Chapter 3: Control Mechanisms and Signalling

Question 1

3 main control mechanisms for cell communications

Answer 1

1) enzymes
2) direct communications
3) indirect communication via chemical messaging

Question 2

3 main methods of direct communication between cells

Answer 2

1) gap junctions: small tunnels that bridge the cytoplasm of neighboring cells and allows the passage of small ions and molecules. also allows for the depolarization of adjacent cells, PERMITTING ELECTRICAL SIGNALS.
2) transient linkages: cells line up on surface markers to temporarily communicate (ex/ antibody/antigen linkaes in the immune system
3) nano tubules: long tubes with internal actin filament support. can transfer larger molecules and organelles, and found in developing cells and immune cells.

Question 3

what chemicals cause gap junctions to close?

Answer 3

gap junctions rapidly close in response to an increase in calcium or H+

Question 4

gap junction tunnels are made of ___ protein

Answer 4

connexin protein

Question 5

The main difference in what gap junctions and nanotubules transfer between cells?

Answer 5

gap junctions can transfer small ions, but nanotubules allow for the transfer of larger molecules and ORGANELLES.

Question 6

in what cells would you find nanotubules

Answer 6

in developing cells and immune cells

Question 7

which type of structural protein would you find with nanotubueles?

Answer 7

microfilament actin

Question 8

when two cells communicate via indirect chemical messaging, the receptor is typically made of ___

Answer 8

transmembrane glycoprotein

Question 9

what is a paracrine chemical and give an example

Answer 9

paracrine chemical: LOCAL chemical messngers produced by a specific cell whose effect is exerted on NEIGHBORING cells for a particular response (ex/ histamine is released by skin cells and trigger vessel dilation around it)

Question 10

what is an autocrine chemical

Answer 10

autocrine chemical: when a cell secretes local messenger and the messenger also affects the cell it was secreted from.

Question 11

_____ are used by neurons which communnicate with the cells they innervate. Are these short or long range?

Answer 11

neurotransmitters. they are short range

Question 12

unlike neurotransmitters, ____ are very long range chemical messengers that are secreted by the endocrine system and is carried by the ____ ____ to exert change on distant organs.

Answer 12

HORMONES are very long range chemical messengers that are secreted by the endocrine system and is carried by the CIRCULATORY FLUID (blood or lymph) to exert change on distant organs.

Question 13

what is a neurohormone?

Answer 13

hormones released by the neurocirculatory neurons: respond to electrical signals like normal neurons, but rather than releasing NTs to innervated cell, they release neurohormones into the BLOOD or LYMPH.

Question 14

example of a neurohormone

Answer 14

just like normal hormones, neurohormones are secreted into the blood or lymph, and are able to target long range targets. an example is ADH.

the hypothalamus has neurosecretory neurons that produce ADH and store them in the pituitary gland. when electrically excited, the neurohormone ADH is released into the hypophyseal circulatory (BLOOD) system.

Question 15

a ____ is typically made in a gland and is released into the environment rather than the extracellular system.

Answer 15

pheromone

Question 16

what is a cytokine

Answer 16

a regulatory peptide with variety of effects. they are not produced by glands, rather thay are made by all body cell types

Question 17

what gland makes cytokines for regulation?

Answer 17

all cells make different types of cytokines.

Question 18

6 ways a cell can undergo indirect chemical messaging communication

Answer 18

1) neurotransmitter (short distance)
2) neurohormone (long distance)
3) hormone (long distance)
4) cytokine (long and short distance)
5) pheromone (environmental)
6) Paracrine or autcrine signalling (local/short distance)

Question 19

primary purine that is used as a signalling molecuel

Answer 19

ATP. often used as a paracine and neurotransmitter

Question 20

common structures of signalling molecules

Answer 20

1) eicosanoids
2) inorganic gases
3) purines
4) amines
5) peptides
6) steroids
7) reinoids (vitamin A derivatives)

Question 21

_____ of receptors cause target cells to be less responsive, and is dependent on _____

Answer 21

DOWNREGULATION of receptors cause target cells to be less responsive, and is dependent on ACCLIMATIZATION

Question 22

usually, hormones delivered by the blood or neurotransmitters released from nerve endings usually do not trigger changes in target cells directly, rather, cell responses are conveyed via ____ ____

Answer 22

signal transduction

Question 23

signal transduction

Answer 23

incoming signals from an extracellular chemical messenger are conveyed to the INTERIOR of a target cell for execution.

Question 24

extracellular messenger interacts with a receptor on the target cell, and triggers a sequence of ___ ___ that control homeostatic maintenance

Answer 24

INTRAcellular events. (the messengers rarely actually enter the target cell, except for hormones)

Question 25

2 broad types of signal transduction

Answer 25

1) lipophilic transduction

2) lipophobic transduction

Question 26

lipophilic transduction

Answer 26

the extracellular messenger actually enters the cell by dissolving into the plasma membrane and binding to receptors INSIDE the target cell.

