The Membrane Of Epithelial Cells

Those cells must receive nutrients and gases in order to undergo the metabolic processes that maintain homeostasis. In paragraph form, explain how you think the nutrients and gases enter the cell. Distinguish between the molecules that can enter by diffusion by simply moving across the membrane and those that must expend energy to cross the cell membrane.

Epithelial-mesenchymal transition (EMT) is a cellular process that is essential for normal processes in many organisms, including embryonic development and wound healing, and is recapitulated in human disease, contributing to organ fibrosis and cancer progression (Thiery et al. 2009; Yang and Weinberg 2008). EMT describes the conversion of a cell with an epithelial phenotype to one with mesenchymal characteristics and can be a partial or complete transformation. Epithelial cells form the borders of tissues and organs, and are characterized by apical-basal polarity, contact with a basement membrane, and strong adherence to other epithelial cells through intercellular junctions including adherens junctions, tight junctions, and desmosomes. Conversely, mesenchymal cells have front-rear polarity and generally lack cell-cell contact, allowing them to be motile. During human embryonic development, EMT is essential for the formation of a variety of tissues, including mesoderm, neural crest, somites, palate, pancreas, liver, reproductive tracts, and heart valves (Thiery et al. 2009; Yang and Weinberg 2008). After development, partial EMT also contributes to wound healing (Thiery et al. 2009). However, EMT can also play a more insidious role by factoring into tumour progression.

First, let's start with entosis. The beginning of the article states that this cell-swallowing process happens in homotypic epithelial cells (Durgan et al.). It is shown that the functions of this process uses clinging junctions and the production of actomyosin-based contractions. A cell pushing into or invading into a deformed one gives a way of engulfment. Durgan also shows that the process just gone over triggers the matrix to break down, causing it to be unstable and unable to resist the force coming from another cell. In a figurative sense, entosis is like bumpers cars. One of the cars has a faulty bumper to protect it because the person in the other car loosened the bolts, causing it to fall off, which makes it useless.

Both of these events occur because of interactions between the cancer cells and the stromal microenvironment (Weinberg et al., 2014). The degradation of extracellular matrix (ECM) and regulation of cell mesenchymal integrity are require steps (Bonnomet et al., 2010; Woessner, 1991). As known that matric metalloproteins (MMPs) are play an important role on ECM degradation. Type IV collagenase and gelatinase (MMP-2 or MMP-9) are major proteases for ECM degradation leading to migration and intravasation (Martin et al., 2007). Several junction proteins, such as E-cadherin and Vascular-Endothelial cadherin (VE-cadherin), are regular the integrity of cell-cell content and cell-mesenchymal contact (Fleming et al., 2000; Micalizzi et al., 2010). During cancer cells leave the original tumor organ to migrate to the target metastasis organ process, adhesion molecules (e.g., integrin-1 and E-selectin) play a key role in regulating the adhesion of tumor cells to endothelium cells (Yates et al., 2014; Okegawa et al., 2002). On the other hand, when cancer cells leave the original tumor organ to migrate to circulate system by intravasation, then they extravasation into the circulatory system to migrate to the target metastasis organ. The regulation of migration, invasion and adhesion may be an effective strategy for improving the prognosis of

In this assignment i will be describing Epithelial and connective tissues, the organs where they are found and their roles.

After lytic granules approach the membrane with the MTOC, additional obstacles are present which prevents them from immediate priming, docking, and fusion with the plasma membrane (Krzewski and Coligan, 2012). In activated NK cells, there is a dense F-actin meshwork occupying the central region of the synapse which could present as a physical barrier to lytic granule exocytosis. Within this are areas of hypodensity ranging from 200 nm to 500 nm, which could allow for the lytic granules (average diameter 300 nm) to pass through (Brown et al., 2011, Rak et al., 2011, Mace and Orange, 2012). Therefore, lytic granules may require actin clearance machinery and myosin IIA motors to finally reach the plasma membrane. In CTLs, it is suggested that lytic granules reach the plasma membrane via the MTOC, and do not require any microtubule-based or actin-based motors (Stinchcombe et al., 2006). However, it is unclear whether all lytic granule transport to the synapse is based on the close approximation of the MTOC to the synapse and independent of microtubule motors.

P1 – Describe the microstructure of a typical animal cell and the functions of the main cell components. A typical animal cell is seen as a tiny, three dimensional sac which is in fact made up of many components, each as important as the other. The microstructure of an animal cell was in fact uncovered mainly through the use of both cell fractionation and electron microscopy. Each main component has its own, individual function which helps a cell to function and maintains the cell membrane. The components that I will be describing include the cell membrane, nucleus, cytoplasm, mitochondria, lysosomes, Golgi bodies, centrioles, endoplasmic reticulum (both smooth and rough) and ribosomes.

