Cell & Cytoskeleton

Desmosomes are cell junctions that connect adjacent cells, providing mechanical stability and preventing separation under tension. Intermediate filaments are a type of cytoskeletal protein that provide structural support to cells. The combo of desmosomes and intermediate filaments helps to distribute and offset pulling forces, such as those experienced when pulling on the skin. This allows tissues to withstand mechanical stress and maintain their integrity. Therefore, the statement that the combo of desmosomes and intermediate filaments offsets pulling forces is true.

Centrioles are cylindrical structures found in animal cells that play a key role in cell division. They are composed of microtubules, which are long, hollow tubes made up of protein subunits called tubulin. Microtubules provide structural support to the centrioles and help in organizing the spindle fibers during cell division. Microfilaments and intermediate filaments are also components of the cytoskeleton, but they are not the main constituents of centrioles. Therefore, the correct answer is microtubules.

Microtubules are long, hollow structures made up of protein subunits called tubulin. They play a crucial role in cell division, providing a framework for the movement of chromosomes. Microtubules also serve as tracks for transporting organelles and vesicles within the cell. Their hollow structure allows for the formation of large pipes or hollow rods, making them suitable for these functions. Microfilaments and intermediate filaments, on the other hand, are not hollow and do not possess the same structural properties as microtubules.

Microtubules are composed of a protein called tubulin. Tubulin is the main structural component of microtubules, forming long, hollow tubes that provide support and shape to cells. These protein structures play crucial roles in various cellular processes such as cell division, intracellular transport, and maintenance of cell structure. Therefore, the correct answer is tubulin, Tubulin.

The correct answer is a list of three types of cytoskeletal proteins: microfilaments, microtubules, and intermediate filaments. Cytoskeletal proteins are responsible for maintaining the shape and structure of cells, as well as facilitating cell movement and intracellular transport. Microfilaments, made up of actin, are involved in cell contraction and movement. Microtubules, composed of tubulin, provide structural support and act as tracks for intracellular transport. Intermediate filaments, made up of various proteins, provide mechanical strength to cells and help anchor organelles in place.

The adult skeleton consists of 206 bones.

Myosin and actin work together. Myosin is a motor protein that interacts with actin to generate the force necessary for muscle contraction and other cellular movements. Actin provides the track or filament for myosin to move along, and the interaction between myosin and actin allows for the sliding of actin filaments, resulting in muscle contraction. Therefore, myosin and actin have a cooperative relationship in various cellular processes.

Tubulun is a dimer means that it is composed of two subunits or monomers. This suggests that tubulun is a larger molecule formed by the combination of two smaller identical units. Therefore, the correct answer is True.

Flagella are long, whip-like structures that are responsible for providing movement to sperm. They are present in many organisms, including sperm cells in animals. The flagella enable the sperm to swim and move towards the egg, aiding in the process of fertilization. Therefore, flagella are crucial for the mobility and successful function of sperm.

Glycolipids are a type of carbohydrate that are covalently bonded to lipids. They are found in cell membranes and play important roles in cell recognition and signaling. Glycolipids consist of a lipid tail and a carbohydrate head group, which can vary in size and composition. They are involved in various cellular processes, including cell adhesion, immune response, and cell signaling. Glycolipids are also important for maintaining the integrity and stability of cell membranes.

Centrioles are small structures found in animal cells that play a role in cell division. They are cylindrical in shape and usually exist in pairs. When two centrioles align together at a 90-degree angle from each other, they form a centrosome. The centrosome is responsible for organizing microtubules during cell division and plays a crucial role in the separation of chromosomes. Therefore, the correct answer is centrosome.

Actin is a protein that plays a crucial role in cell structure and movement. It is known to polymerize into long, filamentous structures. One of the common forms that actin can take is a helix, where individual actin molecules twist around each other to form a spiral structure. This helical arrangement allows actin filaments to provide support and generate forces within cells, enabling various cellular processes such as muscle contraction and cell migration. Therefore, the correct answer is helix.

Gap junctions are a type of "pipe-like" connection between cells that allow for direct communication and exchange of small molecules and ions. They are formed by specialized proteins called connexins, which create channels that connect the cytoplasm of adjacent cells. This allows for the rapid transmission of electrical signals and the coordination of cellular activities. Gap junctions are found in various tissues and play important roles in processes such as cell signaling, embryonic development, and the synchronization of electrical activity in organs like the heart.

