An example of force that acts at distance is gravity and an example of contact force is pushing a chair across the room
The number of protons in a neutral atom equals the number of ELECTRONS.
A relatively large molecule that has an electrical charge associated with it, regardless if it is full charge or partial. Would require facilitated diffusion to enter a cell.
Eg - complex sugars, or disaccharides - fructose, or amino acids, ions - Na + or Ca +.
