Biomedical Basics
The innermost aspect of the cell is the nucleus, containing the DNA, which, holds the instructions for the formation of the various cellular proteins. Particular genes are read from the DNA, transcribed into messenger RNA, which then moves into the cytoplasm and attaches to a ribosome, where the actual protein is built. The particular genes which are transcribed to RNA is controlled by a number of proteins which bind to the DNA strand at certain points. At the beginning of each operon (a series of genes which function together to create a certain end-product protein), there is a region called the promoter - a particular series of nucleotides which allow the RNA polymerase to bind to DNA strand and thus begin the transcription process. There are various proteins which can bind to this region, either blocking the RNA polymerase from binding or inducing it to bind.
The nucleus also contains the nucleolus, an unbounded accumulation of RNA and ribosomal proteins. The nucleus is delimited by the nuclear membrane, composed of two lipid bilayer membranes, the second of which is continuous with the endoplasmic reticulum.
The endoplasmic reticulum is a network of tubular vesicles constructed of a lipid bilayer membrane and containing a fluid called endoplasmic matrix, which has a different constitution from the general cytosol. The endoplasmic reticulum is the site of much protein and lipid synthesis in the cell. The portion of the endoplasmic reticulum with ribosomes attached is called the granular or ribosomal endoplasmic reticulum, and this is the location of protein synthesis, since ribosomes are needed to make a protein from RNA. The smooth or agranular endoplasmic reticulum is the site of lipid synthesis. The endoplasmic reticulum also serves as a system for conveying some of these newly synthesized substances from the site of synthesis to other locations in the cell.
The golgi apparatus is composed of multiple stacked layers (4 or more) of thin, flat vesicles. Vesicles containing substances synthesized in the endoplasmic reticulum pinch off from the endoplasmic reticulum and move to the golgi apparatus, where the substances undergo further processing. From the golgi apparatus, new vesicles pinch off, either to act within the cell or to carry a substance to the cellular membrane for secretion.
Lysosomes are vesicles, formed as usual by a lipid bilayer, which pinch off from the golgi apparatus. The lysosomes contain hydrolase enzymes which, when released, can breakdown ingested food particles, damaged cellular structures, and other unwanted material.
Peroxisomes are another type of free floating vesicle. Unlike the lysosomes, they contain oxidases which are used to breakdown very long chain fatty acids and to denature toxic substances. The peroxisomes do not originate from the golgi apparatus. They can originate from the smooth endoplasmic reticulum or form by self-replication.
Mitochondria and distributed throughout the cytoplasm. They are formed by two lipid bilayers. The outer membrane provides a boundary, while the inner membrane is folded and convoluted, forming shelves, to which oxidizing enzymes are attached. Mitochondria are the site of oxidative phosphorylation, the main process converting nutrients into ATP, the form of readily available energy used in most other cellular processes. The mitochondria contain their own DNA, and can increase their numbers by reproducing itself as needed.
The cellular membrane is composed of a phospho-lipid bilayer interspersed with a number of proteins of various functions. The lipid bilayer is directly permeable to fat soluble substances,including oxygen, carbon dioxide, and alcohol, but water soluble substances, including the electrolytes, must pass through one of the proteins in the membrane. These protein channels are of three basic kinds: passive diffusion, assisted diffusion, and active transport. Passive diffusion channels allow particular molecules to simply pass through, driven by their own on-going motion. Thus as the relative concentration of a given molecule on one side of the membrane increases, the flow rate through the passive diffusion channels will increase proportionally. Some control is still exerted by the passive diffusion channels. First of all, many of these channels are selectively permeable: features of the protein channel, including it size, shape, electrical charge, and chemical affinities, will allow only specific molecules to pass through. Second, many of these channels are gated, meaning that a conformational change in the protein, can either allow or disallow diffusion of the molecules for which that channel is specific.
Assisted diffusion requires the diffusing molecule to bind to the protein channel, inducing a conformational change, before the molecule can pass into or out of the cell. The primary significance of this difference is that these channels limit the maximum diffusion rate, since conformational changes can only occur so quickly. Active transport channels require the use of ATP to move molecules into or out of the cell. These are used to transport molecules against the direction of their natural direction of diffusion, thus allowing for the build-up of certain substances on one side of the membrane, giving the cytosol a distinctly different constitution than the inter-cellular fluid.
Preliminary identifications
The nucleus is an informational organelle which can be identified with the whole shaoyin system. It is Kidney because it stores the essence which passes to the next generation, and it is Heart because it is the source which issues the mandate to the rest of the cell. It is also the literal core of the cell. This collapse of the Kidney-Heart polarity into a single organelle partially accounts for the sense of primitive “roundness” of the cell. There is a tendency to think of the nucleus as the brain of the cell, however I will argue below that the brain is actually more akin to the cellular membrane that to the nucleus. It is interesting to not that the quality of symmetry, which marks is informational organs in the wider human being, is also present in the nucleus with the double strands of opposite, but matching, DNA.
The endoplasmic reticulum is an organelle of anabolism, and it corresponds well to the concept of Wood. It takes the basic instructions from the Nucleus/Water and causes these to grow forth into proteins, and since it is proteins which actually perform most cellular functions, it is thus the initiator of cellular activity. Noting the location of the endoplasmic reticulum, how it surrounds the nucleus, noting also its quasi-circulatory function of distrubuting materials to different parts of the cell, we might consider that its function reaches beyond Wood to includes that of jueyin Pericardium.
The golgi apparatus should probably be grouped loosely with the endoplasmic reticulum in the general wood, shaoyang, and jueyin schema, however, as the source of the lysosomes, we may also want to regard it as Spleen.
