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How Is Cotransport Used To Move Glucose Into The Intestinal Epithelial Cells

Sodium-glucose Transport Proteins

Sodium-glucose Transport Proteins

solute carrier family 5 (sodium/glucose cotransporter), member 1 solute carrier family 5 (sodium/glucose cotransporter), member 2 solute carrier family 5 (low affinity glucose cotransporter), member four Sodium-dependent glucose cotransporters (or sodium-glucose linked transporter, SGLT) are a family of glucose transporter found in the intestinal mucosa ( enterocytes ) of the small intestine (SGLT1) and the proximal tubule of the nephron ( SGLT2 in PCT and SGLT1 in PST ). They contribute to renal glucose reabsorption . In the kidneys, 100% of the filtered glucose in the glomerulus has to be reabsorbed along the nephron (98% in PCT , via SGLT2). If the plasma glucose concentration is too high ( hyperglycemia ), glucose is excreted in urine ( glucosuria ) because SGLT are saturated with the filtered glucose. Glucose is never secreted by a healthy nephron . The two most well known members of SGLT family are SGLT1 and SGLT2, which are members of the SLC5A gene family. In addition to SGLT1 and SGLT2, there are five other members in the human protein family SLC5A, several of which may also be sodium-glucose transporters. [1] SGLT2 inhibitors, also called gliflozins, [4] are used in the treatment of type 2 diabetes . Examples include dapagliflozin (Farxiga in US, Forxiga in EU), canagliflozin (Invokana) and empagliflozin (Jardiance). Firstly, an Na+/K+ ATPase pump on the basolateral membrane of the proximal tubule cell uses ATP molecules to move 3 sodium ions outward into the blood, while bringing in 2 potassium ions. This action creates a downhill sodium ion gradient from the outside to the inside of the proximal tubule cell (that is, in comparison to both the blood and the tubule itself). The SGLT proteins use the energy from this downhill sodium ion gradient created by the Continue reading >>

(fig. 11-3.1, Lodish)

(fig. 11-3.1, Lodish)

1. Transport may involve ions, which are of central importance in the functioning of cells. Of particular imporance is the fact that concentrations of Na+ and Cl- are high outside the cell (as they are in sea water!!!!) and concentrations of K+ and trapped organic anions are high within cells.. Component Intracellular Concentration (mM) Extracellular Concentration (mM) Na+ 5-15 145 K+ 140 5-15 Cl- 5-15 110 Organic ions high 0 2. Carrier proteins are important for transport of many types of substances across both external and internal cell membranes. Simple, "Fick's Law", diffusion, down a concentration gradient from high to low concentration, is only found for small hydrophobic molecules, such as steroid hormones, and gases. These substances move across membranes without the aid of a protein channel. Transport across membranes is mostly through protein channels. Diffusion shows net movement from high concentration to low concentration. Net movement up the concentration gradient, from low to high concentrations, must have energy supplied from somewhere. (fig. 11-3.2, Lodish) (fig. 11-3.3, Lodish) Glucose is moved into cells by facilitated diffusion through a uniport transporter protein that shows enzyme-like kinetics. There is a maximum rate of transport (flux), even if the concentration difference between the two sides of the membrane is very high. (fig. 11-4, Lodish) Most mammalian cells use the GLUT1 uniport transporter protein to moved glucose across cell membranes. All GLUT proteins likely have 12 alpha-helical, membrane-spanning, segments. In animal cells, such as those lining our intestine, glucose and other solutes may be moved into cells by symport cotransport with an ion, usually Na+. Here is a cartoon of the facilitated diffusion cotransport system. Glucose mo Continue reading >>

