Copy of Unit 4 Cellular Communication & Cell Cycle 24-25

Question 1

What is Cell Signaling?

Answer 1

Cell signaling is the series of steps that allow cells to respond to signals from their environment.

Question 2

How do cells respond to accepting a cell signal?

Answer 2

Cells respond by initiating some sort of cellular activity, such as the initiation of the cell cycle.

Question 3

What is a ligand?

Answer 3

A ligand is a chemical signal secreted from the initiating cell that travels to the target cell.

Question 4

What determines a cell’s receptors ability to accept a signal?

Answer 4

Correct shape and charge.
Only cells that have the correct receptor protein will react to the signal molecule.

Question 5

How do cells communicate?

Answer 5

Cells communicate by sending and receiving chemical messengers.

Question 6

What is quorum sensing?

Answer 6

a process of cell communication that allows bacteria to share information based on high cell density and adjust gene expression accordingly. (Like bioluminescence in prokaryotes)

Question 7

What role does adrenaline play in cell communication?

Answer 7

Secretion of the hormone adrenaline achieves cell communication in the fight-or-flight response.

Question 8

What happens during the response step of cell signaling?

Answer 8

The final molecule in the signal pathway initiates transcription of target genes in the nucleus, leading to protein synthesis that causes the cell response.

Question 9

What occurs during the basic transduction step?

Answer 9

Signal is moved from the cell membrane to the nucleus through phosphorylation of a series of proteins until the last one enters the nucleus

Question 10

What occurs during the reception step? What happens to the receptor?

Answer 10

Ligand binds to the receptor, causing a conformational change that transmits the signal inside the cell.

Question 11

What is paracrine signaling?

Answer 11

When the Communicating cell releases a signaling molecule (ligand) that moves to the target (receiving cell). along short or long distances by diffusion

Question 12

How does endocrine signaling work?

Answer 12

Endocrine signaling takes place over long distances and relies on the circulatory system for transport of signaling molecules.

Question 13

What is autocrine signaling?

Answer 13

Autocrine signaling occurs when a cell signals itself by sending a chemical messenger to its own receptor
(such as activated T-cells releasing interleukin-2 to stimulate their own proliferation.)

Question 14

What are gap junctions?

Answer 14

Gap junctions occur in animal cells when the cell membrane of cells fuse and open pores between them.

This allows signals to quickly diffuse and initiate cell response.

Question 15

What are plasmodesmata?

Answer 15

Plasmodesmata are plant cell-specific pores taht open between the cell membrane/wall of two cells.

allows signals to quickly diffuse and initiate cell response.

Question 16

What is traditional cell-cell contact?

Answer 16

Traditional cell-cell contact involves an originating cell expressing a ligand on its membrane and a target cell expressing a receptor protein.

Question 17

What is the difference between cell-to-cell signals and environmental signals?

Answer 17

Cell-to-cell signals are much more specific and intentional compared to environmental signals.

Question 18

What are intracellular receptors? What type of ligands do they bind to?

Answer 18

Intracellular receptors are found in the cytosol and bind to lipid-soluble ligands that diffuse across the membrane and interact with genes in the nucleus.
This complex travels directly to the nucleus to initiate cell response bypassing transduction

Question 19

What are membrane-bound receptors? Why type of ligands bind to them?

Answer 19

Hydrophillic ligands bind to a receptor that is embedded in the cell membrane. The ligands don’t cross the membrane.
Signal is amplified and moved from the membrane to the nucleus via a transduction pathway

Question 20

What is the role of G protein-coupled receptors?

Answer 20

G protein-coupled receptors change conformation upon binding signals and trigger a signal transduction cascade.

Question 21

What is the function of second messengers?

Answer 21

Second messengers amplify signals and drive response mechanisms in target cells.

Question 22

What is the role of phosphatases in relation to second messengers?

Answer 22

Phosphatases deactivate second messengers like cAMP to terminate responses initiated by G protein-coupled receptors.

Question 23

What are receptor-protein kinases?

Answer 23

Receptor-protein kinases have a signal-binding function and an enzyme function activated upon binding the signal. Responses initiated by them are terminated by the release of a signal

Question 24

What are ligand-gated ion channels?

