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Pinocytosis is a continuous process that serves a number of important functions including:
- Intake of nutrients
- Signal transduction
- Bulk transport of substances into the cell
- Some immune functions of macrophages and dendritic cells
What substances does pinocytosis transport?
Also called cell drinking, pinocytosis is a type of endocytosis that involves the inward folding of the cell membrane (plasma membrane) and the formation of membrane-bound, fluid-filled vesicles. These vesicles transport extracellular fluid and dissolved molecules (salts, sugars, etc.)
What is being transported in phagocytosis and pinocytosis?
While phagocytosis involves the ingestion of solid material, pinocytosis is the ingestion of surrounding fluid(s). This type of endocytosis allows a cell to engulf dissolved substances that bind to the cell membrane prior to internalization.
What molecules are being engulfed during pinocytosis?
Cells perform three main types of endocytosis. Phagocytosis is the process by which cells ingest large particles, including other cells, by enclosing the particles in an extension of the cell membrane and budding off a new vacuole. During pinocytosis, cells take in molecules such as water from the extracellular fluid.
What is the difference between endocytosis and pinocytosis?
Definition. Pinocytosis refers to the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane while receptor-mediated endocytosis refers to an endocytotic mechanism in which specific molecules are ingested into the cell.
How do phagocytosis and pinocytosis differ quizlet?
Phagocytosis is the process by which a cell engulfs large particles or whole cells, either as a defense mechanism or as a means to obtain food. Pinocytosis is a method of active transport across the cell membrane in which the cell takes in extracellular fluids. 9.
What is absorbed in pinocytosis?
Pinocytosis is a form of endocytosis involving fluids containing many solutes. In humans, this process occurs in cells lining the small intestine and is used primarily for absorption of fat droplets.
Does pinocytosis require a transport protein?
Once inside the cell, the protein is digested into its constituent amino acids, which are reabsorbed through the basolateral membrane into the interstitial fluid. Because pinocytosis requires energy, it is considered a form of active transport.
What is pinocytosis quizlet?
Pinocytosis. the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.
What type of transport is phagocytosis?
Phagocytosis. Phagocytosis (literally, “cell eating”) is a form of endocytosis in which large particles, such as cells or cellular debris, are transported into the cell.
What type of active transport is phagocytosis?
endocytosisPhagocytosis is a type of endocytosis, which is when cells ingest molecules via active transport as opposed to molecules passively diffusing through a cell membrane.
What is absorbed in pinocytosis?
Pinocytosis is a form of endocytosis involving fluids containing many solutes. In humans, this process occurs in cells lining the small intestine and is used primarily for absorption of fat droplets.
Does pinocytosis require a transport protein?
Once inside the cell, the protein is digested into its constituent amino acids, which are reabsorbed through the basolateral membrane into the interstitial fluid. Because pinocytosis requires energy, it is considered a form of active transport.
What is the process of pinocytosis?
Pinocytosis, also known as cell drinking or fluid-phase endocytosis, is a continuous process occurring in the majority of cells. Fluids and nutrients are ingested by cells in pinocytosis. The presence of certain molecules in a cell's extracellular fluid precipitates the pinocytosis process. Ions, sugar molecules and proteins are some common ...
What are the molecules that are involved in pinocytosis?
These molecules may include proteins, sugar molecules, and ions. The following is a generalized description of the sequence of events that occurs during pinocytosis.
What is the role of micropinocytosis in the cell cycle?
Micropinocytosis and macropinocytosis are the two major pathways that allow the uptake of dissolved molecules and water into cells. As the prefixes denote, micropinocytosis involves the formation of small vesicles while macropinocytosis involves the formation of larger ones. Receptor-mediated endocytosis allows the cell to target ...
What is the process of forming vesicles in the cell membrane?
Also called cell drinking, pinocytosis is a type of endocytosis that involves the inward folding of the cell membrane (plasma membrane) and the formation of membrane-bound, fluid-filled vesicles. These vesicles transport extracellular fluid and dissolved molecules (salts, sugars, etc.) across cells or deposit them in the cytoplasm.
