4.6 Connections between Cells and Cellular Activities
3 min read•june 14, 2024
The (ECM) is a crucial component of tissues, providing support and facilitating communication between cells. It's made up of proteins and sugars that create a scaffold for cells to grow on and interact with each other.
Animal and plant cells have different ways of communicating. Animals use various types of cell junctions, while plants rely on and cell walls. These structures allow cells to exchange information and maintain tissue integrity.
Extracellular Matrix and Cell Communication
Structure and function of extracellular matrix
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- (ECM) non-cellular component present in all tissues and organs provides structural and biochemical support to surrounding cells composed of water, proteins, and polysaccharides
- Main components of ECM include:
- : protein cores with (GAG) chains attract water to form hydrated gel-like substance resist compressive forces
- Fibrous proteins: provides tensile strength, provides elasticity and resilience, and help with cell adhesion and migration
- ECM functions provide structural support and scaffolding for cells, facilitate cell adhesion, migration, and differentiation, regulate cell-to-cell communication and signaling, serve as a reservoir for growth factors and cytokines ()
- (CAMs) mediate interactions between cells and the ECM, playing a crucial role in tissue organization and cellular communication
Plant vs animal cell communication
- Cell junctions in animals:
- seal gaps between cells preventing leakage of extracellular fluids (epithelial tissues)
- provide strong mechanical attachments between cells ()
- allow direct communication and exchange of small molecules between cells (ions, metabolites)
- provide structural support and resist shearing forces ()
- Cell communication in plants:
- channels traverse cell walls allowing direct cytoplasmic connections between adjacent cells facilitate the exchange of small molecules, proteins, and RNA ()
- Cell walls provide structural support and regulate intercellular communication composed of , , and contain and ion channels for signaling ()
Cellular junctions for tissue integrity
- Tight junctions maintain tissue integrity by sealing intercellular spaces, regulate paracellular transport of ions and small molecules, establish apical-basal polarity in epithelial cells ()
- Adherens junctions provide strong mechanical attachments between cells, mediate cell-to-cell adhesion and recognition, play a role in tissue morphogenesis and wound healing ()
- Gap junctions allow direct communication between cells through channels, facilitate the exchange of ions, small molecules, and electrical impulses, coordinate cellular activities and maintain tissue homeostasis (cardiac muscle, neurons)
- provide structural support and resist mechanical stress, anchor intermediate filaments of adjoining cells, maintain tissue integrity in organs subject to mechanical stress (skin, heart)
Cell Signaling and Communication
- involves the transmission of information between cells through chemical or physical means
- on the cell surface recognize and bind specific signaling molecules, initiating cellular responses
- pathways convert external signals into intracellular responses, often involving cascades of protein modifications
- The plays a crucial role in cell signaling by facilitating the movement of signaling molecules and organizing signaling complexes
- are transmembrane receptors that mediate cell-ECM interactions and participate in bidirectional signaling between the cell and its environment
Key Terms to Review (36)
Actin filaments: Actin filaments, also known as microfilaments, are thin, thread-like protein structures that are a key component of the cytoskeleton in eukaryotic cells. They play a crucial role in maintaining cell shape, enabling cell movement, and facilitating intracellular transport. By forming networks and interacting with other proteins, actin filaments are essential for various cellular activities, including muscle contraction and cell division.
Adherens junctions: Adherens junctions are specialized cell-cell adhesion structures that help cells stick together and maintain tissue integrity. They are crucial for establishing strong connections between neighboring cells and play a vital role in the organization and function of tissues by facilitating communication and signaling pathways between cells.
Cadherins: Cadherins are a class of type-1 transmembrane proteins that play essential roles in cell-cell adhesion, allowing cells to stick together to form tissues. They are critical for maintaining the structure and integrity of tissues by facilitating strong connections between adjacent cells through their extracellular domains, which interact with cadherins on neighboring cells. This adhesion is vital for various cellular activities, including signaling processes that regulate cell growth, differentiation, and migration.
Cell adhesion molecules: Cell adhesion molecules (CAMs) are specialized proteins located on the cell surface that facilitate cell-cell and cell-extracellular matrix interactions. These molecules play crucial roles in various biological processes, such as tissue formation, immune response, and wound healing, highlighting their importance in maintaining the structure and function of tissues and organs.
Cell signaling: Cell signaling is the process by which cells communicate with each other to coordinate their activities and responses to various stimuli. This communication is essential for maintaining homeostasis, enabling cellular processes like growth, differentiation, and immune responses. Cell signaling involves signaling molecules, receptors, and a series of biochemical events that relay information from the cell surface to its interior, ultimately influencing cellular behavior.