The catabolic digestive processes driven by the lysosomes and peroxisomes are Yangming and Metal. The fact that these processes take place in the free space of the cytosol, not in a single, localized organelle, can remind us of the fact that the digestive processes in the wider human take place in the hollow organs, in the space that is just an enclosed tube connecting to the outer world on both ends.
Mitochondria are the Kidney Yang or Mingmen. Their separation, indeed their great independence, from the nucleus (containing their own DNA and capable of their own reproduction) helps to re-establish the Fire - Water polarity of the cell. Mitochondria represent a refined catabolic process.
The cytosol might be likened to the triple burner.
The membrane performs a formal/informational role. This is not simply a passive establishment of a boundary, but an active, informed regulation of the intake and outflow of a wide range of different substances, amounting to an informational processing. The membrane can be seen from a zangfu perspective as Lung. In addition to being the “skin” of the cell, it is quite literally the place where cellular respiration occurs. (It also the mouth and anus of the cell, reminding us of the taiyin-yangming connection, although we would not want to claim that the membrane is a yangming organelle.) The image of regulating communication between heaven and earth does a good job of capturing the phenomenal quality of the membrane.
From a six conformation perspective, the membrane is clearly taiyang. By regulating what substances enter and leave the cell it performs the Small Intestine function of separating the pure from the impure. Like the Bladder, it the outward facing aspect of the cell. And again, it is in fact the location through which impure is excreted from the cell.
The Big Picture
The primary motif of the cell is a polarity between the dense, centralized, contained, spheroid informational processes of the nucleus and the dispersed catabolic processes of the lysosomes, peroxisomes, and mitochondria. Between these two lies the intermediate zone of the endoplasmic reticulum, which has a continuous structure, but a structure which is convoluted and holey, and the golgi apparatus which is a collection of vesicles which stay together to form a quasi-structure. At the very outer limit of the cell, the formal and informational pole reappears in the form of the cellular membrane. This appears to be a recapitulation of basic three-fold principle (formal, rhythmic, and metabolic) familiar from anthroposophy, expressed radially rather than vertically. (Note that even in the human form, the symmetrical, informational principle reappears at the lower extreme in the reproductive and urinary system.)
There are a few wrinkles, however. First, we must note that endoplasmic reticulum and golgi apparatus, while they are formally intermediate, play a primarily anabolic function. In this sense they are functionally aligned with the metabolic pole, rather than the rhythmic. The endoplasmic reticulum does have a function of conveying substance throughout the cell, and in this way it might be likened to the circulatory system, but this does not negate the anabolic function of these organelles. The nucleus also has a somewhat rhythmic quality since it tends to have periods of active transcription, during which the nucleolus swells, and periods of quiescence, during which the nucleolus shrinks. We might say that in the cell, rhythmic processes are poorly thematized and that anabolic processes are shifted into the rhythmic zone.
Second, although the nucleus is an informational process. It is not analogous to the brain. Rather, the brain is should be seen as analogous to the cellular membrane. We can see this in two ways. First, neuronal function is primarily an activity involving the cellular membrane. It is along the membrane that the action potential is propagated, and it is through the membrane that neurotransmitters are released and detected. Second, the brain is located in the head, in proximity to the sensory organs. This reveals its basic orientation is toward assessing and structuring our relation to the outer environment. This is quite different than the project of giving instruction on becoming oneself from within oneself, as in the purpose of the nucleus and the shaoyin network). As the site of the DNA, which must be copied during reproduction, the nucleus is more akin to the reproductive organs. We might thus say that there is an inversion between upper and lower informational poles when moving between the cell and the general human organism.
Chinese Medicine Considerations
These reflections on the cell shine some light on a number of features of Chinese Medical theory that are otherwise difficult to explain. Chief among these features is the strange devaluation of the brain and the conflating of the informational processes of the head with the rhythmic processes of the chest. When looking at the whole human organism, the anthroposophical three-fold account seems so refreshingly honest and accurate compared to the contorted, headless three-burner model. However, if we take the Chinese model as a model of the cell, then it makes much more sense. The nucleus (i.e. HT) does combine informational and rhythmic processes, moreover its function is not the same as that of the brain.
Cellular considerations also help explain why the Bladder should be associated with defense against external pathogens, without having to depend on a legend about standing with one’s back to Mt. Kunlun. Namely, the Bladder can be take to refer to the cellular membrane. The Bladder is the lowest organ in the body and thus it in the same position as the cellular membrane, which is radially the most distant from the nucleus. The Bladder is also a Water organ, which indicates it suggests its function as an informational process, but distinct in some way from the shaoyin Kidney.
On this subject let me say that I now think that the brain should be regarded in Chinese Medicine as a aspect of the taiyang, rather than the shaoyin (which is usually argued for by following the connection from Kidney to marrow to Sea of Marrow, but also based on a general idea of the brain playing some role in the Shen processes attributed to the Heart).
Consideration of the oddity of the mitochondria help explain some of the on-going confusions and debates around the idea of Mingmen fire/Kidney Yang: whether this is or is not part of the Kidney, whether there are two distinct Kidneys (left and right, yin and yang), how clearly this can be distinguished from Spleen Yang, etc. The mitochondria do have a Kidney/Water like quality in the sense that they contain their own DNA and manage their own reproduction, giving them an unusual independence from the rest of the cell, yet they have an essentially catabolic function within in the wider cell.
Finally, regarding the endoplasmic reticulum as Liver, helps explain why that organ is assigned responsibility both for anabolism (as Wood) and for “coursing and draining.”
