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What is a ligand?
A signal that is received by the cell usually resulting in a response.
What is a receptor?
A feature on the cell which receives a ligand
How does a receptor respond?
- Intrinsically as an enzyme.
- Associated with an enzyme.
- With the cytoskeleton directly.
What are some responses to a ligand being received?
- Gene expression
What are effector proteins?
They are proteins activated by intracellular signalling proteins
What are three types of effector proteins?
- Metabolic enzyme
- Gene regulatory protein
- Cytoskeletal protein (altered cell shape or movement)
What types of interactions are there between effectors and cells?
- Direct contact between transmembrane molecules of two neighboring cells
- Paracrine system (local)
- Synaptic (neurotransmitters)
- Cytonemes (thin cytoplasmic extensions releasing hormones)
- Endocrine (via bloodstream)
Which type of signalling requires the most signal molecules?
Which type of signalling is not soluble?
- Contact dependent
- Maybe Cytonemes?
What are three types of signalling responses?
- Quick; < 1 hour; protein de/activation; synaptic
- Slow; 18-24 hours; transcription/translation; endocrine
- Single cell or group in development; autocrine
What are four end-results of a cell in response to a signal?
- Grow + Divide
Describe how acetylcholine can cause two different reponses.
- Heart muscle - decreased rate and force of contraction
- Skeletal muscle - contraction
What are two types of signals wrt to water?
- Soluble - interact with transmembrane receptors
- Insoluble - interact with cytoplasmic receptors
Non-soluble signals affect ___.
What are examples of non-soluble signals?
Vitamin D, estrogen, testosterone, cortisol, estradiol, retinoic acid, and thhroxine
Non-soluble signals have a ___ effect due to ___.
- their duration in the blood
Non-soluble signals enter the cytoplasm by ___.
Non-soluble receptor responses include ___.
- Early - first 30 min
- Depends on type of protein and timing of synthesis
Gene expression regulation falls into two general categories:
All nuclear receptors bind as either ___ or ___.
An inactive receptor protein is bound to ___ proteins.
Proteins in the primary response can ____.
Activate other proteins for a delayed/secondary response.
Describe responses to testosterone.
- Early - male characteristics in development
- Delayed - muscle growth
Describe responses to estrogen.
- Early - female characteristics
- Delayed - retention of bone mass
What are three classes of cell-surface receptors?
- Ion-channel-coupled (open channel)
- G-protein-coupled (G activates enzyme)
- Enzyme-coupled (intrinsic and associated enzymatic)
What are three types of "players" that affect the cell?
- First messengers - ligands such as hormones
- Intracellular signaling proteins
- Second messengers - not unique to one pathway
What are examples of second messengers?
cAMP, cGMP, 1,2-diacylglycerol (DAG), IP3, Ca+2
What second messengers require ATP?
What second messengers are derived from phospholipids
Name various proteins/molecules in signalling pathways/cascades.
Anchoring, amplifier, integrator, modular, relay, scaffold, transducer
Describe an anchoring protein.
Anchors proteins to a structure at a precise location where needed.
Describe amplifier proteins.
Greatly increases signal they receive.
Describe Integrator proteins.
Combine signals from two or more pathways before forwarding.
Describe modular proteins.
Modify the activity of signaling proteins to regulate signal strength.
Describe relay proteins.
Pass messages to the next signaling component in the pathway.
Describe scaffold proteins.
Bind to multiple signaling proteins together in a functional complex for quicker and more efficient interaction.
Describe transducer proteins.
Convert singal to a different form.