Information – Energy – Time/Space
All life forms consist of these three elements: information and energy that occupy a space for a period of time. All living systems process information, and without this the living organism ceases to be alive. This information is contained in a molecule called deoxyribonucleic acid or DNA. It is the genetic code of life, that is, the essential information or the database to build and maintain a particular life form.
DNA is composed of two long strands of base pairs along with sugar and phosphate molecules, all spiraling to form a double helix. Like a twisted ladder, the base pairs form the rungs, and the sugar and phosphate molecules form the two vertical sides of the ladder. The information for building all the proteins that our body is made of is encoded in the DNA molecules. In other words, it is the DNA that instructs the cells to make the proteins essential for our growth, development and health.
From the colour of our skin to the colour of our eyes and hair, how tall we are going to be and even the diseases we may develop in time, all the information about our body is contained in the DNA; because we carry such precious information, it is so to say kept under lock and key inside the nucleus of each of our cells.
Protein formation is a very intricate process. When a particular protein is needed, in order to keep the DNA safe and unaltered, the instruction on the DNA molecule to make that protein is copied inside the nucleus onto another molecule called ribonucleic acid, or RNA which is similar to DNA, but instead of two strands it is single stranded, and can be found both in the nucleus and the cytoplasm of each cell.
For all this to work, a power source is required. This source of energy is ultimately the sun, because all forms of energy come from the sun. By the process of photosynthesis, cells with chloroplasts transform solar energy into chemical energy that will feed the cells or provide the raw materials like oxygen for all vital processes in other cells.
We can now biologically define life as being what distinguishes the animal or plant kingdom from minerals and metals, the organic world from the inorganic, or the animate world from the inert one. A living being is an organism that is self-contained and maintains a certain independence from the environment in which it lives and thrives. It keeps an internal equilibrium or homeostasis, and is composed of one or more cells that maintain life via metabolism or biochemical processes. It has the capacity to grow and adapt to its environment, to respond to stimuli, to reproduce and to die.
I believe that life appeared spontaneously on Earth when the right conditions were created for it to emerge. God kicked off with the Big Bang and the rest came about spontaneously, in a continuous succession of cause-effect-cause… and so on until we reached human life.
But all this occurred according to God’s design, who knew beforehand the final result of the sequence of causes and effects; that is to say, He knew that it would lead to the emergence of a being, the human being, in His image and likeness. In fact, like God, human beings also have the capacity to create. The only difference is that God creates out of nothing, while humans mix elements already created to transform them into new things.
We all know that living or organic matter is composed of inorganic elements. However, the passage from the inorganic to the organic is still today the great mystery in biology. Many scientists have sought to recreate the earthly conditions when life first began, placing in this environment the fundamental elements of life, and yet have not managed to create life. Life is God’s creation, it is His property, it belongs to Him, and like the secret of Coca-Cola it is not revealed. Living beings (and we are the living beings created by God) do not create life, they only transmit it.
From the Atom to the Cell
The combination of two or more atoms of different chemical elements forms a compound. The smallest unit that retains the properties of a compound is the molecule, which can be as simple as the water molecule (H2O) or as large and complex (macromolecule) as a molecule of protein or nucleic acid.
The chains of carbon atoms bonded to hydrogen, oxygen, nitrogen, and small amounts of sulfur (S) and phosphorus (P) form the majority of organic compounds found in living matter. Most of these compounds are classified under four groups: proteins, carbohydrates, lipids and nucleic acids, which constitute the raw materials for the formation of the supra molecular structures that make up cells, such as membranes and organelles.
This organic matter still needs inorganic matter in order to obtain life, therefore, in addition to the organic substances, we find in the human body inorganic substances such as water (H2O) and mineral salts. Animal cells are formed chemically by organic compounds and inorganic substances, in different proportions:
Proteins: 17.8 %
Carbohydrates: 6.2 %
Lipids: 11.7 %
Water: 60.0 %
Mineral Salts: 4.3 %
Proteins
Proteins are macromolecules made up of many smaller molecules, or amino acids, composed of carbon, hydrogen, oxygen and nitrogen atoms; some also contain small amounts of sulfur. There are twenty different amino acids that participate in protein structures, eleven of them are synthesized by human cells and the remaining nine must be obtained from protein-rich foods such as soy, legumes and meat.