Epithelial Transport

Epithelial Transport

Epithelia form linings throughout the body. In the small intestine, for instance, the simple columnar epithelium forms a barrier that separates the lumen from the internal environment of the body (note that the internal environment in which body cells exist is the extracellular fluid or ECF). The epithelium forms a barrier because cells are linked by tight junctions, which prevent many substances from diffusing between adjacent cells. For a substance to cross the epithelium, it must be transported across the cell's plasma membranes by membrane transporters. Not only do tight junctions limit the flow of substances between cells, they also define compartments in the plasma membrane. The apical plasma membrane faces the lumen. In the drawing, the apical plasma membrane is drawn as a wavy line, because intestinal epithelial cells have a high degree of apical plasma membrane folding to increase the surface area available for membrane transport (these apical plasma membrane folds are known as microvilli). The basolateral plasma membrane faces the ECF. Epithelial cells are able to transport substances in one direction across the epithelium because different sets of transporters are localized in either the apical or basolateral membranes. Absorption Absorption is the means whereby nutrients such as glucose are taken into the body to nourish cells. Glucose is transported across the apical plasma membrane of the intestine by the sodium-glucose cotransporter (purple). Because transport of Na+ and glucose is coupled, we need to add the free energy inherent in Na+ transport to the free energy inherent in glucose transport to get the overall free energy for the process. Just after a meal, there will be abundant glucose in the lumen of the intestine, favoring absorption. Towards the e Continue reading >>

What Is Active Transport And How Is It Used In The Absorption Of Glucose?

What Is Active Transport And How Is It Used In The Absorption Of Glucose?

Active transport is the movement of molecules or ions against their concentration gradient, using energy in the form of ATP, across a plasma membrane. In glucose absorption, there is an initially high concentration of glucose in the lumen of the gut as carbohydrates break down. This means there is a concentration gradient allowing the diffusion of glucose into the cells. Once the glucose is at equilibrium, it then needs to be taken up by active transport: 1) Sodium ions (Na+) are actively pumped out of the cells of the small intestine and into the blood via Sodium/Potassium (Na+/K+) pumps. 2) This creates an Na+ concentration gradient, where there is a higher concentration of Na+ in the lumen of the small intestine than inside the cells. 3) The Na+ then re-enters the cells of the small intestine via diffusion through a sodium-glucose transporter protein (alongside glucose). 4) The glucose concentration inside the cell increases and a concentration gradient is created between the inside of the cells and the blood. This allows glucose to move via facilitated diffusion into the blood. Continue reading >>

Bio Cells & Processes

Bio Cells & Processes

fx: locomotion, 1 or more attached to cell wall/distributed over cell structure- shorter, thinner, and straighter function- attachment compared to flagella used for locomotion glycolax: protects bacteria from immune attack (external danger) composed of polysaccharides & polypeptides bacteria's main method of reproduction- cells replicate genetic material and divide into daughter cells conjugation does not involve the fusion of gametes or zygotes examples of active transport & they use ATP. channels are less specific than carriers: carriers only allow specific things through, channels allow lots of things so long as they have the right size/cahrge required to build & maintain cell membranes, regulates membrane permeability and fluidity PROBLEM ONE (cell is 2 M placed in a solution w a concentration of 2.5 M): it is possible that the cell is already in equilibrium w its surroundings PROBLEM ONE (cell is 2 M placed in a solution w a concentration of 2.5 M): initially, solute concentration is greater outside the cell than inside PROBLEM ONE (cell is 2 M placed in a solution w a concentration of 2.5 M): water will enter the cell because solute potential is lower inside the cell than outside PROBLEM ONE (cell is 2 M placed in a solution w a concentration of 2.5 M): the cell will become flaccid because the pressure potential is greater outside the cell than inside PROBLEM ONE (cell is 2 M placed in a solution w a concentration of 2.5 M): the cell is already in equilibrium w its surrounding because of the combination of pressure potential and solute potential inside and outside the cell PROBLEM ONE (cell is 2 M placed in a solution w a concentration of 2.5 M): initially the cytoplasm is hypertonic to the surrounding solution PROBLEM ONE (cell is 2 M placed in a solution w a co Continue reading >>

