Cell Components Let’s imagine clouds of cold fog billow up through a circular hatch in the top of a stainless steel tank as a biologist pulls out the lid and its one-foot thickness of styrofoam insulation. As the fog rolls down to the floor, Hay peers into the dark tank, where the temperature is all the time 321 degrees below zero Fahrenheit. It is kept so cold because that is a temperature at which life, normally warm and pulsing with activity, abandons its vital dance and enters limbo – but without dying. Inside the biologist’s stainless steel tank are about 60 billion life-forms gathered from all over the planet. They wait in chilly repose. They neither eat nor sleep.
They do not breathe. Not even the simplest chemical reactions of metabolism take place inside their bodies. By any conventional definition of life, the creatures have surrendered their claim on it. And yet by those definitions, anyone can work a miracle: merely reach into the tank and take out one of the 30,000 hermetically sealed glass vials, or ampoules, each about an inch long and each holding about two million of the inanimate creatures in less than a teaspoonful of frozen fluid. Now let it warm to body temperature. From their icy limbo, the tiny creatures will undergo resurrection in minutes. They will, in the language of an age that could not have imagined what is routine in almost every biomedical laboratory today, “come back to life.” Some of the little organisms begin moving around, crawling over the inside surface of their container.
That Which was Happy was Very Short in Duration In Ernest Hemingways story, The Short Happy Life of Francis Macomber, Francis Macomber, according to Hemingway, is a very unhappy man because of his cowardly display after facing a wounded lion and because of his inability to stand up to his wife. However, Francis Macomber regains his happiness, contentment, self-control and bravery while out hunting ...
They will begin feeding on the nutrients dissolved in the now-melted liquid that surrounds them. And – the surest proof that they are truly alive – the creatures will begin reproducing. The organisms in the ampoules are cells – the fundamental units of life, the microscopic building blocks of which all living organisms are made. They have been removed from the bodies of thousands of different animals of nearly a hundred species. In some of the frozen ampoules are kidney cells from a mouse. In others are skin cells from a chimpanzee.
There are turkey blood cells, armadillo spleen cells, iguana heart cells -dozens of different kinds of cells from scores of different species. And, of course, there are cells of human beings. More than 20,000 frozen ampoules hold about 40 billion human cells in suspended animation. Inside ampoules marked “ATCC CCL 72,” for example, are skin cells taken in 1962 from a nine-month-old baby girl. The child has long since died of a birth defect, but her cells survive, ready to “come back to life” any time anybody removes an ampoule and warms it up. In “ATCC HTB 138” are brain cells removed from a seventy-six-year-old man in 1976.
He too is now dead, but not his brain cells. In ampoule “ATCC CCL 204” are lung cells from a thirty-five-year-old man who died in 1979 and whose body was maintained so that its organs could be transplanted. Before the life support system was switched off, researchers bestowed a kind of immortality on a tiny piece of his lung. They sliced out a chunk containing a few thousand lucky cells and granted them the opportunity to live on, growing and reproducing themselves independently for decades (Singer, 1979, p. 44).
The most famous cultured cells, or cell line, in the annals of biomedical research are those in “ATCC CCL 2,” known worldwide as HeLa cells because they came from Henrietta Lacks, a thirty-one-year-old Baltimore woman who died in 1951 of cervical cancer.
The cells from her tumor have been multiplying in laboratories all over the world ever since. At one time HeLa cells were among the most popular with researchers, who, like gardeners sharing cuttings from a favored plant, freely passed a few cells from their own colony to other researchers. So many dishes and flasks of the HeLa cell line are now alive around the world that it is estimated they weigh far more than Henrietta Lacks ever did (Singer, 1979, p. 47).
Receptor Protein - Protein that binds to a specific single molecule, enabling the cell to respond to the signal molecule. i. e. - The muscles of a person exercising can not contract without receptor proteins and signal molecules that tell the muscles when to contract and when to relax. Second Messenger - Signal molecule produced in response to the binding of a chemical signal. Acts as a signal ...
On the cutting edge of modern medical research, cultured cells are the most intimately studied life-forms. Biologists still use mice, white rats, guinea pigs, and fruit flies. But more and more it has become evident that many of the most challenging questions — from the practical desire to conquer disease to the purely intellectual quest to understand how life works – can only be answered with a detailed knowledge of the innermost workings of individual cells.
Human life, biologists now know, is really the sum of the lives of many individual cells organized in definite ways. And all disease is the result of processes that go awry within cells or among cells. Cancer and the common cold, heart disease and hay fever, even AIDS and arthritis, all afflict people because of failed mechanisms within cells. This is why biologists say basic research – intended for understanding how cells work rather than at conquering any specific disease – promises knowledge that can be used to attack many, and perhaps all, diseases. Sickle-cell anemia, for example, is the result of the slightly flawed shape of one kind of molecule in a person’s blood cells. The errant molecule warps the red blood cell’s normal doughnut shape into a crescent, or sickle, shape.
Some forms of diabetes are caused by faulty molecules called receptors that are embedded in the membranes that enclose cells. These molecules are specialized gatekeepers, intended to recognize only insulin molecules and, when one comes along and binds to it, they will relay the appropriate signal to the cell’s interior. With faulty shapes, the molecules fail to recognize insulin and the body becomes as sick as if it had no insulin at all (Pines, 1998, p. 211).
