cell signalling

Question 1

three stages of cell signaling

Answer 1

ligand-receptor interaction, signal transduction (phosphorylation cascade and signal amplification), cellular response

Question 2

why do ligands have to go through a receptor?

Answer 2

ligands usually too large to pass through transient pores on cell surface membrane, OR are hydrophilic and cannot pass through hydrophobic core of csm

Question 3

three main types of cell surface receptors

Answer 3

g-protein coupled receptors (glucagon receptor), enzymatic receptors (insulin receptor), chemically-gated ion channels

Question 4

signal transduction deftn

Answer 4

series of changes in cellular proteins that converts extracellular chemical signal to specific intracellular response

Question 5

signal transduction function

Answer 5

change cell behaviour

Question 6

phosphorylation cascade deftn

Answer 6

sequence of events where one enzyme phosphorylates another, causing a chain reaction leading to phosphorylation of thousands of proteins

Question 7

signal amplification deftn

Answer 7

producing a large number of intracellular mediators and thus a large response from a relatively small number of extracellular signals

Question 8

what do kinases do?

Answer 8

enzyme that adds phosphate groups from atp to protein, activating it

Question 8

what do phosphatases do

Answer 8

enzyme that removes phosphate group from proteins , inactivating proteins

Question 9

3 types of cellular response

Answer 9

• regulation of gene expression (up or down reg)
• metabolic pathway regulation (activation or inhibition of enzymes)
• change in cytoskeleton like assembly of microtubules

Question 10

points of termination of cellular response

Answer 10

reception (extracellular first messenger degraded by enzymes OR endocytosis of ligand-receptor complex prevents signal transduction)

during signal transduction (increased activity of phosphatases inactivate relay molecules OR production of inhibitors that bind to any signal proteins prevents transduction)

Question 11

advantages of signal transduction pathway (6 - first 3)

Answer 11

1. facilitate signal amplification (small number of signal molecules needed to produce a large response)
2. one signal molecule can trigger multiple ST pathways and thus many diff cellular responses
3. provides multiple checkpoints for regulation (steps that can be regulated or controlled)

Question 12

advantages of signal transduction pathway (6 - last 3)

Answer 12

4. ensures specificity (specific signal molecule binds to specific receptor)
5. one signal allows coordinated activation of many different cells simultaneously
6. activates genes in nucleus without needing to move into nucleus

Question 13

homeostasis deftn

Answer 13

maintenance of stable internal environment independent of fluctuations in external environment by self-regulating and negative feedback mechanisms so organism can function optimally