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60 Cards in this Set

  • Front
  • Back
What is Botox?
It is a recombinant form of Botulism Toxin A used to treat migraine headaches and to temporarily smooth out facial wrinkles.
What is Botulism Toxin A?
It is a protease
What does the communication process in our biochemical circuits or relays consist of?
They consist of protein structural changes that are initiated by the bending of small biomolecules to large receptor proteins.
What do large receptor proteins accomplish?
They trigger a cellular response.
What do some signalling events involve the activation of?
They involve the activation of soluble proteins such as the intracellular receptors which are activated by steroid hormones.
What is an example of direct activation of a signalling protein?
An example is guanylyl cyclase, which is one of the targets of nitric oxide.
What are biomolecules with the property to activate soluble proteins called?
They are called receptor ligands.
What are receptor ligands represented by?
They are represented by hormones such as insulin and neurotransmitters like acetylcholine.
What does the name given to a receptor protein reflect?
It reflects the ligand that activates it.
Explan how this reflects insulin's naming scheme?
Insulin binds the insulin receptor.
Explain how this reflects acetylcholines naming scheme?
Acetylcholine binds to the acetylcholine receptor
What is another major form of cell-cell communication, and what is it mediated by?
It is mediated by hydrophobic receptor ligands derived from cholesterol, which pass through the plasma membrane and bind to intracellular receptor proteins.
What are 3 examples of intracellular receptors?
Estrogen receptor, glucocoricoid receptor, and the vitamin D receptor.
Receptors, target proteins, and ligands function in signalling pathways as what?
They function as first messengers
Signal transductions also involves something that functions as secondary messengers. What are they called?
They are intracellular biomolecules
There are also intermediary signalling proteins, which function to do what three things to the signal?
They transmit, amplify, and terminate the signal.
What do small biomolecules function as?
They function as diffusable signals
Insulin is an example of what level of messenger?
It is a first messenger.
Why is insulin a first messenger?
It binds directly to the insulin receptor.
What do second messengers function to do?
They function to amplify the biochemical signal.
What are the simplest types of first messengers?
The simplest types are small diffusible biomolcules.
How do small diffusible biomolecules act?
They act at a distance through endocrine mechanisms
How else can they act?
They also can function locally as paracrine or autocrine signals
What is nitric oxide and what does it do?
It is a soluble gas that activates signalling pathways by diffusing across cell membranes and directly activating signalling proteins.
What is the primary role of secondary messengers?
The primary role is to amplify the receptor-generated signal to more quickly obtain a maximal response.
What is one of the best characterized secondary messengers, and where is it produced?
Cyclic AMP (cAMP) is produced by the enzyme adenylate cyclase from ATP.
What does receptor activation of adenylate cyclase generate?
It generates large amounts of cAMP.
In generating large amounts of cAMP, what does this accomplish?
It allows cAMP to bind to and activate downstram signalling proteins such as cAMP dependent protein kinase A.
How is the intracellular concentration of cAMP controlled?
It is controlled by the relative levels of receptor-activated adenylate cyclase and soluble forms of cAMP phosphodiesterase (PDE).
What does PDE do?
It converts cAMP to AMP.
Where is cyclic GMP produced?
It is produced from GTP by the enzyme gyanylyl cyclase.
How does Viagra treat sexual dysfunction?
It inhibits the activity of cGMP phosphodisterase (PDE).
What do the G proteins do?
They are small GTPases involved in transmitting intracellular signals from G protein coupled receptors to signalling enzymes such as adenylate cyclase and phospholipase C
What are the five major classes of receptor proteins?
G Protein coupled receptors. Receptor tyrosine kinases. Tumor Necrosis Factor (TNF) family receptors. Ion channel receptors. Intracellular receptors (nuclear receptors)
What is Epinephrine also known as?
It is also known as Adrenaline
What class does epinephrine belong to?
It belongs to a class of first messengers called catecholamines.
What does epinephrine signalling stimulate?
It stimulates glycogen breakdown in liver cells.
What is glucagon?
It is a peptide hormone that signals low glucose levels in the blood and also activates glucose export.
What does activation of adenylate cyclase lead to?
It leads to increased levels of cAMP.
What is glycogen synthesis known as?
What is glycogen degradation known as?
What does activation of adenylate cyclase activity by hormone signalling lead to?
It leads to production of the second messenger cyclic AMP (cAMP).
What does cyclic AMP activate?
It activates a downstream signalling protein called protein kinase A.
What happens when two cAMP molecules bind to each R subunit?
They induce a conformation change in the R subunits that causes them to dissociate from the tetrameric complex as an R2(cAMP)4 dimer.
What is this general mechanism a common theme in?
It is a common theme in regulatory enzymes.
What does this mechanism do?
It is a mechamism of kinase activation by subunit dissociation, or by a ligand-induced protein conformational change.
What are two examples of PKA target proteins?
Phosphorylase kinase and glycogen synthase
What do phosphorylase kinase and glycogen synthase do?
They regulate glycogen metabolism in opposing ways.
What is PKA phosphorylation of phosphorylase kinase?
It is an activating signal
What does it stimulate?
It stimulates the phosphorylation of glycogen phosphorylase.
What does this accomplish?
It triggers the eventual removal of glucose units from glycogen.
What is another important target of PKA which binds to DNA and regulates the transcription of specific genes?
Transcription factor CREB
What are the 4 things Protein Kinase A does?
It phosphorylates protein targets. It inhibits glycogen synthesis. It activates PKA. It activates CREB regulatory activity.
What are Alpha-1 adrenergic receptors coupled to?
They are coupled to a heterotrimeric G protein containing Gq-alpha.
What does this activate?
It activates the enzyme phospholipase C through a mechanism very similar to Gs-alpha stimulation of adenylate cyclase activity.
What is phospholipase C and what does it do?
It is a membrane associated proteint hat catalyzes the hydrolysis of phophatidylinositol 4,5-bisphosphate (PIP2)
What does this accomplish?
It forms the second messengers DAG and IP3.
In summary, G protein coupled receptor signalling involves what five basic mechanistic steps?
Receptor-mediated activation of GDP-GTp exchange in G-alpha subunits. G-alpha stimulation of an effector enzyme that generates 2nd messengers. Activation of a phosphorylation cascade by 2nd messenger signalling. Inactivation of G-alpha by effector stimulation of the intrinsic GTPase activity. Signal duration is controlled by loss of 2ndf messengers and receptor desensitization
What is the role of receptor proteins in signal transduction?
Receptor proteins function as gatekeepers to intracellular signalling pathways
What is the role of seond messenger molecules such as cAMP, cGMP, DAG, IP3, and Ca2+?
They function in cell signalling pathways by activating enzymes and ion channels that amplify the initiating signal