MCB 181 1st Edition Lecture 13Outline of Previous Lecture I. PeroxisomesII. LysosomesIII. VacuolesIV. MitochondrionV. ChloroplastsVI. Cell WallVII. The CytoskeletonVIII. Clicker QuestionsOutline of Current Lecture I. The Cell SurfaceII. Cell CommunicationIII. Types of Cell ConnectionIV. Clicker QuestionsCurrent LectureI. The Cell Surfacea. Almost all animal cells secrete a fiber known as the extracellular matrix (ECM) which consists of protein fibers instead of polysaccharidesb. Each type of tissue produces its own unique ECMII. Cell Communicationa. Cells are not separate entities but rather there is a physical connection between the cells and are held together somehowb. Because different type of cell specialized for particular task, the cell must be able to communicate with each other to function as an integrated wholec. Tissue – consist of groups of similar cells that perform a similar functioni. Several tissues combine to make up the integrated structures called organsd. Animal cells share most of their ions and or small molecules but retain their own organelles, proteins and nucleic acids as it allows the tissue to act as a whole because of the connection through the ECMe. Long distance organs in multicellular organisms have to coordinate their functioni. They will use molecules that carry information about the conditions of our bodiesii. This information will travel using our blood streamf. Hormones – small information carrying moleculesi. Secreted by cells in small amounts and circulate in the blood streamii. Acts in a target cell far from the original cell and have great impact on the activities of the target cellsIII. Types of Cell Connectiona. Tight Junction – a cell to cell attachment composed of specialized proteins in the plasma membrane that line up and bind to one another forming a watertight seali. Common in cells that form a barrier such as in the lining of the stomach and intestinesii. Tight junctions are variable and dynamic for example in the bladder where they are much tighter to prevent ions from passing through the surfaceb. Desmosomes – bind together the cytoskeletons of two cellsi. They are common cell-cell attachment in epithelial cells and in certain types of muscle cellsii. At the center of the desmosomes consists proteins that form a physical link between the cytoskeleton of the adjacent cellsiii. In addition to binding to each other, these proteins bind to a larger protein that is anchored in the intermediate filaments in the cytoskeleton of the two cellsc. Gap Junctions – a unique protein creates channels between adjacent cellsi. Most animal tissues are connected by gap junctionsii. Gap junctions will allow water, ions, and small molecules to move between adjacent cellsiii. These molecules will assist in the coordination of adjacent cells activities by allowing rapid passage of regulatory moleculesIV. Clicker QuestionsAssertion ReasonOne reason why tissues look different is because each secretes a unique combination of molecules into their extracellular space.BecauseThe extracellular matrix provides the cells with support and contributes to the function of the tissue.Assertion is true; Reason is true; Reason is NOT the correct explanation.Assertion ReasonMutations that cause gap junction failure significantly disrupt the development of multicellular organisms and are usually lethal (i.e. the embryo dies before maturing).BecauseGap junctions are important communication structures and are a primary cell-cell channel for ion, small regulatory molecules, amino acids, sugars, and nucleic acids.Assertion is true; Reason is