Signal Transduction and G Protein-Coupled Reactions Flashcards
(52 cards)
How do hydrophobic hormones diffuse through the cell?
Through the cell membrane and activate cytosolic receptors.
How do hydrophobic hormones diffuse through the cell.
They bind to plasma membrane receptors and activate signal transduction pathways.
Some plasma membrane receptors activate G-protein switch proteins that trigger a variety of 1. __________ or induce the generation of 2. ______________.
- Downstream pathways
- Intracellular second messagers
What do Tyrosine Kinases do?
Trigger signal transduction pathways involving sequential activation of downstream kinases.
Give three examples of hydrophobic signals in the cell.
- Steroids
- Retinoids
- Thyroxine
Give three examples of hydrophilic signals in the cell.
- Small molecules
- Peptides
- Proteins
Cells respond to environment signals such as?
- Temperature
- Light
- Oxygen
- Sounds
- Odurs
Give examples of ways cells respond to signals from other cells.
- Hormones
- Growth factors
- Neurotransmitters
What is signal transduction?
The process of sensing external stimuli and conveying the information to intracellular targets.
Extracellular signal –> Intracellular space
Describe the process of hydrophobic signalling molecules.
- Hydrophobic hormones diffuses through the cell membrane into the cytoplasm.
- In the cytoplasm, the hormone binds to a receptor/activator. Very often the receptor is a transcriptional activator residing in the nucleus
- The receptor-hormone complex is recognized by a transporter molecule that takes it to the nucleus.
Some receptors are in the nucleus and are activated by the hormone.
What is ‘Dex’? What does it activate?
Dexamethasone activates the Glucocorticoid receptor.
In the absence of ‘Dex’, where is the Glucocorticoid receptor.
In the cytoplasm
In the presence of ‘Dex’, where is the receptor-hormone complex moved to?
Moved to the nucleus when the hormone activates the receptor site.
The control b-galactosidase is _________ regardless of the presence of ‘Dex”.
Cytoplasmic
Hydrophilic signalling molecules work differently than hydrophobic signalling molecules. Describe the reaction that takes place to enter the cell and the nucleus.
- The binding of the signal molecule to a specific cell surface receptor changes he conformation (shape) of the receptor and its activation.
- The activated receptor initiates downstream signal transduction proteins and/or second messengers.
- Signal transduction leads to the activation of effector protein(s) causing:
- Short term responses (Modification of cellular metabolism, function, movement)
- Long term responses in the nucleus (Modification of gene expression, development)
- Termination (or down-regulation) from negative feedback or removal of the extracellular signal from the receptor.
Membrane receptors bind only a single type of _________ signalling molecules.
Hydrophilic
All hormone receptors are highly _______ for their ligands.
Specific
Each receptor binds only a ______ type of hormone.
Single
When a hormone binds to its specific receptor, the hormone changes the _________ of the receptor sending a signal to the cascade.
Conformation
Give examples of small molecules, peptides, and proteins that are used for hydrophilic signalling molecules.
Small molecules: Adrenaline, acetylcholine
Peptides: Glucagon
Proteins: Insulin, growth hormones
List the four types of extracellular signalling.
- Endocrine signalling
- Paracrine signalling
- Autocrine signalling
- Signalling by plasma-membrane attached proteins
Describe endocrine signalling.
Affects target cells some distance from the site of synthesis.
- Far proximity
- Hormone gets secreted into the blood by the endocrine gland through the blood vessel and is secreted to the distant target cells
- Uses the blood and blood stream
Describe paracrine signalling.
Affects target cells in close proximity.
- Uses secretory cells to secrete hormones to the adjacent target cell.
Describe autocrine signalling.
Cells respond to the signals they produce. The target sites are ON the SAME cell.
- Hormone produced by the SAME cell targets the receptor sites on that cell.
