Diffusion Across a Cell Membrane. Diffusion is the movement of a substance across a membrane. Substances diffuse across cell membranes in a process known as passive transport. This means that the cell does not expend any energy in transporting substances across the cell membrane. Instead, substances move down their concentration gradient as a result of random thermal motion.
401k and profit sharing plans are both forms of retirement plans. They allow employees to make pre-tax contributions to an account where contributions and earnings are not taxed until distributed. Some 401k plans require an employer to make contributions to a plan.
Choosing a Retirement Plan: Profit-Sharing Plan. A profit-sharing plan accepts discretionary employer contributions. There is no set amount that the law requires you to contribute. If you can afford to make some amount of contributions to the plan for a particular year, you can do so. Other years, you do not need to make contributions. Also, your business does not need profits to make contributions to a profit-sharing plan.