Cell Surface of the Extracellular Matrix PDF

Cell Surface of the membrane with the help of transport protein. Extracellular Matrix Cell Membrane Two types of membrane transport - Surrounds the cytoplasm of pr...

Cell Surface of the membrane with the help of transport protein. Extracellular Matrix Cell Membrane Two types of membrane transport - Surrounds the cytoplasm of proteins involved: living cells, physically separating the intracellular A. Channel proteins- contain tunnels/ components from the openings that serve as passageways extracellular environment. of - The cell membrane, also known as the plasma molecules. membrane, is a thin, flexible B. Carrier proteins- undergo barrier that surrounds and temporary binding to molecule it protects the contents of a carries resulting in conformational cell. change that moves the molecule Cell Transport Concept Map through the membrane. Active Process - It is the movement of molecules from low concentration to high concentration with the use of energy in the form of adenosine triphosphate (ATP). Passive Process - Molecules, Ions, and other Bulk Transport small substances can move - The movement of large amount through the plasma membrane of materials in and out of the using various non-energy cell. expending processes. - Bulk transport acts as a Types: transporter of materials across 1. Diffusion - Movement from high the membrane. It provides help concentration to low concentration. in balancing the ions and 2. Osmosis - Movement of water molecules in and out of the cell. through a semipermeable membrane. 3. Facilitated diffusion - Transport of various substances through the There are two types: EXOCYTOSIS 1. Endocytosis - Forces material out of the cell in bulk by invagination and formation of a 2. Exocytosis vesicle. ENDOCYTOSIS - the process in which cells absorb molecules by engulfing. 3 Types of Endocytosis Phagocytocis (cell eating) process by which cells take in large particles by infoldings the cell membrane to form endocytotic vesicle. Pinocytosis CELL ADHESION (cell drinking) process of taking in fluids into the cell by invagination of A process where binding with other cell membrane. Any solute or small cells or with the extracellular matrix particles in the fluid will move into the (ECM) occurs. cell. Receptor-mediated endocytosis Cell adhesion molecules (CAMS) (cell drinking) compared to pinocytosis, It is the subset of cell adhesion is very specific. The plasma membrane proteins located on the cell becomes indented and forms a pit. The surface involved in binding with pit lined with the receptor proteins other cells or with the picks specific molecules from its extracellular matrix. surroundings. The pit will close and pinch off to form a vesicle which will It helps cells stick to each other carry the molecules inside the and to their surroundings. cytoplasm. It plays an integral role in creating force and movement and consequently ensure that organs are able to execute their functions. Important in affecting cellular mechanisms of growth, contact, inhibition, and apoptosis.  Ligand – a chemical signal produced by an organism or received from the environment that is used to control their bodily fucntions. Receptors – are proteins that is specialized and is selective in the molecules they attach to. It composed of three conserved domains: VACUOLE FORMATION 1.An intracellular domain that interacts Vacuoles - are fluid-filled, enclosed with the cytoskeleton structures that are separated from the 2. A transmembrane domain cytoplasm by a single membrane. 3. An extracellular domain FUNCTIONS OF PLANT VACUOLE: TYPES OF BONDING: Turgor Pressure Control 1. Homophilic binding - CAMs bind to Growth of the central vacuole the same CAMs. aids in cell elongation 2. Heterophilic binding - CAMs bind to Storage vacuoles store different CAMs. important minerals, water, nutrients, ions, waste - 3. Extracellular Ligand binding - occurs products, small molecules, between cells and substrate, where a enzymes, and plant pigments. mutual extracellular ligand binds two different CAMs. Molecule degradation SIGNAL TRANSDUCTION Detoxification the process of transferring a signal Protection throughout an organism, especially Seed Germination across or through a cell. It relies on proteins known as receptors, which wait for a chemical, physical, or AUTOLYSIS - a programmed cell electrical signal. death in plants naturally occurring process where the plant’s own enzymes destroy it. The vacuole ruptures releasing its contents in the cytoplasm. The digestive enzyme released from the vacuole degrades the entire cell. Extracellular Matrix Directly translates to “outside of the cell”.  Also called “cellular soup” There are four main fibrous proteins that make up the ECM; Is a fluid matrix composed of substances and structures that 1. COLLAGEN play roles such as maintenance of cell structure, cell adhesion, Main structural component of the migration, division, ECM, as well asmost multicellular differentiation, and apoptosis. animals COMPONENTS OF THE Most abundant fibrous protein EXTRACELLULAR MATRIX: Mostly made up of water, Made from fibroblasts fibrous proteins, and Makes up roughly ⅓ of total protein proteoglycans. mass in animals. Made up of relatively sturdy fibrous proteins: collagens, Stretch resistance and tensile elastin, and laminins. strength (i.e. scarformation during wound healing) The sturdiness of these proteins helps the ECM maintain its 2. ELASTIN environment and resist force, allowing it to withstand Fiber that lends tissues ability to environmental pressures