Choose the statement that describes processes of receptor-mediated endocytosis, exocytosis, and the changes in the membrane organization.

a. endocytosis involves the opsonization of a receptor and its ligand in clathrin-coated vesicles, along with the inward budding of the plasma membrane. in exocytosis, waste material is enveloped in a membrane that fuses with the interior of the plasma membrane via attachment proteins.

b. in endocytosis, waste material is enveloped in a membrane that fuses with the interior of the plasma membrane via attachment proteins. exocytosis involves the opsonization of the receptor and its ligand in a clathrin-coated vesicles.

c. in endocytosis, waste material is enveloped in a membrane that fuses with the interior of the plasma membrane via attachment proteins. exocytosis involves the opsonization of the receptor and its ligand in caveolae-coated vesicles.

d. endocytosis involves the opsonization of the receptor and its ligand in clathrin-coated vesicles. in exocytosis, waste material is enveloped in a membrane that fuses with the exterior of the plasma membrane via attachment proteins.

a. Endocytosis involves the opsonization of a receptor and its ligand in clathrin-coated vesicles, along with the inward budding of the plasma membrane. In exocytosis, waste material is enveloped in a membrane that fuses with the interior of the plasma membrane via attachment proteins.

Explanation:

Endocytosis: entails the external binding of a ligand to its receptor which is located on the external side of the plasma membrane. The membrane buds inwardly for internalization to occur.

Exocytosis: material that has been processed inside the cell is transported by vesicles which fuse to the internal side of the plasma membrane and ultimately transported to the outside of the cell.

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.