The diffusion across a cell membrane is a process of passive and spontaneous net movement of small lipophilic molecules. The molecules move from a high concentration to a low concentrated region along the concentration gradient. The result being a point of equilibrium, this is where a random molecular motion continues but there is no longer any net movement. However, there are things that can affect the rate of diffusion, these being temperature, surface area, concentration, size of the molecule, permeability, diffusion distance and concentration difference. Osmosis is a type of diffusion as it is the movement of water molecules through a semipermeable membrane into a region of higher solute concentration. Equilibrium is reached when the solute concentration is equal on both sides. Water potential is measured in kiloPascals, it is the measuring of the concentration of free water molecules that are able to diffuse compared to pure water, which is 0 kilopascals. It is a measure of the tendency of free water molecules to diffuse from one place to another. The result being, the more free water molecules, the higher the Water Potential. However, Water potential is affected by two factors: pressure and the amount of solute.

The size of syndecans varies between 20 to 45 kDa depending on the syndecan’s type3. They are linked to the cellular cytoskeleton6. Therefore, they regulate the organization of cytoskeleton and actin microfilaments. They also play a role in endocytosis and the regulation of cell surface receptors during cell-cell and cell-matrix interactions7. In addition, syndecan molecule consists of four domains; a single sequence, extracellular domain that has sites for the attachment of heparin sulfate glycosaminoglycan side chains, a transmembrane region and short, highly conservative cytoplasmic domain of about 30 to 35 residues that helps in the interaction of syndecan molecules with cytoskeletal proteins5. The cytoplasmic region consists of two conserved regions; C1 (which is proximal to the plasma membrane) and C2 (which is distal to plasma membrane). A variable region is located between C1 and C2 regions3. Moreover, the extracellular domain is specific for each type of syndecan. It binds to 3 to 5 chains of HS or CS3. Syndecan-2 and 4 bind to HS while Syndecan-1 and 3 bind to CS in addition of HS3. The most prominent member of the syndecan family in the vasculature is syndecan-23. Moreover, Shedding of the extracellular of Syndecan occurs in response to complement activation8, endotoxin9, growth factors and thrombin10, serine and/or cystein proteinases11,

The boundary of all living cells is a plasma membrane that controls the entry of dissolved substances into and out of the cell. The plasma membrane is a living cell in a small compartment with an outer boundary. It has 2% of liver cells and 5% pancreatic cells in the total percentage of cell membranes.

The gene GJB3 (gap junction beta-3) encodes the protein Connexin 31. Connexin 31 is a member of the connexin gene family. Connexins are four-pass transmembrane proteins with both C and N cytoplasmic termini, a cytoplasmic loop (CL) and two extra-cellular loops, (EL-1) and (EL-2). Connexins are a group of proteins that form channels (gap junctions) on the surface of cells. Gap junctions allow direct intercellular communication of low molecular weight substances. Gap junctions open and close to regulate the flow of nutrients, charged atoms (ions), and other signaling molecules from cell to cell. Connexin 31 is found in several different parts of the body, including the outermost layer of the skin (the epidermis). The importance of Cx31

Overall, articular cartilage is a very dense structure, lacking blood vessels and nerves that are found in other tissues77. Chondrocytes are the cell types embedded within cartilage, and produce the structural proteins that form the ECM. The major components of the ECM are water, type II collagens, proteoglycans, aggrecan, and noncollagenous proteins such as fibronectins115,22. The resulting osmotic pressure created within the wet and dry components of the ECM work in harmony to support the mechanical forces applied to cartilage77. The water is retained in the ECM by aggrecan, the primary structural proteoglycan which is based on a long hyaluronic acid backbone with highly charged glycosaminoglycan (GAG) side chains, such as chondroitin sulfate (CS) and keratin sulfate (KS)26. Altogether, these components are what create the depth dependent layers of cartilage: the superficial zone, the middle zone, the deep zone, and the calcified zone (Figure

Identify which of the solutions were isotonic, hypertonic, and hypotonic in relation to the potato.

The 3D environment and the extracellular matrix: One of the key reasons for why a 3D environment promotes neural cell growth and function more closely resembling that seen in vivo is due to a much richer extracellular matrix (ECM). The brain ECM is a ‘hydrogel’ of hyaluronic acid with lamins, fibronectin, collagens, vitronectin, tenacins, and proteoglycans [15]. These structures provide key cell binding domains, and bioactive motifs that coordinate cell-cell interactions, and signaling from growth factors [12, 15]. Altered signaling patterns leads to changes in gene and thus protein expression and subsequently cell behaviour. The ECM is also critical for interaction between glial cells and neurons and this process is dependent not only on astrocyte-neuron interaction but also microglia-neuron interaction and microglia-astrocyte-neuron interactions [15, 35, 39]. In vivo, this occurs in a 3D manner with cells interacting with many other cells, but this is impaired in 2D cultures. A 3D matrix also controls movement of oxygen, nutrient transfer and removal of wastes in a manner that occurs similar to the brain rather than the batch media of 2D cultures that bath cells in high concentrations of compounds and allow rapid diffusion of waste [34, 40]. Formation of the microenvironmental conditions optimal for neural cell function depends on a 3D matrix and its interacting proteins and

Only uncharged, small, polar molecules, (such as water) and hydrophobic molecules, (such as oxygen, carbon dioxide) and lipid-soluble molecules (such as hydrocarbons) can freely pass across the membrane. All ions and large polar molecules (such as glucose) are not permeable to the membrane.