BIOC 384 EXAM 3
If there were a technique that allowed one to isolate EGFR1 and EGFR2 at discrete steps along their activation pathway, which of the following would be isolated? None of these answers are correct. A monomer of EGFR1 that contains phosphotyrosines. A monomer of EGFR2 that contains phosphotyrosines. A dimer in which EGFR1 contains phosphotyrosines but EGFR2 does not. A dimer in which EGFR2 contains phosphotyrosines but EGFR1 does not.
A dimer in which EGFR2 contains phosphotyrosines but EGFR1 does not. EGF binding to each monomer induces receptor dimerization that stimulates kinase activity in one receptor (EGFR1), which phosphorylates tyrosine residues in the paired receptor (EGFR2).
What is the most common type of cancer mutation?
A dominant gain-of-function mutation is the most common type of cancer mutation and need only affect one of the two gene copies in the cell to cause a deleterious phenotype such as uncontrolled cell growth in cancer cells
What is interesting about the switch II subunit in Gsα
A helical region in the Gsα subunit called switch II, has two different conformations depending on the presence of GDP or GTP
How is cAMP made and taken apart?
A well characterized second messenger is 3',5'-cyclic adenosine monophosphate, or cyclic AMP (cAMP), which is produced from ATP by the enzyme adenylate cyclase, and is hydrolyzed by the enzyme cAMP phosphodiesterase (PDE).
What is uridylylation?
ALLOSTERIC CONTROL Regulation of glutamine synthetase (GS) includes control of GS adenylyltransferase activity by uridylylation of Tyr51 by the enzyme uridylyltransferase
Which answer correctly classifies the compound with its relationship to aspartate transcarbamoylase? CTP; allosteric activator None of these answers are correct. ATP; allosteric inhibitor ATP; allosteric activator CTP; substrate
ATP; allosteric activator
How does acetylcholine open the ion channel?
Acetylcholine binding to the nicotinic acetylcholine receptor opens the ion channel by inducing a conformational change that rotates the transmembrane α helices relative to one another
What is allosteric control of enzyme activity?
Allosteric control of enzyme activity often involves the binding of small molecules (metabolites) to regulatory sites on the enzyme located outside of the active site.
How is ATCase regulated?
Aspartate transcarbamoylase (ATCase) is allosterically-regulated by both CTP and ATP Binding of ATP to the regulatory subunit shifts ATCase to the activated R state, whereas CTP binding to the regulatory subunit stabilizes the inactive T-state conformation. The product is N-carbamoyl-L-aspartate
What happens mechanistically in accordance to the kssing bug?
At pH 5 in insect saliva nitric oxide (NO) is bound to heme of the nitrophorin protein. However, at pH of 7, NO is released activating guanylate cyclase and producing cyclic GMP, resulting in vasodilation.
What percentage of genes are involved in signal transduction?
Bioinformatic analyses reveal that 9% of the protein-coding genes in the human genome are involved in signal transduction Most signal transduction genes encode either receptor proteins (G protein-coupled receptors, peptide hormone receptors, nuclear receptors) or protein kinases; humans have ~2,000 signaling genes.
Place the following steps in proper order: A. phosphorylation of RTK cytoplasmic tails B. activation of downstream signaling pathways C. ligand binding, receptor dimerization, and kinase activation D. protein binding to RTK phosphotyrosines and phosphorylation of target proteins C, B, A, D C, D, A, B C, A, D, B B, C, A, D A, B, C, D
C, A, D, B
What is the effect of adnenylylating glutamine synthetase?
COVALENT MODIFICATION Adenylylated glutamine synthetase (GS) is in the inactive T state conformation and the deadenylylated form of GS is in the active R state conformation. The same enzyme catalyzes both reactions
What does calmodulin do?
Calmodulin binds to and activates a wide variety of target proteins. Calmodulin binds four Ca2+ ions and undergoes a large conformational change
Starting with CASP3 how is the fully active CASP8 formed?
Casp8 cleaves caspase 3 to yield a partially active CASP3 called procaspase 3, which then recognizes and cleaves other procaspase 3 molecules to form the fully active CASP3.
Catabolic pathways are always paired with anabolic pathways. Why? Both are amphibolic. Both require ATP to operate. Both require redox reactions to operate. Catabolic pathways break down molecules and anabolic build up new molecules. Catabolic pathways build up new molecules and anabolic break down molecules
Catabolic pathways break down molecules and anabolic build up new molecules
How is catalytic efficiency regulated?