without recoil and stretch without breaking collapsing. Stretch and resilience 3. FIBRONECTIN Regulates division and specialization in many tissue types. Secreted by fibroblast cells in water- soluble form, but quickly changes once assembles in a undissolvable mesh FUNCTIONS OF ECM: Cell migration and positioning within the ECM, and cell division and 1. Filler that lies between cells in a specialization in various tissues. tissue 4. LAMININ 2. Water retention and homeostatic balance Good at assembling itself into sheet- like protein networks that acts as a 3. Provide major support for each glue that connects dissimilar tissue organ and tissue. types ECM is composed of two main classes of macromolecules ; Present at the junctions where 1. Proteoglycans connective tissue meet muscle, nerve, 2. Fibrous protein or epithelial lining tissue. PROTEOGLYCAN TYPES OF CELL SIGNALING: a macromolecule that has a core Juxtacrine signaling - (also known protein with one or more as direct cell signaling) is the process glycosaminoglycan chains. by which cells that are in direct contact with one another communicate with Proteoglycans are a type of each other. glycoproteins present in the body, Paracrine signaling – occurs especially in connective tissues, bone between cells which are close and cartilage, and cell surfaces. together, sometime directly, sometimes via extracellular fluid. GLYCOSAMINOGLYCAN (GAGS) Endocrine signaling - involves signaling over large distances, often Chains of sugar that varies where the signaling molecule is transported in the circulatory system. Highly negatively charged molecule Auto signaling - cell stimulates a produced by animal cells response within itself by releasing signals for its own receptor. EXTRACELLULAR FLUID - is known as interstitial fluid, and surrounds most HOW CELLS RESPOND TO of the cells in the body. SIGNALS? Blood plasma Once a receptor protein receives a signal, it undergoes a conformational - Extracellular fluid that travels in the change, which in turn launches a circulatory system and is the liquid series of biochemical reactions within component of blood. the cell. Interstitial fluid These intracellular signaling pathways, also called signal - Allows cells to carry out processes transduction cascades, typically using the nutrients and oxygen amplify the message, producing provided, and to carry wastes back to multiple intracellular signals for every the blood. one receptor that is bound. Transcellular Fluid Activation of receptors can trigger the synthesis of small molecules called - It is the final fluid which meant to second messengers, which initiate and provide structural support Can be coordinate intracellular signaling found in the eye, joint, and pathways. cerebrospinal fluid. CELL SIGNALING - is a general term referring to the many and varied processes by which communications controlling cell-level activities are generated, maintained, used, and terminated. RECEPTORS FOR CELL SIGNALS They are; A cell surface receptor exists Receptor tyrosine kinases intrinsically embedded in the plasma membrane. Tyrosine kinase associated receptors It has two domains of significance - Receptor-like tyrosine phosphatases the signal molecule binding domain, which is exposed to the exterior of the Receptor serine/ threonine kinases cell and the intra-cellular domain in contact with the cytoplasm. Receptor Guanylyl cyclase’s CELL SURFACE RECEPTORS 3 Histidine kinase associated receptors MAIN CLASSES: 1. LIGAND-GATED ION CHANNEL RECEPTORS - also known as ionotropic receptors, are responsible for the rapid transmission of signals across synapses in the nervous system by allowing a flow of ions across the plasma membrane, which changes the membrane potential, causing an electrical current. 3. G-PROTEIN-COUPLED RECEPTORS - are the largest of all the cell surface receptors. Due to the large variety of cellular processes that GPCR's are involved in, they are usually an attractive target for the development of drugs to treat variety of disorders. 2. ENZYME-COUPLED RECEPTORS - Are transmembrane proteins which as of 2009, only six types were known. TYPES OF RECEPTORS: 3. ENZYME-LINKED RECEPTORS - are cell-surface ▪INTERNAL RECEPTORS, also receptors with intracellular known as intracellular or cytoplasmic domains that are associated receptors, are found in the cytoplasm with an enzyme. of the cell and respond to hydrophobic ligand molecules that are able to travel AGONIST VS ANTAGONIST across the plasma membrane. ▪ An agonist is a ligand that binds ▪ CELL-SURFACE RECEPTORS, also to a receptor and produces a known as transmembrane receptors, biological effect (direct acting) or a are cell surface, membraneanchored, compound that indirectly produces or integral proteins that bind to the same effect of a external ligand molecules. This type of neurotransmitter (indirect acting). receptor spans the plasma membrane and performs signal transduction, ▪ An antagonist is a ligand that converting an extracellular signal into binds to a receptor but does not an intracellular signal. produce biological effect (direct acting) or a compound that 3 MAIN COMPONENTS OF CELL- indirectly inhibits the effect of a SURFACE RECEPTORS: neurotransmitter (indirect acting). These compounds usually, block or 1. External ligand-binding domain inhibit the actions of a (extracellular domain) neurotransmitter. 