Biol 118 1st Edition Lecture 9 Outline of Last Lecture I. Energy TransformationsII. Role of ElectronsIII. DefinitionsIV. Oxidation-ReductionV. Phosphorylation: 3 TypesVI. Ways ATP is Produced VII. Key Players in the Processing of GlucoseVIII. Cellular Respiration has 4 StepsIX. FermentationOutline of Current Lecture I. Review of Plasma Membrane Structure & FunctionII. Primary Cell WallIII. Extracellular MatrixIV. How Do Adjacent Cells Connect and Communicate?V. Connections Between Animal CellsVI. Molecular Basis of Selective AdhesionVII. Cell Communication via Cell-Cell GapsVIII. Summary of Eukaryotic Cell-Cell AttachmentsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.IX. How Do Distant Cells CommunicateX. Steps of Cell-Cell SignalingCurrent LectureReview of Plasma Membrane Structure & Function- The plasma membrane is made up of a phospholipid bilayer with many interspersed proteins o Generally consists of a fiber composite a cross-linked network of long filaments surrounded by a stiff ground substance Rods/filaments protect against tension Ground substance protects against compression- The primary function of the plasma membrane is to create a different environment inside the cell- Selective permeability of the membrane controls the flow of materials into and out of the cellPrimary Cell Wall- When new plant cells form, they secrete a fiber composite called a primary cell wall composed ofo Long strands of cellulose bundled into microfibrils that form a crisscrossed networkExtracellular Matrix- Most animal cells secrete a fiber composite called the extracellular matrix- One of most important functions is structural support- Amount and composition of the ECM depends on the cell type- Consists of:o A ground substance formed of gelatinous polysaccharideo A network of protein fibers- Most common ECM protein fiber is collageno Collagen is more elastic than celluloseo It forms a flexible extracellular layer- ECM also helps cellso Stick togethero Form protein-protein attachmentso Link the ECM directly to the cell’s cytoskeleton - Direct linkage between the cytoskeleton and ECMo Keeps individual cells in placeo Helps adjacent cells adhere to each othero Breakdown can lead to metastasis of cancerous cellHow do Adjacent Cells Connect & Communicate?- Unicellular organisms do not connect to one another- The basis of multicellularity is physical connections between cells- Cells of multicellular organismso Adhere to one anothero Have specific, distinct structures and functions- Tissues are comprised ofo Groups of similar cellso Performing similar functions- The structures that hold cells together vary among multicellular organismsConnections Between Animal Cells- A middle lamella-like layero Made of gelatinous polysaccharideso Exists between cells in many animal tissues- The polysaccharide glue may be reinforced by cable-like proteins that span the ECM to connect adjacent cells- Epithelial tissue is composed of sheets of cellso Covers organso Line body cavities- Many types of structures connect neighboring epithelial cellso Tight junctions o Desmosomes- Tight junctionso Are composed of specialized proteins in the plasma membranes of adjacent animal cellso These proteins line up and bind to each othero Stitching the two cells together to form a watertight seal between the 2 plasma membraneso Are usually found between cells in tissues that form a barrier such as the tissue lining the stomach or bladder- Desmosomeso Made of proteins that link the cytoskeletons of adjacent cellso Common in epithelial and muscle tissueo Bind to each other and to the proteins that anchor cytoskeletal intermediate filamentsMolecular Basis of Selective Adhesion- Animal cells attach to each other selectively because o There are several classes of cell adhesion proteinso Each major cell type has its own cell adhesion proteins- These cell-cell connections are also species and tissue specific - Cadherins are the adhesion proteins in desmosomesCell Communication via Cell-Cell Gaps- Direct connections between cells in the same tissueo Allow cells to communicateo Work together in a coordinated fashion- Plant cells are connected by plasmodesmatao Gaps in cell wallo Where the plasma membrane cytoplasm and smooth ER of two cells connect- In animal tissues, cell communications via cell-cell gaps is through gap junctionso Connect adjacent cells by forming channels o Channels allow the flow of small molecules between cellsSummary of Eukaryotic Cell-Cell Attachments- Bind adjacent cells to each other:o Middle lamella o Continuous ECMo Tight junctionso Desmosomes o Cadherins- Allow adjacent cells to communicate:o Plasmodesmata in plantso Gap junctions in animalsHow do Distant Cells Communicate?- Hormoneso Information carrying moleculeso Secreted from a cello Circulate in the bodyo Act on target cells far from signaling cell- Hormones are usuallyo Small moleculeso Typically present in minute concentrationso Have a large impact on the condition of the organism as a whole- Function and chemical structure of hormones vary widely- May be soluble or insoluble in lipidso Lipid Soluble hormones Usually diffuse across the plasma membrane and go into their target cells’cytoplasmo Lipid Insoluble hormones Are large or hydrophilic Do not cross plasma membrane Instead bind to a receptor on the cell’s plasma membraneSteps of Cell-Cell Signaling- #1: Signal Receptiono Signal receptors are bound by Hormones Other cell-cell signalso The presence of an appropriate receptor protein dictates which cells will be able to respond to a particular hormoneo Identical receptors in diverse cells and tissues Allow long-distance signals to coordinate the activities of cells throughouta multicellular organismo Signal receptors Are proteins that change their shape or activity after binding to a signaling molecule Are dynamic May change in their sensitivity to particular hormones Can be blockedo Signal receptors that bind to lipid-soluble hormones are located inside the cello Other signal receptors are located in the plasma membrane- #2: Signal Processingo Lipid-soluble hormones that cross the plasma membrane produce different cell responses that lipid insoluble hormones that bind to membrane receptorso Lipid-soluble steroid hormones Bind to receptors inside the cell Trigger a change in the
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