling. Which of the following diseases best exemplifies this fact? a. Cystic fibrosis, caused by a mutation in a channel protein, resulting in a buildup of mucus. b. A specific type of cancer, caused by a truncated receptor that becomes stuck in the activated form. c. Familial hypercholesterolemia (high cholesterol in the blood), caused by a decrease in the number of receptors for cholesterol. d. Congestive heart failure, caused by chronic high blood pressure due to excessive sodium intake.

A specific type of cancer, caused by a truncated receptor that becomes stuck in the activated form.

how do cell communicate?

By sending a signaling molecule that binds to a receptor on a responding cell in universal among prokaryote and eukaryotes.

what does a cell surface receptor interact with?

polar signaling molecules that cannot cross the plasma membrane and rely on cell surface receptors

What is the very first effect of ligand binding to a G protein-coupled receptor? a. the release of the alpha subunit of the G protein b.a conformational change in the cytoplasmic domain of the receptor c. the activation of an effector protein d. an exchange of GTP in place of GDP on the alpha subunit of the G protein

Correct: a conformational change in the cytoplasmic domain of the receptor

How is a G protein classified?a. It is a peripheral membrane protein. b. It is a second messenger. c. It is an integral membrane protein. d. It is a transmembrane protein.

It is a peripheral membrane protein.

what happens in the termination step

The response is terminated so that new signals can be received. It also protects the cell from overreacting to existing signals and therefore helps the cell to have an appropriate level of response.

what happening during receptor activation

a g protein coupled receptor is activated when it binds a signaling molecule, which leads to exchange of gdp for gtp on the g protein's α subunit, separation of the α subunit, and downstream effects. activated α subunit covalently link to protein.

phosphorylation

a kinase is an enzyme that catalyzes the transfer of a phosphate group from ATP to a substrate. To catalyze this reaction, it binds both ATP and substrate

quorum sensing

a process by which bacteria are able to determine whether they are at low or high population density and then turn on specific genes across the entire community

g protein coupled receptor

a receptor that couples to G proteins which bind to the guanine nucleotides gtp and gdp

receptor kinase

a receptor that is an enzyme that adds a phosphate group to another molecule

example of endocrine signaling

adrenaline. adrenaline produced in the adrenal glands is carried by the bloodstream to target cells far from signaling cells. estrogen and testosterone travel from the ovaries and testes through the bloodstream.

Which of the following is a cellular response to signal transduction? a. change in the proteins found a the cytosol b. the release of more signal molecules c. a change in the activity of an enzyme d. All of these choices are correct.

all of above

Termination is an important step in adrenaline signaling because: a. it prevents an excessive response to adrenaline. b. it allows organisms to respond to new stresses. c. it allows an appropriate level of response. d. All of these choices are correct.

all of the above

Ligand binding to a receptor kinase results in: a. phosphorylation of the cytoplasmic domain of the receptor. b. binding of cytoplasmic signaling molecules. c. receptor dimerization. d. All of these choices are correct.

all of these choices are correct

cyclic amp (second messenger)

an intermediate cytosolic signaling molecule that transmit signals from a receptor to a target within the cell.

Which of the following is not a true statement about receptors that are localized to the nucleus? a. They bind polar ligands. b. They are synthesized in the cytosol. c. They move through a nuclear pore. d. They carry a nuclear-localization signal.

bind polar ligands

what happens if there is high cell population density?

the peptide is made at high levels and the result is environmental DNA uptake.

The first step following PDGF binding of the receptor is: a. activation of MAP kinase. b. dimerization. c. phosphorylation. d. activation of gene expression.

dimerization

Where would you expect to find the receptor for a nonpolar ligand? a. in the nucleus of the cell b. in the cytosol c. either in the nucleus of the cell or in the cytosol d. on the cell surface

either in the nucleus of the cell or cytosol

Which signaling system involves the longest time interval between release of a signaling molecule and activation of a receptor?

endocrine

what are types of signaling

endrocrine paracrine autocrine juxtacrine

T/F: A cell can only respond to signals from other cells, not from the physical environment.

false

Cellular responses that result from receptor kinase activation tend to: a. be short term. b. involve ion channels. c. involve changes in metabolism. d. involve changes in gene expression.

