41 Questions
What is the typical concentration range of hormones and other signals?
Nanomolar (10–9 mol/L) or picomolar (10–12 mol/L)
What is the purpose of multilayered signal transduction cascades?
To amplify the original signal
What is the role of the receptor in signal transduction?
Both signal transducer and signal amplifier
What is the product of the reaction catalyzed by adenylate cyclase?
cAMP
What is activated by cAMP?
Protein kinase A
What is the result of protein kinase A phosphorylating proteins?
Very large amplification
What is the reactant in the cyclization reaction catalyzed by adenylate cyclase?
ATP
What type of bond is formed in the cyclization reaction?
Phosphodiester bond
What happens to blood glucose levels when glycolysis is suppressed and gluconeogenesis is increased?
Increased
What is activated in the presence of light in the process of vision?
Rhodopsin
What is the effect of increased GMP levels on Na+ channels?
Closure
What is the role of phosphodiesterase in the phototransduction cascade?
Conversion of cGMP to GMP
What is the effect of hyperpolarization on neurotransmitter release?
Decreased release
What happens to the hormone-receptor complex after it forms?
It binds to certain segments of DNA
What is the outcome of the transmission of light impulses to the brain?
Visual interpretation
What happens to the Na+ channels in the dark state?
Opening
What is the result of transcription and translation of the hormone-receptor complex in the nucleus?
Protein synthesis
What is the outcome of the recovery of the rods and cones in the dark state?
Recovery into a passive, dark, and inactive state
What does KD represent in the kinetics of hormone-receptor binding?
The hormone concentration at which half of the receptors are filled
What is the characteristic of the upward slope of the hyperbolic curve?
First-order kinetics
What happens to the reaction at point C in the kinetics of hormone-receptor binding?
The reaction reaches saturation point
What is the relationship between Bmax and KD?
Bmax and KD are similar to Vmax and Km of simple enzymes
What is the function of receptors in hormone signaling?
To transmit signals from hormones
What type of protein are receptors in hormone signaling?
Transmembrane protein
What is the typical state of an Intrinsic Tyrosine Kinase Receptor (ITKR) in the absence of hormone binding?
Monomer
What event triggers the transfer of the γ-phosphate group from ATP via the ITKR activity?
Dimerization of the receptor
What is the role of phosphorylated tyrosine in the signaling pathway?
To serve as a docking site for the intracellular signal transducer or adaptor protein
What is the function of the Intrinsic Tyrosine Kinase Receptor (ITKR) in insulin signaling pathways?
To regulate glucose uptake
What is the structure of the insulin receptor?
Dimer
What is the result of tyrosine phosphorylation in insulin signaling pathways?
Recruitment of multiple adaptor proteins
What is the result of insulin binding to the ITKR?
Dimerization of the receptor
What is the function of SH2 domain-containing proteins in insulin signaling pathways?
To serve as intracellular signal transducers or adaptors
What is the composition of the insulin receptor in the membrane?
A preformed dimer with each half containing an α- and a β-subunit
What happens to the tyrosine residues in the cytoplasmic domain after insulin binding?
They undergo phosphorylation
What is the effect of autophosphorylation of β-subunits?
Activation of the receptor
What binds to the phosphotyrosines on the receptor?
IRS and SH2
What is the outcome of phosphorylation of tyrosine residues?
Activation of signal transduction
What is the final outcome of the signaling cascade initiated by insulin binding?
Activation of gene expression
What is the role of insulin receptor substrate (IRS)?
To activate insulin signaling
What is the location of the tyrosine kinase activity?
In the cytoplasmic domain
What is the effect of insulin binding to its receptor?
Dimerization and phosphorylation of tyrosine residues
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