Catalytic efficiency is regulated by inhibition, allosteric control, covalent modification, and proteolytic processing.
What do cell signaling pathways involve?
Cell signaling pathways also involve first messengers, upstream and downstream signaling proteins, and second messengers.
How is competitive inhibition characterized?
Competitive inhibition is characterized by inhibitors that bind to the free enzyme and inhibit substrate binding at the active site.
What happens with a dominant Ras mutation?
Dominant Ras mutations in the GTPase domain lead to stimulation of the MAPK signaling pathway in the absence of growth factors. Oncogenic Ras proteins are insensitive to GAP regulation (stuck gas pedal without brakes). Even though cancer cells still express an equal amount of wild-type Ras, the phenotype reflects the overstimulation of the MAPK pathway from the unregulated mutant Ras because of the gain-of-function phenotype
What is the effect of EGF in receptor signaling?
EGF binding to each monomer induces receptor dimerization that stimulates kinase activity in one receptor (EGFR1), which phosphorylates tyrosine residues in the paired receptor (EGFR2).
What are the two types of enzyme regulation?
Enzyme regulation could be stimulatory, resulting in an overall increase in enzyme activity, or it could be inhibitory, resulting in a decrease in enzyme activity.
How is enzyme regulation mediated?
Enzyme regulation is mediated by; bioavailability of enzymes in different tissues and cellular compartments, and control of catalytic efficiency through binding of regulatory molecules, covalent modification, and proteolytic processing.
What is the difference between reversible and irreversible inhibition? What is an example of each?
Enzymes are subject to reversible inhibition due to noncovalent binding of small molecules, and irreversible inhibition, in which the inhibitory molecule forms a covalent bond in the enzyme active site. Malonate is a reversible inhibitor of succinate dehydrogenase The irreversible enzyme inhibitor diisopropylfluorophosphate (DFP) is a compound that forms a covalent link with reactive serine residues in proteases, such as chymotrypsin, and phospholipase enzymes.
What are considered first messengers?
First messengers are not all peptide hormones, some are lipids like steroids, and others are even smaller like nitric oxide, Ca2+, and CO2
What do G protein coupled receptors contain?
G protein-coupled receptors contain seven membrane-spanning regions and transmit extracellular signals across the plasma membrane through conformational changes. The intracellular component of GPCR-mediated signaling is the Gαβγ heterotrimeric protein complex which is co-localized to the plasma membrane with the GPCR. Ligand-initiated guanine-nucleotide exchange factor (GEF) function stimulates replacement of GDP in Gα with GTP; intrinsic GTPase activity in Gα is stimulated by interaction with GTPase-activating proteins (GAPs).
How is GPCR signaling terminated?
GPCR signaling is terminated by recycling the receptors through endocytic vesicles. βARK kinase and PKA phosphorylate serine and threonine residues in GPCRs to provide a binding site for β-arrestin.
What kind of pathways do glucagon and beta 2 adrenergic receptors share?
Glucagon and β2 adrenergic receptors activate a shared cAMP-mediated signaling pathway through Gsα whereas epinephrine binding to adrenergic receptors activates parallel pathways through Gsα and Gqα
Levels of diacylglycerol increase in a cell on binding of a ligand to a taste receptor. Which trimeric G protein subunit is most likely to be bound to GTP? Gqalpha Gtalpha Gbetagamma Gialpha
Gqalpha
What is GRB2 and what does it stimulate?
Growth factor receptor-bound 2 (GRB2) is an EGF receptor SH2 adaptor protein that binds phosphotyrosine (pY) residues that also contains a binding module called a Src kinase homology-3 (SH3) domain.
What are growth factors role in RTKs?
Growth factors bind to receptor tyrosine kinases (RTKs) encoding an intrinsic tyrosine kinase activity, which is activated by receptor dimerization and required for autophosphorylation and phosphorylation of target proteins
Which of the following is a GTPase? Gbeta Gsalpha Ggamma Gbeta
Gsalpha
What is the difference between a GEF and a GAP?
Guanine nucleotide exchange factor (GEF) proteins promote GDP-GTP exchange and activate signaling. GTPase activating proteins (GAPs) such as RGS2 stimulate the intrinsic GTPase activity of G proteins to inhibit signal transduction.
What is it called when hormones act at a distance as opposed to locally?
Hormones can act at a distance through endocrine mechanisms, or function locally as paracrine or autocrine signals
What is the molecular basis for cancer?