Carbohydrates
Carbohydrates are molecules made up of carbon, oxygen and hydrogen atoms. The principal characteristic of carbohydrates is its role in energy for action, that is, whenever energy is required by the body to do work, one needs to resort to a diet rich in this compound. These foods are mostly of plant origin such as cereals, legumes, fruits, roots, and starchy foods like potatoes and rice.
Lipids
Fats, also known as lipids, are organic biomolecules composed mainly of hydrogen, oxygen and carbon atoms. Other elements, such as phosphorus, are also part of the lipid composition. Like carbohydrates, they supply energy to the cells, participate in the composition of the cell membranes, and act as thermal insulator in some animals. There are two types of lipids: saturated, of animal origin, and unsaturated, of plant origin.
Nucleic Acids
There are two types of nucleic acids: RNA (ribonucleic acid) and DNA (deoxyribonucleic acid), both are formed from smaller units called nucleotides. Each nucleotide is chemically made up of a phosphate group that confers acidity to the unit, a 5-carbon sugar, and a nitrogenous base (adenine, cytosine, guanine or thymine/uracil). The storage and transmission of the genetic information is the responsibility of the nucleic acids, therefore, they are the most important biomolecules in cellular control because they contain the genetic code.
Recapitulating the path that life takes starting from the atom, the smallest form of matter, this is its course: subatomic particle – atom – molecule – macromolecule – organelle – cell – tissue – organ – organ system – organism or body…
The Cell and Its Internal Structure
Like the atom is the building block of inorganic matter, the cell is the building block of organic or living matter. The cell is in itself a living being, the smallest one in nature; the amoeba, for example, is a single-celled organism. One main difference between the amoeba and other living organisms is in the number of cells. An adult human body contains trillions of cells, although they all began from a single cell, just as all multicellular organisms begin from a single cell at the moment of conception.
All cells can be classified structurally as either prokaryotes or eukaryotes. The prokaryotes are predominantly single-celled organisms of the domains Bacteria and Archaea, and they do not have a nucleus or any other membrane bound organelles. The cells that we are interested in are the eukaryotes, that is, cells with nucleus that are common to all plants and animals including humans.
External Membrane
The cell membrane is the outer boundary of a cell that separates it from the world outside, it is the protective barrier of the cell. It defines the cell as the smallest unit of life – hence the word “cell” from Latin cella, meaning “small room”. It imparts shape and size to the cell, and keep other components within. All cells have a cell membrane. The membrane permits the passage of certain substances and impedes the passage of others, that is, it controls what comes in and what goes out of the cell. In animal cells oxygen and nutrients can enter while carbon dioxide and other waste products can go out.
Cytoplasm
Inside the cell membrane, the cell is filled with a gelatinous substance called the cytoplasm. All the organelles float inside this medium.
What Are Organelles
Organelles are the tiny organs of a cell. A cell is fundamentally a free and independent living being, and like the body of an animal, it contains organs for specific functions: respiration, digestion, elimination of toxins etc. In this way, a cell has its own tiny organs to perform vital functions. Let’s look at the different types of organelles in an eukaryotic cell.
Endoplasmic Reticulum is the transport highway of the materials within the cell; it connects different parts of the cell and helps in the exchange of materials. It can be rough, if its surface is studded with ribosomes, or smooth if it is ribosome-free. The former is involved in the production of protein products and the latter is involved in lipid synthesis and detoxification of drugs and poisons.
Mitochondria is the power plant of the cell where cellular respiration occurs. Although cellular respiration is a combustion reaction, it does not resemble one when it occurs in a living cell because energy is not created from one rapid reaction, but is released slowly from a series of reactions. Nutrients are oxidized in the presence of oxygen, resulting in energy and carbon dioxide. In other words, mitochondria convert the energy from food into a form that can be used by the cells to keep and sustain their lives.
Unlike other organelles, mitochondria are semiautonomous, that is, they have their own DNA which is inherited from the mother only, and can replicate independently of the nucleus. Because of this, researchers believe that mitochondria have evolved from a primitive eukaryote that ingested a prokaryote, with the two developing a symbiotic relationship.
