Signal Transduction

Question 1

What is signal transduction?

Answer 1

Communication inside and between cells; includes: signal transduction pathways, local communication between and within cells, and hormonal signaling

Question 2

What are the key steps in signal transduction?

Answer 2

1. reception - Ligands - primary messengers are induced by a stimulus and are released into the bloodstream in response to a bodily need and aim to initiate a response. This chemical signal binds to a cellular protein, typically at the cell’s surface or inside the cell.
2. transduction - binding leads to a structural change in the receptor that triggers a series of changes in a series of different molecules along a signal-transduction pathway. The molecules in the pathway are called relay molecules
3. response - the transduced signal triggers a specific cellular activity

Question 3

What kind of cellular functions are regulated by signal transduction pathways?

Answer 3

growth, differentiation, metabolism, and survival.

Question 4

Signal transduction is initiated by what?

Answer 4

Binding of signalling molecule to their receptor initiates

signalling pathways that elicit important cellular responses

Question 5

What dictates the response of the cell?

Answer 5

The receptor not the signal

Question 6

What are the two messenger binding sites?

Answer 6

1. cell surface receptors (extracellular)

2. cytosolic or nuclear receptors (intracellular)

Question 7

Name 4 different types of cell surface receptors

Answer 7

G protein coupled receptors (GPCR)
Ion-channel receptors
Tyrosine kinase-linked receptors
Receptors with intrinsic enzymatic activity

Question 8

Describe G protein coupled receptors and give an example of a primary messenger which binds to it

Answer 8

Ligand binding first activates a GTP-binding protein. This G-protein then either activates or inhibits an enzyme that generates a specific 2nd messenger or modulates an ion channel causing a change in membrane potential e.g. epinephrine

Question 9

Describe Ion-channel receptors and give an example of a primary messenger which binds to it

Answer 9

Ligand binding changes the receptor conformation such that a specific ion channel is opened e.g. acetylcholine

Question 10

Describe Tyrosine kinase-linked receptors and give an example of a primary messenger which binds to it

Answer 10

Ligand binding stimulates formation of a dimeric receptor which interacts and activates cytosolic protein tyrosine kinases e.g. erythropoietin

Question 11

Describe receptors with intrinsic enzymatic activity and give an example of a primary messenger which binds to it

Answer 11

Ligand binding changes receptor conformation and activates intrinsic catalytic activity e.g. insulin

Question 12

Signal transduction relies on what?

Answer 12

proteins known as receptors, which wait for a chemical, physical, or electrical signal.
Chemical signals are called ligands, and can be produced by organisms to control their body or received from the environment.

Question 13

What are primary messengers?

Answer 13

Ligands that are made by the body for signaling are called primary messengers, since they are released into the bloodstream in response to a bodily need and aim to initiate a response.
are the signaling molecules (hormones, neurotransmitters, and paracrine/autocrine agents) that reach the cell from the extracellular fluid and bind to their specific receptors

Question 14

What is a ligand?

Answer 14

Ligands are small molecules that transmit signals in between or within cells by binding to a receptor. (primary messengers)

Question 15

What is a hormone?

Answer 15

a substance that is produced in one tissue or organ and released into the blood and carried to other organs (primary messenger)

Question 16

What is the difference between secondary messengers and primary messengers?

Answer 16

Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers.

Question 17

What are signalling molecules?

Answer 17

Signaling molecules are the molecules that are responsible for transmitting information between cells in your body.

Question 18

How are receptors classified?

Answer 18

Based on the ability of a ligand to move across the cellular membrane, there are two classes of receptors. If the ligand can only bind on the outside of a cell, or on its surface, the receptor is called a membrane receptor. If the ligand can move into the cell and bind, the receptor is called a intracellular receptor.

Question 19

How are receptors classified?

Answer 19

Based on the ability of a ligand to move across the cellular membrane, there are two classes of receptors. If the ligand can only bind on the outside of a cell, or on its surface, the receptor is called a membrane receptor. If the ligand can move into the cell and bind, the receptor is called a intracellular receptor.

Question 20

How can hormones be classified and what are the three types?

Answer 20

based on their solubility and receptor location

• Lipophilic hormones with intracellular receptors
• Lipophilic hormones with cell-surface receptors
• Hydrophilic hormones with cell surface receptors

Question 21

Give an example of lipophilic hormones with intracellular receptors

Answer 21

steroid hormones, thyroxine, Vitamin D

Question 22

Give an example of lipophilic hormones with cell-surface receptors

Answer 22

prostaglandins

Question 23

What are the two subclasses of hydrophilic hormones with cell surface receptors and give examples

Answer 23

• Peptide hormones e.g. insulin and glucagon

- Small charged molecules e.g. epinephrine and histamine

Question 24

What is the response of epinephrine and Beta-Adrenergic receptor?

Answer 24

Energy store mobilization

Question 25

What is the response of insulin and insulin receptor?

Answer 25

Increased glucose uptake

Question 26

What is the response of the epidermal growth factor (EPG) and EGF receptor?

Answer 26

Expression of growth-promoting genes