Cellular & Molecular Biology - Chapter 16

____ must receive and adapt to signals from their environment.

Cells

Cells must “__________” their needs.

Communicate

What are extracellular signal molecules made by?

Own body or drugs

Receive information, ears of the cell; transmembrane proteins

Receptor proteins

What is outside the plasma membrane in a cell signaling cascade?

Extracellular signal molecule and receptor protein

What is inside the plasma membrane in a cell signaling cascade?

Intracellular signaling molecules, effector proteins, and target cell responses

Proteins that have physiological effects

Effector proteins

What are some examples of effector proteins?

Metabolic enzyme, cytoskeletal protein, and transcription regulator

What target cell response does the metabolic enzyme do?

Altered metabolism

What target cell response does the cytoskeletal protein do?

Altered cell shape or movement

What target cell response does the transcription regulator do?

Altered gene expression

Once you turn receptor on, that’s going to turn on another protein and that’s going to turn on another protein (repeats!) and this is called a __________ because it’s one thing after the next. Eventually, this will cause effects in the cell. It will do that when we get to effector proteins.

Cell signaling cascade

• Long distance signaling

• One cell doing the talking which releases the message, it is going to go into the bloodstream (bloodstream = everywhere!), now every cell in whole body hears it!

Endocrine

Long distance signaling

Endocrine

One cell doing the talking which releases the message, it is going to go into the bloodstream (bloodstream = everywhere!), now every cell in whole body hears it!

Endocrine

• Localized signaling (within one organ)

• Reaches nearby things

• Does NOT go into bloodstream

• Doesn’t reach every cell in body

Paracrine

Localized signaling (within one organ)

Paracrine

Does NOT go into bloodstream (doesn’t reach every cell in body!)

Paracrine

With neurons, electrical signaling

Neuronal/synaptic

Neurons fires action potential, releases neurotransmitters, binds to target cell

Neuronal/synaptic

• Two cells have to be in physical contact to work

• Whispering

Contact-dependent

Hormones are examples of what?

Endocrine

What is delta notch an example of?

Contact-dependent

One signaling molecule can induce different _____ on different target cells.

Responses

One signaling molecule may have several ______.

Receptors

Receptor response depends upon the _____ of the cell.

Context

What are some examples of what the acetylcholine signaling molecule can do to different cell types?

decreased rate of firing in heart cells, secretion in salivary gland cells, and contraction in skeletal muscle cell

Explain how signaling molecules like acetylcholine can affect different cell types.

Signaling molecules, like acetylcholine, have different effects depending on the cell type and that’s because a lot of things have different receptors on the cell type.

Cells just needs ______ to just stay alive.

Signals

Without cell signaling, what happens to cells?

They die (apoptosis)

Why does a cell require many signals?

Survive, and more to grow, divide, and differentiate

Every cell type displays a specific set of receptor proteins, enabling what?

To respond to a specific set of extracellular signal molecules

Cells need survival factors (signaling) or else what?

They’ll commit program cell suicide (apoptosis)

For cell types, they need even more stuff —> do you want to be an eyeball cell, liver cell, brain cell, all of that requires what?

Additional levels of communication

Grow + divide requires what?

Additional signaling

Differentiate requires what?

Different levels of communication

What cell type in the human body can live without talking to each other?

Cancer cells

Explain the “fast” pathway.

Phosphorylation turning proteins on and off

Explain the “slow” pathway.

Transcription and translation making more proteins

Why are fast pathways fast?

Turning on/off proteins that already exist

What are some examples of a fast pathway?

Phosphorylation, GTP-binding, Quaternary regulation

Why are slow pathways slow?

Have to make new proteins and that isn’t instant

In slow pathways, signal goes into _____ and that turns on/off chains and that’s going to change what proteins we make.

Nucleus

What are some examples of slow pathway effects?

Transcription, translation, deliver these proteins

Changing how we express our genes and what proteins we make

Slow pathway

Viagra blocks phosphodiesterase type 5 (PDE5) which ___________ causing prolonged relaxation of smooth muscle (vasodilation).

breaks down cGMP

Starts with __________, goes through body and we have the endothelial cells releasing nitric oxide.

sexual simulation

What does nitric oxide do with GTP?

Cyclases it into cyclic GMP, and cyclic GMP causes vessels to relax

As long as cyclic GMP is there, you are going to get winding of the vessels and that winding of the vessels allows what?

Erection

What is sildenafil, which directly touches that enzyme and stops it from working?

