Chemical Messengers

Question 1

cell signalling importance

Answer 1

important for regulation of physiological processes and homeostasis
is communication between cells

Question 2

when does communication occur?

Answer 2

signalling cell sends a signal to target cell (usually a chemical messenger). this can involve direct or indirect signalling.

Question 3

gap junction is what sort of signal?

Answer 3

direct signal

Question 4

explain gap junctions

Answer 4

signalling cell and target cell are connected by gap junction (sort of proteins). this way the signal is directly passed from one cell to another. the openings are called pores, and the tubes are the hemichannels, in the connexin proteins

very fast!

draw it! (Slide 4)

Question 5

explain indirect signalling

Answer 5

a way to send signals to distant cells.

signalling cell releases a chemical messenger that binds to receptor on target cell. this induces activation of signal transduction pathways and response in target cell.

draw it! (slide 5)

Question 6

autocrine signalling

Answer 6

chemical message diffuses back to signalling cell
signalling cell and target cell are the same

Question 7

paracrine signalling

Answer 7

chemical message diffuses to nearby cell (ex. neurotransmitters across synaptic cleft)

Question 8

draw the autocrine and paracrine signalling pathway

Answer 8

yes!

slide 5 on chemical messengers

Question 9

draw neural signaling pathway

Answer 9

yes! (slide 5 on chemical signalling)

Question 10

endocrine system (cell signalling)

Answer 10

chemical messenger (hormone) is released by secretory gland, transported by circulatory system
longer lasting, slow acting

Question 11

draw endocrine signalling pathway!

Answer 11

i will! (slide 6 chemical signalling)

Question 12

exocrine signalling

Answer 12

released by one individual and travels through the environment for communication with other animals

Question 13

6 types of chemical messengers

Answer 13

peptides/proteins
steroids
amines
eicosanoids/fatty acid derivatives
purines
gases

structure affects signalling mechanism

Question 14

peptide/protein messengers

Answer 14

hundreds of amino acids, all made in rough ER
secreted by calcium-induced exocytosis
hydrophilic, bind to transmembrane receptors for signal transduction, causing rapid effects

draw the synthesis pathway! (slide 9)

Question 15

steroid messengers

Answer 15

produced from cholesterol, by the gonads and placenta (sex hormones), and adrenal cortex (mineralocorticoids, glucocorticoids and sex hormones)

glucocorticoid and mineralcorticoid names come from functions. (gluco= glucose/metabolism, mineral=ion, then adrenal CORTex, location)

synthesized on demand
secreted by diffusion

hydrophobic, uses carrier proteins, or bind to intracellular receptors

draw pathway! (slide 11)

Question 16

biogenic amine messengers and some examples

Answer 16

have an amine group, and many are made from amino acids

examples:
- catecholamines like dopamine, norepinephrine/epinephrine from tyrosine
-serotonin (sleep and mood) from tryptophan
-thyroid hormones (metabolism and growth) T4 thyroxine and T3 triodo-thyronine, derived from tyrosine

most are hydrophilic, except for thyroid hormones which are hydrophobic.

Question 17

eicosanoids/fatty acid derivatives

Answer 17

lipid messengers made from phospholipids
can act as neurotransmitters (paracrine/autocrine signalling)
often involved in inflammation and pain
diffuse out of membrane of signalling cell, diffuse into target cells where they bind to transmembrane receptors.

Question 18

purines

Answer 18

nucleotide + ribose sugar
includes adenosine and guanosine
ex. AMP, ATP, GMP, GTP
can move across membrane via nuceloside transporters and secretory vesicles
bind to purinergic receptors

Question 19

gases examples as chemical messengers

Answer 19

nitric oxide and hydrogen sulfide and CO are all vasodilators

Question 20

where do chemical messengers bind on target cells? where do hydrophilic/phobic ligands go?

Answer 20

they bind to receptor proteins.

hydrophilic binds to transmembrane receptors
hydrophobic binds to transmembrane or intercellular receptors

ligand-receptor interactions are very specific, the receptor changes shape when ligands are bound. a single cell may have many receptors for different ligands

Question 21

explain ligand mimics and two types

Answer 21

ligand mimics are chemicals with structures similar to the natural ligand that can mimic the binding of that ligand to a receptor. Drugs or poisons can act as ligand mimics.

agonists: chemical mimic that binds to and activates receptor, mimicking response induced by natural ligand
antagonist: chemical mimic that binds to, but does not activate receptor, therefore blocking a natural ligand and inhibiting response

try to draw nad compare!

Question 22

inactivation of ligand receptor interactions

Answer 22

ligand receptor interactions must be interrupted to allow for responses to changing conditions

may be removed by distant tissues
ligand taken up by adjacent cells
ligand degraded by extracellular enzymes
ligand receptor complex removed by endocytosis
receptor inactivation
inactivation of signal transduction pathway

draw some from slide 18!

Question 23

signal transduction pathways

Answer 23

agonist binds receptor, it initiates signal transduction pathway. these usually amplify the signal.
receptor and ligand types and concentrations can affect the response of target cell.
STPs convert change in receptor shape to cellular response

Question 24

types of receptors in STPs

Answer 24

ligand gated ion channel
receptor enzyme
g-protein coupled receptor
intracellular receptor

Question 25

ligand gated ion channels

Answer 25

quick response time
results in change of electrical properties of the cell.

draw this! (slide 20)

Question 26

receptor enzymes (STPs)

Answer 26

ligand binds to transmembrane receptor and alters the activity of the intracellular, catalytic enzyme domain of receptor.
starts phosphorylation cascade, and phosphorylation of intracellular proteins.
*kinases are enzymes that phosphorylate other proteins

draw these (slide 21)

Question 27

G-protein coupled receptors (STPs)

Answer 27

activate intracellular G proteins which begin a signalling cascade
sometimes they regulate other ion channels. they respond slower due to the time required for the G protein subunit to be activated and bind. in this case, the channel itself isn’t the receptor

some Gprotein linked receptors regulate enzymes that produce second messengers (ex. cAMP)

draw this! (slide 22+23)

Question 28

intracellular receptors (STPs)

Answer 28

intracellular receptors bind to hydrophobic messengers (ex. steroids). these receptors act as transcription factors to alter gene expression.
changes in gene expression takes time, so this is a slow acting response.

hydrophobic ligand passes thru membrane, binds to ligand binding domain inside cell, receptor changes shape, the complex moves to the nucleus, and the DNA binding domain of receptor binds and interacts with transcription factors, which alters transcription rate and mRNA.

draw this! (slide 24)

Question 29

what do second messengers do?

Answer 29

they amplify signals.

the intercellular messengers is the “First messenger” ,and as second messengers they amplify this. ex. cAMP

first messenger binds to receptor, many g proteins are activated. each of them activates a second messenger, which triggers an STP.

draw this! (Slide 25)