Plasma membrane structure

CHAPTER I
INTRODUCTION
A. Background

Cell is the smallest fraction of an individual, who control all our activities. Cell has a very large role in our lives. Therefore, the cell will function well if all their needs fulfilled.
Cell has several bagia-part in it, one of which is the plasma membrane. Plasma membrane is one part of the cell serves to protect the cell nucleus and cytoplasm. Wrap the plasma membrane organelles in the cell plasma membrane transport is also a place for the cell, where the turnover of materials needed and not needed by cells to berreproduksi.
Plasma membrane itself is made up of fat and protein, plasma membrane thick approximately ± 8μm. Plasma membrane which has selective permeability, this membrane allows some substances can cross it easily than other substances.
Anatara cell membrane function to protect the contents of other cells, the cell membrane to maintain the contents befungsi regulate cell traffic molecules, the plasma membrane is selectively permeable means there are certain substances that can pass through membranes and some are not. The molecules are useful to maintain the life of the cell; as receptor stimulation from outside the cell, the stimulation of chemical substances such as hormones, poisons, electrical stimulation, and stimulation of cells mekanik.Bagian that serves as the receptor glycoprotein.



B. Problem formulation
1. Is that the plasma membrane?
2. How does the plasma membrane to work or function of the plasma membrane?
3. What are the transportation system contained in the plasma membrane?
4. What is passive transport and active transport it?
5.


C. Purpose
1.Untuk know the relationship between the plasma membrane function and structure of the plasma membrane.
Meet the prerequisites 2.Untuk UTS General Biology courses
D. Benefits
We get benefits after making this paper is the sense of our increasingly intertwined persaudaran stronger, we also know how important the cell membrane or plasma membrane of the cells in our bodies. Where the function of the plasma membrane itself is set up to maintain the contents of the cell traffic molecules, the plasma membrane is selectively permeable means there are certain substances that can pass through membranes and some are not.












Chapter II
Plasma Membrane Structure

A. Definition Plasma Membrane

Plasma membrane is the boundary of life, the boundaries separating the living from the surrounding cells that die. Thin layer of this extraordinary thickness of about ± 8μm. The task is to control the plasma membrane traffic in and out of cells dikelilinginya. Like a biological membrane, the plasma membrane which has selective permeability, this membrane allows some substances can cross it easily than other substances.
(Figure 1.1)

In 1972, Singer and E. S Nicolson says that the membrane is composed of layers of protein. Proteins are dispersed and each tersisip or lost in the double layer of phospholipids (phospholipid bilayer). Etrsisip protein between phospholipid bilayer proteins called ekstrinsk (peripheral). Peripheral proteins are hydrophilic, or draw water. Protein lost in the phospholipid bilayer protein called intrinsic (integral). These proteins are hydrophobic or reject water.



(Figure 1.2)

B. Plasma Membrane Structure

In 1925 Gortel & Grendel (1925) says that should be a phospholipid membrane bilayer. Gortel & Grendel measuring phospholipid content of membranes isolated from red blood cells and the amount of lipid found only enough to cover with two layers of cells.
(Figure 1.3)

(Figure 1.4)
If we assume that the phospholipid bilayer membrane is the main constituent, where we put the protein? Although the head of a phospholipid is hydrophilic, the surface of an artificial membrane composed of phospholipid bilayer attached less strongly to water than the actual biological membrane attachment. Davson & Danielli (1954) proposed a model of a sandwich, a phospholipid bilayer between two layers of globular proteins.
(Figure 1.5)

Phospholipids move through the membrane field quickly, about the size of 2μm length bacterial cells per second. Much larger protein than lipid and move more slowly, but some membrane proteins actually move. Part of membrane proteins and moves in a very directed, may be moved along the fibers of Cytoskeleton by motor proteins associated with the end sitosplasmik membrane.
A membrane remains fluid as the temperature of concrete falls, until finally at the critical temperature of phospholipid composition of sediment in a tight and frozen membrane.


