4-Cell Structure and Function III

Why is cell signaling important?

1. It allows cells to respond to their environment.

2. It allows cells to communicate with each other.

What are the 3 parts to a signaling pathway?

1. A receptor

2. A signal transduction pathway

3. Effector proteins

What part of a signaling pathway detects the signal?

The receptor.

What part of a signaling pathway relays the signal from the receptor to the effector proteins?

The signal transduction pathway.

What part of a signaling pathway carries out the cell's response?

The effector proteins.

What allows a cell to respond to a specific signal?

A receptor.

What are the 5 types of cell to cell communication?

1. Contact-dependent signaling

2. Paracrine signaling

3. Synaptic signaling

4. Endocrine signaling

5. Autocrine signaling

In what type of cell to cell communication is the ligand and receptor tethered to their respective cells? This form involves the cells touching.

Contact-dependent signaling

What type of cell to cell communication is a local form of signaling where one cell releases the ligand which will then bind to a receptor on a neighboring cell?

Paracrine signaling

What form of cell to cell communication is a specialized form of paracrine signaling used by neurons, where the ligand is a neurotransmitter?

Synaptic signaling

What form of cell to cell communication is a form of long distance signaling that involves hormones (the signaling molecules) being released into the blood and acting on cells that are very far away?

Endocrine signaling

What form of cell to cell communication involves a cell releasing a ligand that then binds to a receptor on the same cell?

Autocrine signaling

Can a cells response to a signal depend on the other signals that it is receiving at the same time?

Yes

Can a cells response to a signal depend on the concentration of the signaling molecule?

Yes

What do gap junctions allow?

They allow ions and molecules to flow from the cytoplasm of one cell into the cytoplasm of another cell. Two cells that are connected by gap junctions can communicate in this way.

Why can different cell types respond differently to the same signaling molecule?

1. They may be expressing different receptors for the signaling molecule.

2. They may have different signal transduction pathways that lead to different effector proteins being activated.

3. They may have different effector proteins being activated in response to the signaling molecule.

What is the name given to a molecule that binds to a receptor?

A ligand.

What are the 3 kinds of cell surface receptors?

1. Enzyme-linked receptors

2. G-protein coupled receptors

3. Ligand-gated ion channels

What type of receptor has a portion of it on the inside of the cell that is an enzyme? Binding of the ligand will alter the enzyme activity.

Enzyme-linked receptor

What is a G-protein?

It is a protein that binds GTP and GDP. It is active when bound to GTP and inactive when bound to GDP.

What type of receptor results in the activation of a G-protein when the ligand binds to the receptor?

G-protein coupled receptor

What type of receptor allows ions to flow through it when it binds the ligand?

A ligand-gated ion channel

What are two ways that signals can be relayed by a signal transduction pathway? Remember that signal transduction pathways are relaying the signal from the receptor to the effector proteins.

1. Through kinases and phosphatases that can communicate with other proteins through the addition and removal of phosphate groups.

2. Through G-proteins. G-proteins are active and signal when GTP is bound to them and inactive when GDP is bound to them.

What is it called when a part of a signaling pathway goes back and activates something that acts earlier in the pathway?

Positive feedback

What is it called when a part of the pathway goes back and inhibits something that acts earlier in the pathway?

Negative feedback

What are second messengers?

The first message is the ligand that the receptor recognizes. A second messenger is a molecule or ion that is produced or released on the inside of the cell in response to the ligand binding to the receptor.

What are two examples of a second messenger?

Ca 2+ ions and cAMP

What are two advantages of using second messengers?

1. They increase the speed of the signal.

2. They amplify the signal.