Cilia are small, hair-like structures found on the surface of many cells in the body. They are capable of coordinated, wave-like movements that help move substances along the cell surface. In the case of mucous, cilia help propel it along the respiratory tract, for example, by creating a wave-like motion that moves the mucous layer along the surface of the airway cells. This movement is similar to the way a crowd-surfing motion is created, where individuals in a crowd are passed along by the collective movement of the people around them. Therefore, cilia are responsible for providing movement similar to crowd-surfing along the cell surface.

Carbohydrates that are associated with proteins are called glycoproteins. This term refers to proteins that have attached carbohydrate molecules. These carbohydrates can play various roles in the structure and function of the protein, such as providing stability, aiding in cell recognition, and participating in cellular processes. Glycoproteins are found in various biological systems and have important functions in areas like immune response, cell signaling, and cell adhesion.

Intermediate filaments are a type of cytoskeletal protein that provide structural support and stability to cells. They are composed of a variety of different protein subunits, including keratins, vimentin, desmin, and neurofilaments, among others. These proteins come together to form a network of filaments that help maintain cell shape and integrity. Therefore, the statement that intermediate filaments are made up of many different types of proteins is true.

The microtubule organizing center refers to the structure responsible for the organization and anchoring of microtubules within a cell. The centrosome is a well-known example of a microtubule organizing center. It consists of a pair of centrioles surrounded by pericentriolar material. During cell division, the centrosome plays a crucial role in spindle formation and chromosome segregation. Additionally, it is involved in various cellular processes such as cell motility and intracellular transport. Therefore, the centrosome is the correct answer to the question regarding the microtubule organizing center.

The correct answer is microtubules, intermediate filaments, microfilaments. This is because microtubules have the largest diameter among the three, followed by intermediate filaments, and microfilaments have the smallest diameter.

Desmosomes are cell junctions that provide strong adhesion between cells. They are primarily responsible for connecting cells through the interaction of proteins called cadherins. These cadherins are anchored to intermediate filaments within the cell, which are a type of cytoskeletal protein. Intermediate filaments provide structural support and stability to cells, and their connection to desmosomes allows for the transmission of mechanical forces between cells. Therefore, the correct answer is intermediate filaments.

Intermediate filaments (IFs) are a type of cytoskeletal protein that provide structural support to cells. Unlike microtubules and microfilaments, IFs do not use motor proteins like dynein or myosin for movement or transportation. Instead, IFs are primarily involved in maintaining cell shape and integrity, as well as anchoring organelles within the cell. Therefore, the correct answer is "none" as IFs do not require motor proteins for their function.

Microfilaments are not organized around centrioles. Microfilaments, also known as actin filaments, are a component of the cytoskeleton and are responsible for cell movement, shape, and division. They are not directly associated with centrioles, which are involved in cell division and the organization of microtubules. Therefore, the statement that microfilaments are organized around centrioles is false.

Intermediate filaments are responsible for providing structural support and stability to cells. They form a network of protein filaments that help to maintain the integrity of tissues, including the skin. When we pinch or pull our skin, the intermediate filaments distribute the mechanical stress evenly, preventing the skin from tearing. Therefore, we should thank intermediate filaments for their role in protecting our skin from damage.

Tight junctions are the correct answer because they form a strong, zipper-like connection between cells. These junctions tightly seal the gap between adjacent cells, preventing the passage of molecules and ions between them. This firm connection helps to maintain the integrity and barrier function of tissues, such as the lining of the digestive tract or blood vessels. Tight junctions are essential for maintaining cellular polarity and regulating the movement of substances across epithelial layers.

Microtubules are long, hollow tubes made up of protein subunits called tubulin. They play a crucial role in cell division, providing structural support and acting as tracks for the movement of organelles and vesicles within the cell. Microtubules are also involved in maintaining cell shape and polarity, as well as in the formation of cilia and flagella. Intermediate filaments and microfilaments are also components of the cytoskeleton, but they have different structures and functions compared to microtubules. Therefore, microtubules are the correct answer in this context.

Tight junctions prevent us from swelling up in the shower by forming a barrier between cells, sealing the gaps between them and preventing the leakage of fluids. This tight seal ensures that water does not enter the spaces between cells, preventing them from absorbing excess water and swelling up.

Gap junctions are specialized protein channels that allow for direct communication and exchange of particles between the cytoplasm of neighboring cells. They are found in body areas where cells need to communicate and coordinate their activities, such as in the heart and in bone cells. Gap junctions play a crucial role in synchronizing the contraction of heart cells and in the exchange of nutrients between osteocytes and surface cells.

