Lecture 21 - Cell Signalling and Signal Transduction

Question 1

def: produced far from the target tissues, which they reach via the circulatory system

Answer 1

endocrine

Question 2

def: diffusible and act “locally” or over a short range. their distribution is usually limited by their inherent instability

Answer 2

paracrine

Question 3

def: act on the same cell that produces them

Answer 3

autocrine

Question 4

def: many of these molecules act as neurotransmitters and hormones, such as epinephrine

Answer 4

amino acids and their derivatives

Question 5

def: cholesterol derivatives, which regulate sexual differentiation, pregnancy, carbohydrate metabolism, and ion excretion

Answer 5

steroids

Question 6

def: fatty acids that regulate pain, inflammation, blood pressure, and blood clotting. NSAIDs block their synthesis

Answer 6

eicosanoids

Question 7

def: a wide variety of secreted proteins act as ligands, regulating processes such as cell division, differentiation, cell death/survival and the metabolism

Answer 7

polypeptides and proteins

Question 8

what are the 3 main classes of cell surface receptors?

Answer 8

• G-protein coupled receptors
• enzyme-linked receptors (RTK)
• ion channel linked receptors

Question 9

what is the requirement for cells to respond to a particular ligand?

Answer 9

they must express the receptor that specifically recognizes and binds the messenger

Question 10

receptors have ________ _______ that fits the ligand very closely

Answer 10

binding site

Question 11

ligands bind to receptors in a highly specific way, through _____ _______ ___________-

Answer 11

non-covalent interactions

Question 12

def: relationship between the [ligand] in solution and the number of receptors occupied

Answer 12

receptor affinity

Question 13

def: the [free ligand] needed to produce a state in which half the receptors are occupied

Answer 13

dissociation constant Kd

Question 14

receptors with high affinity for their ligand, have ____ Kd, and vice versa

Answer 14

low

Question 15

def: drugs that activate the receptor they are bound to

Answer 15

agonists

Question 16

def: drugs that bind receptors without activating it, thus preventing the naturally occurring messenger from activating the receptor

Answer 16

antagonists

Question 17

what is isoproterenol used to treat and is it an antagonist or agonist?

Answer 17

• treat asthma
• agonist of the epinephrine G-protein coupled receptor on bronchial smooth muscle

Question 18

what is alprenolol used to treat and is it an antagonist or agonist?

Answer 18

• anxiety attacks or cardiac arrhythmias
• antagonist that blocks the affect of epinephrine responsive receptor on cardiac muscle cells that increases heart rate contraction, therefore slowing the patient’s heart rate

Question 19

what is generally the first step of a cell signalling pathway?

Answer 19

extracellular ligands, called “first messengers” bind to a receptor triggering a signalling cascade

Question 20

what does ligand binding induce in the transmembrane receptor protein and what does it do?

Answer 20

induces a conformation change in the receptor protein which acts to relay the signal across the membrane

Question 21

the _________ __________ _____________ of a transmembrane receptor protein can act as or activate effector molecules

Answer 21

active cytoplasmic domain

Question 22

def: some effectors generate small molecules or ions that relay signals from one location to another in the cell

Answer 22

second messengers

Question 23

once proteins near the “top” of the intracellular signalling pathway are activated, what happens?

Answer 23

a series of protein modifications occur, in a specific sequence

Question 24

each protein in the cascade acts on the subsequence protein, ________ ____ __________, leading to _______ _____ ____________ of the downstream protein

Answer 24

altering its conformation, activation or inhibition

Question 25

what is the most common modification in proteins down the cascade?

Answer 25

phosphorylation

Question 26

________ __________ are eventually reached, which activate a specific cellular process

Answer 26

target proteins

Question 27

def: the ability of a cell to respond to ligand-receptor binding by altering its behaviour or gene expression

Answer 27

signal transduction

Question 28

kinases _______
phosphates ___________

Answer 28

kinases phosphorylate
phosphates dephosphorylate

Question 29

in addition of phosphate groups to hydroxyl groups on (most commonly) :

Answer 29

Serine (S), Threonine (T), Tyrosine (Y)

Question 30

def: changes a proteins charge and generally leads to a conformation change which can alter ligand binding or other features of the protein resulting in an increase or decrease of it’s activity

Answer 30

phosphorylation

Question 31

what are the 4 main stages of the cell signalling pathway?

Answer 31

1. transfer
2. modulation
3. amplification
4. divergence

Question 32

at each step in the resulting cascade of events, a _________ __________ stimulates the production of many molecules needed for the next step

Answer 32

signalling intermediate

Question 33

def: the multiplication of the effect of the signal

Answer 33

signal amplification

Question 34

def: signals from one ligand + receptor can activate effectors in different pathways

Answer 34

divergence

Question 35

def: signals from a variety of unrelated ligands/receptors can converge to activate common effectors

Answer 35

convergence

Question 36

def: signals from different pathways can effect components of multiple pathways, passing information back and forth

Answer 36

crosstalk

Question 37

in general, combinations of signals generate _______ and different cellular responses

Answer 37

crosstalk

Question 38

cells are geared to sense ligand concentration ___________ rather than fixed concentrations

Answer 38

changes

Question 39

def: when receptors are occupied for prolonged periods, the cell adapts to no longer respond to the ligand

Answer 39

receptor down-regulation

Question 40

what are the 2 ways receptor down-regulation can be achieved ?

Answer 40

1. cells reduce the density of receptors on their cell surface via receptor-mediated endocytosis
2. cells can adapt to signals by desensitization, alterations to the receptor that lower its affinity for the ligand

Question 41

def: mediate the uptake of material that will be used by the cell, receptor will deliver the bound material to the early endosome, releasing it because of the lower affinity at higher [H+], then return to the cell membrane

Answer 41

housekeeping receptors

Question 42

def: bind extracellular messengers that change the activity of the cell, these receptors will be degraded, reducing the sensitivity of the cell to further stimulation

Answer 42

signalling receptors