Superior Creation in The Structure of The Cell Membrane
The cell membrane is a thin, elastic structure surrounding the cell. It is just a few molecules thick: 7.5 to 10 nanometers (a nanometer is 1 billionth of a meter). To obtain the thickness of a piece of paper, you would have to place more than 10,000 cell membranes one atop the other. Basically, the membrane is a border protecting the cell from the outside, but it also possesses very many complex features and duties that scientists have still not discovered.
The microbiologist Professor Michael Denton refers to these duties in one of his books:
Cell membranes are vitally important in holding cells together to form tissue in multi-celled organisms. Together with interior membranes surrounding the many organelles within the cell, the overall cell membrane can be likened to the exterior walls surrounding the rooms in a house. Though it separates the cell's protoplasm from the external environment, the membrane is not completely impermeable, but functions as an exceptionally sensitive control mechanism, allowing suitable substances to enter and leave, while preventing others from entering. For instance, it admits food substances and expels waste products. In addition it transmits chemical and electrical signals that induce the cell to produce proteins or else to divide in two. Therefore, the cell membrane is one of the most vital organelles of the cell.
The Cell's Security Line: The Cell Membrane
The cell membrane separates the cell from the external environment, taking in those molecules that the cell requires and expelling those that need to be removed, without wasting any time.
Think of the cell membrane as the surrounding wall that protects a building with the tightest security measures. At all the doorways, special guards are able to recognize everything within the structure and identify those coming from the outside. Everything must enter or leave through these checkpoints. Only those which need to enter the building are allowed in, and those that need to leave are permitted to depart. But the selection in the cell membrane is not fixed and mechanical, but is a very complex process that alters in accordance with conditions.
The evolutionist biologist Hoimar von Ditfurth refers to this selection mechanism with great amazement:
That such a delicate structure, invisible to the naked eye, should possess such a selection mechanism cannot be accounted for in terms of blind coincidences. The cell's selection mechanism, which we shall detail in later chapters, requires intelligence and awareness. It is certainly impossible for cells to feel such a responsibility of their own accord, to decide what is necessary and what is harmful for the body, and to perform this function flawlessly. Anyone looking at the cell membrane with an open mind will see, as in every point in the universe, the inspiration and dominion of Allah.
The Cell Membrane's Special Structure
Its unique structure enables the membrane surrounding the cell to carry out so many important functions. The membrane consists of fat, protein and carbohydrates, and the fat layer has a most important function. Because the cell as a whole is like a mechanism that has to operate underwater, the cell's very survival depends on the membrane not permitting water to pass through in either direction. At the same time, the water required by the cell—which itself consists of 70% water—must be able to enter and leave. The phospholipid molecule is created especially for this purpose. One end of it is hydrophilic—that is, it attracts water—while the other end of it (being hydrophobic), repels it.
The fatty layer making up the greater part of the cell membrane consists of these special phospholipids molecules. The phosphate end attracts water molecules and holds onto them, while the fat end is hydrophobic. As this structure forms, the hydrophilic phosphate groups turn themselves towards water, and the hydrocarbon chain distances itself from water because of its hydrophobic property. As a result, the phospholipid molecules string themselves together to form a cell membrane in which the hydrophilic phosphate sections face the inner and outer surfaces of the membrane. To put it another way, the phospholipids bind to one another end-to-end and form a double-layered membrane. The hydrophilic ends face both the water-based cytoplasm inside the cell and the liquid between the other water-based cells outside. The hydrophobic "tails" are squeezed between the hydrophobic surfaces of the cell membrane.
This arrangement is most important, because the phosphate parts of the phospholipids being on the outside makes the passage of water possible, one of the cell's basic needs. Were the phosphate parts on the inside, the hydrophobic lipids would repel the water, which would be unable to contact the membrane and enter the cell. In that case, chemical reactions within the cell would fail to take place, and life would be endangered.25 Due to their hydrophobic structures, phospholipids are not permeable to such water-soluble contents of the cell as sugar, amino acids and other organic acids. This, as we shall be examining in detail, is essential for bodily functions, and therefore for life itself.
