Signal Transduction Flashcards
What is signal transduction?
Communication inside and between cells; includes: signal transduction pathways, local communication between and within cells, and hormonal signaling
What are the key steps in signal transduction?
- 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.
- 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
- response - the transduced signal triggers a specific cellular activity
What kind of cellular functions are regulated by signal transduction pathways?
growth, differentiation, metabolism, and survival.
Signal transduction is initiated by what?
Binding of signalling molecule to their receptor initiates
signalling pathways that elicit important cellular responses
What dictates the response of the cell?
The receptor not the signal
What are the two messenger binding sites?
- cell surface receptors (extracellular)
2. cytosolic or nuclear receptors (intracellular)
Name 4 different types of cell surface receptors
G protein coupled receptors (GPCR)
Ion-channel receptors
Tyrosine kinase-linked receptors
Receptors with intrinsic enzymatic activity
Describe G protein coupled receptors and give an example of a primary messenger which binds to it
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
Describe Ion-channel receptors and give an example of a primary messenger which binds to it
Ligand binding changes the receptor conformation such that a specific ion channel is opened e.g. acetylcholine
Describe Tyrosine kinase-linked receptors and give an example of a primary messenger which binds to it
Ligand binding stimulates formation of a dimeric receptor which interacts and activates cytosolic protein tyrosine kinases e.g. erythropoietin
Describe receptors with intrinsic enzymatic activity and give an example of a primary messenger which binds to it
Ligand binding changes receptor conformation and activates intrinsic catalytic activity e.g. insulin
Signal transduction relies on what?
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.
What are primary messengers?
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
What is a ligand?
Ligands are small molecules that transmit signals in between or within cells by binding to a receptor. (primary messengers)
What is a hormone?
a substance that is produced in one tissue or organ and released into the blood and carried to other organs (primary messenger)
What is the difference between secondary messengers and primary messengers?
Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers.
What are signalling molecules?
Signaling molecules are the molecules that are responsible for transmitting information between cells in your body.
How are receptors classified?
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.
How are receptors classified?
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.
How can hormones be classified and what are the three types?
based on their solubility and receptor location
- Lipophilic hormones with intracellular receptors
- Lipophilic hormones with cell-surface receptors
- Hydrophilic hormones with cell surface receptors
Give an example of lipophilic hormones with intracellular receptors
steroid hormones, thyroxine, Vitamin D
Give an example of lipophilic hormones with cell-surface receptors
prostaglandins
What are the two subclasses of hydrophilic hormones with cell surface receptors and give examples
- Peptide hormones e.g. insulin and glucagon
- Small charged molecules e.g. epinephrine and histamine
What is the response of epinephrine and Beta-Adrenergic receptor?
Energy store mobilization
What is the response of insulin and insulin receptor?
Increased glucose uptake
What is the response of the epidermal growth factor (EPG) and EGF receptor?
Expression of growth-promoting genes