Phosphodiesterase type 5 (PDE5) inhibitor

If you stop Phosphodiesterase type 5 (PDE5) from working, what does that mean?

cGMP is not broken down

Does inhibiting Phosphodiesterase type 5 (PDE5) mean more or less cGMP?

More cGMP because not breaking it down

cGMP around for longer means you get ____ for longer, which is the winding of the blood vessels.

Effect

What are four things cell signaling cascades can do?

Relay, amplify, integrate, and distribute

Intracellular signaling pathways can ____ the signal onward and thereby help spread it through the cell.

Relay

Pass the signal from one to another

Relay

Intracellular signaling pathways can _____ the signal received, making it stronger, so that a few extracellular signal molecules are enough to evoke a large intracellular response.

Amplify

Make weak signal very strong!

Amplify

Intracellular signaling pathways can receive signals from more than one intracellular pathway and _____ them before relaying a signal onward.

Integrate

Taking information from different places, based on different types of feedback, compress down into one decision.

Integrate

Intracellular signaling pathways can _____ the signal to more than one signaling pathway or effector protein, creating branches in the information flow diagram and evoking a complex response.

Distribute

Gives signal to effector protein, which causes physiological effects/changes

Distribute

Always say “yes! we need more!”

Positive feedback

increase activity of signaling pathway

Positive feedback

Says “we don’t need that much”

Negative feedback

decreases activity of that signaling pathway

Negative feedback

How is homeostasis maintained?

Signaling cascades and feedback regulation

Body strives to maintain a biological ‘set-point’

• body temperature, weight, receptor signaling

Homeostasis

All signaling cascades are ______ and ______ one another.

Connected and influencing

What are the three main classes of cell-surface receptors?

Ion-channel-coupled receptors, g-protein-coupled receptors, and enzyme-coupled receptors

What is the fourth class of cell-surface receptors?

Intracellular receptors

Drugs (exogenous) are effective on our cell surface receptors because they are _________ to proteins that we already made (endogenous).

Structurally similar

What is the reason drugs work?

Same shape as signaling molecules already found in our body

Extracellular signaling molecules can interact with more than one type of receptor to increase the _____ of the cellular response.

Diversity

A signaling molecule can have hundreds of different types of ______ for it.

Receptors

What are some examples of the receptors acetylcholine can have?

Ion-channel-coupled receptor and G-protein-coupled-receptor

What does an ion-channel-coupled receptor in skeletal muscle do in acetylcholine?

Increasing contractions

What does a G-protein-coupled receptor in heart muscle cells do in acetylcholine?

Decreasing rate and force of contractions

Flow of ions across the plasma membrane - changes the membrane potential and produces an electric current

Ion-channel coupled receptors

Neurotransmitters at the postsynaptic membrane

Example of Ion-channel coupled receptors

Ion-channel coupled receptors are the exact same as what ion channel?

Ligand-gated ion channels

How are Ion-channel coupled receptors different than Ligand-gated ion channels?

Uses signaling molecules instead of ligands to turn on/off

Ion-channel coupled receptors are both a _____ and ______ at the exact same time.

(Receiving information and signaling molecule is binding to it)

Receptor and ion channel

Largest family of cell-surface receptors

G-protein-coupled receptors (GPCRs)

Where the vast majority of drugs work!

G-protein-coupled receptors (GPCRs)

About half of all known drugs work through ________.

G-protein-coupled receptors (GPCRs)

G-protein-coupled receptors (GPCRs) are _____ proteins.

Transmembrane

G-protein-coupled receptors (GPCRs) are _____ into membrane as they’re being made.

Stitched

G proteins (alpha and gamma) are associated with the ______.

Membrane

What relays the signal from outside to inside?

Conformational changes

The ______ stays active while signal is bound, activating many ______ (amplification!)

Receptor, G proteins

What is the G protein made of?

Alpha, beta, and gamma subunits

Explain the G protein’s structure when it’s off.

Alpha/gamma/beta are stuck together, making one big quaternary structure

G protein is ______. (physically connected to membrane)

Lipid-linked

When G protein is off, what is it bound to?

GDP

Low energy form

GDP

• G protein needs ________ to bind

• Then turns _____ on

• Changes shape of ________ protein.

Signaling molecule, receptor, transmembrane

Only signaling molecule that fits into the _____ can fit, which changes shape and turns G protein ___.

Receptor, on

What happens when G proteins turn on?

Release GDP and as soon as they have an open space, they’re going to suck up GTP (high energy)

What happens when GTP is sucked up by a G protein?

GTP binds to the alpha subunit and that separates from the beta and gamma complex