How does adsorbtive pinocytosis differ from receptor-mediated endocytosis?
Adsorptive pinocytosis differs from receptor-mediated endocytosis in that specialized receptors are not involved. Charged interactions between molecules and the membrane surface hold the molecules to the surface at clatherine-coated pits. These pits only form for a minute or so before being internalized by the cell.
What is the process of removing the membrane of a cell?
Pinocytosis, sometimes referred to as fluid-phase endocytosis, is a continual process that occurs in most cells and a non-specific means of internalizing fluid and dissolved nutrients. Since pinocytosis involves the removal of portions of the cell membrane in the formation of vesicles, this material must be replaced in order for a cell ...
How do vesicles get recycled?
The vesicle may traverse the cell and be recycled back into the membrane by exocytosis or may fuse with a lysosome. Lysosomes release enzymes that break open vesicles, emptying their contents into the cytoplasm to be utilized by the cell.
What is Pinocytosis in the plasma membrane?
Figure 19.22. Pinocytosis, a type of endocytosis. An invagination of the plasma membrane encapsulates many water-soluble solutes ranging in size from salts to macromolecules.
What is pinocytosis in biology?
Currently, endocytosis refers to all kinds of cellular ingestion. The term pinocytosis refers to fluid-phase endocytosis regardless of endocytic vesicle size. It will be used here to describe activities with undetermined contributions from macro- and micropinocytosis. Macropinocytosis is the process originally imaged by Lewis, the cellular ingestion of extracellular fluid into 0.2 µm or larger pinosomes derived from the plasma membrane.
What sugars inhibit pinocytosis?
As had been found by Hieber et al. ( 12 ), mannose and α-methylmannoside were inhibitors of enzyme pinocytosis at 0.1 M concentration ( Table I ). Two lines of evidence suggested that this inhibition, although weak, was specific. First, comparable concentrations of mannose did not inhibit the rate of nonspecific fluid endocytosis for up to 3 hours. Second, only certain sugars were inhibitory. In fact, any of those sugars tested whose configuration resembled mannose at both the 2 and 4 positions was inhibitory. The very high concentrations of mannose required for inhibition suggested that enzyme recognition involved more than a simple interaction between the receptor and a terminal mannose residue on the enzyme.
How to measure pinocytosis?
Pinocytosis, or bulk interiorization of fluid, is typically assessed by measuring the cellular uptake over a fixed period of time of a marker present in a known concentration in the extracellular fluid. Clearly, the marker must not be interiorized by diffusion or specific transport, must be stable both extracellularly and intracellularly over the period of the experiment, must not be released by the cells once it has been interiorized, and must not itself affect the endogenous pinocytic rate of the cells being studied. In addition, the marker must not bind to cell surfaces, as such absorptive pinocytosis would prevent the uptake of the marker from being a true reflection of the quantity of fluid interiorized. The substrate vessel should be wrapped in aluminum foil and kept covered. Several marker particles including 3 H-labeled sucrose, 14 C-labeled inulin, 125 I-labeled bovine serum albumin, and colloidal gold have been used to assess pinocytic rates. Although in various situations, each of these markers has been useful, it has been found that horseradish peroxidase has fewer drawbacks and is generally more applicable than these alternatives.
How do macromolecules penetrate the impermeable barrier?
Macromolecules and large particles penetrate the impermeable barrier by the process called endocytosis in which material to be absorbed is engulfed by an area of the plasma membrane which forms an enclosed vesicle. There are three mechanisms of endocytosis; phagocytosis, pinocytosis and receptor-mediated endocytosis (Figure 9.5 ).
What is cell sipping?
Pinocytosis (cell sipping) has been thought to be a nonspecific, nonsaturable, non-carrier-mediated form of membrane transport via vesicular uptake of bulk fluid into cells from the surrounding medium (22, 23). This mechanism is most relevant to large particles and polymer conjugates. The term “pinocytosis” has fallen from favor and one suspects that many events previously ascribed to nonspecific pinocytosis are now recognized as being due to specific receptor-mediated endocytosis. Endocytosis is specific and intrinsic to the mechanism of action of many macromolecular drugs. This process is also used to deliver small molecules as prodrugs, and mediates the distribution and clearance of many contemporary pharmacological agents, including many biotechnology products, most peptide hormones, and cytokines (e.g., insulin, growth hormone, erythropoetin, granulocyte colony-stimulating factor, and interleukins) (24).
