Exam 1: Cell signaling Prt 1&2 Flashcards
What is Cell signaling? What does it consist of?
- Communication process that governs activites of cell & cooridnates action
* Growth, development, and lactation
* Reproduction
* Maintenance of internal environment
* Energy production, utilization, and storage
What are the three stages of cell signaling?
- Reception
- Transduction
- Response
What are some biochemical signals?
- Hormones
- Growth factors
- Nutrients
- Neurotransmitters (acetylocholine,etc)
What are some mechanical signals?
- Pressure touch: sensory cells in skin
- Sound waves: sensory cells in ear
- Stretch: skeletal muscle
What does Autocrine mean?
A cell targets itself
What does Paracrine mean?
Action on a nearby cell
What does Endocrine mean?
Cell targets a distant cell through the bloodstream
How exactly does a cell recognize cells and how does it elicit a response?
1.The answer is receptors
2.Providing specfic recognition of signaling molecule (ligand)
3.Interaction with ligan leads to a biological response
What are 3 membrane receptors?
- Ion channel receptor
- G-protein-coupled
- Enzyme-linked receptors
What are Ion channel-linked receptors?
- Legand binds
- Opens a channel through the membrane that allows specific ions to pass through
G-couples recptor general mechanism goes in what order?
From:
1.Signal
2.Receptor (near GDP)
3.-> GTP
4.to Enzyme
5.Having Active 2nd messenger or Inactive 2nd Messenger
6.Effects on cellular function (Gene expression, Enzyme activity, Ion or metabolite transport)
How do G-protein coupled receptors work? (general idea)
It goes in this order:
1. First messenger->
2. G-protein coupled transmembrane receptor->
3. Signal amplification->
4. Second messenger->
5. Cellular response
What can PKA do in terms of responses?
- Can activate transcription factors, affecting gene expression
- Can phosphorylate enzymes, causing a change in activity
How do Enzyme-linked receptors work?
Starts with:
1.Ligand
2.Signal induces receptor dimerization (activated)
3.Allows proteins to phosphorylate each other
4.Phosphorylated sites act as docking sites
What is needed to activate downstream signaling?
Adaptor protein
What is the purpose of ‘adaptor proteins’?
May recruit & activate other proteins
Where are intracellular receptors found? What are their function?
- Receptors located inside cell
- Function as transcription factors
- Proteins bind to a specific DNA sequence
- Control gene transcription from DNA to RNA
In what order does cell response normally go?
- Signal ->
- Receptor->
- Cascade of intracellular reactions->
- Physiological reaction: glucose mobilization or
- Gene expression
What are the characteristics of protein?
- Water soluble
- Usually made in form of precursors
- Must be cleaved for acivation
- Usually do not enter cell
What are the characteristics of amino acid derived?
- Formed from tyrosine
- Cell receptor (epi.) or nuclear receptor (thyroxin)
What are the characteristics of streoids?
- Made of cholesterol
- Hydrophobic
- Can get through the lipid bi-layer
What are the characteristics of fatty acid derived?
- Receptor type varies
When it comes to receptor types how long do:
1.Ligand-gated ion channels
2.G-protein coupled
3.Enzyme-linked
4.Intracellular (Nuclear)
take for each?
- Milliseconds
- seconds-hours
- hours
- hours
What are ligands?
Any molecules or atoms that bind to a receiving protein molecule
What are receptors?
Molecules inside or on the surface of a cell that bind to a specific substance and causes a specific effect in the cell
What are ion channels?
Pore-forming membrane proteins that allow ions to pass through the channel pore
What is a signaling cascade (transduction)?
- Is a series of chemical reactions that occur within a biological cell when initated by a stimulus to amplify a signal
- Mainly consisting of protein kinases
What are secondary messengers?
Intracellular signaling molecules released by the cell in response to exposure to extracelullar signaling molecules
What are kinase?
Enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule
What are transcription factors?
- Proteins that bind to a specific DNA sequence
- Control gene transcription from DNA to RNA
What exactly is an agonist and antagonist?
- Agonist binds and activates a receptor leading to a biological response
- Antagonist is a ligand that blocks a receptor and prevents its activation (weaking the biological response)
- Growth promotants
What does Epinephrine do to counteract a body’s allergic response?
- Counteracts alleric response by:
* Opening airways in lungs
* Constrcts the blood vessels
* Increases heart rate (increases blood flow)
When it comes to steroid implants for feedlot cattle what does it consist of?
- Androgen + estrogen
How is a growth promotant given to an animal and what is its process?
- Administered in ear
- Dissolve slowly into bloodstream
- carried by binding proteins to tissues
- Direct and indirect effects on muscle growth
- Anabolic steroids are rapidly metabolized
What do Beta-agonist do? How are they given?
- Bind to beta-receptors,
- In muscles: start protein synthesis, reduced protein degradation,
- In fat :promotes fat lipolysis (fat breakdown), reduced lipogenesis (fat synthesis)
- Given orally