Phospholipid molecules are irreplaceably important with regard to their arrangements in the cell membrane. The cellular biologist John Trinkaus comments about the molecule's unique structure:
As you see, everything is in the right place and the right form. How do the molecules forming the cell membrane's phospholipid structure know where they need to be during the membrane's construction? In fact, the molecule has the ideal purpose-directed structure. Moreover, no known substance can replace this special structure. The features of viscosity and lack of permeability absolutely must be present in any membrane system surrounding the cell. Yet these features are found together only in the double-layered lipid membrane. To a large extent, the cell's very existence depends on the biochemical and biophysical properties of this double-layered lipid membrane.
In the presence of water, lipids and phospholipids line up alongside one another and can form layers or even spheres. Yet the astonishing information encoded in the membrane distinguishes cells from spheres—necessary for the proteins and other molecules that permit controlled carriage along the length of the cell membrane. Proteins, products of the cell metabolism, permit the cell to function, and the cell is needed to produce them.
In order to maintain life, the proteins, and the data that encode them, and the organelles that produce them must all have appeared simultaneously—an event that is impossible through mere coincidence. This situation, therefore, cannot be explained by Darwinists.
This fact, which demonstrates that coincidence can have no place in the origin of life, is one that Darwinists are forced to accept. Von Ditfurth confesses as much:
All types of lipids contain long hydrophobic chains of carbon and hydrogen atoms, and these chains are either insoluble or only very minimally soluble in water. The fact that many varieties of lipid are insoluble in water is of vital biological importance. Were there no insoluble compounds, it would be impossible for a cell to be divisible into sections and for its components to remain permanent. That would be unsuitable for life. In a similar way, if water were a universal solvent, then no environment suited to life could exist: It would be impossible for the cell to be divided into compartments or to form durable structures. All cell compounds would commingle or melt away and disappear.
In most lipids in the cell, the length of the hydrocarbon chain is generally 16 to 18 carbon atoms. This length is ideal for several reasons. In terms of biological efficiency, chains longer than 18 carbon atoms are insoluble and cannot react in water. Those shorter than 16 carbon atoms are too soluble. At the temperatures at which metabolic processes in living things are carried out, lipids composed of chains of this ideal length are either liquid or in a close to that of liquid state. If chains of this length were solid under typical environmental conditions, then the structures they compose would not be elastic enough to perform any functions within the cell. In addition, in their liquid state, these chains protect living cytoplasm against destructive forces because they are less viscous than water. 29
The hydrophobic (water-repellent) structure of fats lends stability to the cell's structures, borders and compartments. Due to its protective structure, hydrophobic micro-environments independent of water and of vital importance to life can form within the cell. A great many activities essential to the maintenance of life can occur only in water-free environments. In conclusion, were it not for the hydrophobic properties of lipids, carbon-based life would be impossible. This is yet another one of a great many properties especially created for life to exist.
Why is It Important That the Cell Membrane is Fluid?
One of the vital properties of the lipid bilayer (or double layer) membrane is that it's not solid but fluid. With its flawless fluid character, it constantly surrounds the disordered and mobile cytoplasm. Protein molecules in the membrane along the surface of the cell are able to change places. These molecules' ability to extend along the membrane permits free passage through the membrane of certain special substances, as you shall see in detail further on.
The cholesterol molecules in the cell membrane are lipids defining the membrane's fluidity and are present in a dissolved state in the double-layer lipid membrane. Their main function is, by maintaining the fluidity of the cell membrane, to increase permeability against soluble substances in body fluids.
In order for the cell to survive, the cell membrane must possess this fluidity. Lowering the temperatures of liquids outside the cell lead to hardening of the cell membrane and loss of fluidity, obstructing the functions of proteins in the membrane.