What is the process of containing small solutes?
In humans this process occurs in cells lining the small intestine and is used primarily for absorption of fat droplets. In endocytosis the cell plasma membrane extends and folds around desired extra-cellular material forming a pouch that pinches off creating an internalized vesicle (Figure 14.24, [52] ). The invaginated pinocytosis vesicles are much smaller than those generated by phagocytosis. The vesicles eventually fuse with the lysosome whereupon the vesicle contents are digested. Pinocytosis involves a considerable investment of cellular energy in the form of ATP and so is many thousand times less efficient than receptor-mediated endocytosis. Also, in sharp contrast to RME, pinocytosis is non-specific for the substances it accumulates. Pinocytosis is not a recent discovery but was first observed decades before the other transport systems discussed above. Its discovery is attributed to Warren Lewis in 1929.
What is Pinocytosis in the plasma membrane?
Figure 19.22. Pinocytosis, a type of endocytosis. An invagination of the plasma membrane encapsulates many water-soluble solutes ranging in size from salts to macromolecules.
What is the pinocytosis phase?
The pinocytosis phase of the transport process may be a fluid phase (nonselective),67,73,74 adsorptive with nonspecific solute binding (e.g., that between cationized proteins and anionic sites in the plasma membrane of human and guinea pig placenta), 75,76 or mediated by a specific receptor. In receptor-mediated transport, the specific receptors always become associated with specialized regions of the plasma membrane called coated pits, which on electron microscopy can be seen to be covered with a “coat” of the protein clathrin. 77,78 Invaginated coated pits with their associated receptors and receptor-ligand complexes form coated vesicles within the cell.
What is the endocytosis of aminoglycosides?
The endocytosis of aminoglycosides via clathrincoated pits is thought to involve initial binding of the polybasic cationic drugs to anionic lipids. Recently, megalin (also known as gp330 and as low-density lipoprotein receptor-related protein-2), a receptor protein on the brush border, has been implicated (31). Megalin knockout mice accumulate only about 5% as much of an intraperitoneal gentamicin dose in their kidneys as do wild-type mice. This protein is involved in the uptake of many low molecular weight proteins containing positively charged regions, including vitamin-binding proteins, lipoproteins, hormones, and also calcium. Competition for megalin binding between calcium and aminoglycosides may be the basis for the ability of oral calcium loading to attenuate aminoglycoside nephrotoxicity. The megalin receptor is most highly expressed in proximal renal tubule cells. It is also expressed in an eclectic assortment of other cells, including the epithelium of the inner ear, which may explain ototoxicity associated with long-term aminoglycoside treatment (32, 33).
What is the adsorbtive-mediated transcytosis route?
9.3E ), is triggered by an electrostatic interaction between a positively charged substance, usually the charged moiety of a cation peptide or protein, and the negatively charged plasma membrane surface (i.e., heparin sulfate proteoglycans). Adsorptive-mediated transport has a lower affinity but higher capacity than RMT. The development of many new drug delivery technologies focuses on AMT ( Hervé, Ghinea, & Scherrmann, 2008 ). AMT-based drug delivery to the brain can be achieved by using cationic proteins or basic oligopeptides, such as cell-penetrating peptides, as target molecules.
What is cell sipping?
Pinocytosis (cell sipping) has been thought to be a nonspecific, nonsaturable, non-carrier-mediated form of membrane transport via vesicular uptake of bulk fluid into cells from the surrounding medium (22, 23). This mechanism is most relevant to large particles and polymer conjugates. The term “pinocytosis” has fallen from favor and one suspects that many events previously ascribed to nonspecific pinocytosis are now recognized as being due to specific receptor-mediated endocytosis. Endocytosis is specific and intrinsic to the mechanism of action of many macromolecular drugs. This process is also used to deliver small molecules as prodrugs, and mediates the distribution and clearance of many contemporary pharmacological agents, including many biotechnology products, most peptide hormones, and cytokines (e.g., insulin, growth hormone, erythropoetin, granulocyte colony-stimulating factor, and interleukins) (24).
