A few decades ago, thought was preoccupied with "structure" of everything. Then in the inevitable reversal development, everything went to "deconstruction" with the idea that structure was a kind of domination and that by deconstruction, one could discover covert meanings. I first came across the idea of structure, esp in language, when I became adept at diagramming sentences in the 7th grade. Then I learned about semantics in college. Decades later I was writing and discovering that deconstruction wasn't always a source of meaning, but the lack of construction could mean something.
Recently, the word structure is replaced by "architecture" which sounds much more elite and complex. I recently discovered that people talk about "the architecture of the cell," and what we know now destroys the popular idea of a cell as a kind of water-balloon. Water and a membrane are basics, for sure, but there turns out to be a lot of hustle and production in that cell.
The first necessity for cell-based life (which is ALL of the life we know of) is water. Luckily this is a very watery planet. Water is necessary because the molecular patterns that form the shifting dynamics of life are only possible in solutions, "solute" versions of the chemistry of solids.
The second necessity for a cell is the first binary: a membrane separating the solutions of the internal processes from the general water outside where it floats. Life begins with difference.
The third necessity is energy, which powers the processes and comes from difference.
"Although membranes are valuable as a way to segregate the watery interior of the cell from its environment, or to segregate intracellular events from one another, they have other important functions, including energy storage. Because membranes separate watery compartments from one another, if an ion or a molecule dissolved in water is moved through a membrane into a new cellular compartment, it will not be able to diffuse freely out of the compartment into which it was moved. It takes energy to move the molecule, but once moved, the molecule stores that energy by virtue of its entrapment. Formally, this storage of energy is just like the storage of energy in a battery. Therefore, membranes not only delineate compartments, but also serve as active participants in the cell’s dynamism."
Membranes are not just passive barriers, but have layers and characteristics according to the nature of the cell. Some membranes are double. All have "ports of entry" that allow some things in, but not others.
"The passage of water-soluble molecules through membranes is carried out by protein transporters that are embedded in the membrane. Also, cells send information to one another by releasing signaling molecules. The outer membranes of cells have proteins, known appropriately as receptors, that bind the circulating signaling molecules."
Inside the main cell are assorted "organelles" that are also "bagged" in membranes.
"Most organelles are surrounded by a single phospholipid membrane, but several, including the nucleus, are enclosed by two membranes. Each type of organelle plays a unique role in the growth and metabolism of the cell, and each contains a collection of specific enzymes that catalyze requisite chemical reactions. "
They include:
Cytosol which is the general cytoplasm of the cell.
The nucleus that defines the cells of the eukaryotids. (Ours.)
Mitochondria that manages energy and has its own DNA.
Rough and smooth endoplasmic reticula, a network of membranes in which glycoproteins and lipids are synthesized.
Golgi vesicles that organize membranes
Peroxisomes that degrade fatty acids and amino acids.
Lysosomes that do the same for general debris.
"The cytosol of eukaryotic cells contains an array of fibrous proteins collectively called the cytoskeleton . . . The cytoskeleton gives the cell strength and rigidity, thereby helping to maintain cell shape. Cytoskeletal fibers also control movement of structures within the cell; for example, some cytoskeletal fibers connect to organelles or provide tracks along which organelles move."
"The endoplasmic reticulum is a type of organelle found in eukaryotic cells that forms an interconnected network of flattened, membrane-enclosed sacs or tube-like structures known as cisternae. The membranes of the ER are continuous with the outer nuclear membrane. They play a vital role in the formation of the skeletal framework. They play a vital role in the synthesis of proteins, lipids, glycogen and other steroids like cholesterol, progesterone, testosterone, etc."
"The concept that genes are like “beads” strung on a long “string,” the chromosome, was proposed early in the 1900s based on genetic work with the fruit fly Drosophila. The early Drosophila workers could position, or map, the genes responsible for various mutant traits on a chromosome, even though they did not yet know that genes were segments of DNA or that the function of a gene was due to a protein whose sequence was encoded by that gene!"
At this level we stop doing mini-anatomy and are verging on organic chemistry. This is where much of the most interesting research is happening, but the names of the entities are unfamiliar to most of us. Cancer research, diseases that circulate in the blood, energy malfunctions, prions, and so on are hard to perceive, much less analyze for their action in the body. Often we're looking at consequences instead of causes. Our diagrams of teeny-tiny entities masquerade as portraits, but are as unreal as imagining an atom as circling ping-pong balls. It's easy to shrug off this stuff as irrelevant until one suffers from the malfunction of one of them, as in diabetes.
Organs arise from these organelles in cells, so that each has a shrink wrap silvery cover that acts as a boundary. Evidently the pouches of imaginal disks have something to do with them turning out to be sizes that fit the spaces and fit together properly. But imaginal disks are still mysterious. They aren't cells, though some say they are like stem cells, they don't seem to be organelles, and they are far too small to be organs but seem able to control them, even define them.
We know that molecules are interconnected elements arranged in certain patterns but we also know that atoms are mostly energized whirling space on an impossibly small scale. So it is the structure, the architecture, that makes them palpable, detectable, vital.
No comments:
Post a Comment