chapter 6

Question 1

what are the methods of cell communication

Answer 1

1. gap junctions: provide direct cytoplasmic transfer between adjacent cells
2. contact dependent signaling: surface to surface contact between membranes
   -CAM: transfers signals in both directions
3. cells release messengers to the ECF: long distance communication composed of hormones, neurohormones, neurotransmitters and local communication: paracrine and autocrine signals

Question 2

3. cells release messengers: long distance
   hormone

Answer 2

secreted by endocrine glands or cells into the blood. only target cells with receptors for the hormone will respond to the signal

Question 3

3. cells release messengers: long distance
   neurotransmitter

Answer 3

chemicals secreted by neurons that diffuse across a small gap to the target cell. neurons use electrical signals as well. stays in interstitial fluid

Question 4

3. cells release messengers: long distance
   neurohormone

Answer 4

chemicals released by neurons into the blood for action at distant targets

Question 5

3. cells release messengers: local communication
   -paracrine signals

Answer 5

secreted by one cell and diffuse into adjacent cells

Question 6

3. cells release messengers: local communication
   -autocrine signals

Answer 6

act on the same cell that secreted them

Question 7

what are types of cellular messengers

Answer 7

-hormones: release form tissue and travel to target cell through blood
-neurotransmitters: released from neuron to adjacent effector, stays in interstitial
-neurohormone: released from neuron and travels target cell via blood
-paracrine: released to interstitial fluid and affects neighboring cell
-autocrine: released to interstitial fluid and affects the cell that released it

Question 8

communication between cells is also accomplished by?

Answer 8

intercellular chemical messengers and receptors

Question 9

receptor

Answer 9

a protein associated with the membrane or cellular interior which all bind a chemical messenger and exert an effect.
-noncovalent binding
-still affected by env, specificity, affinity, competition, modulation, and saturation

Question 10

beta 2 androgen receptor

Answer 10

1. highly specific
2. high affinity for specific messenger
3. can be saturation or blocked
4. can undergo down regulation: decrease in receptor number in response to chronic elevated levels of messenger.
5. can undergo up regulation: increase in receptor number in response to chronic low levels of messenger

Question 11

rates of messenger pathways

Answer 11

-lipophilic messenger
-lipophobic messenger

Question 12

describe a lipophilic messenger

Answer 12

-hydrophobic, interacts with lipids
-diffuse directly through the membrane to an internal receptor
-considered a slow response
-bind to nucleus receptor which commonly triggers transcription and becomes a transcription factor
-because they are hydrophobic they need to be moved by amphipathic transport proteins to target cell

Question 13

describe a lipophilic messenger

Answer 13

-hydrophilic, polar or charged
-messenger must enter a cell through transport or bind to a surface receptor
-considered fast response
-responses are known as signal transduction

Question 14

signal transduction

Answer 14

the message is conveyed from outside of the cell to a new signal inside of the cell which then creates a cellular response.

Question 15

signal transduction
-transducer

Answer 15

receptor protein, converts extracellular signals into intracellular messages which creates a response
-anything that is not lipophilic requires a transducer

Question 16

signal transduction benefits the cell by?

Answer 16

-signal amplification
-multitasking

Question 17

what are the 4 types of membrane receptors that lipophobic messengers act on?

Answer 17

1. ligand gated channel: receptor proteins act as an in channel
2. receptor enzymes: receptor acts as an enzyme, and messengers binding initiates enzymatic actions in cellular response
3. GTP binding proteins: messengers activate as a G protein which opens ion channel or acts as an enzyme
4. intigrine receptor: cause changes in the cytoplasm

Question 18

mechanisms of signal transduction using ligand gated channel, receptor enzymes, and GTP binding proteins

Answer 18

1. messenger binds to ligand gated channel
2. when activated, receptor enzymes act as enzymes to alter cytoplasmic proteins.
   typically use kinase receptor: includes many families of growth factors, epidermal GF, platelet GF, fibroblasts, and insulin receptors
3. GTP binding protein: 2nd messenger system or G protein coupled receptors
   - in 2nd messenger system: the intracellular messenger (1st messenger) binds noncovalently to a surface protein and activates a G protein that intitiates an internal chemical ( or 2nd messenger) that initiates a cell response

Question 19

signal transduction: lipophilic
1. ligand gated channel describe it and how it can be stopped

Answer 19

-channel remains open as long as messenger is bonded
-ion flows through, cell obtains ion flux based on the gradients which changes membrane potential
-stop message: destroy messenger with degrading enzymes

Question 20

signal transduction: lipophilic
2. receptor enzymes:

Answer 20

-receptor typically acts as a catalyst
-messenger binds, receptor flexes and becomes activated.
-active kinase: phosphorylates protein (covalent modulation).
-kinases break ATP and phosphorylate proteins

Question 21

signal transduction: lipophilic
3. GTP binding protein

Answer 21

-opens a channel or activates an enzyme
-G protein: binds to GTP
-GTP: guanosine triphosphate.
-known as second messenger system
-cAMP system and phospholipase C pathway

Question 22

3. GTP binding protein
   cAMP system

Answer 22

-first messenger binds to receptor protein which has G protein attached (mechanically sensitive)
-G protein activates adenyl cyclase which converts ATP to cyclic AMP.
-cAMP ( second messenger) activates cAMP dependent protein kinase (allosteric activation)
-protein kinase A proceeds and phosphorylates proteins (covalent modulation)
-performs multitasking and amplification

Question 23

3. GTP binding protein
   Phospholipase C pathway
   decribe the beginning of the pathway to the second messenger point

Answer 23

-1st messenger binds to receptor which activates G protein
-g protein activates phospholipase c, which degrades phospholipids to a diacyl glyceride (DAG) and IP3 which is inositol triphosphate which function as second messengers

Question 24

3. GTP binding protein
   Phospholipase C pathway
   DAG pathway (second messenger)

Answer 24

-DAG stays in membrane and acts as the second messenger. activates PK-C (protein kinase C) through allosteric activation
-pk-c: located in the membrane, can phosphorylate proteins and perform covalent modulation

Question 25

3. GTP binding protein Phospholipase C pathway IP3 pathway (second messenger)

Answer 25

-IP3: hydrophilic, remains in the cytoplasm is another 2nd messenger -travels to the ER and opens a calcium channel -calcium is released and interacts with the cytoskeleton

Question 26

agonist

Answer 26

chemical messenger that binds to a receptor and triggers a cell response -can be synthetically made, or like a virus

Question 27

antagonist

Answer 27

molecule that competes with another for a receptor and binds to the receptor but does trigger a cellular response

Question 28

target response depends on

Answer 28

target receptor

Question 29

how to stop the first messenger in signal transduction

Answer 29

-degraded by extracellular enzymes -endocytosis of receptor ligand complex which can then be degraded by lysozymes inside the cell

Question 30

how to stop the second messenger

Answer 30

-degrade, calcium is an exception because it is an element -present an ion pump out of cytoplasm, out of cell, or smooth ER