barm - a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey. yeast. yeast cake - small cake of compressed moist yeast. brewer's yeast - yeast used in fermenting beer. leaven, leavening - a substance used to produce fermentation in dough or a liquid. mother - a stringy slimy substance consisting of yeast cells and bacteria; forms during fermentation and is added to cider or wine to produce vinegar.
1 Viruses, on the other hand, do not have any cells. 2  Viruses are made up of a protein structure called a capsid. 3  Though this capsid contains the virus's genetic material, it lacks the features of a true cell, such as cell walls, transport proteins, cytoplasm, organelles, and so on. Viruses, on the other hand, do not have any cells. 2  Viruses are made up of a protein structure called a capsid. 3  Though this capsid contains the virus's genetic material, it lacks the features of a true cell, such as cell walls, transport proteins, cytoplasm, organelles, and so on.
In order for a virus to infect a cell, it must bring its DNA or RNA into contact with the host cell. Therefore, infection requires that the virus get through the cellular membrane. Some viruses remain outside the cell. They attach to the membrane at specific receptor sites.Once attached the virus injects its DNA or RNA into the cell. Enveloped viruses are enclosed in a membrane similar to that of the host cell. The virus and the envelope fuse and the virus enters the cell through endocytosis.In the first example only the genetic material enters the cell.herefore, infection requires that the virus get through the cellular membrane. Some viruses remain outside the cell. They attach to the membrane at specific receptor sites. Once attached the virus injects its DNA or RNA into the cell. Enveloped viruses are enclosed in a membrane similar to that of the host cell.