Block 1 - Receptors and Messengers

Question 1

What allows the passage of messengers and ions between coupled cells?

Answer 1

Gap Junctions

Question 2

What are the four categories of chemical messengers?

Answer 2

Hormones, neurotransmitters, paracrine agent, autocrine agent

Question 3

The majority of substances are lipid ____

Answer 3

insoluble

Question 4

What does a “classic” membrane receptor look like?

Answer 4

Transmembrane proteins spanning the ENTIRE MEMBRANE with hydrophilic segments extending into extracellular and intracellular space. A chemical messenger binds to the extracellular segment endowing specificity.

Question 5

The highest affinity binding sites have what features between the receptor and the chemical messenger?

Answer 5

Perfect fit AND charge attraction

Question 6

For a water soluble message to stimulate a response in the target cell, what must be used?

Answer 6

A second messenger

Question 7

How do lipid soluble chemical messenger travel within the blood?

Answer 7

On a water soluble protein

Question 8

What is an example of a lipid soluble chemical messenger?

Answer 8

Steroids, thyroid hormones and their derivatives, aldosterone

Question 9

What are the four classes of signal transduction pathways?

Answer 9

Ligand gated ion channels, Enzymes (receptor tyrosine kinases), active cytoplasmic JAK kinases, G protein coupled receptors

Question 10

With ____, the first messenger binds to the surface protein receptor and the second messenger is either the substance that enters once the gate is opened OR a substance created intracellularly because of receptor activation.

Answer 10

Ligand gated ion channels

Question 11

With ____, the receptors ____ group is autophosphorylated which then serves as a dock for cytoplasmic proteins which then bind and activate other proteins (enzymes)

Answer 11

Receptor tyrosine kinases, tyrosine

Question 12

T/F All plasma membrane receptors with inherent enzyme activity function as protein kinases

Answer 12

FALSE

Question 13

One exception to the rule and an example of a receptor functioning as both a receptor and enzyme is the case of ____ cyclase which functions as a receptor and forms ____ which is the second messenger that activates ____ dependent protein kinases

Answer 13

Guanylyl, cGMP, cGMP

Question 14

With ____, the receptor forms a complex with ____ kinases (cytokine receptors) which phosphorylates proteins which cause cell response

Answer 14

JAK Kinases, JAK

Question 15

What is the largest category of membrane bound receptors.

Answer 15

G-coupled proteins

Question 16

What are the three subunits of G-coupled proteins?

Answer 16

Alpha, Beta, Gamma

Question 17

With G-coupled proteins, the ____ binds to the ____ subunit which then activates the ion channel or enzyme.

Answer 17

GTP, alpha

Question 18

What do kinases do?

Answer 18

Phosphorylate

Question 19

What do phosphorylases do?

Answer 19

Dephosphorylate

Question 20

The most important second messenger is…

Answer 20

cAMP

Question 21

T/F cAMP may only activate a membrane enzyme.

Answer 21

FALSE. It may inhibit also. Gs (stimulates) and Gi (inhibits) enzyme activity

Question 22

T/F G-coupled protein responses are faster than those of simple channel openings.

Answer 22

FALSE

Question 23

cAMP binds in the cell to ____

Answer 23

PKA

Question 24

How can a cell response be more widely distributed?

Answer 24

Signal amplification

Question 25

With the second model of G-coupled enzymes, a ____ is broken down by activation of ____ (____) from the G-coupled protein. This ____ is called ____ (____) and it is broken down into ____ and ____.

Answer 25

Phospholipid, phospholipase C (PLC) phospholipid, phosphatidylinositol biphosphate, (PIP2), DAG, IP3

Question 26

With the second model of G-coupled enzymes, the DAG released activates what?

Answer 26

Protein kinase C (PKC)

Question 27

With the second model of G-coupled enzymes, the IP3 released activates what?

Answer 27

Works on the ER or SR to release Ca2+ directly

Question 28

With the second model of G-coupled enzymes, the IP3 indirectly activates what?

Answer 28

Protein kinase C (PKC) by calcium release

Question 29

cAMP is the second messenger from ____

Answer 29

Adenylyl cyclase (AC)

Question 30

Calcium is the second messenger from ____

Answer 30

Ion channel from the ER or SR

Question 31

IP3 and DAG are the second messengers from ____

Answer 31

Phospholipase C (PLC)

Question 32

cGMP is the second messenger from ____

Answer 32

Guanylyl cyclase (GC)

Question 33

How can calcium get into the cytoplasm?

Answer 33

Either through channels or by being released from the ER or SR

Question 34

What is the cause of arachidonic acid (AA) formation?

Answer 34

Cellular damage or inflammation

Question 35

The release of phospholipase A2 leads to the formation of…?

Answer 35

Arachidonic acid (AA)

Question 36

Steroids stop the production of what?

Answer 36

A2 and thus the production of Arachidonic acid (AA)

Question 37

____ mediates the formation of endoperioxides, prostaglandins, and thromboxanes

Answer 37

COX (cyclooxygenase)

Question 38

____ mediates the formation of leukotrienes

Answer 38

LOX (lipoxygenase)

Question 39

What is the regulated step in COX and LOX?

Answer 39

PLA2 (A2)

Question 40

What does ASA inhibit?

Answer 40

COX

Question 41

ASA causes the block of ____,____, ____, and ____ by inhibiting ____

Answer 41

Endoperoxides, PGE, PGA, and thromboxanes