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The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
Biomolecules are an important element of living organisms. They are often endogenous, [2] i.e. produced within the organism, [3] but organisms usually also need exogenous biomolecules, for example certain nutrients, to survive. Biomolecules and their reactions are studied in biology and its subfields of biochemistry and molecular biology.
The elements listed below as "Essential in humans" are those listed by the US Food and Drug Administration as essential nutrients, [9] as well as six additional elements: oxygen, carbon, hydrogen, and nitrogen (the fundamental building blocks of life on Earth), sulfur (essential to all cells) and cobalt (a necessary component of vitamin B 12).
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. [1] [2] All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. [3] Cell biology is the study of the structural and functional ...
Proteins, which are the building blocks from which the structures of living organisms are constructed (this includes almost all enzymes, which catalyse organic chemical reactions). [2] Amino acid, make up proteins, included the use in genetic code of life. [2] Nucleic acids, which carry genetic information. [2] Ribonucleic acid (RNA ...
Also meganucleus. The larger of the two types of nuclei which occur in pairs in the cells of some ciliated protozoa. Macronuclei are highly polyploid and responsible for directing vegetative reproduction, in contrast to the diploid micronuclei, which have important functions during conjugation. macrophage Any of a class of relatively long-lived phagocytic cells of the mammalian immune system ...
Some larger jellyfish are considered planktonic. Plankton are the building blocks of life in the sea. Everything depends on them. Phytoplankton are microscopic plants that can be as small as one cell.
In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions. According to the RNA world hypothesis free-floating ribonucleotides were present in the primitive soup.