In many cases, the molecular basis of cancer is due to altered signaling pathways through DNA mutations in either cancer promoting genes or cancer inhibitory genes.
How can zygomens go from being inactive to active?
Inactive precursor proteins called zymogens are synthesized with an active site that is inaccessible to protein substrates. Removal of a 44-amino acid N-terminal segment of pepsinogen, the zymogen, generates the active form of the enzyme called pepsin .
How do insulin receptors activated PI-3K?
Insulin receptor signaling activates PI-3K through IRS adaptors, which initiates a pathway in liver cells that stimulates glucose uptake and glycogen synthesis.
What are the two pathways for insulin signaling?
Insulin signaling initiates two pathways: one that signals through Ras/MAPK signaling leading to cell growth and the other through PI-3K signaling leading to glucose uptake.
What is the response of Ligand binding to glucagon receptors or β2 adrenergic receptors in liver cells?
Ligand binding to glucagon receptors or β2 adrenergic receptors in liver cells stimulates Gsα signaling, which results in PKA signaling and three distinct metabolic responses leading to glucose export from liver
What is the response of Ligand binding to α1 adrenergic receptors in liver cells?
Ligand binding to α1 adrenergic receptors in liver cells stimulates signaling through Gqα, which activates the enzyme phospholipase C (PLC) and generates the 2nd messengers DAG and IP3 that lead to glucose export.
How does a GPCR produce a signal?
Ligand bound to the extracellular side of the the β2-adrenergic receptor causes conformational changes on the cytosolic side. The inactive Gαβγ complex contains GDP bound to the Gα subunit and associates with the liganded GPCR. Ligand bound GPCR induces a conformational change that stimulates GTP for GDP exchange in Gα. subunit dissociation and downstream signaling
What do ligand gated ion channels do?
Ligand-gated ion channels, control the flow of K+, Na+, and Ca2+ ions across cell membranes in response to ligand binding and represent the fifth most abundant class of receptor proteins in eukaryotes.
How are the 7 transmembrane regions of GPCR oriented?
Ligand-initiated guanine-nucleotide exchange factor (GEF) function stimulates replacement of GDP in Gα with GTP; intrinsic GTPase activity in Gα is stimulated by interaction with GTPase-activating proteins (GAPs).
What is necessary for loss of function mutations?
Loss-of-function mutations must occur in both gene copies to have an effect on cell function, and are more rare as a cause of cancer. One example is retinoblastoma cancer, which is due to inactivating mutations in the tumor suppressor retinoblastoma (Rb).
If protein kinase A is activated in a liver cell in response to glucagon binding to the beta2-adrenergic receptor, which of the following will result? Glucose synthesis will be turned off. None of these answers are correct. Glycogen degradation will be turned off. GLUT1 expression will be upregulated. Glycogen synthesis will be turned on
None of these answers are correct. turns off glycogen synthesis turns on glycogen degradation turns on glucose synthesis
Which of the following best defines substrate-level phosphorylation? None of these are correct. removal of a Pi from ATP indirect transfer of a Pi to glucose direct transfer of a Pi to an ATP indirect transfer of a Pi to an ATP
None of these are correct. Substrate-level phosphorylation is the synthesis of ATP in a reaction
What are mixed inhibitors?
Mixed inhibitors are similar to uncompetitive inhibitors in that they bind to sites distinct from the active site. The main difference is that mixed inhibitors can bind to both the enzyme and the enzyme-substrate complex.
What is the most common covalent modification of enzymes?
Most common covalent modification of enzymes is the phosphorylation of Ser, Thr, and Tyr residues by kinase enzymes, which add a negative charge to the enzyme through the addition of inorganic phosphate (PO32-).
Which mutations are associated with pancreatic cancers?
Nearly 80% of pancreatic cancers are associated with mutations at codon 12, primarily the missense mutations G12D, G12V, and G12R, all of which decrease the intrinsic GTPase activity of the oncogenic Ras protein
What is the effect of sildenafil?
Neuronal input leads to activation of nitric oxide synthase, which produces nitric oxide (NO) and elevated cGMP levels by guanylate cyclase. Sildenafil prolongs NO-mediated vasodilation by inhibiting the activity of cGMP phosphodiesterase
What type of signaling does neuronal transmission require?
Neuronal transmission by visual, olfactory, and gustatory cells requires GPCR-mediated signaling through specific Gα proteins that regulate intracellular levels of second messenger signaling molecules.