2. A hydrophobic membrane-spanning NOTCH SIGNALING region ▪ The Notch signaling pathway is a 3. Intracellular domain inside the cell fundamental signaling system used by neighboring cells to communicate with 3 GENERAL CATEGORIES OF CELL each other in order to assume their SURFACE RECEPTORS proper developmental role. Notch proteins are cell surface 1. ION CHANNEL LINKED transmembrane spanning receptors RECEPTORS - bind a ligand which mediate critically important and open a channel through the cellular functions through direct cell- membrane that allows specific cell contact. ions to through. To form a of cellsurface receptor has an ▪ The Notch pathway regulates cell extensive membrane-spanning proliferation, cell fate, differentiation, region. and cell death in all metazoans. 2. G-PROTEIN-LINKED RECEPTORS - bind a ligand TYPES OF CELLS SIGNALING and activate a membrane 1. DIRECT CONTACT - When cells protein called a G-protein. The are very close to one another, activated G-protein then some of the molecules on the cells' interacts with either an ion plasma membranes may bind channel an enzyme in the together in specific ways. membrane. 2. PARACRINE SIGNALING - Like direct contact, paracrine signaling  plays an important role in early b.) Enzymatic receptors - single- development, coordinating the pass transmembrane proteins, activities of clusters of neighboring with the part binding the signal cells. molecule outside the cell and 3. ENDOCRINE SIGNALING - These the enzymatic part exposed to longer-lived signal molecules, the cell's interior. which may affect cells very distant c.) G-Protein Linked Receptors - from the releasing cell, are called indirectly influence enzymes or hormones, and this type of ion channels in the cell intercellular communication is membrane with the help of a known as endocrine signaling. protein called a G protein. 4. SYNAPTIC SIGNALING - The narrow gap between the two cells C. INTRACELLULAR ADHESION is called a chemical synapse. JUNCTION While paracrine signals move Connections between cells within through the fluid between cells, tissues. neurotransmitters cross the are not just casual touches but are synapse and persist only briefly long-lasting and essential for maintaining the structure and A. RECEPTORS THAT ACT AS functions of tissues in a GENE REGULATORS multicellular organism. CORTISOL - is a steroid hormone 3 CATEGORIES produced by the adrenal glands in 1. TIGHT JUNCTIONS - connect the response to stress and various plasma membranes of adjacent physiological signals. cells in a sheet, preventing small cortisol is released into the blood molecules from leaking between stream; it circulates throughout the the cells and through the sheet body. 2. ANCHORING JUNCTIONS - Inside target cells, cortisol binds to mechanically attach the specific intracellular receptors cytoskeleton of a cell to the This binding activates the cytoskeletons of other cells or to glucocorticoid receptor, and the the extracellular matrix. hormone receptor complex then 3. COMMUNICATIONG JUNCTIONS enters the cell nucleus - establish direct physical In the nucleus, the cortisol- connections that link the cytoplasm activated receptor binds to specific of two cells together, permitting DNA sequences, called small molecules or ions to pass glucocorticoid response elements from one to the other. (GREs), to regulate the transcription of genes involved in TYPES OF ANCHORING JUNCTION various cellular processes, Gap Junctions - specialized structures including metabolism and immune found in animal cells that serve as response communicating junctions. B. CELL SURFACE RECEPTORS Connexons: Each connexon is made up a.) Chemically gated channel - of six identical transmembrane proteins. When cells are very close to These proteins are arranged in a circular one another, some of the pattern, creating a channel through the molecules on the cells' plasma cell's plasma membrane membranes may bind together in specific ways. Channel Formation: Connexons create channels that protrude several nanometers from the cell's surface. Aligning Connexons: A functional gap junction is formed when the connexons of two neighboring cells align perfectly, creating an open channel that spans the plasma membranes of both cells. Passage of Small Substances: They permit the passage of small substances like simple sugars and amino acids, which are important for cell communication and coordination Size Selectivity: This selectivity is essential for maintaining cellular integrity and preventing the movement of potentially harmful substances between cells Connexon Dynamics: Gap junction channels are dynamic structures that can open or close in response to various factors, including the presence of calcium ions (Ca²⁺) and hydrogen ions (H⁺). This ability to open and close is known as "gating." Protective Function: Gap junctions serve a protective function as well. When a cell is damaged, its plasma membrane may become leaky, allowing ions in high concentrations outside the cell, like calcium ions (Ca²⁺), to flow into the damaged cell. References: Admin. (2020, July 20). Active Transport - Definition and types of active transport. BYJUS. https://byjus.com/biology/active-transport/ Biology Dictionary. (2019, October 4). Diffusion. https://biologydictionary.net/diffusion/ Karki, K. (2023, August 3). Beyond the membrane: understanding bulk transport. Microbe Notes. https://microbenotes.com/bulk-transport/ Libretexts. (2022, May 7). 5.7: cell transport. Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Human_Biology/Human_Biology_%28Wakim_a nd_Grewal%29/05%3A_Cells/5.07%3A_Cell_Transport The Editors of Encyclopaedia Britannica. (1998a, July 20). Diffusion | Definition & Examples. Encyclopedia Britannica. https://www.britannica.com/science/diffusion