Question 27

Lipophobic transduction

Answer 27

when the extracellular messenger binds to plasma membrane receptors, whcih alter ion channels or trigger phosphorylating protein .

Question 28

3 general changes that lipophobic transduction signalling triggers

Answer 28

1) open or close specific channels
2) activate an enzyme that phosphorylates a protein
3) transfers a signal to an intracellular chemical messenger to produce second messengers

Question 29

lipophobic messengers that use lipophobic transduction are often called ____ _____

Answer 29

first messengers

Question 30

intracrine signalling

Answer 30

when lipophilic messengers have been found to act on receptors within the SAME CELL that produced them.

Question 31

3 main types of membrane gated receptors

Answer 31

1) ligand gated channels
2) voltage gated channels
3) mechanically gated channels

Question 32

the ___ and ___ of a molecule affect the rate of passage through a channel

Answer 32

size and charge of a molecule

Question 33

types of receptors according to MODE OF ACTION

Answer 33

1) chemically gated receptor channel
2) receptor enzyme (receptor that also functions as an exnzyme)
3) GPCR/second messenger system receptor.

Question 34

Mechanism of a receptor enzyme

Answer 34

1) extracellular messenger binds to receptor
2) binding of messenger activates catalytic properties of enzyme (typically kinase properties)
3) activated kinase phosphorylates designated protein
4) phosphorylated protein brings on desired response

Question 35

mechanism of a GPCR second messenger system

Answer 35

1) extracellular first messenger binds to receptor (GPCR)
2) receptor recruites G protein intracellularly
3) Gprotein exchanges GDP for GTP and partially dissociates, activating an EFFECTOR PROTEIN (ex/ adenylyl cyclase)
4) effector protein produces second messengers (cAMP)
5) cAMP can activate other proteins like PKA.
6) PKA and other kinases can activate other proteins to bring the desired response.

Question 36

GPCR second messenger system can allow for signal ____

Answer 36

amplification

Question 37

2 different cellular events that ionic movements can cause

Answer 37

1) a small short lived movement of Na+ or K+ across a membrane to alter electrical activity
2) a flow of Calcium into the cell to trigger an alteration in shape or function of specific proteins.

Question 38

what is protein kinase? How is it activated?

Answer 38

an enzyme that phosphorylates a target protein. typically activated when a first messenger binds to a receptor.

Question 39

What is a TKR? Explain its mechanism

Answer 39

a TKR is a tyrosine kinase receptor. It is a receptor that PHOSPHORYLATES tyrosine on proteins, INCLUDING ITSELF. After a ligand (insulin) binds to a TKR, it activates itself and undergoes autophosphorylation. CErtain proteins now recognize the phosphorylated TKR and bind to it intracellularly.

THe TKR can then phosphorylate the newly-bound proteins, enabling them to bring upon a desired response.

Question 40

2 major GPCR pathways

Answer 40

cAMP and diacylglycerol inositol triphosphate.

Question 41

describe the GPCR mechanism that produces cAMP

Answer 41

1) an extracellular FIRST MESSENGER bings to a GPCR
2) the GPCR is now activated, and recruits an inactive G protein

Gprotein: inactive- all 3 subunits and GDP is bound to the alpha subunit.

3) the Gprotein attaches GTP to its alpha subunit and the alpha subunit loses affinity to the beta and gamma subunits, causing it to drift away as alpha-GTP
4) alpha-GTP activates the effector protein (ADENYLYL CYCLASE), where it converts ATP into cAMP

5) cAMP activates PKA
6) PKA-activated can now phosphorylate inactive designated proteins, activating the designated proteins
7) the phosphorylated desginated proteins are now active and can induce cellular response (ex/ glycogen catabolism)

Question 42

cAMP is quickly degraded by _____ or by the removal of ____

Answer 42

cAMP is quickly degraded by PHOSPHODIESTERASE or by the removal of the FIRST MESSENGER, because adenylyl cyclase is deactivated.

Question 43

____ block a step in a communication pathway, typically by blocking the binding of the normal signal molecule

Answer 43

antagonists

Question 44

____ activate a step in communication pathways by mimicing a signal molecule

Answer 44

agonists

Question 45

2 methods to transport a molecule that is impermeable in the membrane

Answer 45

1) channel or carrier mediated transported for transfer of water soluble/small substances
2) vesicular transport for large molecule movement.

Question 46

major osmolytes of the eCF

Answer 46

Na and Cl-

Question 47

major osmolytes of the ICF

Answer 47

K+ and A-