As scientists probe the innermost workings of these microscopic parts of the human body, they are beginning to understand one of the most profound mysteries ever contemplated-the nature of life and how it works. Now just imagine that the room in which you are sitting is one gigantic cell. You are inside the cell, sitting comfortably, and simply by looking around the room you can study the internal workings of this improbably huge cell. If you are in an average-sized living room, the nucleus (which holds the genetic blueprints in the form of the chemical called DNA) would be nearly the size of a Volkswagen Beetle – parked, let’s say, over against the wall to your left.
Chapter 6 Unit III Eukaroyte Cell 1. bulk transport -- - eukaroytes have it. 2. cell receptor -- -binds to other molecules. 3. endocytosis -- -engulfs a large molecule. 4. endoplasmic reticulum-for the translation of proteins. 5. Exocytosis -- - secretes whole antibody molecules. 6. Golgi apparatus -- - for packaging materials to be secreted. 7 ligand -- - any type molecule that a receptor binds ...
But of course don’t forget that typical human cells are really so small that 250 could nestle side by side on top of the period at the end of this sentence. Take a close look at the tiny ridges of skin that make up your fingerprints. Each ridge is about twenty cells wide. A patch of skin measuring just one square inch has more than one million cells in the top layer alone. As it happens, not all cells are so small. The record holder is the ostrich egg, which is somewhat bigger than a grapefruit and, like all eggs, consists of a single cell.
Even within the human body there are some respectably large cells. Muscle cells are long, thin filaments that can stretch an inch and a half. Still longer are the nerve cells that extend out from the spinal cord to the tips of the fingers or toes. Still, the size of the vast majority of cells – certainly most of those in the human body – is so tiny that it is very hard to think about what goes on inside them while imagining them at their true, sub-Lilliputian scale. Cell biologists can get around this by using powerful microscopes to see cells, microscopes with such magnifying power that a photograph of the inside of one cell taken through such a microscope can show details as clearly as an ordinary snapshot of your living room. The imaginary living room cell – roughly 300,000 times bigger than a typical real cell – allows one to study cells with a kind of mental microscope – a visual metaphor that makes it easier to understand how life works. This is so because most of what happens in cells involves physical objects interacting in ways that take many words to describe but which really are no harder to understand than how Lego blocks fit together or why each size of bolt requires a special wrench to turn it.
Looking in the mirror I now see how warped my views of my own body's appearance must have been. My body now looks healthier and I do not look so weak that I could fall apart if someone were to gently touch me. I have more color in my face and my eyes look brighter. I feel better about the decisions I am now making for my life. As I stand here I also remember the times where it was more difficult ...
If you can visualize Lego blocks or wrenches, it’s a lot easier to understand how they work than if you read a description of them in words. Like all cells, the living-room cell is jammed full of organelles from wall to wall. In the living-room cell the force of gravity is negligible, as it is in real cells, and many objects float as if they were weightless in space; others are stuck to various surfaces and move with them. Along with the huge VW-sized nucleus there are half a dozen floppy stacks of beanbag chairs undulating softly in the air. The “air,” of course, is the water inside a cell, which is thick with all the molecules and other structures in it, so thick that it is viscous, or jellylike. From time to time, a little bit of a beanbag pinches off to form a bubble about the size of a golf ball.
It drifts slowly, like a soap bubble, bumps into a long rope that reaches off to the wall, and suddenly begins gliding along the rope, headed for the far wall. That was a vesicle being transported by a motor molecule, probably the kinesin. There is a dense web of ropes and strings running every which way throughout the room. Some are straight. Others look more like a filigree, branching like the limbs of a tree. Some strings seem to wrap around the nucleus and then stretch off to attachment points on the walls. Other ropes line the walls, pinned to it at intervals.
Scores of long sausages slither about. Some of them also seem to glide along ropes, also carried by motor molecules. There are vast areas of great floppy sheets, like a deflated hot air balloon that has been folded loosely and studded with thousands of marbles. The layers and layers of balloon wrap around the VW nucleus, almost concealing it. The strings around the nucleus pick their way through holes in the sheets or between them. And there are hundreds of grapefruits and some basketballs hovering all through the room. Let’s look more attentively at all the “staff”. Just imagine that every cell in the human body must, like any organism, consume food to live. The cell membrane, among its many roles, is also the cell’s mouth.
For example, macrophages, the amoebalike creatures, whose main role in the body is eating, gobble up bacteria and other invaders as well as worn-out cells. When a macrophage engulfs a morsel of food, it gradually embraces it with its own cell membrane. The enclosed volume then is inside a bubble of membrane – a vesicle, or endosome, as it is often called – that breaks away from the outer surface of the cell and drifts inward (Fausto-Sterling, 2003, p. 127).
The cell is the fundamental structural unit of all living organisms. Some cells are complete organisms, such as the unicellular bacteria and protozoa; others, such as nerve, liver, and muscle cells, are specialized components of multi-cellular organisms. Cells range in size from the smallest bacteria-like, which are 0. 1 micrometer in diameter, to the egg yolks of ostriches, which are about 8 cm ( ...
The plasma membrane simultaneously seals itself, as if your fingers closed around a coin in the palm of your hand and the skin of your fingers and palm fused. The coin would now be inside your body. When a macrophage has completely enveloped a morsel of food, the vesicle containing it moves inward to meet one of the cell’s many stomachs, organelles called lynosomes, from the Greek lysis meaning to “loosen or break apart,” and the Greek soma meaning “body.” In the living-room cell there are about a hundred or so grapefruit-sized to basketball-sized lynosomes hanging about, each enclosed by a membrane similar to the one that surrounds the entire cell.
Inside each lysosome there are about fifty different kinds of digestive enzymes, a corrosive brew so powerful that if a lysosome ruptured and spilled its contents, the cell ….