G protein‑coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) are two basic receptor types by which cells transduce signals. Classify each statement as describing GPCRs, RTKs, both types of receptors, or neither.

1) phosphorylation of receptor can terminate signal or desensitize receptor
2) autophosphorylation of receptor can initiate signal
3) structure contains seven transmembrane helices
4) ligand binding induces conformational change in receptor
5) receptor activation causes phosphorylation of its cytosolic subunits
6) an example is the insulin receptor
7) transports some ligands through the membrane
8) an example is the epinephrine receptor
9) activate heterotrimeric G proteins directly

Explanation:

1) Phosphorylation of receptor can terminate signal or desensitize receptor: GPCRs because when signal persists a protein kinase receptor is activated,this further catalyse the phosphorylation of several serine residue at cytosolic phase of 7 transmembrane

Phosphorylated transmembrane recognized by arrestin protein blocks interaction between trimeric G protein and receptor thus blocks signal transduction

2) Autophosphorylation of receptor can initiate signal: RTKs because receptor dimerization activates intrinsic tyrosine kinase activity by which they phosphorylate its own tyrosine residue on cytosolic phase

3) Structure contains seven transmembrane helices: GPCRs because it consists of single polypeptide and spans the membrane 7 times hence called 7 transmembrane;it recognizes external signal and activates trimeric G protein

4) Ligand binding induces conformational change in receptor: RTKs because normally RTK exist in monomeric form in absence of any ligand molecule but when any ligand molecule binds receptor starts to dimerize

5) Receptor activation causes phosphorylation of its cytosolic subunits: RTKs because when receptor gets activates the intrinsic tyrosine kinase activity by which they phosphorylate its cytosolic subunits

6) An example is the insulin receptor: Insulin receptor is present on plasma membrane and belongs to RTK family and always exist in dimeric form

7) Transports some ligands through the membrane: Neither GPCR nor RTK;ligand gets transported through the membrane through ligand gated channel

8) An example is the epinephrine receptor: Epinephrine is an endocrine  hormone produced by adrenal glands in stress condition and prepare body for fight and flight;Epinephrine uses GPCR signalling pathway by four different types of membrane receptors in different tissues

9) Activate heterotrimeric G proteins directly: Transmembrane protein of GPCR recognizes the external signal and activates G protein,activated G protein binds with effector enzyme and activate it which further produce or destroy secondary messenger that carry message from cell surface to cell interior

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transcription is a process in which information is rewritten. it is something our cells must do, in a more specialized and narrowly defined way. in biology, transcription is the process of copying out the dna sequence of a gene in the similar alphabet of rna. it needs to happen in the nucleus because that's where the dna is. dna is always inside the nucleus unless the cell is dividing.

transcription is the first step in gene expression, which involves copying a gene's dna sequence to make an rna molecule. transcription is performed by rna polymerases. it has three stages: initiation, elongation, and termination. rna molecules must be processed after transcription in eukaryotes.

explanation:

long version:

the protein synthesis consists two processes which are, transcription and translation. transcription takes place in the nucleus. it uses dna as a template to make an rna molecule. rna then leaves the nucleus and goes to a ribosome in the cytoplasm, where translation occurs. transcription is the first part of the central dogma of molecular biology: dna → rna. it is the transfer of genetic instructions in dna to messenger rna (mrna). during transcription, a strand of mrna is made that is complementary to a strand of dna.  

these three stages are:

  initiation: in which   is the beginning of transcription.occuring 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.

    elongation: in which 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.

    termination: in which 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.