(Figure 1.6)
Cholesterol is a steroid that was wedged between phospholipid molecules in the plasma membrane of animal help stabilize the membrane. At relatively warm temperatures at 37 ° C, cholesterol makes the membrane less fluid is by controlling the movement of phospholipids.
(Figure 1.7)

Integral protein is generally a transmembrane protein, with hydrophobic regions that stretched all the hydrophobic interior. Integral protein hydrophobic region consists of one or more non-polar stretch of amino acids which are usually rolled into the helix. Peripheral protein was not embedded in the lipid bilayer, this protein is a member of a loosely bound to the surface membrane.

(Figure 1.8)







C. Carbohydrates in Membrane

Introduction of cells is done by giving the key to the molecular surface. These molecules are often in the form of carbohydrates in the plasma membrane. Carbohydrates membrane usually branched oligosaccharide with less than 15 units of sugar. Some of the oligosaccharide is covalently bound to the lipid to form glycolipids. Most of the oligosaccharide is covalently bound to proteins and are called glycoproteins.
Maintain cell membrane components of the cell remained isolated from the outside environment. Cell membrane also serves as a medium of communication between the cells with the environment. Biological membrane organelles limit. In the cell, endoplasmic reticulum, Golgi, lysosomes, vesicles and vacuoles surrounded by a single biological membrane. Mitochondria and the nucleus is surrounded by two layers of membrane. Cell membrane are involved in regulating the flow of materials into and out of cells and mediate intercellular communication, adhesion and other functions.
Cell membrane is permeable to ions and polar molecules specific. Hydrophilic substance to avoid contact with the lipid bilayer by passing the protein across the membrane transport. Some functions of membrane proteins is (Campbell et al., 2000):
Membrane 1.Protein stretching hidofilik provide a channel through the membrane that is selective for a particular solute. ATP hydrolysis by several transport proteins to pump substances across the membrane actively.
2.Protein inside membrane may be an enzyme with its active side exposed to the substances in the solution side.
3.Protein membrane may have a binding site with a specific form according to the mesenjer forms of chemical, such as hormone. Signal can cause a protein conformational change that channel message to the inside of the cell.
4.Protein membranes of adjacent cells may be linked together in various forms of junctions.
5.Beberapa glycoprotein functions as identification labels that specifically recognized by other cells.
6.Mikrofilamen Cytoskeleton or other elements may be bound to the membrane proteins. This is a function that helps memperahankan cell shape and determine the location of certain membrane proteins. Protein closer to the extracellular matrix may coordinate extracellular and intracellular changes.
Diffusion is an event due to thermal motion. Thermal motion is the kinetic energy possessed intrinsic molecules. In the diffusion in the absence of other forces, a substance will diffuse from high concentration to lower concentration. Every substance will diffuse down the concentration gradient. Events desebut diffusion passive transport, because the cells do not have to spend energy. Concentration gradient itself is the direct potential energy diffusion.
Hypertonic solution is a solution with solute concentration is higher. While a solution with lower solute is hypotonic. Solution with the concentration of the same solute is called isotonic. Diffusion of water across selectively permeable membrane is an event of osmosis. Water diffuses through the membrane from hypotonic solution to hypertonic solution.
Some transport proteins can move solutes against their concentration gradient across the plasma membrane from one side of a concentration of less terlarutnya to the concentration of the higher terlarutnya. This process is in need enrgi called active transport.
Work done by the active transport of specific proteins that are embedded in the membrane. ATP provides energy for most active transport. ATP terminal phosphate transfer directly to the transport protein. This causes the protein to be konformasinya change mentranslokasikan a solute that is bound to proteins across membranes.





