A prokaryote is a unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle. The word prokaryote comes from the Greek πρό before and καρυόν nut or kernel, prokaryotes can be divided into two domains and bacteria. In contrast, species with nuclei and organelles are placed in the domain Eukaryota, in the prokaryotes, all the intracellular water-soluble components are located together in the cytoplasm enclosed by the cell membrane, rather than in separate cellular compartments. Bacteria, however, do possess protein-based bacterial microcompartments, which are thought to act as primitive organelles enclosed in protein shells, some prokaryotes, such as cyanobacteria may form large colonies. Others, such as myxobacteria, have multicellular stages in their life cycles, molecular studies have provided insight into the evolution and interrelationships of the three domains of biological species. Eukaryotes are organisms, including humans, whose cells have a well defined membrane-bound nucleus, the division between prokaryotes and eukaryotes reflects the existence of two very different levels of cellular organization.
Distinctive types of prokaryotes include extremophiles and methanogens, these are common in extreme environments. Prokaryotes have a cytoskeleton, albeit more primitive than that of the eukaryotes. At least some contain intracellular structures that can be seen as primitive organelles. Membranous organelles are known in some groups of prokaryotes, such as vacuoles or membrane systems devoted to special metabolic properties, in addition, some species contain carbohydrate-enclosed microcompartments, which have distinct physiological roles. Most prokaryotes are between 1 µm and 10 µm, but they can vary in size from 0.2 µm to 750 µm, Bacteria and archaea reproduce through asexual reproduction, usually by binary fission. DNA transfer between prokaryotic cells occurs in bacteria and archaea, although it has mainly studied in bacteria. In bacteria, gene transfer occurs by three processes and these are bacterial virus -mediated transduction, plasmid-mediated conjugation, and natural transformation.
Transduction of bacterial genes by bacteriophage appears to reflect an occasional error during intracellular assembly of virus particles, the transfer of bacterial DNA is under the control of the bacteriophage’s genes rather than bacterial genes. Conjugation in the well-studied E. coli system is controlled by plasmid genes, infrequently during this process, a plasmid may integrate into the host bacterial chromosome, and subsequently transfer part of the host bacterial DNA to another bacterium. Plasmid mediated transfer of host bacterial DNA appears to be a process rather than a bacterial adaptation. Natural bacterial transformation involves the transfer of DNA from one bacterium to another through the intervening medium, for a bacterium to bind, take up and recombine donor DNA into its own chromosome, it must first enter a special physiological state called competence. About 40 genes are required in Bacillus subtilis for the development of competence, the length of DNA transferred during B. subtilis transformation can be as much as a third to the whole chromosome
, very common Chinese surname, relatively common Chinese family name, rare Chinese surname Fèng is a rare Chinese surname. In Cantonese Fung, in Middle Chinese Bong, origin of, in Shaanxi the Qin, the Citizen of Yíng get surname Fèng in Shandong the Qi, Jiang family get surname Fèng in Zhejiang the Yue, Yue people get surname Fèng Fēng is a Chinese family name. It is No.208 in the Baijiaxing, and 257 in the modern census, there are two recorded origins for the name. The first according to the Xingyuan from a prince originally with the name Jiang, the second according to Weishu Guanshizhi 《魏书·官氏志》 the name Fu was changed to Feng. Feng Deyi, formal name Feng Lun chancellor to the emperors of the Tang Dynasty Feng Changqing (Chinese, 封常清, pinyin, Fēng Chángqīng, Wade–Giles, Feng Changching a general of the Tang Dynasty
In organic chemistry, amines are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group, important amines include amino acids, biogenic amines and aniline, see Category, Amines for a list of amines. Inorganic derivatives of ammonia are called amines, such as chloramine, see Category, compounds with a nitrogen atom attached to a carbonyl group, thus having the structure R–CO–NR′R″, are called amides and have different chemical properties from amines. An aliphatic amine has no aromatic ring attached directly to the nitrogen atom, aromatic amines have the nitrogen atom connected to an aromatic ring as in the various anilines. The aromatic ring decreases the alkalinity of the amine, depending on its substituents, the presence of an amine group strongly increases the reactivity of the aromatic ring, due to an electron-donating effect.
