Cell Communication

Question 1

What is the importance of cellular communication?

Answer 1

Coordinates body functions, fights infections, manages sympathetic and parasympathetic responses.

Question 2

What do cells use to communicate?

Answer 2

Chemical signals bind to receptors.

Question 3

What is a receptor?

Answer 3

A protein that responds to a specific ligand.

Question 4

What is a ligand?

Answer 4

A signaling molecule that binds specifically to another protein.

Question 5

What is paracrine signaling?

Answer 5

Release of signals that act on nearby cells (e.g., Fibroblast Growth Factor).

Question 6

What is synaptic signaling?

Answer 6

Electrical signaling that allows neurotransmitter release at the axon terminal (e.g., Acetylcholine).

Question 7

What is endocrine signaling?

Answer 7

Hormones released from endocrine cells travel via the cardiovascular system (e.g., Insulin from B-cells in the pancreas).

Question 8

What are the main steps involved in cell signaling?

Answer 8

1. Reception 2. Signal transduction 3. Response 4. Termination of the signal

Question 9

What happens during reception in cell signaling?

Answer 9

Ligand binds to a receptor protein, changing its shape or chemical state.

Question 10

What occurs during transduction?

Answer 10

Activated protein causes a relay of changes; enzymes are activated by phosphorylation cascades.

Question 11

What is the response in cell signaling?

Answer 11

Activated enzymes cause changes within the cell.

Question 12

What is the importance of termination in cell signaling?

Answer 12

The signal transduction pathway needs to be turned off.

Question 13

What is receptor specificity?

Answer 13

Only the target receptor on the target cell interacts with the ligand due to the receptor’s 3D shape.

Question 14

What are cytosolic/nuclear receptors?

Answer 14

Ligands must cross the plasma membrane and are hydrophobic or small.

Question 15

What are membrane-bound receptors?

Answer 15

Ligands are hydrophilic or large and require a plasma membrane protein to cross.

Question 16

What are G Protein Coupled Receptors (GPCRs)?

Answer 16

The receptor is unbound at rest; ligand binding activates the G protein.

Question 17

What is the G protein’s activity after hydrolyzing GTP?

Answer 17

It has GTPase activity, allowing it to dissociate from the enzyme and return to its resting state.

Question 18

How many times does a transmembrane protein pass the plasma membrane?

Answer 18

It passes the plasma membrane 7 times.

Question 19

What happens when the primary messenger binds to the receptor?

Answer 19

The receptor undergoes a conformational change, opening a channel for ion flow.

Question 20

What is the role of ligand-gated ion channels in the nervous system?

Answer 20

They allow ion influx, propagating an action potential in neurons.

Question 21

What is an ion channel?

Answer 21

A membrane protein through which specific ions can travel.

Question 22

What is a phosphorylation cascade?

Answer 22

A series of reactions relaying signals from receptors to target molecules, typically involving protein kinases.

Question 23

What do protein kinases do?

Answer 23

They transfer a phosphate group from ATP to activate an enzyme.

Question 24

What are the two important second messengers?

Answer 24

cAMP and IP3.

Question 25

What does cAMP activate?

Answer 25

It activates protein kinase A.

Question 26

What happens to calcium concentrations in the cell?

Answer 26

Calcium is kept at very low concentrations to prevent cell damage.

Question 27

What does phospholipase C convert PIP2 into?

Answer 27

It converts PIP2 to IP3 and DAG.

Question 28

What does IP3 do?

Answer 28

It binds to an IP3-gated calcium channel on the ER, allowing calcium ions to enter the cytosol.

Question 29

What does IP3 bind to in the cell?

Answer 29

An IP3-gated calcium channel on the ER.

Question 30

What happens when the IP3-gated calcium channel opens?

Answer 30

Calcium ions enter the cytosol down their electrochemical gradient.

Question 31

What role do calcium ions play in cells?

Answer 31

They act as a second messenger, activating proteins in a signal transduction pathway.

Question 32

What is one result of calcium ions acting as second messengers?

Answer 32

A cellular response occurs.

Question 33

Why are there multiple steps in signal transduction?

Answer 33

Amplifies the signal, allows for coordination with other pathways, provides control points, allows for specificity of response.

Question 34

How may a cell respond to signals?

Answer 34

Altered gene expression, activation or regulation of protein activity, metabolic functions, opening/closing ion channels, organizing or altering organelle function.

Question 35

What is a characteristic of cellular signals?

Answer 35

They are temporary and of short duration.

Question 36

What is the importance of deactivation in signal transduction?

Answer 36

Prevents excessive response, allows the cell to be ready to respond again, prevents desensitization to signals.

Question 37

How is cAMP deactivated?

Answer 37

cAMP is broken down by phosphodiesterase.

Question 38

What effect does caffeine have on cAMP?

Answer 38

Caffeine inhibits phosphodiesterase, increasing cAMP levels.

Question 39

What is the effect of Viagra on cGMP?

Answer 39

Viagra inhibits a specific cGMP-degrading phosphodiesterase, causing smooth muscle relaxation.

Question 40

What is the lock-and-key model in enzyme activity?

Answer 40

The substrate and enzyme active site have complementary shapes.

Question 41

What initiates the activation of a G protein in signal transduction?

Answer 41

The binding of a hormone or environmental stimulus to the receptor.

Question 42

What does adenylyl cyclase do in the signaling pathway?

Answer 42

It catalyzes the conversion of ATP to cAMP.

Question 43

What is the role of protein kinases in the cytoplasm?

Answer 43

They phosphorylate proteins, activating them to alter cellular functions.

Question 44

What activates protein kinases in the signaling pathway?

Answer 44

cAMP activates protein kinases.

Question 45

What do protein kinases phosphorylate in the cytoplasm?

Answer 45

Proteins in the cytoplasm.

Question 46

What do activated proteins allow to alter?

Answer 46

Cell activity.

Question 47

What type of hormones are water-soluble?

Answer 47

Membrane-insoluble hormones.

Question 48

Where do water-soluble hormones bind?

Answer 48

To membrane receptors.

Question 49

What activates a G protein in the signaling pathway?

Answer 49

The binding of a signal molecule.

Question 50

What does the activated G protein activate?

Answer 50

Adenylyl cyclase.

Question 51

What does adenylyl cyclase catalyze the conversion of ATP to?

Answer 51

cAMP, the secondary messenger.