In his book Nature's Destiny, the microbiologist Michael Denton draws attention to the essential nature of this structure of the cell membrane:
In conclusion, the lipid double-layer membrane possesses at once a high level of fluidity, but also the viscosity of olive oil. If the membrane possessed many flawless properties but lacked only that viscosity, then the cell could not survive. These properties, all essentially important to the continuation of life, show us the final detail and balances in Allah's Creation. Anyone who sees these proofs of Creation must realize His existence, know that he owes his life to Allah and give thanks to Him.
How Do Substances Enter and Leave the Cell Without Damaging the Membrane?
The cell membrane's fat-based lipid structure prevents water within the cell and the solutes dissolved in it from leaking out. But how are waste products carried outside the cell through a membrane that admits no leakage, without the cell being ruptured or swelling up and bursting? And how do nutrients manage to get inside?
The double-layer lipid membrane represents the main barrier to substances soluble in water such as glucose, urea and ions. At the same time, the lipids in the membrane's structure prevent water and any substances dissolved in it from moving freely from one region to another. But oxygen, nitrogen, and other small molecules are easily dissolved in lipids and thus can move back and forth through the cell membrane. Substances that dissolve in fat, such as carbon dioxide and alcohol, can easily pass through these sections of the membrane. Although the water molecule is insoluble in fat, because of its small size and electrical charge, it easily passes through the cell membrane. The physicist and biologist Professor Gerald Schroeder describes the importance of this special characteristic of the cell membrane:
The intellect and Creation excitedly referred to by the author belong to our Lord, Who causes His superior knowledge to manifest in all things. The way that the membrane's structure is not damaged during entries and exits from the cell, how it permits constant entry to a number of substances without splitting or tearing, and also removes substances from the cell are miraculous phenomena taking place in a dimension too small to be seen with the naked eye. Yet they occur through the will of our Lord, as is revealed in the verses: "No leaf falls without His knowing it." (Surat al-An'am, 59) and "Not even the smallest speck eludes your Lord, either on Earth or in heaven ... " (Surah Yunus, 61).
Proteins in the Cell Membrane
The cell membrane basically consists of a bi-lipid layer and a large number of protein molecules floating inside it. Because of the membrane's fluid property described earlier, proteins in the membrane act like a security checkpoint. Large molecules like proteins and sugar cannot pass through without assistance. Proteins within the membrane serve to carry these substances into and out of the cell.
The cell membrane lipids are not permeable to electrically-charged molecules, no matter how small they may be, because phospholipid molecules consist of an electrically-charged polar "head" and two non-polar fatty-acid "tails." As in water, the lipid parts repel ions and other polar substances, and so many substances are able to enter and leave the cell only by means of special protein molecules within the cell membrane. As Gerald Schroeder asks, "Who or what decides what should enter and leave?" 32
Viewed from the outside, the cell membrane consisting of fat molecules can be compared to a sphere made out of marbles. Once you enter the "wall" around this sphere, the wall's contents resemble potatoes and rod-like objects. These are the protein molecules that perform the cell membrane's functions, identifying those substances outside the cell that need to be carried inside. They allow these substances in and, depending on their properties, perform functions such as transportation.
The proteins assume a most critical responsibility. The supervision of entry and exit in the cell membrane is comparable to the advanced security checks at the entrance to an important building. Anyone wanting to enter is first searched, and any bags or packages he may be carrying are passed through an X-ray machine. If necessary, his identity is confirmed with optical scanners or fingerprint checks, and only then is the individual allowed in. The security officials performing these duties must make no mistakes and should implement every precaution. One error could threaten the whole building. However, during all these checks trained personnel and technological equipment developed by engineers are employed. Not a single detail can be explained in terms of chance, because an flawless foresight is followed at every stage.
