Topic 5 - Intro to Cell Signalling

Question 1

In order for cells to be able to differentiate systematically, cells need this ability

Answer 1

Ability to communicate with each other

Question 2

What steps are key in proper signalling between cells?

Answer 2

1. Initiating a signal

2. Terminating a signal

Question 3

What are the 3 general effects signalling pathways can exert on cells?

Answer 3

1. Induce changes in the cytoskeleton (shape/movement of the cell)
2. Alter gene expression
3. Affect cellular metabolism

Question 4

What kinds of cells are able to communicate via signalling? (e.g. prokaryotes, eukaryotes, unicellular, multicellular…)

Answer 4

All cells

Question 5

In S. cerevisiae (yeast), when mating factors are released, this induces the formation of this protrusion [name]

Answer 5

Shmoo

Question 6

Describe the makeup of a gap junction

Answer 6

Gap junctions made of 2 hemichannels called CONNEXONS, each connexon is made of 6 CONNEXINS

Question 7

What can be exchanged through gap junctions?

Answer 7

Water, small water-soluble molecules, inorganic ions

Question 8

Gap junctions are common in this kind of cell

Answer 8

Animal cell

Question 9

What is the plant equivalent of a gap junction?

Answer 9

Plasmodesmata

Question 10

Are all cells connected to each other via gap junctions?

Answer 10

No

Question 11

In what 3 ways are signalling molecules released into the extracellular space?

Answer 11

1. Exocytosis
2. Diffusion (when the molecule is hydrophobic)
3. Stay attached to the membrane but project out of the cell extracellularly

Question 12

Describe how cells economize their signalling molecules

Answer 12

Different combinations of signalling pathways produce specific results, therefore fewer individual signalling molecules are required

Question 13

When a cell receives no signals, what does it do?

Answer 13

Undergoes apoptosis

Question 14

Small hydrophobic signalling molecules tend to bind to this kind of signalling receptor

Answer 14

Nuclear receptor

Question 15

Small hydrophobic signalling molecules are transported outside the cell bound to…

Answer 15

Carrier proteins

Question 16

Hydrophilic signalling molecules bind to this class of receptor

Answer 16

Cell surface receptors

Question 17

How many kinds of nuclear receptors have been identified in humans?

Answer 17

48

Question 18

What are the 3 domains of a nuclear receptor?

Answer 18

1. DNA-binding domain
2. Transcription-activating domain
3. Ligand-binding domain

Question 19

What is an orphan nuclear receptor?

Answer 19

A nuclear receptor for which the ligand is unknown

Question 20

Active nuclear receptors are often bound to this kind of protein

Answer 20

Coactivator proteins

Question 21

Do nuclear receptors always activate gene transcription?

Answer 21

No, sometimes they repress it

Question 22

Describe where nuclear receptors are when not active

Answer 22

Can be in cytosol, nucleus, already bound to DNA

Question 23

What are the 3 major classes of cell surface receptors?

Answer 23

1. Ion channel-coupled receptors
2. G-protein-coupled receptors
3. Enzyme-coupled receptors

Question 24

How does a cell surface receptor work, briefly

Answer 24

Ligand binds to extracellular receptor which induces a change on the intracellular side of the cell, initiates a signal transduction cascade

Question 25

GPCRs are coupled to a ( )-imer intracellularly

Answer 25

Heterotrimer

Question 26

Describe contact-dependent cell signalling

Answer 26

Cells initiate signalling to each other through interactions with each other’s membranes - they physically touch without sending out signals

Question 27

Contact-dependent cell signalling is especially important during…

Answer 27

Early development

Question 28

Describe paracrine signalling

Answer 28

A cells signals to nearby cells

Question 29

What are 4 reasons a signal might be paracrine?

Answer 29

Will be paracrine if it is not able to reach far-away cells. This could happen if:

1. The signal is taken up rapidly by neighbouring cells
2. The signal is destroyed by the extracellular matrix
3. The signal is immobilized by the extracellular matrix
4. Antagonists to the signal block its activity (ligand can’t bind to the receptor anymore)

Question 30

Describe autocrine signalling

Answer 30

A cell sends out signals and responds to its own signal

Question 31

Autocrine signalling is common in this kind of cell

Answer 31

Cancer cell

Question 32

During synaptic signalling, the local concentration of neurotransmitter is (high/low)

Answer 32

HIGH

Question 33

During endocrine signalling, the concentration of hormones in the bloodstream is (high/low)

Answer 33

LOW

Question 34

What is the maximum speed of a synapse?

Answer 34

100 m/s

Question 35

Describe the speed of hormonal signalling compared to synaptic signalling

Answer 35

VERY slow