I can tell you that amino acids are the building blocks for proteins, and I think mRNA is the transcription of DNA
Selective permeability, made possible in cells by the phospholipid bilayer that makes up the plasma membrane, is basically monitoring and regulating what can and can't enter the cell. It is carried out by a series of membrane proteins that act as channels to polar molecules, opening to allow them in and closing to prevent their entry. This is possible because the hydrophobic tails of the phospholipid molecules repel polar molecules and so prevent their entry unless through a channel.
As it gets colder, the molecules get less dense which causes it to get smaller.
A reflex is a built in operation that performs without orders from your mind.
A habit is something you as a person forms and we can train our minds to stop the habit.
