Cell Signaling I

Question 1

Two components required for cell-cell communication

Answer 1

Signal molecule and a signal receptor

Question 2

Cell-Surface Receptor

Answer 2

The signal molecule is hydrophillic so that it cannot go through the plasma membrane. The receptor is on the cell surface (the ECM side).

Question 3

Intracellular Receptor

Answer 3

The signal molecule is hydrophobic so that it can pass through the membrane either passively or via a transporter. The signal receptor is found within the cell- usually in or on the nucleus. These molecules that enter the cell are sometimes transcription factors.

Question 4

Contact Dependent

Answer 4

(Touch me) Signaling molecule is transmembrane so the only way for it to signal is for the cells to come into contact with each other.

Question 5

Paracine

Answer 5

(Hi neighbor) A cell releases a molecule and this molecule travels a short distance to a neighboring cell (local mediator).

Question 6

Autocrine

Answer 6

(I don’t need no man) A cell releases a signaling molecule but it also contains the signaling receptor for that molecule so it can regulate itself. It can also occur that the cell that releases the signaling molecule, has the molecule travel to the exact same cell for binding of their signaling receptor.

Question 7

Synaptic

Answer 7

(Give me some kind of signal) In neurons- it forms a synapse with a target cell. Action potentials leads to a sodium influx, calcium goes into the cell and the secretory vesicles bud off and travel a very short distance to get to the receptor on the target cell~fast

Question 8

Endocrine

Answer 8

(Endocrine is hormones) A hormone is released into the blood and travels throughout the circulatory system in order to reach its target cell and its receptor~slow.

Question 9

Acetylcholine

Answer 9

Skeletal Muscle
Causes contraction
Heart Muscle
Decreases rate and force of contraction
Salivary Glands
Secretion of saliva contents

Question 10

What types of hormones have intracellular receptors?

Answer 10

Steroids-cholesterol based

Question 11

Early Primary Responses

Answer 11

Hormone-receptor complex dimerizes and it recognizes and binds to the DNA to regulate transcription of specific genes. In the end you get these proteins, some of which are transcription factors.

Question 12

Delayed Secondary Responses

Answer 12

A primary response protein turns on secondary response (which is why it is delayed). These proteins recognize a specific sequence of DNA and regulate transcription. Some of the proteins end up being repressors as they act as feedback inhibitors for this process.

Question 13

Structure of Nuclear Superfamily Receptors

Answer 13

Has DNA binding domain, the C-terminus is where the hormones bind, the N-terminus is variable (in size) and it contains a transcription activating domain so that it can bind proteins that either enhance or repress transcription.

Question 14

Ion Channel

Answer 14

Binding of hormones to the ion channel, which can cause either the opening or closing of the channels.

Question 15

Enzyme Coupled Receptors

Answer 15

1. Some plasma membrane receptors have enzyme activity as part of its structure so that in the absence of a hormone it is inactive. When the hormone binds, it brings the two monomers together, which activates the enzyme- this can then continue on to phosphorylate each other and other proteins.
2. Some receptors don’t have an enzyme as part of its structure but it can bind an enzyme. When the signaling molecule binds, it brings the two domains together and then an activated enzyme comes in and associates with the domains.

Question 16

G-Protein Coupled Receptors

Answer 16

A signal molecule binds and it allows the G protein to bind to it and the hormone receptor complex activates the G protein which can then activate the enzyme/ion channel.

Question 17

Structural Features of G-protein

Answer 17

Heterotrimer- 3 different subunits. The alpha subunit has a hydrophobic piece that is attached into the membrane. The beta subunit and the gamma subunits are attached to each other and the gamma subunit is bound to the membrane through hydrophobic tails. In the resting condition, the alpha subunit is bound to GDP.

Question 18

Structural Features of GPCR

Answer 18

N-terminus is in the extracellular space, followed by 7 transmembrane units and the C terminus in the cytoplasm. The (larger) hormones bind to the N-terminus (duh). The smaller hormones are able to interact with the 7-transmembrane loops.

Question 19

How cAMP, acting through PKA, can alter gene transcription.

Answer 19

PKA is small enough to get through the nuclear pores and in the nucleus it is able to phosphorylate specific proteins (including CREB). CREB binds to a specific sequence, it can attract the binding of a CREB binding protein CBP which allows it to bind to a receptor and regulate transcription.

Question 20

Cholera Toxin

Answer 20

Toxic ADP-Ribosylation puts a ribose on Arginine which prevents GTP from being hydrolyzed into GDP which leads to a continually active Gs protein. Because of this you get the loss of sodium, cholride, and water, which leads to diarrhea and infection. It is a treatable disease.

Question 21

Gi Protein

Answer 21

Inhibits adenylyl cyclase which would decrease cAMP, therefore inhibit gene transcription and translation.