Glutamine synthetase is in the R state when Tyr397 is adenylated. phosphorylated. dephosphorylated. None of these answers are correct. uridylated.
None of these answers are correct. Adenylylated glutamine synthetase is in the inactive T-state conformation, and the deadenylylated form of GS is in the active R state conformation.
Which of the following is true of procaspase 8? It is a kinase. It can be activated by phophorylation. It is proteolytically active. It can cleave caspase 3. None of these answers are correct.
None of these answers are correct. Apoptotic Pathway 1. TNF receptor mediates the assembly of DD and DED protein complexes. 2. DD sequences recruit TRADD which recruits FADD (FADD has a DED domain that interacts with procaspase 8) 3. Procaspase 8 is auto-cleaved generating an active CASP8 4. CASP8 cleaves procaspase 3, generating a CASP3. 5. CASP3 cleaves cellular proteins and leads to cell death.
What are nuclear receptors and how do they invoke a physiological response?
Nuclear receptors are ligand activated transcription factors that control a wide range of physiological responses governed by 1) ligand bioavailability, 2) receptor expression, and 3) target DNA accessibility.
What is the Raf MEK ERK pathway?
Once activated by Src-mediated phosphorylation, Raf in turn phosphorylates serine residues on MEK, which activates its kinase activity so it can phosphorylate ERK. Phosphorylated ERK forms a homodimer that translocates to the nucleus, where it phosphorylates target proteins
What are the two pathways that insulin can activate and what do they each do?
One branch activates the MAPK pathway, leading to altered gene expression and cell division., and the other activates PI-3K and leads to increased glucose uptake and stimulation of glycogen synthesis
What happens in the PI-3K pathway?
Phosphatidylinositol-3 kinase (PI-3K) catalyzes the phosphorylation of phosphatidylinositol 4,5-bisphosphate (PIP2) to form phosphatidylinositol 3,4,5-trisphosphate (PIP3). PI-3K signaling is terminated by the phosphatase enzyme phosphatase and tensin homolog (PTEN).
Where are Phosphotyrosine binding (PTB) domains found?
Phosphotyrosine binding (PTB) domains are present in the insulin receptor adaptor proteins Shc and IRS-1
Which processes affect enzyme bioavailability?
Processes affecting enzyme bioavailability are RNA synthesis, processing, protein synthesis, protein degradation, and protein targeting.
How do protein-protein interactions mediate downstream signaling?
Protein-protein interactions mediate downstream signaling by recruiting proteins to the plasma membrane, one example the Tumor Necrosis Factor (TNF) signaling pathway.
What is the initiation step of a receptor tyrosine kinase?
Receptor Tyrosine Kinase (RTK) proteins autophosphorylate the cytoplasmic domain as an initiating step in a phosphorylation-mediated signaling cascade.
If you regulate an enzyme with proteolytic cleavage, what kind of process does that make it?
Regulation of enzyme activity by proteolytic cleavage is by its very nature an irreversible process.
What are the three classes of reversible inhibitors?
Reversible inhibition can be exploited as a strategy to develop structure-based pharmaceutical. There are three classes of reversible inhibitors: competitive inhibitors, uncompetitive inhibitors, and mixed inhibitors.
What is the structure of a rhodopsin protein?
Rhodopsin protein is a GPCR that detects light through a tightly bound retinal molecule located within a hydrophobic pocket formed by the seven transmembrane α helices.
What does signal transduction activate?
Signal transduction activates a receptor protein leading to the modification of intracellular target proteins, which control a variety of cellular responses.
What is a C3R3 complex?
Structure and organization of three ATCase dimers, each containing one catalytic subunit and one regulatory subunit, forming a C3R3 protein complex.
Which two pathways does TNF receptor initiate?
TNF Receptor signaling initiates two downstream pathways in cells; one leading to caspase-mediated cell death (apoptosis) and the other cell survival by inducing expression of genes that block caspase activation.
What are adaptor proteins in TNF receptor signaling?
TNF Receptor signaling is mediated by the assembly of adaptor protein complexes consisting of protein-protein interaction modules called death domains (DD) and death effector domains (DED).
How is the outcome of TNF receptor signaling pathways regulated?
TNF receptor signaling regulates opposing cell death and cell survival pathways, with the outcome being determined by the relative abundance of downstream signaling proteins.
What do SODD and TRADD do for TNF receptor signaling?
TNF-α binding induces a conformational change that promotes exchange of an inhibitory protein called silence of dead domain (SODD) for a downstream signaling protein called TNF receptor death domain (TRADD).