Amines are organized into four subcategories, Primary amines — Primary amines arise when one of three atoms in ammonia is replaced by an alkyl or aromatic. Important primary alkyl amines include, most amino acids, Secondary amines — Secondary amines have two organic substituents bound to the nitrogen together with one hydrogen. Important representatives include dimethylamine, while an example of an aromatic amine would be diphenylamine, tertiary amines — In tertiary amines, nitrogen has three organic substituents. Examples include trimethylamine, which has a fishy smell. Cyclic amines — Cyclic amines are either secondary or tertiary amines, examples of cyclic amines include the 3-membered ring aziridine and the six-membered ring piperidine. N-methylpiperidine and N-phenylpiperidine are examples of tertiary amines. It is possible to have four organic substituents on the nitrogen and these species are not amines but are quaternary ammonium cations and have a charged nitrogen center. Quaternary ammonium salts exist with many kinds of anions, Amines are named in several ways.
Typically, the compound is given the prefix amino- or the suffix, the prefix N- shows substitution on the nitrogen atom. An organic compound with multiple amino groups is called a diamine, tetraamine, systematic names for some common amines, Hydrogen bonding significantly influences the properties of primary and secondary amines. Thus the melting point and boiling point of amines is higher than those of the corresponding phosphines, for example and ethyl amines are gases under standard conditions, whereas the corresponding methyl and ethyl alcohols are liquids. Amines possess a characteristic smell, liquid amines have a distinctive fishy smell. The nitrogen atom features a lone pair that can bind H+ to form an ammonium ion R3NH+
Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods, Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, acidic hot springs, radioactive waste, Bacteria live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology, There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants, Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of bodies and bacteria are responsible for the putrefaction stage in this process.
In March 2013, data reported by researchers in October 2012, was published and it was suggested that bacteria thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, You can find microbes everywhere—theyre extremely adaptable to conditions, the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial particularly in the gut flora. However several species of bacteria are pathogenic and cause diseases, including cholera, anthrax, leprosy. The most common fatal diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year. In developed countries, antibiotics are used to treat infections and are used in farming, making antibiotic resistance a growing problem.
Once regarded as constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and these evolutionary domains are called Bacteria and Archaea. The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, for about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. In 2008, fossils of macroorganisms were discovered and named as the Francevillian biota, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. Bacteria were involved in the second great evolutionary divergence, that of the archaea, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea
The green algae are a large, informal grouping of algae consisting of the Chlorophyte and Charophyte algae, which are now placed in separate divisions. The land plants, or Embryophytes, are thought to have emerged from the Charophytes, cladistically, Embryophytes belong to green algae as well. However, as the Embryophytes are traditionally classified as neither algae nor green algae, the clade that includes both green algae and embryophytes is monophyletic and is referred to as the clade Viridiplantae and as the kingdom Plantae. The green algae include unicellular and colonial flagellates, most with two flagella per cell, as well as various colonial and filamentous forms, and macroscopic, in the Charales, the closest relatives of higher plants, full cellular differentiation of tissues occurs. There are about 8,000 species of green algae, many species live most of their lives as single cells, while other species form coenobia, long filaments, or highly differentiated macroscopic seaweeds. A few other organisms rely on green algae to conduct photosynthesis for them, the chloroplasts in euglenids and chlorarachniophytes were acquired from ingested green algae, and in the latter retain a nucleomorph.
Green algae are found symbiotically in the ciliate Paramecium, and in Hydra viridissima, some species of green algae, particularly of genera Trebouxia of the class Trebouxiophyceae and Trentepohlia, can be found in symbiotic associations with fungi to form lichens. In general the species that partner in lichens cannot live on their own. Trentepohlia is a green alga that can live independently on humid soil. Green algae have chloroplasts that contain chlorophyll a and b, giving them a green color, as well as the accessory pigments beta carotene and xanthophylls. The cell walls of green algae usually contain cellulose, and they store carbohydrate in the form of starch, all green algae have mitochondria with flat cristae. When present, paired flagella are used to move the cell and they are anchored by a cross-shaped system of microtubules and fibrous strands. Flagella are only present in the male gametes of charophytes and are absent from the gametes of Pinophyta. Members of the class Chlorophyceae undergo closed mitosis in the most common form of division among the green algae.
By contrast, charophyte green algae and land plants undergo open mitosis without centrioles, instead, a raft of microtubules, the phragmoplast, is formed from the mitotic spindle and cell division involves the use of this phragmoplast in the production of a cell plate. This primary endosymbiosis event gave rise to three autotrophic clades with primary plastids, the plants, the red algae and the glaucophytes. Green algae are classified with their embryophyte descendants in the green plant clade Viridiplantae. Viridiplantae, together with red algae and glaucophyte algae, form the supergroup Primoplantae, the Viridiplantae diverged into two clades
Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions, the molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called enzymology, enzymes are known to catalyze more than 5,000 biochemical reaction types. Most enzymes are proteins, although a few are catalytic RNA molecules, enzymes specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy, some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5-phosphate decarboxylase, which allows a reaction that would take millions of years to occur in milliseconds.
Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules, inhibitors are molecules that decrease enzyme activity, many drugs and poisons are enzyme inhibitors. An enzymes activity decreases markedly outside its optimal temperature and pH, some enzymes are used commercially, for example, in the synthesis of antibiotics. French chemist Anselme Payen was the first to discover an enzyme, diastase and he wrote that alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells. In 1877, German physiologist Wilhelm Kühne first used the term enzyme, the word enzyme was used to refer to nonliving substances such as pepsin, and the word ferment was used to refer to chemical activity produced by living organisms. Eduard Buchner submitted his first paper on the study of yeast extracts in 1897, in a series of experiments at the University of Berlin, he found that sugar was fermented by yeast extracts even when there were no living yeast cells in the mixture.
He named the enzyme that brought about the fermentation of sucrose zymase, in 1907, he received the Nobel Prize in Chemistry for his discovery of cell-free fermentation. Following Buchners example, enzymes are usually named according to the reaction they carry out, the biochemical identity of enzymes was still unknown in the early 1900s. Sumner showed that the enzyme urease was a protein and crystallized it. These three scientists were awarded the 1946 Nobel Prize in Chemistry, the discovery that enzymes could be crystallized eventually allowed their structures to be solved by x-ray crystallography. This high-resolution structure of lysozyme marked the beginning of the field of structural biology, an enzymes name is often derived from its substrate or the chemical reaction it catalyzes, with the word ending in -ase
The ornithine cycle is a cycle of biochemical reactions occurring in many animals that produce urea from ammonia. This cycle was the first metabolic cycle discovered, five years before the discovery of the TCA cycle, in mammals, the urea cycle takes place primarily in the liver, and to a lesser extent in the kidney. Organisms that cannot easily and quickly remove nitrogen usually have to convert it to other substance, like urea or uric acid. Insufficiency of the cycle occurs in some genetic disorders. The result of failure is accumulation of nitrogenous waste, mainly ammonia. The urea cycle consists of five reactions, two mitochondrial and three cytosolic, the cycle converts two amino groups, one from NH4+ and one from Asp, and a carbon atom from HCO3−, to the relatively nontoxic excretion product urea at the cost of four high-energy phosphate bonds. Ornithine is the carrier of these carbon and nitrogen atoms and these NADH are produced in two ways, One NADH molecule is produced by the enzyme glutamate dehydrogenase in the conversion of glutamate to ammonium and α-ketoglutarate.
Glutamate is the carrier of amine groups. This provides the ammonium ion used in the synthesis of carbamoyl phosphate. The fumarate released in the cytosol is hydrated to malate by cytosolic fumarase and this malate is oxidized to oxaloacetate by cytosolic malate dehydrogenase, generating a reduced NADH in the cytosol. Oxaloacetate is one of the keto acids preferred by transaminases, and so will be recycled to aspartate, however, if gluconeogenesis is underway in the cytosol, the latter reducing equivalent is used to drive the reversal of the GAPDH step instead of generating ATP. The fate of oxaloacetate is either to produce aspartate via transamination or to be converted to phosphoenolpyruvate, the synthesis of carbamoyl phosphate and the urea cycle are dependent on the presence of NAcGlu, which allosterically activates CPS1. NAcGlu is an activator of carbamoyl phosphate synthetase. So Glu not only is a substrate for NAGS but serves as an activator for the urea cycle, the remaining enzymes of the cycle are controlled by the concentrations of their substrates.
Thus, inherited deficiencies in cycle enzymes other than ARG1 do not result in significant decreases in urea production, the deficient enzymes substrate builds up, increasing the rate of the deficient reaction to normal. The anomalous substrate buildup is not without cost, the substrate concentrations become elevated all the way back up the cycle to NH4+, resulting in hyperammonemia. Although the root cause of NH4+ toxicity is not completely understood and this clearing system involves GLUD1 and GLUL, which decrease the 2-oxoglutarate and Glu pools. The brain is most sensitive to the depletion of these pools, depletion of 2OG decreases the rate of TCAC, whereas Glu is both a neurotransmitter and a precursor to GABA, another neurotransmitter
Vertebrates /ˈvɜːrtᵻbrᵻts/ comprise all species of animals within the subphylum Vertebrata /-ɑː/. Vertebrates represent the majority of the phylum Chordata, with currently about 66,000 species described. Vertebrates include the fish and the jawed vertebrates, which include the cartilaginous fish. A bony fish known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, vertebrates make up less than five percent of all described animal species, the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, hagfish do, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as Craniata when discussing morphology, molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so are vertebrates in a monophyletic sense.
