Select the correct statement from the following regarding cell membrane:-
1) Lipids are arranged in a bilayer with polar heads towards the inner part
2) Na⁺ and K⁺ ions move across cell membrane by passive transport
3) Fluid mosaic model of cell membrane was proposed by singer and nicolson
4) Proteins make up 60 to 70% of the cell membrane
3) Fluid mosaic model of cell membrane was proposed by singer and nicolson