Answer 24

Ligand-gated ion channels are proteins that have signal binding and ion channels that can open or close to alter ion movements across the membrane, allowing rapid communication (ex in neurons.)

Question 25

What do hydrophobic signaling molecules do?

Answer 25

Readily enter receptor proteins in cells that together can turn genes on or off by altering protein synthesis in the response pathway.

Question 26

Whats an example of a hydrophobic signal?

Answer 26

Steroid hormones,

Question 27

How do cells respond to signal transduction?

Answer 27

initiating transcription of target genes and producing proteins.

Question 28

What are examples of cell responses?

Answer 28

Examples include initiation of gene expression, cell growth, secretion of molecules, and initiation of cell death.

Question 29

What happens when there are mutations in signaling pathways?

Answer 29

Mutations can change or stop the cell response from occurring properly. It can also change chemical afffinity

Question 30

How do medicines and toxins affect signaling pathways?

Answer 30

Many medicines and toxins work by activating or inhibiting signaling pathways.
Like paralysis causing neurotransmitters not to be released

Question 31

What is an agonist?

Answer 31

An agonist stimulates a response in a target cell.

Question 32

What is an antagonist?

Answer 32

An antagonist prevents a response in a target cell, even when the normal ligand is present.

Question 33

How can genetic mutations affect signal transduction?

Answer 33

Mutations can interfere with the signal transduction pathway, affecting the cell’s responses.

Question 34

What do membrane-bound receptors require to move the signal from the membrane to the nucleus?

Answer 34

Transduction

Question 35

What happens when a ligand binds to a receptor?

Answer 35

The receptor changes shape, transmitting the signal into the cell

Question 36

What is a second messenger in signal transduction?

Answer 36

A molecule that is activated, such as cyclic AMP, to phosphorylate the next protein in the chain

Question 37

What does the activation of proteins in the signal transduction pathway lead to?

Answer 37

The activation of the last protein, usually a transcription factor, which enters the nucleus

Question 38

Fill in the blank: A ligand binds to the receptor, causing it to change shape, which transmits the signal into the _______.

Answer 38

cell

Question 39

True or False: The last protein in the signal transduction pathway is typically a transcription factor.

Answer 39

True

Question 40

What is the role of cyclic AMP in the signal transduction process?

Answer 40

It acts as a second messenger that phosphorylates the next protein in the chain

Question 41

What initiates the cell response after the signal transduction pathway is activated?

Answer 41

A transcription factor enters the nucleus

Question 42

signal transduction step by step with a G protein (yes this is long)

Answer 42

Ligand binds to receptor causing it to change shape allowing a G protein with GDP to leave and a GTP to take it’s place. Then it uses G proteins on the membrane to trigger a signal transduction cascade by activating adenylyl Cyclase to convert ATP to cAMP, a secondary messenger. Many cAMP then phosphorylates the protein kinase activating it and it does do many times (this is the phosphorylation cascade). each kinase enzyme then phosphorylates many target proteins

Question 43

signal transduction with a G protein after the ligand leaves the receptor

Answer 43

cAMP is deactivated by phosphatases to terminate response initiated by G protein-coupled receptors

Question 44

what are the steps in Basic Transduction? (without a
G protein) p.s this is long

Answer 44

Ligand binds to membrane bound receptor which sends a signal and activates a protein. This protein then hands off the phosphate it got from cAMP until it reaches the last protein in the pathway (usually a transcription factor) enters the nucleus and initiates cell response.

Question 45

Exactly what happens after a ligand leaves a receptor protein that had a G complex? - semi long answer

Answer 45

The protein conforms back to normal a the activated G protein deactivates itself by converting GTP to GDP. Then enzymes in the cytosol degrade cAMP, stopping the phosphorylation and activating of target proteins. (Now that there’s no cAMP, kinase can’t be activated and it can’t advocate any more proteins). Afterwards phosphotase removes phosphate groups from activated targeted proteins, inactivating them.

Question 46

Identify 3 locations of cellular receptors

Answer 46

Membrane,cytosol,nucleus

Question 47

Identify the properties of a ligand that has an intracellular receptor

Answer 47

Small (to get through membrane), hydrophobic, nonpolar

Question 48

Identify the properties of a ligand that has an extra cellular receptor

Answer 48

Size of the membrane blind receptor, polar, hydrophilic