 |
| Sel diafragma (membran plasma) |
The cell membrane is a thin layer with a thickness of approximately 8 nm, which limits the contents of the cell with the surrounding environment. Cell membranes are selectivelypermeable or semipermeable because it can only be passed by ions, molecules, andcompounds. On human and animal cells, the cell membrane located in the outer part, while on the plant cell membrane the cell walls bounded. plasma membrane composed of lipid materials(phospholipids), proteins and carbohydrates.
Model of cell membrane structure was conceived by j. g. Singer and Nicolson in 1972, calledfluid mosaic. Fluid mosaic model States that a plasma membrane is dynamic because molecules of lipids and proteins constituting can move like liquid (fluid). Plasma membrane is composed of two layers (a bilayer) phospholipids, and Phospholipid bilayer fluid matrix on the spread of many types of proteins (e.g. on the plasma membrane of red blood cells there are over 50 types of protein). One unit consists of phospholipids
A. the head of Phosphate on the surface of membrane, which are hydrophilic or water-like
B. fatty acids in the tail section, which was hidden inside the membrane, and is hydrophilic ordon't like water.
On the basis of place, membrane proteins can be distinguished into two types namely
A. integral Proteins (intrinsic), embedded between the bilayer phospholipids. Integral proteinshave an outer membrane on both sides which are hydrophilic and the inside that is hydrophobic
B. peripheral Proteins (extrinsic), loosely bound on the surface of membranes or proteins single
Lipid and protein composition between inner and outer side of the side of the membrane areasymmetrical (not the same). On the surface membrane there are carbohydrates in the form ofoligosakarida. Oligosakarida lipid with covalently bonded, later called glycolipids, whereasoligosakarida bound by proteins called glycoproteins. Molecular diversity and location of cellmembrane surface can oligosakarida functioning as a marker, for instance blood type A, B, ABand O have ologisakarida on the surface of red blood cells (erythrocytes)
The function of the cell membrane is as follows
A. controlling the entry and discharge of substances out of or into the cell
B. as a patron for content of the cell is not out
C. as a receptor (receive stimuli) from outside the cell
0 Comment:
Posting Komentar