Metabolism

metabolicmetabolizedmetabolic pathwaysmetabolizemetabolic activitybiosynthetic pathwaycellular metabolismmetabolic ratemetabolicallymetabolic processes
Metabolism (, from μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms.wikipedia
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Life

livinglife on Earthbiota
Metabolism (, from μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms.
One popular definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve.

Cellular respiration

respirationaerobic respirationaerobic
Metabolic reactions may be categorized as catabolic - the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic - the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids).
Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.

Enzyme

enzymologyenzymesenzymatic
These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme.
Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life.

Metabolic waste

nitrogenous wasteuricotelicureotelic
The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of nitrogenous wastes.
Metabolic wastes or excretements are substances left over from metabolic processes (such as cellular respiration) which cannot be used by the organism (they are surplus or toxic), and must therefore be excreted.

Chemical reaction

reactionchemical reactionsreactions
Metabolism (, from μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms.
Enzymes increase the rates of biochemical reactions, so that metabolic syntheses and decompositions impossible under ordinary conditions can occur at the temperatures and concentrations present within a cell.

Protein

proteinsproteinaceousstructural proteins
The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of nitrogenous wastes.
Many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism.

Lipid

lipidsglycerolipidfat
The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of nitrogenous wastes.
Although humans and other mammals use various biosynthetic pathways both to break down and to synthesize lipids, some essential lipids can't be made this way and must be obtained from the diet.

Evolutionary history of life

Prehistoric lifeevolutionary historyhistory of life
These similarities in metabolic pathways are likely due to their early appearance in evolutionary history, and their retention because of their efficacy.
The evolution of photosynthesis, around 3.5 Ga, eventually led to a buildup of its waste product, oxygen, in the atmosphere, leading to the great oxygenation event, beginning around 2.4 Ga. The earliest evidence of eukaryotes (complex cells with organelles) dates from 1.85 Ga, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism.

Nutrition

nutrition sciencenutritionalnutritional science
The metabolic system of a particular organism determines which substances it will find nutritious and which poisonous.
Also in the 16th century, scientist and artist Leonardo da Vinci compared metabolism to a burning candle.

Carbohydrate

carbohydratessaccharidecomplex carbohydrates
The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of nitrogenous wastes.
Other polysaccharides contained in dietary fiber include resistant starch and inulin, which feed some bacteria in the microbiota of the large intestine, and are metabolized by these bacteria to yield short-chain fatty acids.

Organism

organismsflora and faunaliving organisms
Metabolism (, from μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms.
Viruses are not typically considered to be organisms because they are incapable of autonomous reproduction, growth or metabolism.

Citric acid cycle

Krebs cycleTCA cycletricarboxylic acid cycle
For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium Escherichia coli and huge multicellular organisms like elephants.
Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may have originated abiogenically.

Nucleotide

nucleotidesntdinucleotide
The two nucleic acids, DNA and RNA, are polymers of nucleotides.
Nucleotides also play a central role in metabolism at a fundamental, cellular level.

Basal metabolic rate

metabolic ratebasal metabolismBMR
The basal metabolic rate of an organism is the measure of the amount of energy consumed by all of these chemical reactions.
Studies of energy metabolism using both methods provide convincing evidence for the validity of the respiratory quotient (RQ), which measures the inherent composition and utilization of carbohydrates, fats and proteins as they are converted to energy substrate units that can be used by the body as energy.

DNA repair

DNA damagerepairtranslesion synthesis
This information is protected by DNA repair mechanisms and propagated through DNA replication.
In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day.

Metabolic pathway

metabolic pathwayspathwaypathways
The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme.
Pathways are required for the maintenance of homeostasis within an organism and the flux of metabolites through a pathway is regulated depending on the needs of the cell and the availability of the substrate.

Starch

starcheswheat starchrice starch
Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals).
The glucose is used to generate the chemical energy required for general metabolism, to make organic compounds such as nucleic acids, lipids, proteins and structural polysaccharides such as cellulose, or is stored in the form of starch granules, in amyloplasts.

Phosphate

phosphatesphosphate groupinorganic phosphate
Several variations on this basic structure exist, including alternate backbones such as sphingosine in the sphingolipids, and hydrophilic groups such as phosphate as in phospholipids.
In biology, adding phosphates to—and removing them from—proteins in cells are both pivotal in the regulation of metabolic processes.

Energy

energy transferenergiestotal energy
The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of nitrogenous wastes. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals).
In human terms, the human equivalent (H-e) (Human energy conversion) indicates, for a given amount of energy expenditure, the relative quantity of energy needed for human metabolism, assuming an average human energy expenditure of 12,500 kJ per day and a basal metabolic rate of 80 watts.

Catabolism

cataboliccatabolizedcatabolize
Metabolic reactions may be categorized as catabolic - the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic - the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids).
Catabolism is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions.

Vitamin

vitaminsfat-soluble vitaminsfat-soluble vitamin
A vitamin is an organic compound needed in small quantities that cannot be made in cells.
A vitamin is an organic molecule (or related set of molecules) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism.

Adenosine triphosphate

ATPadenosine triphosphate (ATP)adenosine 5'-triphosphate
One central coenzyme is adenosine triphosphate (ATP), the universal energy currency of cells.
When consumed in metabolic processes, it converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP).

Nicotinamide adenine dinucleotide

NAD + NADHNAD
Nicotinamide adenine dinucleotide (NAD + ), a derivative of vitamin B 3 (niacin), is an important coenzyme that acts as a hydrogen acceptor.
In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another.

Anabolism

anabolicanabolic effectsanabolic pathway
Metabolic reactions may be categorized as catabolic - the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic - the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids).
Anabolism is the building-up aspect of metabolism, whereas catabolism is the breaking-down aspect.

Hemoglobin

haemoglobinoxyhemoglobindeoxyhemoglobin
These metals are used in some proteins as cofactors and are essential for the activity of enzymes such as catalase and oxygen-carrier proteins such as hemoglobin.
There it releases the oxygen to permit aerobic respiration to provide energy to power the functions of the organism in the process called metabolism.