Keratin is the correct answer because it is the intermediate filament type found specifically in the cytoplasm of cells on the body surface or in internal parts of the body where there is a lot of friction or abrasion. Keratin is a structural protein that helps to provide strength and protection to the cells and tissues, especially in areas prone to wear and tear. It is commonly found in the skin, hair, nails, and other structures of the body.

Desmosomes are cell structures that play a crucial role in holding cells together, especially in tissues that undergo stretching or mechanical distortion. They provide strong adhesion between cells, preventing them from separating under stress. Desmosomes are particularly important in tissues like heart cells and the uterus during fetal development, where the cells need to remain tightly connected despite external forces. Unlike tight junctions, which form a seal between cells, and gap junctions, which allow for direct communication between cells, desmosomes primarily function as anchoring junctions.

The glycocalyx is a sugar coating that surrounds the cell. It is composed of glycoproteins and glycolipids that help protect the cell from damage, aid in cell recognition and signaling, and provide a surface for cell adhesion. The glycocalyx plays a crucial role in cell-cell interactions and is involved in various cellular processes such as immune response, cell adhesion, and cell signaling.

When the luminal surface is oriented towards the body surface instead of the lumen, it is referred to as the apical surface. The apical surface is typically found in epithelial cells and is responsible for various functions such as absorption, secretion, and protection. This surface is often exposed to the external environment or a body cavity, making it crucial for maintaining homeostasis and interacting with the surrounding environment.

Cilia are located on the apical surface of the cell. The apical surface refers to the surface of a cell that is facing towards a body cavity, lumen, or external environment. Cilia are hair-like structures that extend from the apical surface of certain cells and play a role in various functions such as movement of fluids or particles across the cell surface. Therefore, the correct answer is apical.

A basal body is made up of one centriole and is located at the base of a cilium. The centriole is a small, cylindrical structure that plays a crucial role in cell division. The basal body acts as a template for the formation of the cilium, which is a slender, hair-like structure that protrudes from the cell surface and is involved in various cellular functions such as movement and sensory perception. Therefore, the basal body is responsible for anchoring and organizing the cilium, allowing it to function effectively.

Cilia are small hair-like structures found on the surface of cells. While they are involved in various functions such as movement and sensory perception, they do not directly move things across the cell membrane. Instead, cilia are primarily responsible for moving substances along the cell surface or creating fluid movement around the cell. Therefore, the statement that cilia can move things across the cell membrane is false.

A desmosome is a type of cell junction that acts like a "button-like connection" between cells. It provides strong adhesion between cells and helps to anchor cells together, especially in tissues that experience mechanical stress, such as the skin and heart. Desmosomes are made up of proteins called cadherins, which connect to the cytoskeleton inside the cells. This allows desmosomes to provide structural support and prevent cells from separating under tension or stretching forces. Therefore, the correct answer is desmosome.

Tight junctions are specialized protein structures that hold cells together in a tight seal, preventing substances from passing between the cells. This allows cells to create separate compartments within the cell membrane, with different sides having distinct functions and compositions. Tight junctions play a crucial role in maintaining the integrity and barrier function of tissues, such as in the lining of the digestive tract or blood vessels.

Microtubules and microfilaments are both components of the cytoskeleton, which provides structural support and facilitates cell movement. Microtubules are dynamic structures composed of tubulin proteins and are involved in various cellular processes such as cell division and intracellular transport. Microfilaments, on the other hand, are made up of actin proteins and play a role in cell contraction, cell shape maintenance, and cell movement. Both microtubules and microfilaments exhibit dynamic behavior, constantly assembling and disassembling, allowing cells to adapt and respond to their environment. Intermediate filaments, however, do not display dynamic behavior and are primarily responsible for providing mechanical strength to cells.

Cadherins are linker proteins that make up the intracellular filaments extending from protein plaques across the para-cellular pathway in desmosomes. They play a crucial role in cell adhesion by connecting adjacent cells together and providing structural integrity to tissues. Cadherins are transmembrane proteins that interact with other cadherins on neighboring cells, forming strong adhesive contacts. This allows desmosomes to withstand mechanical stress and maintain the integrity of tissues, particularly in tissues subject to stretching and shearing forces, such as the skin and heart muscles.

