TS EAMCET Medical 9 May 2019 Shift 1 Paper

Which of the following statements are correct?
i) Shape of the receptor changes after attachment of chemical messenger.
ii) Receptor regains its shape after the removal of chemical messenger.
iii) Chemical messenger gives message to the cell by entering the cell.
iv) Binding of drug at allosteric site of enzyme does not change the shape of the active site.