What does generating second messengers do?
The generation of second messengers by an upstream signaling protein results in signal amplification through the activation of one or more downstream target proteins.
How many different G alpha, beta and gamma genes are there?
The human genome contains 17 Gα, 5 Gβ, and 12 Gγ genes, which could result in the formation of almost 1000 different Gαβγ complexes that could lead to the regulation of distinct downstream pathways
What is an insulin receptor composed of?
The insulin receptor consists of an α2β2 tetrameric complex linked together by disulfide bonds. The α and β subunits are proteolytically processed from a single polypeptide chain
What are intracellular levels of DAG and IP3 controlled by?
The intracellular levels of diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) are controlled by the activity of a membrane-associated enzyme called phospholipase C (PLC)
What does PLC control & what happens when PLC is activated?
The intracellular levels of diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) are controlled by the activity of a membrane-associated enzyme called phospholipase C (PLC). Receptor-mediated activation of phospholipase C (PLC) leads to an increase in IP3 and DAG levels and stimulation of downstream signaling. DAG binds to and stimulates the activity of protein kinase C (PKC), which target proteins.
When PKA is inactive, which of the following is true? The regulatory subunits are bound by GTP. ATP is unable to bind the catalytic subunits. None of these answers are correct. The regulatory subunits are bound by cAMP. The pseudosubstrate of the PKA regulatory subunits is bound in the active site of the catalytic subunits.
The pseudosubstrate of the PKA regulatory subunits is bound in the active site of the catalytic subunits.
What characteristic is true for both RTKs and GPCRs? The receptor undergoes a conformational change on activation. The receptor transmits ions. None of these answers are correct. The receptor binds to intracellular proteins only when activated. When activated, the receptor has enzymatic activity.
The receptor undergoes a conformational change on activation.
What are the two major types of nuclear receptors and what do they bind?
There are two major types of nuclear receptors, 1) the steroid receptors that bind as homodimers to DNA sequences, and 2) metabolite receptors that bind as heterodimers to direct repeat DNA sequences.
What are three common receptor proteins?
Three common receptor protein types are receptor tyrosine kinases, nuclear receptors, and G protein-coupled receptors
An enzyme undergoes a mutation that causes it to lose the ability to be regulated via phosphorylation. Which of the following mutations may lead to this loss of regulation? Assume that the overall structure is not altered by the mutation. Ser -> Tyr Tyr -> Phe Ser -> Thr None of these answers are correct. Thr -> Ser
Tyr -> Phe polar -> nonpolar
How do uncompetitive inhibitors influence vmax and Km?
Uncompetitive inhibitors decrease both the vmax and apparent Km kinetic parameters by the same factor; uncompetitive inhibition is not overcome by increasing substrate concentration.
What links RTK to the G protein ras?
Upstream EGF receptor signaling involves adaptor proteins GRB2 and SOS. These proteins link the RTK to the G protein Ras that stimulates downstream signaling pathways and is related to the Gs family of proteins.
What happens to Km with increasing concentration of a competitive inhibitor?
With increasing concentration of a competitive inhibitor ([I]), the apparent Km of the enzyme increases, reflecting the requirement of higher substrate concentration to reach 1/2 vmax, however, not the vmax.
A ligand binds to a transmembrane protein. This causes a conformational change in the protein that is detected by an intracellular protein. The intracellular protein is an enzyme that adds phosphate groups to target proteins. The phosphorylated proteins cause a physiological change within the cell. This is an example of homeostasis. a signal transduction pathway. a metabolic pathway. chemotaxis. an allosteric inhibition pathway.
a signal transduction pathway.
A signaling pathway consists of five signaling proteins that mediate four signaling processes; A->B->C->D->E. Protein A is a receptor and protein E is a transcription factor. Proteins B, C, and D are kinases. a) What is the net level of amplification in the pathway if the first two processes amplify the signal 125-fold each, and the second two processes amplify the signal 250-fold each? b) What would the net amplification be in the pathway if the function of protein D was completely inhibited by a toxic compound? c) If elevated gene expression resulted in twice the amount of protein A, how many molecules of protein B would be activated by protein A under these conditions? a) ~1 x 10^8, b) ~16 x 10^3, c) ~3 x 10^2 a) ~1 x 10^8, b) ~32 x 10^3, c) ~150 a) ~5 x 10^8, b) ~16 x 10^3, c) ~30 x 10^2 a) ~1 x 10^-8, b) ~32 x 10^3, c) ~15 x 10^2 a) ~1 x 10^8, b) ~8 x 10^3, c) ~6 x 10^2
a) ~1 x 10^8, b) ~16 x 10^3, c) ~3 x 10^2
Which of the following is an energy conversion pathway? nitrogen fixation and assimilation citrate cycle fatty acid degradation and synthesis urea cycle gluconeogenesis
citrate cycle Aerobic metabolism: Pyruvate enters the mitochondria and goes through the citrate cycle and is expelled as waste as CO2 and H2O, but it powers oxidative phosphorylation and the production of ATP.