Cilia are cell surface extensions that have a predictable 9+2 tubulin shape. The 9+2 arrangement refers to the nine outer microtubule doublets surrounding a central pair of microtubules. Dynein, a motor protein, is responsible for the movement of cilia. Cilia play various roles in the body, including the movement of mucus in the respiratory tract, the propulsion of sperm, and the coordination of fluid flow in the fallopian tubes.

Intermediate filaments are a component of the cytoskeleton in cells. They form irregular networks in the cytoplasm, providing structural support and stability to the cell. Unlike microtubules and microfilaments, intermediate filaments do not have a specific function in cell movement or cell division. Instead, they are responsible for specialized functions such as maintaining cell shape, anchoring organelles, and providing mechanical strength to cells. Therefore, the given statement accurately describes the role of intermediate filaments in the cell.

The functional group that anchors cholesterol to the phospholipid bilayer is the hydroxyl group (OH). This group is a characteristic feature of alcohols and is present in cholesterol as well. The hydroxyl group forms hydrogen bonds with the polar head groups of phospholipids, helping to stabilize the cholesterol molecule within the lipid bilayer.

Glycoproteins act as cell identity markers, which means they play a role in distinguishing one cell from another. These molecules are composed of both protein and carbohydrate components, with the carbohydrate portion being responsible for their identification function. By displaying unique patterns of glycoproteins on their surface, cells can be recognized and differentiated by other cells in the body. This helps in various biological processes, including immune responses, cell signaling, and cell-to-cell communication.

The cytoskeleton is a network of protein filaments that provides structural support to the cell and helps maintain its shape. It also plays a crucial role in cell motility by facilitating the movement of cellular components and the cell as a whole. Additionally, the cytoskeleton helps fix the position of certain cytoskeletal elements, such as organelles, within the cell. This stability is important for maintaining the overall structure and organization of the cell. Therefore, the functions mentioned in the answer are all accurate descriptions of the roles of the cytoskeleton.

Gap junctions are specialized intercellular channels that allow for direct communication and exchange of small molecules between adjacent cells. These channels are formed by the alignment and interaction of proteins called connexins. Connexons are the individual proteins that make up the gap junctions. They are composed of six connexin subunits arranged in a ring-like structure. When connexons from neighboring cells align, they form a complete gap junction channel, allowing for the passage of ions, metabolites, and signaling molecules between cells.

Microfilaments (MFs) are composed of actin proteins, which form a double helix structure. These actin filaments can interact with myosin, a motor protein, to generate movement within the cell. Myosin binds to actin filaments and undergoes a conformational change, causing the filaments to slide past each other. This sliding movement is responsible for various cellular processes, such as muscle contraction and cell migration. Therefore, the correct answer is myosin, actin, actin, myosin, as myosin interacts with actin filaments to generate movement.

tight junction function: "to occlude the space between cells"

Protein plaques refer to a grouping of proteins that interact with each other and form a single structure on the intracellular side of the cell membrane in desmosomes. These protein plaques play a crucial role in cell adhesion and provide structural support to cells. They help in maintaining the integrity and stability of tissues by connecting adjacent cells together.

The given answer, basolateral surface, is correct because it refers to the surface of a cell or tissue that is oriented towards the base (bottom) and sides (lateral) of the structure. In this context, when it is stated that "this surface faces the other side," it implies that the surface being referred to is not facing the top or apical side, but rather the opposite side. Therefore, the correct term to describe this surface is the basolateral surface.

The luminal and basolateral surfaces of a membrane create a "membrane asymmetry" that ensures the membrane is specialized. This means that each surface has a different composition and function, allowing for specific interactions and processes to occur on each side. This specialization is crucial for the proper functioning of the membrane and the cell as a whole.

Epidermal cells that cover the outer body are called keratinocytes. Keratinocytes are the main type of cells found in the epidermis, the outermost layer of the skin. These cells produce a protein called keratin, which helps to provide strength and protection to the skin. Keratinocytes also play a role in forming the skin barrier and regulating water loss from the body. Overall, keratinocytes are crucial for maintaining the integrity and function of the skin.

Cells typically organize their microfilaments in the cortex (outer rim of cytoplasm) into an arrangement called the terminal web. The terminal web is a dense network of actin filaments and associated proteins that provides structural support to the cell membrane. It helps maintain cell shape, stabilize the plasma membrane, and anchor transmembrane proteins. The terminal web is particularly important in cells with high mechanical stress, such as epithelial cells lining the intestines or kidney tubules. It also plays a role in cell motility and intracellular transport.