biologue zone

  Fluid mosaic model The currently accepted model for the structure of the plasma membrane, called the  fluid mosaic model , was first proposed in 1972. This model has evolved over time, but it still provides a good basic description of the structure and behaviour of membranes in many cells. According to the fluid mosaic model, the plasma membrane is a mosaic of components—primarily, phospholipids, cholesterol, and proteins—that move freely and fluidly in the plane of the membrane. In other words, a diagram of the membrane (like the one below) is just a snapshot of a dynamic process in which phospholipids and proteins are continually sliding past one another. Interestingly enough, this fluidity means that if you insert a very fine needle into a cell, the membrane will simply part to flow around the needle; once the needle is removed, the membrane will flow back together seamlessly. Image of the plasma membrane, showing the phospholipid bilayer with peripheral and int...

  Mitochondria Definition ·        Mitochondria are oxygen-consuming ribbon-shaped cellular organelles of immense importance floating free throughout the cell. ·        They are known as the “powerhouse of the cell” since these organelles supply all the necessary biological energy to the cell by oxidizing the substrates available. ·        The enzymatic oxidation of chemical compounds in the mitochondria releases energy.  ·        Since mitochondria act as the power-houses, they are abundantly found on those sites where energy is earnestly required such as sperm tail, muscle cell, liver cell (up to 1600 mitochondria), microvilli, oocyte (more than 300,000 mitochondria), etc. ·        Typically, there are about 2000 mitochondria per cell, representing around 25% of the cell volume. ·      ...