Transport Across Epithelia

Transport Across Epithelia

Go to: The Intestinal Epithelium Is Highly Polarized An epithelial cell is said to be polarized because one side differs in structure and function from the other. In particular, its plasma membrane is organized into at least two discrete regions, each with different sets of transport proteins. In the epithelial cells that line the intestine, for example, that portion of the plasma membrane facing the intestine, the apical surface, is specialized for absorption; the rest of the plasma membrane, the lateral and basal surfaces, often referred to as the basolateral surface, mediates transport of nutrients from the cell to the surrounding fluids which lead to the blood and forms junctions with adjacent cells and the underlying extracellular matrix called the basal lamina (Figure 15-23). Extending from the lumenal (apical) surface of intestinal epithelial cells are numerous fingerlike projections (100 nm in diameter) called microvilli (singular, microvillus). Often referred to collectively as the brush border because of their appearance, microvilli greatly increase the area of the apical surface and thus the number of transport proteins it can contain, enhancing the absorptive capacity of the intestinal epithelium. A bundle of actin filaments that runs down the center of each microvillus gives rigidity to the projection. Overlying the brush border is the glycocalyx, a loose network composed of the oligosaccharide side chains of integral membrane glycoproteins, glycolipids, and enzymes that catalyze the final stages in the digestion of ingested carbohydrates and proteins (Figure 15-24). The action of these enzymes produces monosaccharides and amino acids, which are transported across the intestinal epithelium and eventually into the bloodstream. Go to: Transepithelial Movement Continue reading >>

How Is Co-transport Used To Move Glucose Into The Intestinal Epithelial Cells?

How Is Co-transport Used To Move Glucose Into The Intestinal Epithelial Cells?

How is co-transport used to move glucose into the intestinal epithelial cells? Are you sure you want to delete this answer? Best Answer: Sodium Glucose co-transport glucose molecules can pass with the aid of cells via osmosis. even in spite of the undeniable fact that some glucose won't be able to pass with the aid of. whilst say a glucose molecules is going right into a cellular, a phosphate team is extra to it so as that i does not pass decrease back out of the cellular. Our physique shops glucose into fat so as that the glucose dosnt pass in the process the cellular whilst it isn't any longer needed I think this question violates the Community Guidelines Chat or rant, adult content, spam, insulting other members, show more I think this question violates the Terms of Service Harm to minors, violence or threats, harassment or privacy invasion, impersonation or misrepresentation, fraud or phishing, show more If you believe your intellectual property has been infringed and would like to file a complaint, please see our Copyright/IP Policy I think this answer violates the Community Guidelines Chat or rant, adult content, spam, insulting other members, show more I think this answer violates the Terms of Service Harm to minors, violence or threats, harassment or privacy invasion, impersonation or misrepresentation, fraud or phishing, show more If you believe your intellectual property has been infringed and would like to file a complaint, please see our Copyright/IP Policy I think this comment violates the Community Guidelines Chat or rant, adult content, spam, insulting other members, show more I think this comment violates the Terms of Service Harm to minors, violence or threats, harassment or privacy invasion, impersonation or misrepresentation, fraud or phishing, show Continue reading >>

