The Mutual Interdependence of Cellular Systems
Cell’s Unbelievable Cytoskeleton: Molecular Evolution?
In the last article, we saw how the bioscientists in the 1950s were able to produce monomers spontaneously in a laboratory under conditions that simulated the early Earth. This experiment was incredibly inspiring as monomers are the building blocks of the all the biochemicals necessary for Life. Yet, the early excitement turned into disappointment. Despite prodigious efforts in the last half century, they have been unable to build these simpler monomers into the more complicated biochemicals.
However, the inability to create biomolecules is not the most significant problem when it comes to understanding how Life supposedly evolved from Matter. Dr. Nowicki provides the scientific perspective: “The most difficult problem for the origin of life is understanding how early cells (or organisms in general) can reproduce while maintaining continuity of biological information.” Simplifying, how were the first bacteria able to replicate their genetic information (DNA)? Certainly a major question.
But this somewhat reductionist formulation focuses only upon certain parts while ignoring an even larger picture. A far more challenging problem is associated with how Matter self-organizes its parts into the mutually interdependent systems required for cellular life.
Life’s four biomolecules are organized into many complex systems, for instance metabolic pathways, DNA, a cellular membrane and a cytoskeleton. This extraordinary intricate organization of interacting parts enables cells to survive, reproduce, and interact with their environment. Cellular systems with their myriad functions are mutually interdependent. They can’t exist without each other. Codependent, they need each other for survival.
These cellular qualities evoke one big, seemingly insurmountable question: As each system is both necessary for life and dependent upon the others, how could these individual systems evolve separately? A multi-factor variation of the ‘chicken first or egg’ question.
To facilitate understanding and evoke awe at the cell’s complexity, let’s look at some specifics. Every cell has metabolic systems, a reproductive system and a sensory-motor system. In eukaryotic cells, the reproductive system is in the nucleus (DNA), the sensory-motor network in the membrane, and the metabolic pathways in between to coordinate activities.
Metabolic pathways contained inside the membrane create the four types of bio-molecules (cellular substance) from raw materials. These inanimate molecules come primarily from outside the cellular membrane. They also produce the cell’s energy requirements (ATP molecules). Metabolic pathways consist of huge biomolecules, e.g. enzymes and proteins.. These same pathways produce their own biomolecules and require the bioenergy that they produce to perform their work. A huge question: If metabolic pathways are required to produce biomolecules, how did the first metabolism obtain its substance (proteins) and energy (ATP)?
Similar problems are associated with the origination of our genetic system that is required for reproduction, evolution, and survival. The genes that are embedded in the DNA provide the blueprints and operating instructions for both cellular and multi-cellular operations. As such, DNA provides instructions on how to construct itself and the thousands of proteins a single cell requires for operation. How did the first DNA molecules construct themselves without instructions?
In like fashion, the metabolic pathways require the DNA recipes to cook up the enzymes and proteins necessary for operation. No recipes – no proteins. Plus, the DNA requires the bioenergy (ATP molecules) produced by the metabolic pathways to do its work.
Our metabolism requires DNA instructions and the DNA requires energy produced in the metabolic pathways to do its work of producing proteins. How could one evolve without the other? This question is a controversial topic in origins research. One subset of researchers holds the viewpoint that DNA came first; another claims that metabolism was first; and a third group holds that DNA and metabolism emerged simultaneously.
The same mutual interdependence holds for the membrane of the cell. Both the metabolic pathways and the DNA systems are contained inside a membrane. The membrane separates the inside of the cell from the outside. Due to the necessity of environmental interaction, the cell membrane must be permeable.
This function is performed by Integral Membrane Proteins (IMPs). The structure of each IMP is matched to a specific environmental signal. The IMPs open and close in response to these signals from the interior and exterior of the cell. This movement triggers a reflexive response. In such a way, these IMPs are the basis of our sensory-motor network.
The metabolic pathways and the DNA must be contained inside a membrane to be concentrated enough to do their work. The membrane’s permeable component consists of proteins (IMPs) that are produced in the metabolic pathways with directions from the DNA. How could these IMPs have evolved independently of a metabolism and DNA? How could metabolic pathways and DNA evolve without a membrane to enclose and concentrate their holistic work?
