6 The Nucleus Nuclear envelope (membrane) Barrier of the nucleus Consists of a double membraneContains nuclear pores (relatively large) that allow for exchange of material with the rest of the cellNucleoplasm – jellylike fluid in which the nucleoli and chromatin are suspended.
7 The Nucleus Nucleoli Nucleus contains one or more nucleoli Sites of ribosome assemblyRibosomes migrate into the cytoplasm through nuclear poresServe as the actual sites of protein synthesis
8 The Nucleus Chromatin Composed of DNA and protein Present when the cell is not dividingScattered throughout the nucleusCondenses to form chromosomes when the cell divides
10 Plasma Membrane Proteins Scattered through out lipid bilayer. Responsible for most specialized functionsEnzymesReceptors, or bindings sites, for hormonesChemical messengersMost are involved in transport functions
11 Plasma Membrane Cholesterol Located in the plasma membrane Helps to stabilize membraneHelps keep membrane fluid
12 Plasma Membrane Glycoproteins Branching sugar groups attached to most proteins.Found on the extracellular sideGives the cell a fuzzy, sticky, sugar-rich surfaceDetermine your blood typeAct as receptors for bacteria, viruses or toxins
14 Plasma Membrane Specializations MicrovilliFinger-like projections that increase surface area for absorption
15 Plasma Membrane Specializations Membrane junctionsTight junctionsImpermeable junctionsBind cells together into leakproof sheetsSmall intestines – prevent digestive enzymes from seeping into bloodstream.
16 Plasma Membrane Specializations Membrane junctionsDesmosomesAnchoring junctions that prevent cells from being pulled apartButtonlikeConnected by fine protein filaments
17 Plasma Membrane Specializations Membrane junctionsGap junctionsAllow communication between cellsCommon with heart and embryonic cells.Cells are connected by hollow cylinder composed of proteins - connexons