BIO 360 - Exam 1 - Chapter 7 Hormones SP 2023 PowerPoint Flashcards
What is a hormone?
chemical messenger released from glands or neurons into bloodstream.
Hormone vs. neurotransmitters:
act close to site of release via chemical synapse.
Hormone vs. paracrine factors:
(1) chemical messengers released into extracellular fluid
(2) move by diffusion
(3) act locally
Hormone vs. contact-dependent:
molecules on cell surface.
A cell responds to a particular chemical signal only
if…
the target has a receptor.
Signal ______ is process of ______ chemical signal to an intracellular response and requires a “receptor.”
transduction / converting
Most hormones, neurotransmitters are polar or large and act via receptors embedded in the plasma membrane.
However, some (e.g. steroid hormones) are ______ ______ and diffuse right through the plasma membrane to a receptor ______ ______ ______.
lipid soluble / in the cytoplasm.
______ are proteins found on plasma membranes (except family of receptors for steroid and thyroid hormones).
Receptors
- Bind chemical messengers and initiate cellular responses amplify signal and provide specificity.
How many receptor subtypes bind to a hormone?
- Each receptor subtype usually binds only one hormone or transmitter.
- Most hormones and transmitters bind to more than one receptor subtype.
The ______ and the intracellular signaling ______ gives ______.
receptor / cascade / specificity.
______ signal molecules Diffuse through the cell
membrane Bind to receptors in the cytosol or nucleus.
______ signal molecules Bind to receptors on the cell
membrane.
Lipophilic / Lipophobic
How do most chemical messengers elicit responses in target cells?
- chemical signal is 1st messenger
- signal transduction –> cellular response often via 2nd messenger
- receptors (elevate or suppress) production of 2nd messenger within cell
- most often via change in protein phosphorylation
Figure 6.6c Signal Transduction: Cascades and Amplification
Know the second messenger, amplifier enzymes, & Actions of everything.
Cascade of hormone signaling with cAMP
(Draw out on paper)
1) Hormone binds to and activates receptor in plasma
membrane
2) R* binds to and activates Gs protein; GTP binds
3) G protein* a subunit dissociates from bg subunits
4) a subunit*-GTP binds to effector molecule (adenylate
cyclase; cytoplasmic side of plasma membrane) –>, Increase or
decrease activity.
4) Adenylate cyclase produces 2nd messenger (catalyzes
conversion of ATP to cAMP)
5) cAMP diffuses and activates cAMP-dependent protein
kinase A
6) PKA phosphorylates cellular proteins and increase or decrease activity.
Modulation of Signal Pathways
One receptor may have ______ ______.
One ligand may have ______ ______.
* ______ vs. ______
multiple ligands / multiple receptors / agonist vs. antagonist
What about feedback within cells to turnoff
signaling?
1) All cells that produce cAMP have an enzyme that
degrades and inactivates cAMP.
2) G protein a subunit has intrinsic GTPase activity
3) Receptor desensitization
All cells that produce cAMP have an enzyme that
degrades and inactivates cAMP: _______.
* terminates ______.
* prevents persistent activation of ______.
phosphodiesterase / cascade / PKA
G protein a subunit has intrinsic GTPase activity.
hydrolysis of ____ ____ ____ inactivates G protein.
GTP to GDP
Receptor desensitization is often due to ______.
Decreases affinity for ligand or its ability to activate.
phosphorylation
Why is it so important to terminate signaling?
- uncontrolled cell division, cancers
- major disturbance in homeostasis may occur, as in
- cholera: G proteins can’t be turned off
How does one chemical signal stimulate but another inhibit cAMP production?
It’s the G proteins
Different receptors interact with different G proteins
*Gs stimulates adenylate cyclase –>, increase [cAMP]
*Gi inhibits adenylate cyclase –>, decrease [cAMP]
______ can produce opposite effects in different cells.
Epinephrine
Steroid hormones are derived from ______.
cholesterol
Why are steroid hormones so powerful? Why do people
take “steroids?
Steroids regulate gene expression and cellular protein synthesis.
