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Konstantin Mereschkowski proposed a symbiotic origin for cells with nuclei. The concept of the eukaryote has been attributed to the French biologist Edouard Chatton The terms prokaryote and eukaryote were more definitively reintroduced by the Canadian microbiologist Roger Stanier and the Dutch-American microbiologist C.
In his work Titres et Travaux Scientifiques, Chatton had proposed the two terms, calling the bacteria prokaryotes and organisms with nuclei in their cells eukaryotes.
However he mentioned this in only one paragraph, and the idea was effectively ignored until Chatton's statement was rediscovered by Stanier and van Niel. Plants had thus inherited photosynthesis from cyanobacteria.
This helped to uncover the origin of the eukaryotes and the symbiogenesis of two important eukaryote organellesmitochondria and chloroplasts. Wheeler renamed this the Archaea. Dring suggested that the eukaryotic cell's nucleus came from the ability of Gram-positive bacteria to form endospores.
In and later papers, Thomas Cavalier-Smith proposed instead that the membranes of the nucleus and endoplasmic reticulum first formed by infolding a prokaryote's plasma membrane. In the s, several other biologists proposed endosymbiotic origins for the nucleus, effectively reviving Mereschkowski's theory.
Eukaryotic DNA is divided into several linear bundles called chromosomeswhich are separated by a microtubular spindle during nuclear division. Internal membrane[ edit ] The endomembrane system and its components Eukaryote cells include a variety of membrane-bound structures, collectively referred to as the endomembrane system.
Many cells ingest food and other materials through a process of endocytosiswhere the outer membrane invaginates and then pinches off to form a vesicle. Alternatively some products produced by the cell can leave in a vesicle through exocytosis. The nucleus is surrounded by a double membrane commonly referred to as a nuclear membrane or nuclear envelopewith pores that allow material to move in and out.
It includes the rough endoplasmic reticulum where ribosomes are attached to synthesize proteins, which enter the interior space or lumen. Subsequently, they generally enter vesicles, which bud off from the smooth endoplasmic reticulum.
For instance, lysosomes contain digestive enzymes that break down most biomolecules in the cytoplasm. Many protozoans have contractile vacuoles, which collect and expel excess water, and extrusomeswhich expel material used to deflect predators or capture prey.
In higher plants, most of a cell's volume is taken up by a central vacuole, which mostly contains water and primarily maintains its osmotic pressure. Mitochondria and plastids[ edit ] Simplified structure of a mitochondrion Mitochondria are organelles found in all but one [note 1] eukaryote. Mitochondria provide energy to the eukaryote cell by converting sugars into ATP.Pearson, as an active contributor to the biology learning community, is pleased to provide free access to the Classic edition of The Biology Place to all educators and their students.
Start studying AP Biology: Cell Respiration. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The classification of archaea, and of prokaryotes in general, is a rapidly moving and contentious field.
Current classification systems aim to organize archaea into groups of organisms that share structural features and common ancestors. These classifications rely heavily on the use of the sequence of ribosomal RNA genes to reveal relationships between organisms (molecular phylogenetics).
Notes for AP Biology: Cellular respiration and fermentation harvest free energy from sugars to produce free energy carriers (ATP.) The free energy available in sugars drives metabolic pathways in cells. Photosynthesis and . Molecular biology (Support your answer with suitable, well labeled and colored diagrams) A) Structure and Functions of Nucleic acids.
i) Give a detailed account of the structure of DNA and differentiate between three major forms of DNA in a tabular manner.. ii) Differentiate between RNA and DNA in a tabular manner.. iii) Give a diagrammatic representation of secondary structure of t- RNA.
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