交生体 - - 一个在进化过程中短暂的有机体

The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the nucleus-first hypothesis, the ancestral prokaryote first evolved a membrane to enclose DNA and form the nucleus. Conversely, the mitochondria-first hypothesis suggests that the nucleus was formed after endosymbiosis of mitochondria.
Contrary to the endosymbiont theory, the eukaryote-first hypothesis proposes that the simpler prokaryotic and...

One of the distinguishing features of eukaryotic cells is that they contain membrane-bound organelles, such as the nucleus and mitochondria, that carry out specialized functions. Since biological membranes are only selectively permeable to solutes, they help create a compartment with controlled conditions inside an organelle. These microenvironments are tailored to the organelle's specific functions and help isolate them from the surrounding cytosol.
For example, lysosomes in the animal...

Green algae and plants, including green stems and unripe fruit, harbor specialized organelles called chloroplasts to carry out photosynthesis. They coordinate both stages of photosynthesis — the light-dependent reactions and the light-independent reactions. The light-dependent reactions use sunlight to release oxygen and produce chemical energy in the form of ATP and NADPH, and the light-independent reactions capture CO2 and use ATP and NADPH to produce sugar.
Structure of...

A eukaryotic cell can have up to three different types of genetic systems: nuclear, mitochondrial, and chloroplast. During evolution, organelles have exported many genes to the nucleus; this transfer is still ongoing in some plant species. Approximately 18% of the Arabidopsis thaliana nuclear genome is thought to be derived from the chloroplast’s cyanobacterial ancestor, and around 75% of the yeast genome derived from the mitochondria’s bacterial ancestor. This export has occurred...

The recycling endosome, also known as the endosomal recycling compartment (ERC), is a part of the slow-recycling process of the endocytic pathway. Molecules internalized through receptor-mediated endocytosis are either degraded in the lysosomes or are recycled to the plasma membrane through the fast- or slow-recycling route.
The recycling endosome is not a single organelle but an extensively tubulated network of recycling pathways. It functions in storing molecules or transporting them across...

Proteins and neurotransmitters in secretory vesicles can be released from a cell upon vesicle docking, priming, and fusion with the plasma membrane. Vesicles are docked and primed in preparation for the quick exocytosis of their contents in response to a stimulus. The fusion process is mainly carried out by a SNAP Receptor or SNARE complex, consisting of synaptobrevin, syntaxin-1, and SNAP-25.
In 1993, Jim Rothman proposed that the antiparallel pairing of vesicular and transmembrane SNAREs, or...