gene expression

what is the importance of Kit receptor kinases

important for the production of pigment in skin, feathers, scales, and hair

ligand gated ion channels

ion channels open when bound by their ligand channel proteins help ions and other molecules diffuse into and out of the cell by providing a hydrophilic pathway through the hydrophobic core of the plasma membrane

what is the important of phosphorylation

it affects the activity of the substrate. a protein is phosphorylated by a kinases and becomes active

contact-dependent signaling

it requires that the two communicating cells be in physical contact with each other. A transmembrane protein on the surface of one cell acts as the signaling molecule, and a transmembrane protein on the surface of an adjacent cell acts as the receptor

what are the three types of cell surface receptors

light switch g protein coupled receptors receptor kinases ligand gated ion channel

ligand binding site

location on the receptor to which the ligand binds

what is the importance of autocrine signaling?

multicellular organisms during the development of embryo

what happens in muscle contractions

myosin undergoes a conformational change, sliding actin filaments relative to myosin. the result is a shortening of the muscle cell

what do intracellular receptors interact?

non-polar signaling molecules that can freely pass through the plasma membrane and activate cytoplasmic receptors

Ras is a type of G protein because it: a. triggers the formation of cyclic AMP. b. responds to the activation of G protein-coupled receptors. c. is only active when it binds GTP. d. All of these choices are correct.

only active when it binds GTP

Growth factors such as platelet-derived growth factor function in: a.endocrine signaling. b.autocrine signaling. c.paracrine signaling. d.contact-dependent signaling.

paracrine

dephosphorylation

phosphates remove a phosphate group. it becomes in active

whats the first step in cell signaling

receptor activation

In many signaling pathways, once a signaling molecule binds to a receptor, the receptor becomes phosphorylated. This initial phosphorylation step best demonstrates: a. signal transduction. b. receptor activation. c. cellular response. d. either cellular response or signal transduction. e. termination.

receptor activiation

Which type of cell-surface receptor undergoes changes in phosphorylation in response to binding of its ligand?

receptor kinase

what is paracrine signaling

signaling by a molecule that travels a short distance to the nearest neighboring cell to bind its receptor and deliver its message

what is endocrine sigaling

signaling by molecules that travel through the bloodstream acts over long distance

autocrine sigaling

signaling cell and the responding cell are one and the same

ligand

signaling molecule

amplification of G protein coupled signaling

signaling through G protein coupled receptors is amplified at several places so a small amount of signal can produce a large response in the cell

what happens at the response step

take different forms depending on the nature of the signal and the type of responding cell. the cell responds ( activating an enzyme, cell shape change, cell division)

what happens at the receptor activation step

the 'turning on' of a receptor, which often occurs when a signaling molecule binds to a receptor on a responding cell

In order for a G protein to be active: a. the beta and gamma subunits must separate from the alpha subunit. b. the alpha subunit must bind GTP. c. both the beta and gamma subunits must bind GTP. d. the alpha subunit must bind GTP and the beta and gamma subunits must separate from the alpha subunit.

the alpha subunit must bind GTP and the beta and gamma subunits must separate from the alpha subunit.

Ras is most similar to: a. the gamma subunit of three-subunit G proteins. b. the alpha subunit of three-subunit G proteins. c. the beta subunit of three-subunit G proteins. d. receptor kinases. e. ion channels.

the alpha subunit of three-subunit G proteins.

binding affinity

the length of time a signaling molecule remains bound to its receptor depends on how tightly the receptor hold on to it

What determines the specificity of a receptor protein?

the ligand-binding site

what happens if there is low cell population density?

this peptide is made at low levels, and the result is it that the genes for taking up the environmental DNA are also low.

How does an "activated" receptor transfer information into the cell? a. through a conformational change of the receptor b. by decreased phosphorylation of the receptor c. by increased translation of the receptor d. by altering the ligand-binding site of the receptor

through a conformational change of the receptor

What is the function of adenylyl cyclase?

to form cyclic AMP

Signaling molecules involved in paracrine and autocrine signaling: remain attached to the plasma membrane. travel by diffusion. travel in the circulatory system.

travel by diffusion

growth factor

type of signaling molecule that causes the responding cell to grow, divide or differentiate.