The proteins inside the cell membrane performing such tasks as recognition, transportation and reception, operate according to a plan, just as if they knew the vital responsibility they have undertaken. Any single error will lead to the death of the cell, and thus damage the organ of which it is a part, or the whole body. Is it therefore possible for protein molecules themselves to display this great intelligence and expertise, and for all the proteins in the cell to adopt these common plans? It is of course impossible for the intelligence and foresight displayed to belong to the proteins, consisting of unconscious atoms, themselves. It is Almighty Allah, Who creates the proteins and, through His command, makes them the kind of molecules which remain loyal to their duties and employ flawless methods to accomplish their goals.
The cell membrane proteins may be classified into three groups, each with its own enormous expertise:
Some of the proteins in the cell membrane acts as transporters, assisting in regulating what enters and leaves the cell. These proteins have two important parts: the fat-friendly part that adheres to the cell membrane itself, and the other part that binds to substances that need to be transported. These proteins bind to the given substance, change the load's course and carry it along the cell membrane.
These transport proteins adhere to specific molecules and carry only these into the cell. While they perform these functions, their shape changes, and sometimes they require energy to pass substances through the cell membrane. There are no holes in the cell membrane itself. Therefore, water, protein, nucleic acid and certain small molecules unable to pass directly through the cell membrane's lipid double layer all enter the cell by means of these transport proteins.
Due to their three-dimensional amino acid strings, these carrier proteins can easily construct a narrow passage. Substances of a particular size are thus able to enter that space and pass through the channel. Size alone is not enough to be able to pass through, however: the selective cell membrane allows only those substances the cell needs to be taken inside.
These proteins function like molecular flags and signposts. Rod-like protrusions generally consisting of sugar on these proteins extend outside the cell membrane, allowing cells to recognize and make connections with one another. Because these proteins, leukocyte cells for example can distinguish the body's own cells from foreign bodies like viruses and bacteria. Cells such as the T-cells in the immune system use recognition proteins to tell whether any particular cell belongs to the body or not. Since surgically transplanted tissue possesses the wrong recognition proteins, the immune system rejects such organs unless it is suppressed. These same proteins also permit the sperm cells to recognize the egg cell.
The recognition proteins in the cell membrane are the target of viruses and bacteria, because toxins bind to recognition proteins in order to kill cells. Under typical conditions, as a result of these proteins, the connections between cells regulate cell growth. But in a cancer cell, for example, the number of recognition proteins is very low. For that reason, the immune system cannot identify the cancer cells that need to be eliminated. 33
Some proteins form channels along the length of the cell membrane. These proteins have two special sections: the fat-friendly part that adheres to material in the cell membrane, and the water-friendly part that forms in the inner part of the channel. In this way, a route is formed for water-soluble substances to move in and out of the cell. These proteins, function like gates and regulate the movement of molecules entering and leaving the cell, forming particular gaps in the cell membrane that are always open.
Protein channels are accepted to be the waterways in the interior of protein molecules. Using these channels, some substances to be taken into the cell can easily pass from one side of the cell membrane to the other. Protein channels can be distinguished by two important properties: They are generally selective and permeable to specific substances, and most channels open and close with gates (whose features we shall be examining in due course).
23. Michael J. Denton, Nature's Destiny, New York: The Free Press, , 1998, p. 209.
24. Hoimar Von Dithfurt, Im Anfang War Der Wasserstoff ("Secret Night of the Dinosaurs"), Vol. 3 (pp. 37-38 in Turkish edition).
25. Arthur C. Guyton, John E. Hall, Medical Physiology, 10th edition, W.B. Saunders &Co., 2000.
26. Michael J. Denton, Nature's Destiny, New York: The Free Press, , 1998, pp. 215-216.
27. Gerald L. Schroeder, How Science Reveals the Ultimate Truth, p. 65.
28. Hoimar Von Dithfurt, Im Anfang War Der Wasserstoff ("Secret Night of the Dinosaurs"), Vol. 1 (p. 124 in Turkish edition).
29. Michael J. Denton, Nature's Destiny, New York: The Free Press, , 1998, p. 213.
30. Ibid., p. 215.
31. Gerald L. Schroeder, How Science Reveals the Ultimate Truth, p. 64.
32. Ibid., p. 62.