Lecture 13 - Principles of Cell Communication

Question 1

In multicellular organisms, cells must communicate to

Answer 1

Organise themselves into a functioning unit

Question 2

Cells sending signals must be able to

Answer 2

Control the signals

Question 3

Cells receiving signals must be able to

Answer 3

Interpret the information accurately

Question 4

Communication is mediated by

Answer 4

Extracellular signalling molecules

Question 5

Signalling molecules can

Answer 5

Interact with receptor molecules in the plasma membrane

Question 6

The receptors in the plasma membrane

Answer 6

Transmit the signal inside the cell to activate a signalling cascade

Question 7

What can a signalling cascade do? (4)

Answer 7

Changes enzymatic activity
Metabolism
Gene expression
Induce rearrangements of the cytoskeleton (movement etc.)

Question 8

Signal transduction

Answer 8

When the signal is transmitted into a cell

Question 9

Effector molecules alter the

Answer 9

Behaviour of the cell in response to a signal

Question 10

Examples of signalling molecules

Answer 10

Nucleotides (cAMP, NADPH)
Adrenalin (small molecules)
Oestrogen (steroids)
Insulin (proteins and peptides)
Mal-CoA (fatty acids)
Nitirc oxide (dissolved gases

Question 11

Nitric oxide

Answer 11

Is used as a signal to relax smooth muscle in blood vessels

Increases blood flow

Question 12

How viagra works

Answer 12

Inhibits phosphodiesterase Type 5 from degrading cGMP

Question 13

NO signalling

Answer 13

1. NO synthase upregulated
2. Smooth muscle cells activate Guanylyl Cyclase
3. Guanylyl cyclase produces more cGMP
4. Blood flow is increased as vessels relax

Question 14

Extracellular signals can act over

Answer 14

Long or short distances

Question 15

Cell signalling is mediated by

Answer 15

Contacts with the target cell

Question 16

The 5 ways of getting a signal to the right place

Answer 16

1. Contact dependent
2. Paracrine
3. Synaptic
4. Endocrine
5. Gap junctions

Question 17

Contact dependent cell signalling

Answer 17

Via membrane bound receptors and membrane bound signalling molecules

Important in immune response and development
Involved in determining cell fate

Question 18

Paracrine cell signalling

Answer 18

Release of signalling molecules into the extracellular fluid

Acts locally only
Rapidly taken up and sequestered/destroyed by neighbouring cells

Question 19

Synaptic cell signalling

Answer 19

Chemical secreted across a space as a result of an electrical impulse

Short range (from perspective of cell-cell contact)
Long range (due to of length of cell)
Fast 
Specific
High concentrations
Low affinity

Question 20

Endocrine cell signalling

Answer 20

Long range signalling to distant cells

Hormones secreted into the bloodstream
Specific
Highly dilute
Low concentrations
High affinity

Question 21

Gap junction cell signalling

Answer 21

Direct communication between neighbouring cells

Narrow cytoplasmic filled channels
Exchange of ions and small molecules (Ca2+, cAMP)
Directionality of signal (not all cells have GJ)

Question 22

Connexins

Answer 22

6 subunit protein that forms GAP junctions (small channels in cell membranes)
Twist open or closed

Question 23

Gap junctions are important in cell signalling in

Answer 23

The heart (Ca2+)
The bones (cells surrounded by bone supplied by nutrients by GJ)

Question 24

Extracellular signals are communicated inside the cell by (2)

Answer 24

1. Directly - signal passes into cell (steroids, GJ)

2. Indirectly - binds a receptor, induces conformational change

Question 25

Signalling inside the cell: Ion channel coupled (indirect)

Answer 25

Rapid synaptic signalling
Muscle cells
Gated channels (conformational change as charged residues are removed, allowing ion influx)

Question 26

Signalling inside the cell: G protein coupled (GPCRs)

Answer 26

Receptors have 7 transmembrane domains (serpentine)
Ligand binds, complexes with trimeric G proteins (alpha beta gamma subunits)
Activate an enzyme at the plasma membrane
Transmits a signal
e.g generation of cAMP by adenylyl cyclase

Question 27

40% of modern drugs target

Answer 27

G protein coupled receptors

Question 28

Signalling inside the cell: Enzyme coupled receptors

Answer 28

Transmembrane proteins, either an enzyme or directly bound to it (dimerises or form complexes)
Most common are Receptor Tyrosine Kinases
Autophosphorylation causes docking sites for downstream receptors

Question 29

When Receptor Tyrosine Kinases bind a signalling molecule they form

Answer 29

Dimers in the membrane
Activates phosphorylation domains in the cytosol
Beginning of signal transduction cascade