Cell wall integrity sensing: Cell wall integrity sensing is the mechanism by which cells monitor and respond to the structural and functional state of their cell walls. This process is crucial for maintaining cellular shape, regulating growth, and ensuring proper responses to environmental stresses. By detecting changes in the cell wall, cells can activate signaling pathways that help them adapt and survive in varying conditions.
Cellulose: Cellulose is a complex carbohydrate and a key structural component of plant cell walls. It is composed of linear chains of glucose molecules linked by β-1,4-glycosidic bonds.
Cellulose: Cellulose is a complex carbohydrate, specifically a polysaccharide made up of long chains of glucose molecules linked together by β(1→4) glycosidic bonds. It serves as a key structural component in the cell walls of plants, providing rigidity and strength while playing an essential role in the synthesis of biological macromolecules and cellular interactions.
Collagen: Collagen is a structural protein that forms a key component of connective tissues in animals, providing strength and elasticity. It plays a vital role in maintaining the integrity of various tissues, including skin, bones, cartilage, and tendons, linking it to essential functions in cellular activities and tissue structure.
Connexon: A connexon is a protein structure composed of six connexin proteins that form a channel allowing for the direct communication between adjacent cells. These channels are crucial for the formation of gap junctions, enabling the transfer of ions and small molecules, which facilitates various cellular activities such as signal transduction and metabolic cooperation.
Cytoskeleton: The cytoskeleton is a network of protein filaments and tubules that provides structure, shape, and movement to the cell. It plays crucial roles in intracellular transport and cellular division.
Cytoskeleton: The cytoskeleton is a dynamic network of protein filaments and tubules that provides structural support, shape, and organization to cells. It plays a crucial role in various cellular functions, including movement, division, and maintaining the integrity of the cell, making it essential for both prokaryotic and eukaryotic cells.
Desmosomes: Desmosomes are specialized intercellular junctions that provide strong adhesion between cells, particularly in tissues subjected to mechanical stress. They are composed of cadherin proteins and anchor to intermediate filaments within the cell.
Desmosomes: Desmosomes are specialized cell structures that provide strong adhesion between adjacent cells, ensuring the integrity and stability of tissues under mechanical stress. They consist of protein complexes that anchor the cytoskeleton of one cell to that of another, forming a resilient connection that is crucial in tissues like the skin and heart, where cells experience significant tension and strain.
Elastin: Elastin is a key protein in the connective tissue that provides elasticity and resilience to various structures in the body, allowing them to return to their original shape after being stretched or deformed. This protein plays a crucial role in maintaining the structural integrity and functionality of organs and tissues, such as skin, blood vessels, and lungs, ensuring they can withstand mechanical stress.
Extracellular matrix: The extracellular matrix (ECM) is a complex network of proteins and polysaccharides secreted by cells into their external environment. It provides structural and biochemical support to surrounding cells in tissues.
Extracellular matrix: The extracellular matrix (ECM) is a complex network of proteins and carbohydrates that provides structural and biochemical support to surrounding cells. It plays a crucial role in cell communication, differentiation, and the overall integrity of tissues, making it essential for maintaining tissue architecture and function.
Fibronectin: Fibronectin is a glycoprotein that plays a crucial role in cell adhesion, growth, migration, and differentiation. It is a key component of the extracellular matrix (ECM) and facilitates the connection between cells and their environment, impacting various cellular activities such as wound healing, tissue repair, and embryonic development.
Gap junctions: Gap junctions are specialized intercellular connections that allow direct communication between adjacent cells by forming channels through which ions and small molecules can pass. These structures play a crucial role in coordinating cellular activities and maintaining tissue homeostasis, particularly in animal primary tissues such as cardiac muscle, where rapid electrical signaling is essential for proper function.
Glycosaminoglycan: Glycosaminoglycans (GAGs) are long, unbranched polysaccharides composed of repeating disaccharide units that play a crucial role in the extracellular matrix. These molecules are essential for maintaining the structural integrity of tissues and facilitating cell signaling, as they interact with proteins and other biomolecules to influence cellular activities and connections between cells.
Hemicellulose: Hemicellulose is a complex carbohydrate that forms part of the cell wall in plants, serving as a matrix that supports cellulose fibers. It is composed of various sugar monomers, making it more soluble and less rigid than cellulose, which allows it to play a critical role in maintaining cell wall structure and integrity. Hemicellulose is crucial for plant growth, development, and cellular activities, particularly in how cells connect and communicate with each other.
