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.
All viruses have genes constructed from either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA)âlong helical molecules that carry genetic information. All viruses have a protein coat that protects these genes, and some are wrapped in a viral envelope of fat that surrounds them when they are outside a cell.(Viroids do not have a protein coat and prions contain neither RNA nor DNA). virus is a microscopic organism that can replicate only inside the cells of a host organism. Most viruses are so tiny they are only observable with at least a conventional optical microscope.