Others consider them a group of vertebrates in the common taxon of craniata. The word origin of vertebrate derives from the Latin word vertebratus, the Proto-Indo-European language origins are still unclear. Vertebrate is derived from the vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic body plan, a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it. In all vertebrates, the mouth is found at, or right below, the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon, jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills, the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior.
Each gill is supported by a cartilagenous or bony gill arch, the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their relatives have more than 50 pairs of gills. In amphibians and some primitive fishes, the larvae bear external gills. These are reduced in adulthood, their function taken over by the gills proper in fishes, some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods
Cysteine is a semi-essential proteinogenic amino acid with the formula HO2CCHCH2SH. It is encoded by the codons UGU and UGC, the thiol side chain in cysteine often participates in enzymatic reactions, as a nucleophile. The thiol is susceptible to oxidization to give the disulfide derivative cystine, when used as a food additive, it has the E number E920. It can be seen as serine, but with one of the oxygen replaced with sulfur. Cysteine can usually be synthesized by the body under normal physiological conditions if a sufficient quantity of methionine is available. Cysteine is catabolized in the tract and blood plasma. In contrast, cystine travels safely through the GI tract and blood plasma and is reduced to the two cysteine molecules upon cell entry. Like other amino acids, cysteine has an amphoteric character, the majority of L-cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair. Despite widespread belief otherwise, there is evidence that human hair is used as a source material.
Synthetically produced L-cysteine, compliant with Jewish kosher and Muslim halal laws, is available, the synthetic route involves fermentation using a mutant of E. coli. Degussa introduced a route from substituted thiazolines, following this technology, L-cysteine is produced by the hydrolysis of racemic 2-amino-Δ2-thiazoline-4-carboxylic acid using Pseudomonas thiazolinophilum. In animals, biosynthesis begins with the amino acid serine, the sulfur is derived from methionine, which is converted to homocysteine through the intermediate S-adenosylmethionine. Cystathionine beta-synthase combines homocysteine and serine to form the asymmetrical thioether cystathionine, the enzyme cystathionine gamma-lyase converts the cystathionine into cysteine and alpha-ketobutyrate. In plants and bacteria, cysteine biosynthesis starts from serine, the enzyme O-acetylserine -lyase, using sulfide sources, converts this ester into cysteine, releasing acetate. The cysteine thiol group is nucleophilic and easily oxidized, the reactivity is enhanced when the thiol is ionized, and cysteine residues in proteins have pKa values close to neutrality, so are often in their reactive thiolate form in the cell.
Because of its reactivity, the thiol group of cysteine has numerous biological functions. Due to the ability of thiols to undergo reactions, cysteine has antioxidant properties. Cysteines antioxidant properties are typically expressed in the tripeptide glutathione, which occurs in humans as well as other organisms, the systemic availability of oral glutathione is negligible, so it must be biosynthesized from its constituent amino acids, cysteine and glutamic acid
UniProt is a freely accessible database of protein sequence and functional information, many entries being derived from genome sequencing projects. It contains an amount of information about the biological function of proteins derived from the research literature. The UniProt consortium comprises the European Bioinformatics Institute, the Swiss Institute of Bioinformatics, EBI, located at the Wellcome Trust Genome Campus in Hinxton, UK, hosts a large resource of bioinformatics databases and services. SIB, located in Geneva, maintains the ExPASy servers that are a resource for proteomics tools. In 2002, EBI, SIB, and PIR joined forces as the UniProt consortium, each consortium member is heavily involved in protein database maintenance and annotation. Until recently, EBI and SIB together produced the Swiss-Prot and TrEMBL databases and these databases coexisted with differing protein sequence coverage and annotation priorities. Swiss-Prot aimed to provide reliable protein sequences associated with a level of annotation.
Recognizing that sequence data were being generated at a pace exceeding Swiss-Prots ability to keep up, meanwhile, PIR maintained the PIR-PSD and related databases, including iProClass, a database of protein sequences and curated families. The consortium members pooled their resources and expertise, and launched UniProt in December 2003. UniProt provides four core databases, UniProtKB, UniParc, UniRef, UniProt Knowledgebase is a protein database partially curated by experts, consisting of two sections, UniProtKB/Swiss-Prot and UniProtKB/TrEMBL. As of 19 March 2014, release 2014_03 of UniProtKB/Swiss-Prot contains 542,782 sequence entries, UniProtKB/Swiss-Prot is a manually annotated, non-redundant protein sequence database. It combines information extracted from literature and biocurator-evaluated computational analysis. The aim of UniProtKB/Swiss-Prot is to all known relevant information about a particular protein. Annotation is regularly reviewed to keep up with current scientific findings, the manual annotation of an entry involves detailed analysis of the protein sequence and of the scientific literature.