Our metabolism, DNA, and the cell membrane, all require proteins to maintain and operate their systems. Yet the cell requires both DNA and a metabolism to produce proteins. These proteins are huge molecules that are ‘designed’ to react to specific environmental conditions. How could these thousands of individual mega-molecules that are necessary for cellular survival have evolved without a membrane to enclose, a metabolism to produce, and DNA to provide instructions?
Origins of life researchers have made some substantial and astounding steps. In a laboratory, they have produced: 1) a self-organizing membrane (albeit no proteins to enable interaction), 2) a metabolic-like process, 3) a self-replicating system and even 4) a system that evolves.
Yet they are seemingly lifetimes away from getting these individual parts – these particular systems inside a membrane that both senses and reacts appropriately to relevant environmental information. Further they continue to be baffled as to how the instruction manuals of the DNA and the metabolic pathways that produce the energy and proteins could have evolved either separately or simultaneously.
Put more simply: biomass and energy come from a system that requires biomass and energy to operate. Further this system doesn’t function automatically, but instead requires directions. The directions also require biomass and energy to operate.
Further, these interlocking systems must be enclosed in a membrane that takes in raw materials from the outside that can be transformed into the biomass and energy required to drive the internal systems. It takes the instruction manual, the biomass and bio energy to create the proteins and fats contained in the membrane that allows raw materials inside to become proteins, fats and instructions.
How could the cellular membrane have evolved independently, i.e. without biomolecules and bioenergy produced by metabolic systems and without the instruction molecules of our genetic code? The mutual interdependence of the systems and structure of a single cell make the ‘chicken or egg first’ problem look simple in comparison.
Dr. Nowichi: “Cells are important because of their packaging; it separates inside from outside and concentrates the appropriate molecules in the interior.”
The cellular membrane isolates the cell’s internal environment, where all the work is done, from the external environment. This membrane must be semi-permeable to allow raw materials to enter and to eliminate waste materials. This function is performed by Integral Membrane Proteins (IMPs).
There are tens of thousands of these special proteins embedded in the cell’s incredibly thin membrane (only discovered with the advent of the electron microscope). This complex variety of proteins enable the transfer of inanimate molecules between the cell’s interior and exterior. These tiny ‘particles’ are essential for the operation of enormously complex interlocking processes that are devoted to the survival of an entity, whose content is not fixed, but dynamic. Due to this crucial function, IMPs are an essential feature of the cellular membrane. This interactive system is a major and distinct feature of the mutually interdependent systems that are necessary for the cell’s survival.
Due to their critical importance, let us learn a little more about the special talents of these exceptional proteins. Many of the tens of thousands of IMPs are a special type called Receptor Proteins. Receptors are proteins whose form is an exact image of a specific environmental signal. Once triggered by this signal, the receptor protein changes shape. This shape-changing ignites an automatic cascade of changes in another type of IMP, e.g. effector proteins. The first change is the stimulus and the second change is the response.
This process is frequently likened to the gears of a clock. The movement of receptor IMPs (the initial gear) initiates a cascading sequence of movements in the effector IMPs (the other gears). The process results in the appropriate response to environmental stimuli. This stimulus-response system is essential to the cell’s survival.
This crucial process that is a feature of every cell evokes a series of questions about the ‘evolution’ of inanimate matter into the first bacterium. How did the receptor IMPs end up being a functionally perfect image of a specific environmental signal? How did the effector IMPs evolve separately into a perfect match for the receptor IMPs? How did this receptor-effector system happen to result in a functionally near-perfect response to specific environmental stimuli?
Consider two key ongoing examples from the life of a cell. How did inanimate molecules ‘evolve’ into a system that allows a food molecule, say glucose, from the exterior of the cell into the interior. Or how did matter self-organize into a system that releases waste molecules, e.g. oxygen molecules, from the interior into the exterior? How did these IMPs even get into the membrane?
Beyond these examples, there a host of other intricate cellular functions that are dependent upon the membrane for their operation. For example, the cellular membrane with its tens of thousands of IMPs evolved to enable the complex internal processes of the cell. How did these proteins evolve separately from the very processes they enable?
