Cell | Definition, Types, Functions, Diagram, Division, Theory,
2024年10月31日 · The overall process of cellular reproduction occurs in two steps: cell growth and cell division. During cell growth, the cell ingests certain molecules from its surroundings by selectively carrying them through its cell membrane .
Lipid | Definition, Structure, Examples, Functions, Types, & Facts ...
Lipids are a diverse group of compounds and serve many different functions. At a cellular level, phospholipids and cholesterol are some of the primary components of the membranes that separate a cell from its environment.
Cell membrane | Definition, Function, & Structure | Britannica
2024年11月18日 · The chemical structure of the cell membrane makes it remarkably flexible, the ideal boundary for rapidly growing and dividing cells. Yet the membrane is also a formidable barrier, allowing some dissolved substances, or solutes, to pass while blocking others.
Organelle | Cellular Structure, Function & Processes | Britannica
5 天之前 · Organelle, any of the specialized structures within a cell that perform a specific function (e.g., mitochondria, ribosomes, endoplasmic reticulum). Organelles in unicellular organisms are the equivalent of organs in multicellular organisms. …
Cell - Structure, Organelles, Metabolism | Britannica
2024年10月31日 · Cell - Structure, Organelles, Metabolism: Like the cell membrane, membranes of some organelles contain transport proteins, or permeases, that allow chemical communication between organelles.
Wood - Cellulose, Lignin, Tracheids | Britannica
2024年11月13日 · Because of differences in cellular composition and arrangement, the structure of wood varies among species. This variation influences appearance and properties and makes for a wide choice of woods for different uses, and it provides the basis for wood identification.
DNA | Definition, Discovery, Function, Bases, Facts, & Structure ...
2024年11月21日 · DNA, organic chemical of complex molecular structure found in all prokaryotic and eukaryotic cells. It codes genetic information for the transmission of inherited traits. The structure of DNA was described in 1953, leading to further understanding of DNA replication and hereditary control of cellular activities.
Cell theory | Definition, History, Importance, Scientists, First ...
2024年10月24日 · Schleiden and Schwann’s descriptive statements concerning the cellular basis of biologic structure are straightforward and acceptable to modern thought. They recognized the common features of cells to be the membrane , nucleus , and cell body and described them in comparisons of various animal and plant tissues.
Structure and types of cells | Britannica - Encyclopedia Britannica
Chloroplast, structure within the cells of plants and green algae that is the site of photosynthesis, the process by which light energy is converted to chemical energy, resulting in the production of oxygen and energy-rich organic compounds.
Nucleic acid | Definition, Function, Structure, & Types | Britannica
2024年11月22日 · Basic structure. Nucleic acids are polynucleotides—that is, long chainlike molecules composed of a series of nearly identical building blocks called nucleotides. Each nucleotide consists of a nitrogen-containing aromatic base attached to a pentose (five-carbon) sugar, which is in turn attached to a phosphate group.