human cell foundation for all life

let us look at a foundation for all life, the cell. Let's look at a human cell, since all of us who will read this will be human, and thus we all have cells in common. Some of us were told in school that cells are a simple structure, however we have learned in the last decade or so that actually cells are extremely complex structures and they even contain complex structures in them!
Here are a few complex parts of cells that are common to every cell in every species.

DNA (Deoxyribonucleic acid) is the molecule that contains the chemical instructions for cells to manufacture various proteins.


Chromosome – a carrier of genes and one of the 46 molecules of DNA. It comes in 23 pairs, and is found in each cell in the human body, together contains all the genes. These chromosomes contain the instructions to make all the proteins that are needed. Other species contain more or fewer chromosomes. One member of each pair of the 23 pairs comes from the gamete of each parent.


Gene – Is the basic unit for the transmission of heredity, consisting of a string of chemicals coding for the manufacture of certain proteins. The instructions from the 46 chromosomes are organized into genes on the chromosome. Each gene is a separate section of a chromosome, and every gene contains instructions for specific proteins. Each gene has chemicals (amino acids) that are paired and then arranged in groups of three (triplets). Genes direct the creation of 20 types of amino acids.

Also consider this:
Human genome – Is the full set of all the 25,000 or so genes on 46 chromosomes that are the instructions for making a human. There is a genome for every species, even plants. Every human except for mono zygotic twins has a slightly different code, otherwise the human genome is 99.99% the same for any two people.

Is there any one out there who can tell me that how by chance amino acids would ever get together and form genes, and then form chromosomes, and then make DNA? Also explain to me why these complex structures whose instructions are specific would randomly do anything, let alone randomly form a whole different creature from what is currently is? The purpose of the DNA of the cell is to guide it to do what needs to be done. A muscular cell does not try to think, nor does a hair cell try to flex. Most cells also reproduce; you do not have blood cells try to make a cell for the stomach. Yes, we do occasionally we have cancer cells, a group of cells that are similar to normal cells yet abnormal and uncontrollably multiply and destroy healthy tissues. However from cancer we do not find another whole species being created. There was a cellular malfunction. This look at cells is a very crude and simple glance; I am not doing it justice. Yet can you deny the complexity of the cell?

How about looking at a different cell, or just one part of a different cell; the flagellum motor of a bacterium. The flagellum is a hair like structure on bacteria that propels a bacterium around.

human embryonic stem cells

Human embryonic stem cells have been cultured under chemically controlled conditions without the use of animal substances, which is essential for future clinical uses. The method has been developed by researchers at Karolinska Institute and is presented in the journal Nature Biotechnology.

Embryonic stem cells can be turned into any other type of cell in the body and have potential uses in treatments where sick cells need to be replaced. One problem, however, is that it is difficult to culture and develop human embryonic stem cells without simultaneously contaminating them. They are currently cultured with the help of proteins from animals, which rules out subsequent use in the treatment of humans. Alternatively the stem cells can be cultured on other human cells, known as feeder cells, but these release thousands of uncontrolled proteins and therefore lead to unreliable research results.

A research team at the Department of Medical Biochemistry and Biophysics, Karolinska Institute has now managed to produce human stem cells entirely without the use of other cells or substances from animals. Instead they are cultured on a matrix of a single human protein: laminin-511.

"Now, for the first time, we can produce large quantities of human embryonic stem cells in an environment that is completely chemically defined," says professor Karl Tryggvason, who led the study.

"This opens up new opportunities for developing different types of cell which can then be tested for the treatment of disease."

Together with researchers at the Harvard Stem Cell Institute, the researchers have also shown that in the same way they can culture what are known as reprogrammed stem cells, which have been converted back from tissue cells to stem cells.

Laminin-511 is part of our connective tissue and acts in the body as a matrix to which cells can attach. In the newly formed embryo, the protein is also needed to keep stem cells as stem cells. Once the embryo begins to develop different types of tissue, other types of laminin are needed.

Until now, different types of laminin have not been available to researchers, because they are almost impossible to extract from tissues and difficult to produce. Over the last couple of decades, Karl Tryggvason’s research group has cloned the genes for most human laminins, studied their biological role, described two genetic laminin diseases and, in recent years, even managed to produce several types of laminin using gene technology. In this latest experiment, the researchers produced the laminin-511 using recombinant techniques.

Subcellular components of Cell

All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, separates its interior from its environment, regulates what moves in and out (selectively permeable), and maintains the electric potential of the cell. Inside the membrane, a salty cytoplasm takes up most of the cell volume. All cells possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells. This article will list these primary components of the cell, then briefly describe their function.

Cell membrane: A cell's defining boundary
The cytoplasm of a cell is surrounded by a plasma membrane. The plasma membrane in plants and prokaryotes is usually covered by a cell wall. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of lipids (hydrophobic fat-like molecules) and hydrophilic phosphorus molecules. Hence, the layer is called a phospholipid bilayer. It may also be called a fluid mosaic membrane. Embedded within this membrane is a variety of protein molecules that act as channels and pumps that move different molecules into and out of the cell. The membrane is said to be 'semi-permeable', in that it can either let a substance (molecule or ion) pass through freely, pass through to a limited extent or not pass through at all. Cell surface membranes also contain receptor proteins that allow cells to detect external signalling molecules such as hormones.

Cytoskeleton: A cell's scaffold
The cytoskeleton acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosis, the uptake of external materials by a cell, and cytokinesis, the separation of daughter cells after cell division; and moves parts of the cell in processes of growth and mobility. The eukaryotic cytoskeleton is composed of microfilaments, intermediate filaments and microtubules. There is a great number of proteins associated with them, each controlling a cell's structure by directing, bundling, and aligning filaments. The prokaryotic cytoskeleton is less well-studied but is involved in the maintenance of cell shape, polarity and cytokinesis.
Genetic material
Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Most organisms use DNA for their long-term information storage, but some viruses (e.g., retroviruses) have RNA as their genetic material. The biological information contained in an organism is encoded in its DNA or RNA sequence. RNA is also used for information transport (e.g., mRNA) and enzymatic functions (e.g., ribosomal RNA) in organisms that use DNA for the genetic code itself.
Prokaryotic genetic material is organized in a simple circular DNA molecule (the bacterial chromosome) in the nucleoid region of the cytoplasm. Eukaryotic genetic material is divided into different, linear molecules called chromosomes inside a discrete nucleus, usually with additional genetic material in some organelles like mitochondria and chloroplasts (see endosymbiotic theory).
A human cell has genetic material in the nucleus (the nuclear genome) and in the mitochondria (the mitochondrial genome). In humans the nuclear genome is divided into 46 linear DNA molecules called chromosomes. The mitochondrial genome is a circular DNA molecule separate from the nuclear DNA. Although the mitochondrial genome is very small, it codes for some important proteins.
Foreign genetic material (most commonly DNA) can also be artificially introduced into the cell by a process called transfection. This can be transient, if the DNA is not inserted into the cell's genome, or stable, if it is.

Organelles
The human body contains many different organs, such as the heart, lung, and kidney, with each organ performing a different function. Cells also have a set of "little organs," called organelles, that are adapted and/or specialized for carrying out one or more vital functions. Membrane-bound organelles are found only in eukaryotes.
Credit by Wikipedia

RNA comparison with DNA

RNA and DNA differ in three main ways. First, unlike DNA which is double-stranded, RNA is a single-stranded molecule in most of its biological roles and has a much shorter chain of nucleotides. Secondly, while DNA contains deoxyribonucleic acid, RNA contains ribonucleic acid, (there is no hydroxyl group attached to the pentose ring in the 2' position in DNA, whereas RNA has two hydroxyl groups). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. In light of this, several types of RNA (tRNA, rRNA) contain a great deal of secondary structure, which help promote stability. Thirdly, the base-pair of adenine is not thymine, as it is in DNA, but rather uracil, which is a unmethylated form of thymine.
Like DNA, most biologically active RNAs including tRNA, rRNA, snRNAs and other non-coding RNAs (such as the SRP RNAs) are extensively base paired to form double stranded helices. Structural analysis of these RNAs have revealed that they are not, "single-stranded" but rather highly structured. Unlike DNA, this structure is not just limited to long double-stranded helices but rather collections of short helices packed together into structures akin to proteins. In this fashion, RNAs can achieve chemical catalysis, like enzymes. For instance, determination of the structure of the ribosome in 2000 revealed that the active site of this enzyme that catalyzes peptide bond formation is composed entirely of RNA.

Transcription is the process through which a DNA sequence is enzymatically copied by an RNA polymerase to produce a complementary RNA. So to say, it is the transfer of genetic information from DNA into RNA. In the case of protein-encoding DNA, transcription is the beginning of the process that ultimately leads to the translation of the genetic code (via the mRNA intermediate) into a functional peptide or protein. The stretch of DNA that is transcribed into an RNA molecule is called a transcription unit. Transcription has some proofreading mechanisms, but they are fewer and less effective than the controls for copying DNA; therefore, transcription has a lower copying fidelity than DNA replication.[citation needed]
As in DNA replication, transcription proceeds in the 5' → 3' direction (i.e. the old polymer is read in the 3' → 5' direction and the new, complementary fragments are generated in the 5' → 3' direction). Transcription is divided into 3 stages: initiation, elongation and termination.

DNA and RNA Introduction

Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organism. The main role of DNA is the long-term storage of information and it is often compared to a set of blueprints, since DNA contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Chemically, DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate atoms joined by ester bonds. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription. Most of these RNA molecules are used to synthesize proteins, but others are used directly in structures such as ribosomes and spliceosomes.

Within cells, DNA is organized into structures called chromosomes and the set of chromosomes within a cell make up a genome. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms such as animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes such as bacteria it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA, which helps control its interactions with other proteins and thereby control which genes are transcribed.

Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions of ribosomes, and acts as an essential carrier molecule for amino acids to be used in protein synthesis.
RNA is very similar to DNA, but differs in a few important structural details: RNA nucleotides contain ribose sugars while DNA contains deoxyribose and RNA uses predominantly uracil instead of thymine present in DNA. RNA is transcribe (synthesize) from DNA by enzymes called RNA polymerases and further processed by other enzymes. RNA serves as the template for translation of genes into proteins, transferring amino acids to the ribosome to form proteins, and also translating the transcript into proteins. Nucleic acids were discovered in 1868 (some sources indicate 1869) by Johann Friedrich Miescher (1844-1895), who called the material 'nuclein' since it was found in the nucleus. It was later discovered that prokaryotic cells, which do not have a nucleus, also contain nucleic acids. The role of RNA in protein synthesis had been suspected since 1939, based on experiments carried out by Torbjörn Caspersson, Jean Brachet and Jack Schultz. Hubert Chantrenne elucidated the messenger role played by RNA in the synthesis of proteins in ribosome. The sequence of the 77 nucleotides of a yeast RNA was found by Robert W. Holley in 1964, winning Holley the 1968 Nobel Prize for Medicine. In 1976, Walter Fiers and his team at the University of Ghent determined the complete nucleotide sequence of bacteriophage MS2-RNA.

DNA and RNA Structure and Functions

DNA (deoxyribonucleic acid) is the genetic material and is largely found in the chromosomes. RNA (ribonucleic acid) is made up of nucleotides containing sugar ribose. When these two work together, they build the amino acid sequence in a protein. This section is going to look at them individually.

DNA

Here is the structure of a DNA. As many have heard, or possibly made models of, the DNA is a double helix. This simply means it has two strands that spiral around each other. In the middle of these strands are nucleotides that are bonded by hydrogen bonding. The bonds created are: A with T, and G with C. These are called complimentary paired bases.

The function of DNA is to replicate. Its job is to make an exact replica of itself. The fancy scientific term for this process is called: DNA replication. Here is a brief explanation of how DNA replicates. This is pulled straight from our text book, but I found it to be the simplest and most clear.

   1. Before replication starts, the two strands of the original DNA are hydrogen-bonded together.
   2. An enzyme unwinds and “unzips” the DNA
   3. New complementary DNA nucleotides, which are always in the nucleus, fit into place by the process of complimentary base pairing. These position and are then joined by the enzyme DNA polymerase.
   4. To complete replication, an enzyme seals any breaks in the sugar-phosphate backbone
   5. The two double-helix molecules are identical to each other and the original DNA.

RNA

Now for an RNA structure. We now know that DNA is made up of the A,T,G, and, C nucleotides. RNA, on the other hand, is made up of C,G,A, an U nucleotides. RNA is also single stranded. There are also three types of RNA.

The first is Ribosomal RNA or rRNA. It is produced in the nucleolus and its main job is to join with proteins made in the cytoplasm to form the subunits of ribosomes.

Structure of DNA and RNA molecules

We know that all organisms produce offsprings of their own kind whether it is a single celled animal like Amoeba or a multicellular animal like a horse. Amoeba produces a daughter amoeba, and a horse produces a baby horse. All this is possible just because a very special molecule that is termed as deoxyribonucleic acid or DNA. The DNA contains the hereditary material which makes every individual unique and this material is transferred from the parents to the offsprings. The DNA is present in a special organelle of the cell called the nucleus. As the size of the cell is very small and each organism has many molecules of DNA so the DNA must be tightly packed inside the nucleus and this packed form of DNA is called as chromosome. DNA spends it most of the time inside the cell in the form of chromosome. During cell division, the DNA unwinds so that it can be copied and transferred to the daughter cells. DNA also carries instructions for protein synthesis so that other biological processes can be regulated normally. The DNA present inside the nucleus is termed as nuclear DNA and the complete set of nuclear DNA is designated as genome. Apart from its occurrence inside the nucleus, DNA is also present in the cell organelle named as mitochondria which are the power houses of the cells. During sexual reproduction the offsprings inherit half of the nuclear DNA from the father and half from the mother but the mitochondrial DNA is inherited completely from the mother as the sperm cells do not bear mitochondria after fertilization.

The DNA molecule was first observed in the late 1800s by a German biochemist Frederich Miescher. But nearly a century passed after that and the scientists couldn't succeed in unraveling the mystery of the DNA molecule. The mystery of the DNA was solved in 1953 by the eminent works of James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin. By using X-ray diffraction technique the scientists pointed out the double helical structure of DNA that encodes the genetic information of every organism living on this earth.

The chemical building blocks of DNA are called as nucleotides. The nucleotides are formed of three components: a phosphate group, a sugar and one of the four types of nitrogenous bases. To form a complete strand of DNA nucleotides are linked in the form of chains with alternating arrangement of phosphate groups and sugars. The four types of nucleotide bases that form DNA are adenine (A), guanine (G), cytosine (C) and Thymine (T). The arrangement of these nitrogenous bases within a DNA molecule is very specific. The adenine can always pair with thymine on one side of the DNA helix and cytosine can also pair with guanine on one side of the DNA helix. This specific arrangement of base pairs in a DNA strand follows a rule called as Chargaff's rule which plays a very important role in the replication of the DNA molecule.

The process of DNA replication proceeds after the breaking of the weak chemical bonds between the two poly nucleotide chains by an enzyme. The DNA strand breaks in the middle separating the base pairs. These newly separated strands now work as templates from which the new strands of DNA will be obtained. Inside the nucleus many extra nucleotides are present. The bases first bond with the bases present on the template which will match just according to the Chargaff's rule. When the base pairing is completed the phosphate groups and the sugar is added to form other poly nucleotide chain. This procedure is repeated with both the template strands of DNA. The whole process is repeated thousands of time in order to form the two molecules of DNA which are exactly the replicates of the original DNA molecule and all this happens during mitosis so the daughter cells receive the exact similar character of the DNA. When an error occurs during the process of DNA replication mutation occurs. The mutation causes either deletion or addition of base pairs and the proteins also get defected by having wrong pairs of amino acids.

One of the important functions of DNA is protein synthesis. The process of protein synthesis is completed in two steps. The first step is transcription and the second step is translation. In transcription the cell uses the information from a gene in order to form a protein. Both the DNA and RNA molecules are similar in structure except the fact that RNA is shorter than DNA and bears the sugar ribose instead of deoxyribose that is present in DNA. RNA also differs from DNA in having a base uracil in place of thymine. During transcription, the type of RNA that is created is called mRNA or messenger RNA because it is used as a "messenger" to send information from a gene on DNA to a ribosome so that protein can be created. RNA polymerase recognizes and attaches to a DNA nucleotide chain at the beginning of the gene, at a place called the promoter. The promoter positions the RNA polymerase on the right strand of DNA and guides it to the right direction. As the RNA polymerase moves, it creates a new chain from the extra nucleotides. The RNA polymerase continues until it reaches a stop signal at the end of the gene. The RNA polymerase then detaches itself from the DNA and the RNA chain is released, creating mRNA.

When the mRNA sends the information from the DNA to the ribosomes it is converted into the language of amino acids. When amino acids are formed a protein is created. The mRNA transfers the information from the DNA to the ribosomes in the language of nucleotides. The ribosomes attach on a particular place on the mRNA which is called start codon which is made up of three nucleotide bases indicating that it is ready to read a message. The amino acids that will later form protein come across the transfer RNA or tRNA while they are attached to the ribosomes. The tRNA moves the amino acids along the mRNAs so that the message can feed across the ribosome. There the amino acids are all linked together to form a protein chain. Every organism on uses this process to make proteins.

Thus, it can be concluded that DNA is very essential component of an organism's life.