Berzelius was the first person to show the difference between organic compounds (those made with carbon), and inorganic compounds. He helped Gerhardus Johannes Mulder in his analysis of organic compounds such as coffee, tea and many proteins. The term "protein" itself was created by Berzelius, after Mulder noticed that all proteins seemed to have the same formula and might be made of a single type of a (very large) molecule.
Berzelius wrote a great deal. He helped many leading scientists (such as Mulder, Claude Louis Berthollet, Humphry Davy, Friedrich Wöhler and Eilhard Mitscherlich), and many less-notable scientists.
Antibody
Antibodies (also called immunoglobulins) are large Y-shaped proteins that can stick to the surface of bacteria and viruses. They are found in the blood or other body fluids of vertebrates. Antibodies are the key element in the adaptive immune system.
The antibody recognizes a unique part of the foreign target called an antigen. Each tip of the "Y" of an antibody contains a structure (like a lock) that fits one particular key-like structure on an antigen. This binds the two structures together.
Using this binding mechanism, an antibody can "tag" a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly. The production of antibodies is the main function of humoral immunity.
Each antibody is different. They are all designed to attack only one kind of antigen (in practice, this means virus or bacteria). For instance, an antibody designed to destroy smallpox is unable to hit the bubonic plague or the common cold.
Though the general structure of all antibodies is very similar, that small region at the tip of the protein is extremely variable. This allows millions of antibodies with different tip structures to exist. Each of these variants can bind to a different antigen. This enormous diversity of antibodies allows the immune system to recognize an equally wide variety of antigens.
Although a huge variety of different antibodies is made in a single individual, "the number of genes available to make these proteins is limited by the size of the genome".
There are a vast number of microbe strains, and so vertebrates need millions of different antibodies. Actually, humans generate about 10 billion different antibodies, each capable of binding a distinct antigen site. This must be done with a very much smaller number of genes: the total human genome has only about 20,000 genes.
Several complex genetic mechanisms have evolved. These allow vertebrate B cells to generate a huge pool of antibodies from a relatively small number of antibody genes. The full details are not presented here, just a summary.
The variety of antibodies is got by combining segments from a pool of genes in many different ways. Then, hyper-mutations occur in the binding site area of the antibody gene. This creates further diversity.
Antibodies are glycoproteins belonging to the immunoglobulin superfamily; the terms "antibody" and "immunoglobulin" are often used interchangeably. Antibodies are typically made of basic structural units—each with two large "heavy chains" and two small "light chains". There are several different types of antibody heavy chains, and several different kinds of antibodies, which are grouped into different "isotypes" based on which heavy chain they possess. Five different antibody isotypes are known in mammals. They help direct the appropriate immune response for each different type of foreign object they encounter.
Though the general structure of all antibodies is very similar, a small region at the tip of the protein is extremely variable, allowing millions of antibodies with slightly different tip structures, or antigen binding sites, to exist. This region is known as the "hypervariable region". Each of these variants can bind to a different antigen. This enormous diversity of antibodies allows the immune system to recognize an equally wide variety of antigens. The large and diverse population of antibodies is generated by random combinations of a set of gene segments that encode different antigen binding sites (or "paratopes"), followed by random mutations in this area of the antibody gene, which create further diversity. Antibody genes also re-organize in a process called class switching, which allows a single antibody to be used by several different parts of the immune system.
Anura
The order Anura includes the frogs and toads. They are the most successful living amphibia, judged by number of species. There are about 7400 different species of amphibians, and about 6500 are in the Anura.
There is no fundamental difference between frogs and toads. Frogs have a short body, webbed digits (fingers or toes), protruding eyes, forked tongue and no tail. They are exceptional jumpers: many of their features, particularly their long, powerful legs, are adaptations to improve jumping performance. They often live in semi-aquatic or humid areas.
A popular distinction is often made between frogs and toads on the basis of their appearance. The warty skin of toads is an adaptation for making their toxic slime. Apart from these glands, their skin is dry, and that is an adaptation to drier habitats. These features have evolved a number of times independently: convergent evolution. The distinction has no taxonomic basis: the Anura are not divided into frogs and toads. The only family exclusively given the common name "toad" is the Bufonidae (the "true toads"), but many species from other families are also called "toads".
Frogs have smooth (soft) skin, while toads have rough (hard) skin. Frogs need their skin to be wet in order for them to get oxygen. Frogs and toads have broad heads and plump bodies. They have short fore limbs and long webbed hind feet. This helps them to move and swim in water. They can also use their legs to crawl, hop and leap. Frogs are good jumpers, and some can leap up to six feet in the air. Tree frogs can climb on any surfaces, they use their sticky hands to do this. The tympanum membrane can only be seen on frogs. The tympanum membrane can be found between the frog's ears and eyes. Frogs have tiny teeth inside their mouths. They are found on the lower jaw. The African bullfrog is the only species where the males are longer than the females. Males can reach up to 9½-10 inches in length, while the female only grows up to 4½ inches. Frogs belonging to the suborder Neobatrachia, such as the poison dart frogs and Mantellinae frogs, can kill humans. Like most poisonous animals, they get their toxin from their food.
Most frogs and toads lives near slow moving waters like rivers, swamps, lakes and ponds. Others such as tree frogs and poison dart frogs lives in forests. Frogs and toads can be found almost everywhere except Antarctica. Frogs and toads squeak or make calls when they are touched or feel threatened. They also make those sounds to communicate with others in their habitat. They make these sounds by expanding their throats with air and letting the air go out. Male bullfrogs will roar while mating with a female. Most frogs and toads are territorial. This means that they go to battle when an animal of their own kind gets close to where they live. They will jump, wrestle and even chase any animal away. They do this to also attract females to their territory. Females choose a territory where there is enough food for her to eat and if there is a lot of water to swim and lay her eggs.
Toads spend most of their time on land, while frogs spend most of their time in the water. Tailed frogs looks similar to toads because of their hard skin. A tailed frogs "tail" is really an organ they use to release sperm in fast-moving waters. They are the only frogs with this organ. The genus "Eleutherodactylus" are terrestrial frogs. This means that they lay eggs on land. Spadefoot toads make crying sounds during a rainstorm.