C2006/f2402 '11 -- Outline For Lecture #6

C2006/f2402 '11 -- Outline For Lecture #6

Handouts: 6A-- Transport of glucose through body (gif) 6A-- pdf 6B -- RME (gif) 6B --RME (pdf) 6C -- Structure of Capillaries & Transcytosis (Posted on Courseworks). Here are links for a diagram of a capillary, a diagram of transcytosis, and an electron micrograph of a capillary. I. Putting all the Methods of Transport of Small Molecules Together or What Good is All This? A. How glucose gets from lumen of intestine → muscle and adipose cells. An example of how the various types of transport are used. (Handout 6A) Steps in the process: 1. How glucose exits lumen. Glucose crosses apical surface of epithelial cells primarily by Na+/Glucose co-transport. (2o act. transport). 2. Role of Na+/K+ pump. Pump in basolateral (BL) surface keeps Na+ in cell low, so Na+ gradient favors entry of Na+. (1o act. transport) 3. How glucose exits epithelial cells. a. Glucose (except that used for metabolism of epithelial cell) exits BL surface of cell by facilitated diffusion = carrier mediated transport. b. Transporter protein = GLUT2 (more details on GLUT family of proteins below). c. When glucose leaves cells it enters the interstitial fluid = IF = fluid in between body cells. 4. How glucose enters and leaves capillaries -- by simple diffusion through spaces between the cells. Cells surrounding capillaries in most of body are not joined by tight junctions. a. Material does NOT enter capillaries by diffusion across a membrane. Material diffuses through liquid in spaces (pores) between the cells. b. For structure of capillaries, see handout 6C, bottom. (Also see links at start of lecture.)Pictures are provided on handout since function is hard to understand without the anatomy. Picture shows how endothelial cells surround capillary lumen, forming pores between cells. Pores allow diffusio Continue reading >>

Biology Flashcards | Quizlet

Biology Flashcards | Quizlet

Involved in the manufacture of substances, detoxifying harmful products and the storage and release of substances. Both are involved in transporting different materials within cells, but are not passive channels like pipes List one similarity between rough ER and smooth ER The rough ER transports proteins and has a network of channels while the smooth ER uses its outer membrane surface as a site of synthesis and detoxifies harmful products. Identify 2 differences between the rough ER and the smooth ER, one structural and one functional a slender thread-like structure, especially a microscopic whip-like appendage which enables many protozoa, bacteria, spermatozoa, etc. to swim. Minute hairlike organelles, identical in structure to flagella, that line the surfaces of certain cells and beat in rhythmic waves, providing locomotion to ciliate protozoans and moving liquids along internal epithelial tissue in animals a microscopic network of protein filaments and tubules in the cytoplasm of many living cells, giving them shape and coherence. a minute particle consisting of RNA and associated proteins found in large numbers in the cytoplasm of living cells. They bind messenger RNA and transfer RNA to synthesize polypeptides and proteins. -Solubility in lipids - lipophilic molecules cross easily -Charge - positive or negative charge molecules have difficulty crossing - uncharged cross easily -Concentration gradient - substances more likely to cross with concentration gradient Factors affecting transport across the plasma membrane Bacteria in deep sea vents use chemicals to produce own energy Glucose + Oxygen -> Carbon dioxide + water + energy (ATP) Water + Carbon dioxide -> glucose + oxygen Smaller diameters have a higher SA:V ratio What are the two major components of a plasma Continue reading >>

Facilitated Diffusion And Active Transport Of Glucose

Facilitated Diffusion And Active Transport Of Glucose

Concept 4 Review Whether a cell uses facilitated diffusion or active transport depends on the specific needs of the cell. For example, the sugar glucose is transported by active transport from the gut into intestinal epithelial cells, but by facilitated diffusion across the membrane of red blood cells. Why? Consider how different these two environments are. Epithelial cells lining the gut need to bring glucose made available from digestion into the body and must prevent the reverse flow of glucose from body to gut. We need a mechanism to ensure that glucose always flows into intestinal cells and gets transported into the bloodstream, no matter what the gut concentration of glucose. Imagine what would happen if this were not so, and intestinal cells used facilitated diffusion carriers for glucose. Immediately after you ate a candy bar or other food rich in sugar, the concentration of glucose in the gut would be high, and glucose would flow "downhill" from the gut into your body. But an hour later, when your intestines were empty and glucose concentrations in the intestines were lower than in your blood and tissues, facilitated diffusion carriers would allow the glucose in blood and tissues to flow "downhill," back into the gut. This would quickly deplete your short-term energy reserves. Because this situation would be biologically wasteful and probably lethal, it is worth the additional energy cost of active transport to make sure that glucose transport is a one-way process. By contrast, erythrocytes (red blood cells) and most other tissues in your body move glucose by facilitated diffusion carriers, not by active transport. Facilitated diffusion makes sense in this context because the environment is different for red blood cells and the gut. Whereas the gut experiences Continue reading >>

