Answer:
The cell membrane's main trait is its selective permeability, which means that it allows some substances to cross it easily, but not others. Small molecules that are nonpolar (have no charge) can cross the membrane easily through diffusion, but ions (charged molecules) and larger molecules typically cannot. A concentration gradient is a just a region of space over which the concentration of a substance changes, and substances will naturally move down their gradients, from an area of higher to an area of lower concentration.
In cells, some molecules can move down their concentration gradients by crossing the lipid portion of the membrane directly, while others must pass through membrane proteins in a process called facilitated diffusion.
Explanation:
there are your two reasons molecules cannot pass easily through the cell membrane and what part of the cell membrane helps them get through is concentration gradient
J.J. Thomson discovered the electron 1897
Answer:
its D Her speed is 4.4 m/s, and her velocity is 4.4 m/s.
Explanation:
i took the quiz
solution:
You need to find the frequency, and they have already given you the wavelength. And since you already know the speed of light, you can use formula (2) to answer this problem. Remember to convert the nano meters to meters because the speed of light is in meters. 
Answer:
LOL i belive its 200 because i did this exact same thing yesterday for homework and got it right so yeah, it should work. if it doesnt im sorry! but yeah XD sub to my yt channel too! DB_PLAYS <3
Explanation:
