Ch 15A (pt. 1): TA Review

Question 1

What is signal transduction?

Answer 1

The process by which a cell responds to substances outside the cell through signaling molecules found on the surface of and inside the cell.

Question 1

What are the principles of cell signaling?

Answer 1

-Cells send and receive signals

-Signalling cells produce a type of signal molecule that is detected by target cells (e. budding yeast)

-Signal transduction: successive transmission of signals and conversion of one type of signal to another type of signal (eg. radio signal in, and out comes sound)
*extracellular signal in, intracellular signaling out

Question 2

Cell surface receptors relay extracellular signals via….

Answer 2

intracellular signaling

Question 3

Where are the receptors that extracellular signal molecules bind to?

Answer 3

Extracellular signal molecules bind to the receptor proteins in the plasma membrane.

Question 4

What activates intracellular signaling proteins?

Answer 4

The trigger

Question 5

What do intracellular signaling proteins activate?

Answer 5

effector proteins that do the functions you need the signaling response to do from the signaling molecule

Question 6

What is an effector protein?

Answer 6

A small molecule that selectively binds to a protein to regulate its biological activity.

(In this manner, effector molecules act as ligands that can increase or decrease enzyme activity, gene expression, influence cell signaling, or other protein functions.)

Question 7

What do effector proteins act as in cell signaling?

Answer 7

ligands that increase or decrease anzyme activity, gene expression, influence cell signalling or other protein functions.

Question 8

What are the four types of extracellular signaling?

Answer 8

Contact-dependant
Paracrine (also related to autocrine)
Endocrine
Neuronal (synaptic)

Question 9

What is the function of contact-dependent signaling?

Answer 9

cells signal to each other by direct physical contact

(Need a physical contact between the cells via a membrane signaling receptor and membrane bound signal molecule (only cells that are directly bound to the signal can receive the signal)
Membrane bound, causes response in neighboring cell that it is bound to)

Question 10

Where are transmembrane inhibitory signal protein bound?

Answer 10

to cell membrane

Question 11

Only cells that are bound directly to the signal can receive the signal.

A. Contact-dependant
B. Endocrine
C. Paracrine
D. Autocrine
E. Synaptic

Answer 11

A. Contact-dependant

Question 12

What is the function of paracrine signaling?

Answer 12

extracellular signals rather
than entering through blood, diffuse locally through extracellular fluid and stay close to the vicinity of the cell that secreted it

(These signals act as local mediators on nearby cells
○ If the local mediators or signaling molecules act on the same cells that release them - it is autocrine signaling
● Local mediator released by the signaling cell triggers responses in neighboring cells (paracrine), or back to the signaling cell (autocrine))

Question 13

Which extracellular signaling as as local mediators on nearby cells?

Answer 13

Paracrine signaling

Question 14

Which extracellular signaling act as local mediators on the same cell?

Answer 14

Autocrine signaling

Question 15

What is the function of neuronal (synaptic) signaling?

Answer 15

how nerve cells deliver messages

○ Axon of a neuron terminates at specialized junctions called synapses on target cell that lie far from neuronal cell body
○ Electrical signals in neurons are converted to chemical signals at
nerve terminal to release molecule - neurotransmitter reaches the target cell
■ Neurotransmitters are formed in vesicles in the presynaptic cell which bind to receptors on the postsynaptic cell

Question 16

Neurotransmitters are formed in vesicles in the _______ cell which bind to receptors on the ________ cell.

A. presynaptic, postsynaptic
B. postsynaptic, presynaptic

Answer 16

A. presynaptic, postsynaptic

Question 17

What is the function of endocrine signaling?

Answer 17

extracellular signal-hormones produced by endocrine cells

○ E.g. pancreas endocrine gland produces insulin causes glucose uptake in cells of the body
○ Travels the most distance - long distance communication response
■ Endocrine cell releases a signal, signal travels through the
blood to reach the target cell, signal binds to receptor on the target cell inducing a response

Question 18

Which extracellular signaling travels the most distance for communication response?

Answer 18

Endocrine signaling

Question 19

What is the function of cell surface receptors?

Answer 19

Extracellular signal binds to cell surface receptor protein on the PM of the cell, binding induces an intracellular signaling molecule to become activated inducing change (secondary messenger)

Question 20

What is the function of intracellular receptors?

Answer 20

Small hydrophobic signal molecule diffuses through the plasma membrane of the cell, binds to an intracellular receptor that is in an organelle/ within the cell, causes a response.

Question 21

What is acetylcholine’s effect on heart pacemaker cells?

Answer 21

acetylcholine binds to GPCR protein, causing a decreased rate of firing = a lower heart rate

Question 22

What is acetylcholine’s effect on salivary gland cells?

Answer 22

acetylcholine binds to GPCR and induces secretion of salivary molecules that were entrapped in vesicles within the cell (similar to action potential neurotransmitter release)

Question 23

What is acetylcholine’s effect on skeletal muscle cells?

Answer 23

acetylcholine binds to ion channel coupled receptors, causing contraction in the cell

Question 24

What are the three classes of cell-surface receptors?

Answer 24

Ion-channel coupled receptors
(GPCRs) G-protein-coupled receptors)
Enzyme-coupled receptors

Question 25

What is the function of Ion-channel coupled receptors?

Answer 25

bind to extracellular signal and alter the permeability to selective ions and alter membrane potential

○ Neuronal signaling, also referred to as transmitter-gated ion channels
○ Ions bind and change channel orientation as open or closed

Question 26

What is the function of G protein- coupled receptors (GPCRs)?

Answer 26

Large trimeric GTP binding proteins relay messages from GPCRs that are
seven-pass transmembrane proteins

○ When GPCR binds to a signal molecule, the activated receptor signals to a G protein on the cytosolic side of the PM, which in turn switches an enzyme or channel on the same membrane on (or can be off)
■ Must be coupled with intracellular TRIMERIC GTP-binding proteins

○ Aids in sight and smell senses

○ Causes activation of an enzyme and signaling cascade

Question 27

What is the function of Enzyme-coupled receptors?

Answer 27

Binds its extracellular signal molecule which switches on the enzyme activity of the receptor itself or an enzyme associated with the receptor

○ Two monomers come together when a dimer signal molecule binds, forming an active catalytic domain dimer from the inactive catalytic domain monomers

■ Or a monomeric signaling molecule binds, bringing the two monomer receptors together, which activates an associated enzyme