Cell signalling

Question 1

What is an example of system of communication?

Answer 1

Endocrine system

Question 2

What does the endocrine system uses to “communicate”?

Answer 2

Release hormones into the bloodstream to facilitate communication

Question 3

What does hormones initiate?

Answer 3

Chemical signalling

(…when hormones bind to receptors…)

Question 4

What does the chemical signalling consists of? (vaguely)

Answer 4

1. Reception
2. Transduction
3. Response

Question 5

What does chemical signalling bring about?

Answer 5

Homeostasis

Question 6

What is homeostasis?

Answer 6

The maintenance of a constant internal environment.

Question 7

What is an example of chemical signalling?

Answer 7

Regulation of blood glucose concentration

Question 8

What is the blood glucose concentration of a healthy person?

Answer 8

800 mg/dm3

Question 9

What are the main stages of cell signalling?

Answer 9

1. Ligand-receptor interaction
2. Signal transduction (phosphorylation cascade and signal amplification)
3. Cellular response (change in gene expression)

Question 10

What occurs during ligand-receptor interaction?

(2 steps)

Answer 10

1. Ligand has a 3D conformation complementary to the active site of the receptor and binds to it.
2. Binding of ligand to receptor forms a ligand-receptor complex, causing receptor protein to undergo a change in 3D conformation.

Question 11

What affects the location of where the hormone binds to?

Answer 11

Solubility of the hormone

Question 12

Where are the different locations of hormones binding to the receptors?

Answer 12

1. Receptors in cell surface membrane (CSM) - soluble hormone
2. Receptors in the cytoplasm or nucleus (Intracellular receptors) - insoluble hormone

Question 13

What does the activated intracellular receptor do?

Answer 13

The activated receptor acts as transcription factor and binds to control elements in the DNA to regulate transcription and gene expression -> causing a response -
- carries out the complete transduction of the signal

Question 14

What occurs in the signal transduction stage?

(3 summarised steps)

Answer 14

1. A combination of small and large intracellular signalling molecules relay signals received by the receptors at the cell surface into the cell interior.
2. The activated receptor activates another protein which then activates another molecule and so on.
3. The resulting chain of intracellular signalling events ultimately alters effector proteins and are responsible for modifying the behaviour of the cell.

Question 15

What are the 2 types of intracellular signalling molecules of a signal-transduction pathways?

Answer 15

1. Second messengers
2. Relay proteins

Question 16

What are second messengers and what do they contribute to signal transduction?

Answer 16

• small, non-protein molecules/ions
• they pass signal from the hormone (1 messenger) by binding to and altering 3D conformation of relay and effector proteins

Question 17

Name an example of second messenger.

Answer 17

Cyclic adenosine monophosphate (cAMP)

Question 18

How is cAMP produced?

Answer 18

1. Binding of a hormone (glucagon) to the receptor (GPLR) … would lead to activation of the enzyme adenyl cyclase.
2. Activated adenyl cyclase converts ATP to cAMP.

Question 19

What is the function of cAMP?

Answer 19

cAMP activates protein kinase which phosphorylates other proteins, giving rise to cellular response.

Question 20

What are the features of second messengers that benefit/cost them in their functions?

Answer 20

Small :
1. can store large amounts in cell
2. diffuse quickly throughout the cell

Non-polar :
3. will not be degraded by protease in cell
4. not easily affected by change in pH/temp in cell
5. protein synthesis takes a longer time -> unsuitable for rapid action
6. protein synthesis takes alot of energy resources.

Question 21

What causes degradation of cAMP?

Answer 21

enzyme Phosphodiesterase -> converts cAMP to an inactive product, AMP

Question 22

What is negative feedback?