Integrins: Integrins are transmembrane proteins that facilitate cell adhesion and communication by connecting the extracellular matrix to the cell's cytoskeleton. They play a crucial role in various cellular activities, including signaling pathways, migration, and maintaining tissue integrity. Integrins are essential for the structural and functional organization of tissues, linking cells together and allowing them to respond to changes in their environment.
Intermediate filaments: Intermediate filaments are a type of cytoskeletal component found in eukaryotic cells that provide structural support and mechanical strength. They are thicker than microfilaments but thinner than microtubules, playing a crucial role in maintaining cell shape and integrity, as well as anchoring organelles. These filaments connect various cellular components, contributing to cell-cell and cell-matrix connections, which are essential for overall cellular function.
Laminin: Laminin is a crucial glycoprotein found in the extracellular matrix that plays an essential role in the structure and function of tissues. It helps to provide support and anchorage for cells, influencing cellular activities such as adhesion, migration, and differentiation. Laminin interacts with other components of the extracellular matrix and cell surface receptors, facilitating connections between cells and their environment, which is vital for maintaining tissue integrity and function.
Membrane receptors: Membrane receptors are specialized proteins located on the surface of cells that bind to signaling molecules, allowing the cell to respond to external stimuli. These receptors play a crucial role in facilitating communication between cells and their environment, influencing various cellular activities such as growth, differentiation, and metabolism.
Pectin: Pectin is a natural polysaccharide found in the cell walls of plants, particularly in fruits, where it acts as a structural component. It plays a crucial role in the connections between plant cells and influences various cellular activities, such as growth and fruit ripening. Pectin also has important applications in food science, particularly as a gelling agent in jams and jellies.
Plasmodesmata: Plasmodesmata are microscopic channels that traverse the cell walls of plant cells, facilitating communication and transport between them. These channels allow the movement of substances such as nutrients, signaling molecules, and genetic material.
Plasmodesmata: Plasmodesmata are microscopic channels that traverse the cell walls of plant cells, allowing for communication and transport of materials between adjacent cells. These structures play a crucial role in maintaining cellular activities by enabling the exchange of ions, nutrients, and signaling molecules, thereby facilitating the coordination of physiological processes across plant tissues.
Proteoglycans: Proteoglycans are large molecules consisting of a core protein covalently bonded to one or more glycosaminoglycan (GAG) chains, which play crucial roles in the structure and function of various tissues. They are essential components of the extracellular matrix, providing support and hydration to tissues while also influencing cell signaling and interactions between cells.
Receptor-like kinases: Receptor-like kinases are a type of protein that play crucial roles in cellular communication by receiving signals from the environment and triggering specific cellular responses. These proteins are similar to traditional receptors but are often involved in regulating growth, development, and responses to stress in plants and some other organisms. Their function is essential for the connections between cells, allowing them to process external cues and coordinate activities within the organism.
Signal transduction: Signal transduction is the process by which cells convert external signals into functional responses, allowing them to communicate and adapt to their environment. This involves a series of molecular events, including the reception of signaling molecules, propagation of the signal through cellular pathways, and eventual cellular responses that influence activities such as growth, metabolism, and immune reactions.
Symplastic transport: Symplastic transport refers to the movement of water and solutes through the cytoplasm of plant cells, interconnected by plasmodesmata, which are microscopic channels that allow for direct communication and exchange between adjacent cells. This pathway is crucial for maintaining cellular homeostasis and facilitating nutrient transport within plants, contributing to overall plant growth and function.
Tight junction: Tight junctions are specialized connections between adjacent epithelial cells that create a nearly impermeable barrier to fluid. They play a crucial role in maintaining the polarity and integrity of tissues by preventing the passage of molecules between cells.
Tight junctions: Tight junctions are specialized connections between adjacent cells that create a barrier to regulate the passage of substances through the intercellular space. These structures play a critical role in maintaining the integrity of tissue layers and ensuring selective permeability, which is vital for processes like absorption and secretion in epithelial tissues.
Transforming growth factor-β: Transforming growth factor-β (TGF-β) is a multifunctional cytokine that plays a crucial role in regulating cellular activities, including cell growth, differentiation, and immune response. This protein is involved in various biological processes such as tissue repair, inflammation, and the development of the extracellular matrix, connecting its functions to how cells interact with each other and their environment.
Zonula occludens: Zonula occludens, commonly known as tight junctions, are specialized structures that form a seal between adjacent epithelial cells, preventing the passage of substances between them. These junctions play a crucial role in maintaining cell polarity, regulating paracellular permeability, and facilitating communication between cells, thereby influencing various cellular activities and functions.