Answer:
Tertiary.
Explanation:
Primary structure of proteins refers to the order of amino acids that make up the protein. The heme is an nonprotein non-amino acid, so it is not involved at this stage.
Tertiary structure of proteins is the overall 3-D folding of the protein (it comes after secondary, which involves folding into a repeated pattern). The heme bonds to its correct position on the hemoglobin during this stage and helps in correct folding.
The correct statements are:
•An NLS can be a monopartite or bipartite signal which includes a significant number of basic amino acids.
• The recycling of importins back to their original conformation requires GTP hydrolysis in the cytoplasm.
The other answers are incorrect because GTP is not required for an importin to bind to an NLS but for the release of importin and an NES or nuclear export signal is the sequence in a protein for export from the cell nucleus to the cytoplasm, not to the nucleolus.
The one which is responsible for transmitting an impulse across a synapse to another cell is the neurotransmitters. It allows the transmission of signals from one neuron to the next across synapses.
The correct answer among the choices is letter C.