CHAPTER III
Plasma Membrane Functions

A. Plasma Membrane Function

Plasma membrane is very important unuk maintain cell life. Anatara cell membrane function to protect the contents of other cells, the cell membrane to maintain the contents befungsi regulate cell traffic molecules, the plasma membrane is selectively permeable means there are certain substances that can pass through membranes and some are not. The molecules are useful to maintain the life of the cell; as receptor stimulation from outside the cell, the stimulation of chemical substances such as hormones, poisons, electrical stimulation, and stimulation of cells mekanik.Bagian that serves as the receptor glycoprotein.
A soft traffic of small molecules and ions move across the plasma membrane in both directions. Note the chemical exchange between the muscle cells with extracellular fluid is soaked. Sugars, amino acids and other nutrients into the cell, and metabolic waste products leave the cell. Cells absorb oxygen for cellular respiration and remove carbon dioxide. The cell was also set anorganiknya ion concentration, such as Na +, K +, Ca2 +, and Cl-, by turning him from one direction to another direction across the plasma membrane. Although the traffic through this dense membrane, the cell membrane selectively permeable, and the substances can not cross these obstacles arbitrarily. These cells can take a variety of small molecules and ions and reject others. In addition, the substances move across the membrane at a speed different.




B. Traffic Across Membranes which

Biological membrane is a perfect example of Supramolecular structures are organized into levels of higher organization with new properties that appear over the properties of individual molecules.
A traffic consisting of small molecules and ions that move across the plasma membrane in both directions. Sugars, amino acids and other nutrients into the cell, and metabolic waste products leave the cell. Although this traffic through a solid membrane, the cell membrane selectively permeable, and the substances can not be crossed these obstacles arbitrarily. In addition, the substances move across the membrane at a speed different.
Lipid Bilayer permeability
Hydrophobic core of membrane transport of ions and blocking polar molecules that are hydrophilic. Hydrophobic molecules, such as hydrocarbons, carbon dioxide, and oxygen can be dissolved in the membrane and cross it with ease. Lipid Bilayer not very permeable to uncharged polar molecules larger, such as glucose and other sugars. Bilayer is also relatively non-permeable to all ions, although small ions such as H and Na.
Protein Transport
Cell membrane is permeable to ions and polar molecules specific. Hydrophilic substance to avoid contact with the lipid bilayer with transport proteins through the membentangi (across) the membrane. A number of transport protein function that has a hydrophilic channel that is used by certain molecules to pass through the membrane. As for other transport proteins that bind the compounds and physically carried him across the membrane menggerakannya.





(Figure 2.1)


Cell membranes are semipermeable, which controls the movement of materials to and from outside the cell. Transport through the cell membrane can be divided into two types, namely passive transport and active transport.
Passive transport
Passive transport is the transport that does not require energy occurs because of differences in concentration between the solution with a solution of one another. Passive transport are divided into two kinds, namely diffusion and osmosis.
Diffusion is the movement of a substance from a highly concentrated solution (hypertonic) to solutions that have a low concentration (hypotonic) so that its concentration becomes equal or balanced.
(Figure 2.2)

While osmosis is the movement of water from the solutions that have low concentrations (hipotonis) to a solution that has a high concentration (hipertonis) through a semipermeable membrane. Osmotis pressure is the pressure needed to prevent the water moves through a semipermeable membrane, osmotis pressure contained in a solution called osmotis potential.
Active Transport
Active transport is the opposite of passive transport and is not spontaneous. Direction of the displacement of this transport against a concentration gradient. Active transport requires the help of several proteins, examples of proteins involved in active transport include carrier proteins and channel proteins, as well as ionophore.
Which include active transport is coupled carrier, ATP driven pumps, and light driven pumps. In using coupled active transport carriers known two terms, namely simporter and antiporter. Simporter are proteins that transport both in the same direction subtrat, seadangkan antiporter second subtrat transfer in the opposite direction.

