Biosignaling Flashcards
3 types of chemical biologicals signals that our cells use to respond to tehir surroundings, communicate with other cells, and alter their own internal environments
Hormones, cytokines, and neurotransmitters
Hormones can be
Peptide-
Steroid-
Amino acid-derived molecules
These are small proteins that modulate our immune system
Cytokines
Chemicals that transmit information between neurons
Neurotransmitters
Biochemical classes that biological signals can belong to
Lipids, amino acids, proteins, and gases (nitric oxide for neurotransmitters)
Signals that act within the cell that synthesizes them
Intracrine signals
Signals are released, then bind to receptors on the cell that synthesizes them. But they first get out of the cell that synthesized them and then bind to its receptors
Autocrine signals
These target cells that are directly attached to the signaling cell
Juxtacrine signals
These target cells that in the general vicinity of the cell that emits the signal
Paracrine signals
Signals (hormones) travel between distant cells through circulatory system
Endocrine signals
Inflammation involves the release of ________, which generally affect nearby cells via _________ signaling
Cytokines ; paracrine
Neurotransmitters are what kind of signaling molecules
Paracrine
When the signaling molecule binds to a receptor, the signaling molecule is called what
Ligand
The ligand that binds to the receptor in the cell membrane is called the _______ _________ since it initiates the signaling pathway
First messenger
If the receptor triggers another biosignal inside the cell, the internal signaling molecule is called what?
Second messenger
Common second messengers
Calcium ions and cAMP
Receptors can be divided into 2 categories
Membrane receptors and nuclear receptors
These receptors are attached to the plasma membrane and often contain tab least one transmembrane domain, so it can relay message from outside of the cell to the interior of the cell
Membrane receptors
A protein domain which passes through the cell membrane; mostly made of hydrophobic amino acids
Transmembrane domain
Ligands that bind to membrane receptors are typically?
Polar (charged or have a lot of polar functional groups)
These receptors bind to non polar or lipid-based ligands, such as steroid and thyroid hormones which can diffuse directly through the cell membrane
Nuclear receptors
Are receptors found either in the nucleus or cytoplasm, and when the ligand binds the ligand-receptor complex migrates to the nucleus if it’s not already there
Free-floating Nuclear receptors
When bound to their ligands, nuclear receptors essentially function as what?
Transcription factors- they regulate the rate of gene transcription (turn it up or down)
3 types of membrane receptors
- Ion channel-linked
- Enzyme-linked (Catalytic)
- G protein-coupled (GPCR)
These receptors contain transmembrane pores that allow charged species (ions) to pass through when channel is open. For this to open, it must be bound to its ligand
Ion channel-linked or ligand-gated ion channels
Example of ion channel-linked receptors
Neurotransmitter receptors
These receptors are either enzymes themselves or are directly associated with the enzymes that they activate. What are the most common examples?
Enzyme-linked (catalytic) ; protein kinases
Receptor tyrosine kinases (RTKs) are an example of what receptors?
Enzyme-linked
These are receptors for a bunch of different hormones and growth factors . When functioning properly, these play a key role in cell growth.
RTKs= receptor tyrosine kinases
A highly contagious respiratory disease causing uncontrollable, violent coughing
Pertussis or whooping cough
An infectious an often fatal bacterial disease of the small intestine, causing severe vomiting and diarrhea
Cholera
Membrane receptors that are involved in an enormous range of cellular functions. This contains seven transmembrane domains, meaning that the protein sequence passes all the way through the plasma membrane seven times.
GPCRs
What does the G represent in G-protein
Guanine
A hetero trimeric protein that binds to the guanine nucleotide: GTP and GDP
G-Protein
The subunits in the heterotrimeric G protein
Alpha, Beta, gamma
This subunit of the G protein is capable of binding either GTP or GDP
Alpha
What activates the alpha subunit of the G-protein?
GTP
What deactivates the alpha unit of the G protein?
GDP
The two requirements for GPCR system activation.
- Activated by ligand
2. Needs GTP as an energy source
When the GPCR system is activated and the alpha subunit is bound by a GTP molecule what happens?
The alpha subunit with its GTP separate with the beta and gamma subunit. These 2 units independently interact with other molecules
Cyclic AMP pathway of the G protein coupled receptor
The alpha subunit acts on the enzyme adenylyl cyclase top stimulate product of cAMP which then goes on to activate a kinase known as protein kinase A, which can phosphorylation a wide variety of proteins
What are the two possible pathways for the activation of GPCRs
cAMP pathway and IP3 pathway
Inositol Triphosphate (IP3) Pathway
Uses the second messengers IP3 and calcium ions to activate protein kinase C.
