| A | B |
|---|
| selectively permeable | some substances can pass through the membrane while others cannot |
| diffusion | main method by which small molecules move across the cell membrane from a high concentration to an area of low concentration |
| osmosis | the diffusion of water molecules though a selectively permeable membrane |
| passive transport | movement of dissolved materials through a cell membrane without using cellular energy |
| active transport | movement of materials through a cell membrane using cellular energy |
| element | any substance that cannot be broken down into simpler substances |
| compound | when 2 or more elements combine chemically |
| carbohydrate | an energy-rich organic compound made of the elements, carbon, hydrogen, and oxygen |
| lipids | Fats, oils, and waxes |
| proteins | large organic molecules made of carbon, hydrogen, oxygen, nitrogen, and , in some cases, sulfur |
| amino acids | small molecule that is linked chemically to other amino acids to form proteins |
| enzyme | type of protein that speeds up a chemical reaction in a living thing |
| nucleic acids | very long organic molecules made of carbon, hydrogen, nitrogen, and phosphorus |
| DNA | genetic material that carries information about an organism and is passed from parent to offspring |
| RNA | plays an importnat role in the production of proteins |