What is a cationic BSA liposome?
Cationic BSA (CBSA)-modified liposomes, in which CBSA was covalently conjugated to polyethylene glycol (PEG)-modified liposomes (PEGylated liposomes) as a drug carrier via the tips of the functional PEG strands, proved to be successful in brain delivery ( Thole, Nobmann, Huwyler, Bartmann, & Fricker, 2002 ). The CBSA-coupled liposomes could bind to cellular surfaces of monolayers of porcine BCECs and exhibited high intracellular accumulation in a time-dependent manner. CBSA-conjugated liposomes were also taken up by freshly isolated porcine brain capillaries. In contrast, native BSA-coupled liposomes did not interact with endothelial cells or brain capillaries. Cellular uptake of CBSA-coupled liposomes could be inhibited by free CBSA, indicating AMT involving delivery of CBSA-coupled liposomes to the brain ( Lu, 2012; Thole et al., 2002 ). It was reported that cell-penetrating peptide TAT (AYGRKKRRQRRR) was covalently conjugated to cholesterol to prepare doxorubicin-loaded liposomes for glioma therapy via adsorptive-mediated transcytosis. The biodistribution in the brain and heart demonstrated higher efficiency of brain delivery and lower cardiotoxicity. The survival time of the glioma-bearing rats treated with TAT-modified liposomes was significantly prolonged ( Qin et al., 2011 ).
What is the process of transcytosis?
Transcytosis is the receptor-mediated uptake of a ligand on one side of the cell , vesicular transport across the cell, and exocytosis of the vesicle contents on the opposite side. This process is responsible for the uptake of the iron-binding protein transferrin (Tf) across the blood–brain barrier (BBB) by the transferrin receptor (TfR). Monoclonal antibodies that recognize the transferrin receptor (mABTfR) are also carried across the cell and have been used to deliver various cargos. An early demonstration used mABTfR conjugated to avidin to deliver vasoactive intestinal peptide (VIPa) disulfide-linked to biotin. Reductases in the brain cleaved the disulfide linkage, releasing VIPa to express its pharmacological effect ( Figure 14.3) (34, 35).
How does pinocytosis work?
By taking in extracellular fluid along with dissolved nutrients through pinocytosis, duct cells separate important nutrients and fluids from urine which is expelled from the body. This ensures that important materials are retained while waste material is removed from the body. Pinocytosis by some immune cells - While cells ...
What is Pinocytosis?
Discovered by Warren Lewis in the late 1920s, pinocytosis is a type of endocytosis through which cells take in fluids along with dissolved solutes/nutrients from the extracellular matrix.
What is the difference between pinocytosis and phagocytosis?
Whereas phagocytosis involves the ingestion/internalization of solid material (e.g. invading pathogens) and foreign particles, pinocytosis involves the uptake of fluids from the extracellular matrix as well as some solutes.
What is clathrin mediated pinocytosis?
Clathrin-mediated pinocytosis is a type of pinocytosis through which cells take up a range of molecules including proteins and various metabolites. As is the case with macropinocytosis, the cell membrane will also undergo a conformational change following the attachment of these molecules to the membrane receptors in Clathrin-mediated pinocytosis.
What are some examples of pinocytosis?
Therefore, there are several types of pinocytosis which include: Absorption of nutrients in the gastrointestinal tract - Here, one of the best examples of pinocytosis is the absorption of extracellular fluid and dissolved solutes through the microvilli ...
How many types of pinocytosis are there?
There are two main types of pinocytosis based on the size of the material being taken into the cell.
Which type of cell is involved in phagocytosis?
Cell type - While cells are involved in both processes, phagocytosis is especially common in the immune system (in immune cells like granulocytes) while pinocytosis can be observed in different types of cells in the body (endothelial cells, epithelial cells, immune cells, etc.).