Which of the following list includes ONLY first messengers? insulin, glucagon, glucose nitric oxide, estradiol, heme cytochrome c, insulin, estrogen receptor cortisol, insulin, prostaglandins Ca2+, testosterone, protein kinase A
cortisol, insulin, prostaglandins
Caspase 3 is responsible for dephosphorylating FasL. activating caspase 8. phosphorylating Fas. None of these answers are correct. degrading key regulatory molecules.
degrading key regulatory molecules.
When compared with the T state of aspartate transcarbamoylase, the R state has dissociated into two C3R3 complexes. has greater separation of the catalytic subunits. None of these answers are correct. has substrate bound in the ATP binding site. is bound to CTP.
has greater separation of the catalytic subunits.
An estrogen-dependent breast cancer cell line is grown in a medium that contains estrogen. Cell proliferation is monitored over time. In a separate experiment, the cell line is grown in a medium that lacks estrogen but includes bisphenol A, a compound found in polycarbonate plastics. When monitored, cell proliferation is higher than in the presence of estrogen. A possible explanation of these results is that bisphenol A is an agonist of the estrogen receptor. is toxic to the cell line. it stimulates aquaporin function. inhibits the binding of estrogen to the estrogen receptor. inhibits adenylate cyclase.
is an agonist of the estrogen receptor.
Shared intermediates are used so effectively in coupled reactions because they decrease the value of Q. allow products to diffuse through membrane to increase concentration gradient. None of these answers are correct. limit product diffusion and allow intermediates to channel from one enzyme to the next. increase the value of deltaG'
limit product diffusion and allow intermediates to channel from one enzyme to the next.
Acetylcholine is a neurotransmitter that stimulates muscle contraction. Acetylcholine is acting as a(n) transcription factor. second messenger. autocrine signal. endocrine signal. paracrine signal.
paracrine signal.
If GRB2 were truncated so that the N-terminal domain was missing, the truncated protein would be unable to bind the phosphorylated Tyr of the SOS protein. protein-rich sequence of the RTK substrate. phosphorylated Tyr of the RTK substrate. proline-rich sequence of the SOS protein. active site of adenylate kinase.
proline-rich sequence of the SOS protein. GRB2 SH2 domain binds the pTyr and Asn containing sequences of the EGFR receptor. The GRB2 SH3 domain binds the Proline rich sequence of the SOS protein.
A mutation causes a cell to divide uncontrollably. Analysis of the cell shows that both copies of the gene must have the mutation. From this information, it can be determined that the mutation is in a gene coding a kinase. a missense mutation. dominant. recessive. in a tumor suppressor gene.
recessive.
Cyclic GMP is the __________ during vasodilation. second messenger phosphodiesterase activator of nitric oxide synthetase paracrine signal first messenger
second messenger
What is signal transduction?
signal transduction refers to the biochemical mechanism responsible for transmitting extracellular signals across the plasma membrane and throughout the cell.
On binding of an insulin molecule to the insulin receptor, a conformational change occurs that stimulates tyrosine autophosphorylation in the beta subunits. causes the dimerization of the receptor. brings the L1 region of the mc040-1.jpg subunit closer to the membrane. None of these answers are correct. increases the affinity of a second insulin binding site.
stimulates tyrosine autophosphorylation in the beta subunits. PTB domains on the insulin receptor proteins, on the adaptor protein Shc for the MAPK path, and IRS1 proteins for the PI-3K pathway. The tyrosine autophosphorylation leads to the recruitment and phosphorylation of substrates for both pathways
For the following reaction A→ B, if at equilibrium ∆G' > 0, what can be said about the directionality of the reaction? strongly favored in the forward direction Not enough information is given. strongly favored in the reverse direction strongly favored in both directions Too much information is given.
strongly favored in the reverse direction
What is the difference between the T and R state?
t is inactive and r is active?
