Cell Mol Semi Chapter 7

• Epithelial Tissue - consist largely of closely packed cells attached to each other . these contacs provide a mecnanisam for cell to communicate
• Cells are attached to basal lamina which is a sheet of extracellular matrix allowing them to stay put
• Connective Tissue consist largely of extracellular material, including a variety of distinct fibers that interact with each other in specific ways
• Cell membrane - outer surface has a cloud like black layer.
• The outer portion of the cell membrane is Carbohydrate
• Glycocalyx or the cell coat mediates cell - environmental interactions. It has a Carbohydrate layer.
• The Functions of Basal lamina includes:

  Provides covering for muscle cells

  As a sheath that surrounds cell

  Anchorage for cell in the epithelium

  Barrier between the blood in blood vessels and urine in the kidney
• What are the components of ECM

  Collagen, Proteoglycan, Fibronectin, Laminin, Integrin
• Collagen - fibrous in physical appearance and structure, and has a high tensile strength which is composed of a monomer that is of 3 alpha helixes
• Type I collagen - structural collagen fibrils that are found in dermis which helps skin become elastic
• Collagen comprises the cornea of the eye
• Type IV collagen is present in the basal lamina and is arranged like a network
• Proteoglycans is the opposite of collagen which has high compressional strength and is found in the extracellular matrix
• Why proteoglycan can withstand being compressed

  The presence of sulfate in proteoglycan attracts water molecules
• Fibronectin - made up of 2 chains attached together at one end. They are for cell migration and the presence of this allows cells to adhere to surfaces
• Laminins - cross-like in shape and is made of 3 chains.
• Made up the sheath structure of the basal lamina

  Laminins + Type IV collagen
• Matrix Metalloproteinases (MMPs) are enzymes that helps break the integrity of ECM which also help the digesting of the components. They need Zn2+ and Ca2+ to work
• Use of MMPs includes


  For tissue remodeling

  Embryonic development

  Wound healing

  formation of blood vessels
• What are the results of excessive MMPs in cancer

  they are able to eat through the ECM and basal lamina entering through the other parts of the body
• Integrin is embedded in the membrane of the cell. They help cell attach and interact with the rest of molecules in the ECM
• Integrin is involved in focal adhesions and hemidesmosome
• How integrins help in the attachment of RBC to another RBC during injury

  Integrins of the cell attaches to a fibrinogen which fibrinogen catches platelets that pass through. Platelets will lodge and chemical reaction happens making a plug to stop the bleeding
• ReoPro Antibody - blocks integrins in the RBC from catching a fibrinogen to prevent the formation of blood clot during surgery
• Focal Adhesion can be activated when cell is placed in a foreign surface.
• Integrin is the hand that are grasping the surface during focal adhesion while Actin Fibers provides strength with the holding unto the surface
• Hemidesmosome is when the cell is in their native environment. The cell holds unto the basal lamina and how they hold into the ECM.
• 3 Types of Cell-Cell adhesion

  Selectin, IgSF, Cadherins
• Selectin - molecules on the surface of the cell that recognizes carbohydrates ligands
• Immunoglobulin SuperFamily - IgG domain contains RGD sequence which binds together with another RGD sequence. They attach to integrins
• Cadherins - calcium ions activated. They stick with the other same type of adhesion like a zipper
• Explain Morphogenesis and Cadherins

  Mechanism is that there are parts where cells are starting to express another type of cadherin. They will be different with their other side which means they will separate from those other cells and will group themselves to form a neutral tube
• 4 intercellular Junction

  Adherens Junction

  Desmosome

  Tight Junction

  Gap Junction
• Adherens Junction involves cadherins in the recognition of other cells
• Cadherins in Adherens Junction is connected to Catenin while this is also connected to Actins
• Desmosome involves Desmoglein and Desmocollin in the recognition and this connected to Desmoplakin which is also connected to the Intermediate filaments
• Tight Junction doesn't allow fluids to flow through between the two cells
• Gap Junction is composed of protein which is called connexin which sticks together to form connexon. This aligns themselves with other cell like a magnet to allow passage from the cell to the other cell
• The boundary of the cell in plants is called Plasmodesmata
• Plasmodesmata is a channels between cell walls with two plant cell allowing them to communicate with each other