Secondary Active Transport - Physiologyweb

Secondary Active Transport - Physiologyweb

Home > Lecture Notes > Transport Across Cell Membranes > Active Transport > Secondary Active Transport Secondary active transport is a form of active transport across a biological membrane in which a transporter protein couples the movement of an ion (typically Na+ or H+) down its electrochemical gradient to the uphill movement of another molecule or ion against a concentration/electrochemical gradient. Thus, energy stored in the electrochemical gradient of an ion is used to drive the transport of another solute against a concentration or electrochemical gradient. The ion moving down its electrochemical gradient is referred to as the driving ion because it is movement of this ion that drives the uphill movement of another ion/molecule (driven ion/molecule). Secondary active transport is also commonly referred to as ion-coupled transport and, in fact, coupling between the driving and driven species is obligatory. That is to say that both the driving and driven species must be bound to the transporter for translocation across the membrane to occur. Unlike in primary active transport in which ATP hydrolysis provides the free energy needed to move solutes against a concentration gradient, in secondary active transport, the free energy needed to perform active transport is provided by the concentration gradient of the driving ion. To call this process secondary active transport is appropriate since the existence and maintenance of the concentration gradient of the driving ion is accomplished by primary active transporters (i.e., pumps). Sodium serves as the driving ion in many (but not all) secondary active transporters located in the plasma membrane of various cells. This is appropriate as there is a steep Na+ concentration gradient across the plasma membrane that is maint Continue reading >>

Sugar Transport - An Overview | Sciencedirect Topics

Sugar Transport - An Overview | Sciencedirect Topics

Mobeen Raja2, ... Rolf Kinne1, in Current Topics in Membranes , 2012 SodiumGlucose Symport as the Basis for Active Transepithelial Glucose Transport The first step in the active sugar transport across epithelial cells of the small intestine and the renal proximal tubule involves sodiumd-glucose cotransport. Sodium and sugar are translocated together across the brush border membrane. Sodium moves down its electrochemical potential difference, whereas glucose is accumulated inside the cell. The development of this concept represents a major step in understanding a large number of transport phenomena in nature. Such transport processes are termed secondary active, because the driving forces for solute movement against a concentration difference are not derived from a direct coupling of the transport to an energy-yielding chemical reaction. In animal cells, the secondary active transport of organic or inorganic solutes is usually coupled to the sodium gradient, in bacteria, symport with protons predominates. In both instances, the ion providing the driving forces is subsequently removed from the cell by a primary active transport system such as the Na-K-ATPase or an H-ATPase. The concept for sodiumsugar cotransport was developed and proven between 1960 and 1975. As reviewed in 1973 (Kimmich, 1973), Riklis and Quastel observed in perfused guinea pig intestine that complete replacement of sodium by potassium abolished all active transport of d-glucose (Riklis & Quastel, 1958). Csaky and Thale (1960) confirmed the sodium dependence of active sugar transport in toad intestine and Clarkson and Rothstein (1960) noted the sodium dependence in rat intestine. In the same year, Crane suggested that the sugar movement across the membrane involves a carrier mechanism and depends, via Continue reading >>

Epithelia

Epithelia

Lodish 4th edition: Chapter 21 pages 921 - 924 Epithelia: stomach, intestine and kidney etc. We are going to use a few examples of different epithelial to illustrate how ATPase pumps and transporters work together Epithelial cells have a specialized structure with a clear separation between the apical surface and the basal surface Usually the apical side faces the lumen of the stomach, intestine, kidney etc and the basal side faces the body cavity or blood The apical side will have a completely different complement of proteins compared to the basal side and this difference is maintained by a series of specialized junctions found near the apical side There are two types of junctions at the apical side of vertebrate epithelial cells. Adherens junctions that function to keep the cells in contact and tight junctions. We will talk about tight junctions for this part. Tight junctions are created by two sets of proteins from apposing membranes that form a tight seal when brought into contact. A specialized set of proteins called claudins and occludins are found at these junctions and are necessary for its formation The junction is impermeable meaning that water, ions etc can not pass between the cells. This is an essential function of tight junctions. Just think what would happen if your stomach lining lost its tight junctions You can test the barrier function by adding an electron dense ion like lanthanum to one side of the epithelium and then do EM analysis. In this example the ion can not cross the junction. Figure 1. Schematic diagram showing the organization of the gastric mucosa, gastric gland, gastric parietal cell and the gastric H/K ATPase. The parietal cells are one of a group of specialized epithelia cells that line the stomach. Diagram of a parietal cell. The lowe Continue reading >>

