You recently identified a molecule that you believe is a primary messenger for a signal transduction mechanism. All you know about this ligand is that it is hydrophilic. Where would you expect to find initial interaction of the molecule with its receptor

Receptor on the outer cell surface.

Explanation:

Hydrophilic signal molecules are the water soluble molecules, they are polar polar and therefore cannot pass through the non-polar center of the plasma membrane without any mediator. Water-soluble ligands bind to the extracellular domain of cell surface receptors. Signal molecules cannot enter the cell and thus plasma membrane receptor is required. Plasma membrane receptor form an important class of integral membrane proteins that transmit signals from the extracellular space into the cytoplasm. This group of signal molecules is quite diverse and most are based on amino acids. In some cases the unmodified amino acid is the signal molecule, in others the amino acid is modified into a derivative and in still others amino acids are combined into peptides and proteins.

answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation:

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.