Review4 Chapter 8 9 Biosc 0150 Foundations of Biology I 1 Review Chapter 8 Cell cell interactions In addition to plasma membrane some cells also contain primary cell wall What is the function of the primary cell wall The primary cell wall defines the shape of a cells provides structural support and protection a What is the primary structural component of the cell wall of a cell extracted from corn mushroom green algae and spider The primary component of the cell wall of is cellulose in corn and green algae and chitin in mushroom Spider is an insect and their cells do not have cell wall b In plants what consequence would there be for cells if their primary cell wall did not have cross linked cellulose strands It would not be as strong so it would be easier to damage and it would have difficulty withstanding the force that water exerts on it via turgor pressure c What is the purpose of pectins in the primary cell wall Pectin is the gelatinous polysaccharide between micro fibrils that holds large amounts of water to keep a cell wall moist and helps keep the structure firm by holding that water d Explain how the primary cell wall is responsible for defining the shape of plant cells The primary cell wall helps define shape due to turgor pressure When concentrations of solutes are higher inside the cell tan outside water enters via osmosis The incoming water inflates the plasma membrane which exerts a force against the primary cell wall This force is known as turgor pressure So thanks to this the plasma membrane is pushed against the primary cell wall which is what defines its shape The primary cell wall prevents the cell from bursting due to the incoming water e Why do plants wilt when not properly watered How is the cell wall affected during drought Plant wilting is the result of an insufficient turgor pressure During drought the cell wall helps maintaining the structural integrity of the green parts of the plant such as stems and leaves Extensive drought may result in dehydration of the cell wall matrix made of pectins and the cell wall would collapse 2 Name the main components of animals extracellular matrix The animal extracellular matrix ECM consists of collagen gel forming polysaccharides integrins and fibronectins a What is the function of the ECM The ECM main function is structural support b What is so special about collagen and the other ECM proteins that is advantageous for the structure and function of animal cells Collagen the main component is very elastic and bendable compared to cellulose of plants which makes the structure pliable It is not rigid so it can adjust itself depending on its environment c You are given a picture of a certain group of cells and are asked to identify whether they are bone cells or skin cells How can you decide what sort of cells you are looking at It would be helpful to look at the ECM of bone and skin see google images Bone has relatively few cells but lots of ECM while skin cells have many cells tightly packed together with limited ECM d Using the example of bone and skin how does the structure of ECM relates to the function The amount of ECM relates to the function of the cells bone is supporting structure thus contain large amount of extracellular supporting material ECM that consists of collagen fibers embedded in a matrix rich in calcium and phosphorus Skin cells form epithelial tissue that lines surface of the body making waterproof coat that protects underlining structures thus cells in skin are tightly packed together with limited ECM e In certain research labs the enzyme trypsin is used to break apart cells from each other and the surface What might trypsin be doing Trypsin is a peptidase a digestive enzyme produced by Adel Anthony Kathleen Megan Dr Swigonova Page 1 of 14 Biosc 0150 Foundations of Biology I Review4 Chapter 8 9 pancreas as a proenzyme trypsinogen that hydrolyses proteins by cleaving peptide chains at specific sites The target proteins are the surface proteins involved in cell adhesion When the ECM is broken down cells will have a hard time attaching themselves to surfaces as well as other cells 3 Explain the relation of each of the following structural components of the ECM integrin fibronectin collagen Draw a picture and label the structures The transmembrane protein integrins attached to actin filament inside the cell helps hold a cell in place by binding to nearby proteins including fibronectins which bind to collagen fibers This linkage is between the integrin fibronectins and collagen is what holds a cell in place a If integrin were removed from a cell what would be the consequences The cell would probably not be able to stay in place b What must happen for cells to metastasize and migrate through the body The cell s cytoskeleton ECM linkage must break down to allow the cell to move form one place to the other c Where are most ECM components synthesized They are mostly synthesized in the RER d Through what process are these components moved out of the cell These components are secreted from the cell via exocytosis don t forget the endomembrane system and how it works 4 Cell Cell Attachments a The extracellular space between adjacent plant cells comprises of how many layers Name these layers What is this glue like middle layer made up of Draw a picture and lable the components 3 Cell wall middle lamella cell wall gelatinous pectins b Compare and contrast primary and secondary cell wall Primary cell wall is produced first and is relatively thin and flexible allowing the cells to grow Once cells cease to grow they commonly secrete secondary cell wall that is found between the plasma membrane and the primary cell wall The secondary cell wall is much thicker and more rigid than primary wall The primary cell wall contain approximately equal amount of cellulose and pectin while the secondary cell walls lack pectin and contain mostly cellulose some are further strengthened by lignin or suberin c Where can you find epithelial cells Provide examples of at least two epithelial tissues Name two types of cell cell attachment structures that exist between epithelial cells Epithelial cells form epithelial tissues that cover surfaces Examples skin surface of respiratory and digestive passages surfaces of excretory passages etc They act to seal preventing the mixing of solutions from adjacent organs or structures Tight junctions and desmosomes d In tight junctions which form watertight seals how do any ions or molecules get