Sequences from the gene and the same species are merged into the same database entry. Differences between sequences are identified, and their cause documented, a range of sequence analysis tools is used in the annotation of UniProtKB/Swiss-Prot entries. Computer-predictions are manually evaluated, and relevant results selected for inclusion in the entry and these predictions include post-translational modifications, transmembrane domains and topology, signal peptides, domain identification, and protein family classification. Relevant publications are identified by searching databases such as PubMed, the full text of each paper is read, and information is extracted and added to the entry
An enzyme inhibitor is a molecule that binds to an enzyme and decreases its activity. Since blocking an enzymes activity can kill a pathogen or correct a metabolic imbalance and they are used in pesticides. The binding of an inhibitor can stop a substrate from entering the active site and/or hinder the enzyme from catalyzing its reaction. Inhibitor binding is reversible or irreversible. Irreversible inhibitors usually react with the enzyme and change it chemically and these inhibitors modify key amino acid residues needed for enzymatic activity. In contrast, reversible inhibitors bind non-covalently and different types of inhibition are produced depending on whether these inhibitors bind to the enzyme, many drug molecules are enzyme inhibitors, so their discovery and improvement is an active area of research in biochemistry and pharmacology. A medicinal enzyme inhibitor is often judged by its specificity and its potency, a high specificity and potency ensure that a drug will have few side effects and thus low toxicity.
Enzyme inhibitors occur naturally and are involved in the regulation of metabolism, for example, enzymes in a metabolic pathway can be inhibited by downstream products. This type of negative feedback slows the production line when products begin to build up and is an important way to maintain homeostasis in a cell, other cellular enzyme inhibitors are proteins that specifically bind to and inhibit an enzyme target. This can help control enzymes that may be damaging to a cell, a well-characterised example of this is the ribonuclease inhibitor, which binds to ribonucleases in one of the tightest known protein–protein interactions. Natural enzyme inhibitors can be poisons and are used as defences against predators or as ways of killing prey, reversible inhibitors attach to enzymes with non-covalent interactions such as hydrogen bonds, hydrophobic interactions and ionic bonds. Multiple weak bonds between the inhibitor and the active site combine to produce strong and specific binding, in contrast to substrates and irreversible inhibitors, reversible inhibitors generally do not undergo chemical reactions when bound to the enzyme and can be easily removed by dilution or dialysis.
There are four kinds of reversible enzyme inhibitors and they are classified according to the effect of varying the concentration of the enzymes substrate on the inhibitor. In competitive inhibition, the substrate and inhibitor cannot bind to the enzyme at the same time, as shown in the figure on the right. This usually results from the inhibitor having an affinity for the site of an enzyme where the substrate binds. This type of inhibition can be overcome by high concentrations of substrate. However, the apparent Km will increase as it takes a higher concentration of the substrate to reach the Km point, competitive inhibitors are often similar in structure to the real substrate. In uncompetitive inhibition, the inhibitor binds only to the substrate-enzyme complex and this type of inhibition causes Vmax to decrease and Km to decrease
Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. The term is generally limited to the green plants, which form an unranked clade Viridiplantae. This includes the plants and other gymnosperms, clubmosses, liverworts and the green algae. Green plants have cell walls containing cellulose and obtain most of their energy from sunlight via photosynthesis by primary chloroplasts and their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic and have lost the ability to produce amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although reproduction is common. There are about 300–315 thousand species of plants, of which the great majority, green plants provide most of the worlds molecular oxygen and are the basis of most of Earths ecologies, especially on land. Plants that produce grains and vegetables form humankinds basic foodstuffs, Plants play many roles in culture.
They are used as ornaments and, until recently and in variety, they have served as the source of most medicines. The scientific study of plants is known as botany, a branch of biology, Plants are one of the two groups into which all living things were traditionally divided, the other is animals. The division goes back at least as far as Aristotle, who distinguished between plants, which generally do not move, and animals, which often are mobile to catch their food. Much later, when Linnaeus created the basis of the system of scientific classification. Since then, it has become clear that the plant kingdom as originally defined included several unrelated groups, these organisms are still often considered plants, particularly in popular contexts. When the name Plantae or plant is applied to a group of organisms or taxon. The evolutionary history of plants is not yet settled. Those which have been called plants are in bold, the way in which the groups of green algae are combined and named varies considerably between authors.
Algae comprise several different groups of organisms which produce energy through photosynthesis, most conspicuous among the algae are the seaweeds, multicellular algae that may roughly resemble land plants, but are classified among the brown and green algae. Each of these groups includes various microscopic and single-celled organisms