Chapter 5: Signal Transduction

Question 1

Transduction

Answer 1

How cells communicate with each other

Question 2

Receptors

Answer 2

Specific target-cell proteins that bind chemical messengers

Question 3

Properties of most chemical messengers (2)

Answer 3

-water soluble
-bind at plasma membrane

Question 4

Properties of steroids (2)

Answer 4

-lipid soluble
-bind to an intracellular receptor

Question 5

Transmembrane protein

Answer 5

goes all the way through a membrane

Question 6

Water soluble signal transduction

Answer 6

Induces a shape change on a portion of the protein

Question 7

Water insoluble lipid transduction

Answer 7

Directly changes transcriptional profile of DNA

Question 8

Antagonist

Answer 8

Anything that blocks a ligand from binding

Question 9

Agonist

Answer 9

Binds to a receptor and enhances/mimics the receptor

Question 10

Down-regulation

Answer 10

Decreases number of receptors if ligand is present

Question 11

Up-regulation

Answer 11

Increase in number of receptors if ligand is lower in concentration

Question 12

Specificity

Answer 12

Each cell responds to its own set of chemical messengers

Question 13

Competition

Answer 13

Ability of different molecules to compete with a ligand for binding to its receptor

Question 14

Speed of lipid soluble messengers

Answer 14

Slower but sustained

Question 15

Speed of water soluble messenegers

Answer 15

Faster but less sustained

Question 16

First messenger

Answer 16

Extracellular chemical messenger that binds to specific plasma membrane receptors

Question 17

Examples of first messengers

Answer 17

Hormones, neurotransmitters

Question 18

Second messengers

Answer 18

A substance generated in response to the first messenger

Question 19

Examples of second messenegers

Answer 19

cyclic AMP, Ca2+

Question 20

Where are second messengers generated?

Answer 20

Cytoplasm

Question 21

Ligand-gated ion channels

Answer 21

Conformational change of receptor to open the channel

Question 22

What opens a ligand-gated ion channel?

Answer 22

First messenger

Question 23

Receptor tyrosine kinases

Answer 23

Have intrinsic enzyme activity that specifically phosphorylate tyrosine residues

Question 24

What’s one thing all receptor kinases have in common?

Answer 24

All involve activation of cytoplasmic proteins by phosphorylation

Question 25

What can the first messenger bound receptor turns on an enzyme to create guanylyl cyclase, what is the secondary product formed?

Answer 25

cyclicGMP

Question 26

cGMP-dependent protein kinase

Answer 26

-Activated by cGMP -phosphorylates other proteins

Question 27

Where is the cGMP pathway found?

Answer 27

In the retina of the eye

Question 28

Kinase

Answer 28

Receptor itself is an enzyme

Question 29

Janus kinases (JAKs)

Answer 29

Receptor is just a receptor

Question 30

What happens when the first messenger binds to the janus kinase?

Answer 30

Induces a conformational change

Question 31

Where are JAK proteins used?

Answer 31

Immune reactions

Question 32

What is an important molecule in protein binding to change conformation?

Answer 32

G protein

Question 33

G protein is composed of three subunits. What are they and what are their functions?

Answer 33

alpha: binds to GDP beta and gamma: anchor alpha subunit to membrane

Question 34

Where is the G protein located?

Answer 34

Inside the membrane

Question 35

What is Gs' effector protein?

Answer 35

Adenylyl cyclase

Question 36

What does adenylyl cyclase produce?

Answer 36

Cyclic AMP

Question 37

What is the most important secondary messenger?

Answer 37

Cyclic AMP

Question 38

What enzyme catalyzes the breakdown of cAMP into AMP?

Answer 38

cAMP phosphodiesterase

Question 39

Increased cAMP in the cell means _______

Answer 39

Increased function

Question 40

Inside the cell, what does cAMP bind to to create a cascade of cellular events?

Answer 40

cAMP-dependent protein kinase

Question 41

True or false: all G proteins stimulate cAMP.

Answer 41

False; some are Gi, "inhibitory"

Question 42

What is the main function of a G protein?

Answer 42

Controls ions channels

Question 43

Direct regulation

Answer 43

G protein interacts with channel without second messengers

Question 44

Indirect regulation

Answer 44

Second-messenger pathways used

Question 45

What activated Gq?

Answer 45

Receptor bound to first messenger

Question 46

Activated Gq activates plasma membrane effector enzyme _______

Answer 46

Phospholipase C (PLC)

Question 47

Phospholipase C catalyzes the breakdown of what plasma membrane phospholipid?

Answer 47

PIP2

Question 48

What is PIP2 broken down into by phospholipase C, and what is their function?

Answer 48

DAG and IP3, second messengers

Question 49

DAG

Answer 49

activates another kinase by phosphorylating other proteins

Question 50

IP3

Answer 50

binds to Ca2+ receptors on ER, increasing Ca2+ concentration in cytosol to help activate protein kinase C

Question 51

What does the presence of Ca2+ create in the cell?

Answer 51

An electrochemical gradient

Question 52

Where does the electrochemical gradient favour the higher concentration of Ca2+?

Answer 52

Into the cytosol

Question 53

What is the second messenger associated with Ca2+?

Answer 53

IP3

Question 54

IP3 regulates the release of Ca2+ from where?

Answer 54

ER

Question 55

What protein undergoes a conformation change when activated, and can activate or inhibit other enzymes, when bound to Ca2+?

Answer 55

Calmodulin

Question 56

What type are the Ca2+ channels in the plasma membrane?

Answer 56

Voltage-gated ion channels

Question 57

When the first messenger subsides, what happens to the second messenger?

Answer 57

Intracellular concentration (of second messenger) decreases