C. Eksositosis and endocytosis transport large molecules

Water and solute entering and leaving the cell by crossing the plasma membrane lipid bilayer, or with pumped or transported across the membrane by a protein transport. Large molecules such as proteins and polysaccharides, generally across the membrane by different mechanisms involving vasikula. Tues secrete macromolecules vasikula by combining with the plasma membrane, is called eksositosis. Transport vesicles are separated from the Golgi apparatus was moved by the Cytoskeleton to the plasma membrane. When the membrane vesicles and the plasma membrane meet, the second lipid bilayer molecules rearrange themselves so that the two membranes joined. Gynecology vesikulanya then spilled out of the cell.
In endocytosis, macromolecules enter the cell and a very small matter in a way mambentuk new vesicles from the plasma membrane. A small portion of plasma membrane area sank into a bag shape. Once more in this bag, the bag is squeezed, forming vesicles that contain material that has been found outside the cell.
There are three types of endocytosis: phagocytosis (pemakanan mobile (cellular eating)), pinositosis (potation mobile (cellular drinking)), and receptor-mediated endocytosis.
In phagocytosis, cells swallowing a particle with a pseudopod wrapped around these particles and wrapped in a padded bag-membrane large enough to be classified as a vacuole bias.
These particles digested after joining the lysosome vacuoles containing hydrolytic enzymes. In pinositosis, cell "sipping" extracellular fluid droplets in small vesicles. Because one or all of the solute dissolved in the droplets is inserted into the cell, non-specific pinositosis in ditranspornya substance. In contrast, receptor-mediated endocytosis is very specific. Which is embedded in the membrane is a protein with a specific receptor exposed to the extracellular fluid. Bound to extracellular receptors called ligand, a general term for any molecule that bound specifically to the receptor molecule where else. Receptor protein are usually clustered in membrane regions called coated membrane, which side is coated by a layer sitoplasmiknya Samara proteins. These coating proteins may help to deepen the hole and form vesicles.
Receptor-mediated endocytosis allows cells to acquire specific substance in a number of abundant, though iu substance may not be high concentration in the extracellular fluid. Vesicles not only transports the substance between the cell and its surroundings, these vesicles also provides a mechanism for memudakan and reshape the plasma membrane. Endocytosis and continuously eksositosis occur to some degree in most eukaryotic cells, but the amount of plasma membrane in cells that do not grow rather constant for a long time. Presumably, penembahan membrane by a process of membrane loss offset by other processes.
Pinositosis movement is brought into fluid materials, in particular extracellular fluid. First time, the plasma membrane to form a curve in a region in the membrane layer. This curve becomes more profound, and eventually will form a curve that contains fluid vesicles. Through this vesicle fluid ekstrseluler brought into the cell.