Lysosomes are the sacs containing enzymes that aid in the breaking down of food ingested by the cell. They are also important in removing old cellular components and replacing with newer ones. Sometimes they are called to destroy the cell itself, and are therefore called the suicide cell sacs.
Golgi Apparatus is where proteins are mixed with other chemicals and repackaged, and then released from the cell surface.
Ribosomes float freely inside the cytoplasm or are bound to the surface of the endoplasmic reticulum; their job is to produce proteins. The bounded ribosomes produce proteins that are released from the cell to be used elsewhere, and the free ribosomes produce proteins that are used inside of the cell itself.
Chloroplasts are solar power centers in cells of plants and algae where photosynthesis takes place, that is, the generation of energy using water, carbon dioxide, and sunlight. They are the counterparts of mitochondria in animal cells, where cellular respiration or combustion takes place. Like mitochondria, they also contain their own DNA and are also believed to have evolved via symbiosis.
Vacuoles are the wrappings used to store and move substances that are ingested, excreted, processed or digested by the cell. Vacuoles are found in both animal and plant cells, but are much larger in the latter.
Nucleus
It is the brain of the cell that controls all its vital functions, and allows the cell to function like an independent living being. The nucleus is separated from the cytoplasm by a porous membrane that allows certain molecules to enter and exit the nucleus. The chromosomes are contained within the nucleus which carry the genetic code responsible for hereditary traits.
In the DNA of most cell in the human body, we can find the complete blueprint for all the proteins that are necessary for somatic life. The genetic information encoded in the DNA is transcribed into the messenger RNA which carries the code to the ribosomes in the cytoplasm, and these in turn take the information and translate it into proteins.
As a living organism, a cell can be compared to the social life within a medieval castle made of external walls, inner walls and the keep or tower where the royal family lives. The external walls represent the membrane, that protects the cell from the outside and controls what comes in and what goes out; the inner walls, between the keep and the external walls where people live and interact, represent the cytoplasm where all chemical reactions inherent to life occur; the keep or tower where the royal family lives represents the nucleus of the cell where the DNA that commands all cell operations reside.
Cancer, Disease of the Cell
The cell is the simplest element of any organism. The average human body is made up of an estimated 30 to 40 trillion cells. Since each cell is a living organism, our body is formed by trillions of living organisms that stick together because they all originated from a primordial cell that was formed by the union and fusion of a half cell from each of our parents.
As we have said above, cells, like all living organisms whether plants, animals or humans, are born, grow, reproduce, and die. Each cell, before dying, transmits its genetic material to its descendants, so that it can continue to fulfill the same function as its “parent”. In a simple way, cancer occurs when cells refuse to die and instead, keep multiplying in a disorderly manner.
In reality, cancer is nothing but a civil war within one’s own body: some cells resolve to multiply in a disorderly and uncontrolled fashion. These cells are in a way suicidal, because by completely dominating the body, precipitating its death, they end up dying themselves. Deep down they are suicide bombers, they kill by dying or they die by killing.
Human cells are continuously regenerating. The human body produces roughly a million billion cells in a lifetime. Each time a cell divides to give rise to another, its DNA is copied. The daughter cells resulting from cell divisions must be the exact copy of the parent cell. In other words, the genes of the daughter cells must be identical to that of the parent cell.
In practice, however, small alterations in the DNA molecules that we call mutations can arise, which may be caused by several factors or may simply be random errors. Cancer cells are cells with gene mutation and therefore they don’t have the proper instructions to carry out the duties of their counterparts. Instead they divide out of control, are immature and do not do the job they are created for, they don’t stick to their own kind, and can spread to other parts of the body to attack other tissues and organs.
Even if we were to rid ourselves of all internal, emotional and physical carcinogenic factors, as well as external ones, we would not be completely free from the scourge of cancer, because the error may be a random event during cell division. Fortunately, most errors result in cell death. However even Egyptian mummies have been found with cancer, which leads us to conclude that this is as old as humanity.
It is therefore a real game of Russian roulette whether we get cancer or not during the course of our lifetime, with the likelihood increasing the longer we live. The only hope is that science will develop more sophisticated methods of detecting gene mutation shortly after it occurs, and thus be able to correct it before the mutated cells have the chance to divide out of control.
Fr. Jorge Amaro, IMC
No comments:
Post a Comment