More generally, how could the emergent properties of the random interactions of inanimate matter produce the internal integrity of this cascading set of systems that are essential to the life of every cell? Are these interlocking interdependent processes associated with IMPs merely due to the chemical ‘evolution’ of inanimate Matter?
We are certainly faced with many problematic transitions regarding the creation of the first cell. Do these IMP-related questions represent additional problems for the Chemical model for the Origin of Life? Might it be time to entertain a new model? Even though it might violate the Materialist Dogma that is held by so many in the scientific community, shouldn’t we contemplate a novel vision of reality that offers a more productive approach?
Another feature that every cell, hence every living system, possesses is a cytoskeleton. The embedded term ‘skeleton’ gives away its function. A hard outer shell or covering of a living system, such as a clam shell, is called an ‘exo’-skeleton,. A hard interior structure, such as our bones, is called the ‘endo’-skeleton of the organism. Cytoskeleton is the name given to a cell’s bones, its skeleton.
The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells. The micro-filaments and micro-tubules that make up the cytoskeleton consist of a specific type of protein that has the ability to make strong connections to other proteins of a similar nature. As their names suggest, some of these protein chains are like hollow tubes, while others could be likened to wires.
The cytoskeleton provides three functions: 1) Just like our skeleton, its relatively firm structure provides the cell with shape and form. 2) As with our bones, the interlocking proteins allow the cell to move as a unit. 3) The harder structure also provides a channel for the metabolic pathways.
For example, every cell’s hard structure must enable the passage of environmental nutrition into and the expulsion of waste products out. This channeling function both concentrates the necessary molecules, e.g. enzymes, and provides tunnels for the process. The cytoskeletal structure is necessary for the cellular operations of providing shape, enabling movement, and channeling activities.
Let’s ask a few simple questions regarding the cytoskeleton’s relationship to the cell’s mutually interdependent systems. In order to be complete, chemical origins of life theorists must provide plausible models that address this interdependency.
How could the cytoskeleton have evolved independently of the other parts that it is meant to serve, e.g. the metabolic pathways and the membrane? How could these systems have evolved without a precise cytoskeleton to provide structure?
For instance, how did IMPs evolve into just the right combination of stimulus-response reactions that are necessary to generate and maintain the cell’s cytoskeleton? It is important to recall that this interior scaffolding binds the metabolic pathways that are necessary for the internal production of bio-energy and bio-mass that are in turn required to produce IMPs. It is difficult to conceive how the IMPs could have evolved independently of the cytoskeleton, when the cytoskeleton provides the framework for the creation for the IMPs themselves.
It is well known that cellular form follows cellular function. How could inanimate molecules that lack the function of cellular movement have ‘evolved’ into a collection of mega-molecule proteins whose form is perfectly matched to enable cellular movement? How did these molecules self-organize into a skeletal structure without a membrane to contain them, without metabolic pathways to provide them with material and energy, and without directions to tell them how to arrange the parts?
These questions regarding the cytoskeleton along with other ‘insurmountable’ problems related to the cell’s mutually interdependent systems point to the inadequacies of the Chemical Origins of Life Model. We are not challenging the chemistry-based research. We are only questioning the exclusivity of the model’s position. Despite enormous holes in their theory, the bio-scientific community seems to be committed to the dogma that Life is only a function of the laws of Matter, nothing more.
The enormous gaps in understanding merely indicate that other options must be seriously considered, or at least can’t be ignored. If the advocates of the Material Model were closing in on some plausible answers to these ‘impossible’ questions, they could casually discard alternative viewpoints. But since these advocates are nowhere close to an ultimate solution, it might be time to entertain other possibilities – perhaps make other assumptions - and see where they lead. We suggest that Life, while relying upon the physical laws of inanimate Matter, must inherently be associated with the rules that govern the nature of Attention, i.e. Life’s ability to intentionally interact with Information.
But the problems confronted by the origins researchers are not the only ‘insurmountable problem areas’ associated with the Chemical Model of Life. Rather there are other ‘insoluble riddles’ that have not been adequately addressed by the entire bio-scientific community. Identifying these riddles is the topic of next chapter.