Cell Biology #6

Front 1

What are three examples of effector protein?

Back 1

1. Metabolic enzyme - alters metabolism
2. Gene regulatory protein - alters gene expression
3. Cytoskeletal protein - alters cell shape or movement

Front 2

What are gap junctions?

Back 2

- narrow water filled channels that allow neighbouring cells to communicate directly
- exchange inorganic ions and small water soluble molecules
- formed by 2 connexons each composed of 6 subunits

Front 3

What are three ways of releasing signal molecules into the extracellular space?

Back 3

1. Exocytosis
2. Diffusion through membrane
3. Attached to extracellular surface of cell

Front 4

What is required for a cell to respond to a signal?

Back 4

a receptor

Front 5

Are you losing your mind yet?

Back 5

YES!!!!

Front 6

How does an intracellular receptor work?

Back 6

- signal is brought to the cell by a carrier protein and then signal enters the cell and goes to the intracellular receptor, often on the nucleus to control transcription
- signal must be small and hydrophobic since it has to diffuse across the membrane

Front 7

Where are most signal receptors located?

Back 7

on the cell surface

Front 8

What does the nuclear receptor superfamily do?

Back 8

- control transcription
- bind to specific DNA sequences and activate transcription
- some require binding of ligand

Front 9

How many nuclear receptors are there in humans?

Back 9

in humans there are about 48 nuclear receptors

Front 10

What are the three classes of cell surface receptors?

Back 10

1. Ion-channel coupled receptors - transmitter gated ion channels
2. G-protein coupled receptors - inactive receptor and inactive G-protein are coupled and activated by a signal molecules which in turn allows the activation of associated membrane
3. Enzyme-coupled receptors - signal molecule activates receptor which in turn directly activates an enzyme

Front 11

What are the two types of short distance signaling?

Back 11

1. Contact dependent - membrane bound signal molecules and receptor on two different cells come together
2. Paracrine - signal is released to the outside by exocytosis or diffusion and acts locally

Front 12

What is the difference between paracrine and autocrine?

Back 12

Paracrine - signaling cell and target cell are different type
Autocrine - they are the same type

Front 13

What four ways can a paracrine signal act and what controls this?

Back 13

1. Signal taken up rapidly by target cells
2. Can be destroyed in ECM
3. Can be immobilized by ECM
4. Can have antagonists that bind to signal molecule or receptors that then prevent further minding
- this is all to make sure it only acts locally
- and these are all controlled by a local mediator

Front 14

What are the two types of long distance signaling?

Back 14

1. Synaptic - very fast, electric pulses 100 m/sc
- high local concentration of neurotransmitter

2. Endocrine - hormone released into blood stream, much more slow, low concentration of hormones

Front 15

What types of cell signaling responses are Slow (minutes to hours) and what types are Fast (seconds to minutes)?

Back 15

Slow: cell growth and division which require changes in gene expression, also the synthesis of new proteins

Fast: cell movement, secretion, metabolism

Front 16

How does primary and secondary transcriptional responses work?

Back 16

- Signal comes in which causes activation of primary response genes
- these in turn induce synthesis of primary response proteins
- these proteins then may activate a secondary response or cause negative feedback in which primary response genes are shut down

Front 17

What happens if there are no signals received by cells?

Back 17

apoptosis

Front 18

What are ways for the same signal to have different responses?

Back 18

- different receptors can cause different responses
- so can different intracellular signaling proteins becuase they cause different cascades
- different effector proteins
- different activated genes
- and different concentration of a signal