Historical Examples. 1  It will be seen that the valves v on the other side of the annular chamber are closed. 2  The angle of the anterior chamber is a true angle and not an annular sinus. 3  Johnston suggests that the reference is to an annular eclipse which he finds occurred on August 14, at about 8Â¼ h. in the morning.
Cellular nutrients come in many forms, including sugars and fats. In order to provide a cell with energy, these molecules have to pass across the cell membrane, which functions as a barrier â but not an impassable one.
Like a city wall, it surrounds the cell and allows the cell to maintain its environment. The membrane is a barrier, but it allows important molecules to pass into and out of the cell, just as travellers can pass into and out of city gates. We can find proteins, lipids, and carbohydrates in the membrane. Carbohydrates help to protect the cell from the outside world.