Membrane Transport

Membrane Transport

across the plasma membrane at the basolateral surface of the cell into the interstitial fluid ( Link to discussion of the apical and basolateral surfaces of epithelia) and As the process continues and more and more glucose is removed from the fluid, the concentration gradient up which the glucose must be pumped by active transport increases. What is the free energy needed to move glucose back from the tubular fluid to the blood when the concentration in the tubular fluid has dropped to 0.005 mM? The problem is to pump glucose into the cell (where it is about 0.5 mM) and then across the plasma membrane at the basolateral surface of the cell into the interstitial fluid , where the glucose concentration is 5 mM (the same as in the blood). So the total gradient through which the glucose must be pumped is 0.005 mM -> 5 mM. = 620 ln (1000) = (620)(6.91) = + 4284 cal/mole Is this enough to move a mole of glucose? No, but there is another force we must consider. Sodium ions carry a single positive charge and the interior of the cell is negatively charged [ link to discussion of how this comes about ]. So the attraction between opposite charges provides a second force for bringing Na+ into the cell. z = the charge on the ion (+1 in this case) F = 23,062 = the calories released as one mole of charge moves down a voltage gradient of 1 volt (1000 mV) Vm = the membrane potential, about 70 mV in mammalian cells.G = (+1)(23,062)(- 0.07) = 1,614 cal/mole (1.6 kcal/mole) Adding this to the free energy available from the concentration difference ( 1637 cal/mole) gives us a total yield of 3.3 kcal/mole from this combined or electrochemical gradient. Still not enough to move a mole of glucose, so at least two sodium ions are needed to bring one molecule of glucose into the cell. So the dr Continue reading >>

Outline For Lecture #5

Outline For Lecture #5

a. Theoretically, all pumps (like Na+/K+ pump) are reversible -- a pump can break down ATP and use the energy to drive ions up their gradient, or (if ion gradient is large enough) ions running down their gradient can provide enough delta G to drive phosphorylation of ADP to ATP.Therefore, proteins that catalyze active transport are sometimes called "ATPases" or pumps, whether their normal function is to hydrolyze ATP or to synthesize ATP. b. Practically speaking, inside cells, most pumps are irreversible. Most (but not all) individual "pump" proteins work only one way in cells, because the standard delta G for the "usual" direction is very negative. Therefore it takes very high concentrations of products (very high ATP or very high ion concentrations, depending on the reaction) to push the reaction in the "reverse" direction. The concentrations needed to reverse the reaction are not reached in cells, but can be achieved in test tubes (by adding ATP, setting up ion gradients, etc.). So in vitro (in test tubes), but not in vivo (in living cells), you can make the pumps run in either direction. Two examples of important pumps that are reversible (in vitro), but usually run in one direction (in vivo): (1). In the inner membranes of mitochondria and chloroplasts, chemical or light energy is used via electron transport to set up a proton gradient, which then runs down; driving phosphorylation of ATP. So these systems almost always act to make ATP while ions run down their gradient. (2). The Na+/K+ pump in the plasma membrane almost always uses up ATP -- this system drives ions up their gradients at the expense of ATP. For more examples, see Becker table 8-3. II. Putting all the Methods of Transport of Small Molecules Together or What Good is All This? A. How glucose gets fro Continue reading >>

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