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