Theme 1, module 1-the structure of the cell. Prokaryotic (bacterial cells): do not contain a true nucleus, provide essential functions throughout our physiological system. Microbiome: populations of microbiotic organisms, microorganisms or microbes within our body. Microorganism: organisms that aren"t visible to the naked eye. Microbe: prokaryotic bacteria and small eukaryotic organisms. Four classes of macromolecules: nucleic acids, proteins, polysaccharides, phospholipids. The cell membrane is made of: lipid macromolecules: contain both hydrophilic and hydrophobic properties central hydrophobic and peripheral hydrophilic. Each phospholipid consists of a glycerol molecule linked to a phosphate (hydrophilic) and two fatty acids (hydrophobic) Spontaneously aggregate to form lipid micelles (absorb fat soluble vitamins: steroids (ex cholesterol): also contain a hydrophilic head and hydrophobic tail. Cholesterol constrains fluidity by packing closely to neighbouring molecules. The fluid mosaic model: membranes consist of proteins and carbohydrates embedded in fluid phospholipid bilayer. Macromolecules can move laterally within the cell membrane because of the fluidity of the cell membrane.