Carbohydrates provide structural support, in the form of cellulose in cell walls, for plants in addition to providing energy for the organism Proteins are essential for muscle tissue's growth and development as well as, in the form of hormones and hormonal regulation, maintaining an organism's homeostasis. Lipids make up the bilayer of cell membranes, and also aid hormonal signaling. Nucleic acids store genetic information, and allow for ribosomal protein synthesis.
Some molecules can move down their concentration gradients by crossing to the lipid portion of the membrane directly,while others must pass through membrane protein s in a process called Facilitated Diffusion
