Royal jelly, a thick, milky substance secreted by young nurse honeybees to feed a bee colonyâs larvae, most notably the queen larvae, is a rich source of nutrients, as well as acetycholine, a neurotransmitter that plays a critical role in cognitive function.
The origin of the eukaryotic cell is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The timing of this series of events is hard to determine; Knoll (2006) suggests they developed approximately 1.6â2.1 billion years ago.
Eukaryotic cells contain a nucleus and membrane-bound organelles. All multicellular organisms consist of eukaryotic cells. Eukaryotic cells are thought to have evolved from primitive single-celled prokaryotic cells. All cells are surrounded by a cell membrane (plasma membrane). The cell membrane is semipermeable, allowing some substances to pass into the cell and blocking others. It is composed of a double layer of phospholipids and embedded proteins. Plant cells have an additional layer surrounding them called the cell wall. The cell wall is made of nonliving material called cellulose. The centrosome (also called the microtubule organizing center) is a small body located near the nucleus. The centrosome is where microtubules are made.