D. Relationship Between Plasma Membrane Function in Plasma Membrane Structure

Cell membrane is often also called the plasma membrane. Cell membrane is the outer part that limits the content of the surrounding cells (except in plant cells, there are outer cell wall or cell wall).
Cell membrane of a thin layer of remarkable. Thickness of about 8 nm. 8000 needed to match the cell membrane of the thick paper that we usually use to write.
Lipid and protein is the main constituent material of the membrane, although carbohydrates are also important elements. Combined lipids and proteins called lipoproteins. We have an acceptable model for the preparation of molecules in a membrane-molekultersebut is the fluid mosaic model.
Cell membrane is not a rigid sheet or silent and tied in place or solid mosaic. However, the cell membrane is a fluid membrane structure or the fluid mosaic mosaic, which is a model that has a membrane constituent molecules are constantly moving and has a varied constituent molecules and randomly arranged, such as carbohydrates, lipids, and proteins.
Fluid nature of membranes can be made to work and perform its function properly. Cell membrane is fluid because the activities of the movement of constituent molecules. The molecules on the membrane (primarily phospholipid) in constant motion and move randomly. Phospholipids move with high speed, whereas proteins larger move slowly. Lipids move laterally or laterally in two dimensions on a membrane. This movement often occur. Another form of movement with the movement of exchange places in three dimensions, but such movement is rare. Movement of proteins that often happens is that the rotational and lateral diffusion.
Membrane fluidity can be maintained at low temperature with the unsaturated phospholipid because it has a tangled structure of lipids that phospholipids are not easily freeze. cholesterol between phospholipid molecules in the plasma membrane and helps stabilize the membrane. In warm temperatures, cholesterol makes the membrane is less fluid. Besides cholesterol also inhibit the cell membrane in freezing low temperatures.
Not only the cell membrane composed of lipids, but there are other molecules, including proteins and carbohydrates. Composition of lipids, proteins and carbohydrates are scattered and random, so that the plasma membrane are said to be mosaic. Membrane protein consists of two main types namely, integral proteins embedded in a double layer of phospholipids and peripheral protein embedded in phospholipid layer or attached to the integral proteins, as well as trans-membrane proteins across membranes. Carbohydrate molecules found in the form of glycolipids (covalent bond between the oligosaccharide with lipid) and glycoproteins.
1.Sistem Endomembran
Endomembran system is in the membrane system (membrane surrounding the organelles) found in the cell and continuous (connected) to one another. Membranes that are covered endomembran system connected through a direct physical connection or through a transfer through the vesicle membrane segments or vesicles (small bubble-wrapped membrane). Endomembran system (the membrane system) only found in eukaryotic cells. Endomembran system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, various types of vacuoles and the plasma membrane.
Membrane Function 1.Kontinuitas and Endomembran
Between the membrane and interconnected endomembran (continuous) to perform a function, one of which is the product or macromolecule secretion out of cells through the relationship between the organelles with the plasma membrane. The process is as follows:
5 mins: Product or sekretori proteins contained in the endoplasmic reticulum endomembran line will pass through from the cell through several other endomembran organelles. The first time, the product will go through a rough endoplasmic reticulum to the Golgi complex. Products to the Golgi complex with the help of transport vesicles. After reaching the Golgi complex, the product will be forwarded to the outside of the cell by transport vesicles.
20 mins: Products derived from the Golgi complex, more and more transported by vesicles. In the picture, there are about 3 that have been filled vesicles to be secreted products from the cell.
40 mins: Products of vesicles around Golgi gradually transported via other vesicles to the plasma membrane. When the membrane vesicles with the plasma membrane meet, phospholipid molecules in a double layer of membrane rearrange membrane structure so that the two membranes together. As a result there are products that will be spilled in the vesicles from the cell.









CHAPTER IV
CLOSING
A. Conclusion
Plasma membrane or cell membrane is composed of fat and protein molecules. Fat molecule consists of two layers are located in the middle of the membrane. On the exterior there is a layer of peripheral proteins (protein bank), which make up the outer and inner membrane. In addition to peripheral proteins, there are also molecules of a certain protein that comes into the layer of fat. There are even coming up through two layers of fat. Protein into the fat layer is called the integral proteins. In certain places are limited pore formed by protein molecules. Thickness ranges from the plasma membrane 5-10nm.
Protein and fat molecules that are not static, but constantly moving. Fat molecule can be imagined as a "liquid" is on top and inside the protein molecule that "swimming-pool". That's why such a membrane structure called the "fluid mosaic".
Fats are composed of membrane phospholipids (fatty bersenyawa with phosphate), glycolipids (bersenyawa fats with carbohydrates), and sterols (bersenyawa fat and cholesterol). While membrane proteins composed of glycoproteins (proteins with carbohydrate bersenyawa).



B. SUGGESTIONS

The cell membrane or plasma membrane is an important role in the lives of us all, because the cell membrane serves to protect all the organelles within the cell. If there is one that damaged cells then other cells will berreproduksi to replace these damaged cells.
Take care of health is one way to keep cells healthy and working well. If the cell membrane or plasma membrane of a cell is damaged then the cells also were damaged, it is because there is nothing to protect the organelles inside the cell if the plasma membrane is damaged.



Bibliography

Campbell, 2002. Biology. Translations, the fifth edition. Publisher.

http://www.information-centre-dhyayi.blogspot.com / 200710membran-plasma.html, October 26, 2007.

Dwisang, Luvina Evi, 2007. Inti Sari Biology. Publisher Scientific Press. Ciputat. Tangerang.