239:, which often moves material from area of low concentration to area of higher concentration, and therefore referred to as moving the material "against the concentration gradient"). However, in many cases (e.g. passive drug transport) the driving force of passive transport can not be simplified to the concentration gradient. If there are different solutions at the two sides of the membrane with different equilibrium solubility of the drug, the difference in the degree of saturation is the driving force of passive membrane transport. It is also true for supersaturated solutions which are more and more important owing to the spreading of the application of amorphous solid dispersions for drug
654:
potential (external pressure e.g. cell wall). There are three types of
Osmosis solutions: the isotonic solution, hypotonic solution, and hypertonic solution. Isotonic solution is when the extracellular solute concentration is balanced with the concentration inside the cell. In the Isotonic solution, the water molecules still move between the solutions, but the rates are the same from both directions, thus the water movement is balanced between the inside of the cell as well as the outside of the cell. A hypotonic solution is when the solute concentration outside the cell is lower than the concentration inside the cell. In hypotonic solutions, the water
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across a selectively permeable membrane from an area of high water potential to an area of low water potential. A cell with a less negative water potential will draw in water, but this depends on other factors as well such as solute potential (pressure in the cell e.g. solute molecules) and pressure
472:
moves in the opposite direction, diffusing across the membrane of the capillaries and entering into the alveoli, where it can be exhaled. The process of moving oxygen into the cells, and carbon dioxide out, occurs because of the concentration gradient of these substances, each moving away from their
423:
This can be seen in material transport within the cell. Prokaryotes typically have small bodies, allowing diffusion to suffice for material transport within the cell. Larger cells like eukaryotes would either have very low metabolic rate to accommodate the slowness of diffusion, or invest in complex
658:
the cell, down its concentration gradient (from higher to lower water concentrations). That can cause the cell to swell. Cells that don't have a cell wall, such as animal cells, could burst in this solution. A hypertonic solution is when the solute concentration is higher (think of hyper - as high)
246:
Simple diffusion and osmosis are in some ways similar. Simple diffusion is the passive movement of solute from a high concentration to a lower concentration until the concentration of the solute is uniform throughout and reaches equilibrium. Osmosis is much like simple diffusion but it specifically
512:
Facilitated diffusion, also called carrier-mediated osmosis, is the movement of molecules across the cell membrane via special transport proteins that are embedded in the plasma membrane by actively taking up or excluding ions . Through facilitated diffusion, energy is not required in order for
247:
describes the movement of water (not the solute) across a selectively permeable membrane until there is an equal concentration of water and solute on both sides of the membrane. Simple diffusion and osmosis are both forms of passive transport and require none of the cell's
235:, and diffusion will continue until this gradient has been eliminated. Since diffusion moves materials from an area of higher concentration to an area of lower concentration, it is described as moving solutes "down the concentration gradient" (compared with
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477:
is the cause of the low concentration of oxygen and high concentration of carbon dioxide within the blood which creates the concentration gradient. Because the gasses are small and uncharged, they are able to pass directly through the
577:. With GLUT2 in place after a meal and the relative high concentration of glucose outside of these cells as compared to within them, the concentration gradient drives glucose across the cell membrane through GLUT2.
229:
Diffusion is the net movement of material from an area of high concentration to an area with lower concentration. The difference of concentration between the two areas is often termed as the
305:
849:
Borbas, E.; et al. (2016). "Investigation and
Mathematical Description of the Real Driving Force of Passive Transport of Drug Molecules from Supersaturated Solutions".
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to 'facilitate' or assist the substance through the membrane. After a meal, the cell is signaled to move GLUT2 into membranes of the cells lining the intestines called
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and into cells. When diffusing into a cell through GLUT2, the driving force that moves glucose into the cell is the concentration gradient. The main difference between
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allowing for facilitated passive transport of particular ions such as potassium down their charge gradient through high affinity transporters and channels.
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623:
cells are extremely large, but not forgetting cells are extremely small to allow a variety of solutes to pass through and be metabolized.
611:. Depending on the size of the membrane pores, only solutes of a certain size may pass through it. For example, the membrane pores of the
420:. This means that in the same physical environment, diffusion is fast when the distance is small, but less when the distance is large.
89:
61:
825:"12.7 Molecular Transport Phenomena: Diffusion, Osmosis, and Related Processes - College Physics for AP® Courses | OpenStax"
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68:
42:
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889:"The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases"
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619:, the smallest of the proteins, have any chance of being filtered through. On the other hand, the membrane pores of
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989:
Palmgren, Michael G. (2001-01-01). "PLANT PLASMA MEMBRANE H+-ATPases: Powerhouses for
Nutrient Uptake".
553:, and are therefore not examples of passive transport. Since glucose is a large molecule, it requires a
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without any special membrane proteins. No energy is required because the movement of the gasses follows
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of the cell membrane, which, in turn, depends on the organization and characteristics of the membrane
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Filtration is movement of water and solute molecules across the cell membrane due to hydrostatic
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Sadava, David; H. Craig Heller; Gordon H. Orians; William K. Purves; David M. Hillis (2007).
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to drive the movement of substances across cell membranes. Fundamentally, substances follow
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For passive diffusion, the law of diffusion states that the mean squared displacement is
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Kellett, George L.; Brot-Laroche, Edith; Mace, Oliver J.; Leturque, Armelle (2008).
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than the concentration inside the cell. In hypertonic solution, the water will
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1144:"Regulation of Intestinal Glucose Absorption by Ion Channels and Transporters"
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respective areas of higher concentration toward areas of lower concentration.
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1224:. Illustrations by John Bergdahl. New York: Random House. pp. 24–25.
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cellular machinery to allow active transport within the cell, such as
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molecules to pass through the cell membrane. Active transport of
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785:"Life's a Gas: A Thermodynamic Theory of Biological Evolution"
1249:(8th ed.). Sunderland, MA: Sinauer Associates. pp.
991:
Annual Review of Plant
Physiology and Plant Molecular Biology
620:
542:
177:
1220:
Alcamo, I. Edward (1997). "Chapter 2–5: Passive transport".
965:"3.1 The Cell Membrane - Anatomy and Physiology | OpenStax"
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Effect of osmosis on blood cells under different solutions.
453:
528:
1242:"What are the passive processes of membrane transport?"
940:"22.4 Gas Exchange - Anatomy and Physiology | OpenStax"
1090:"Sugar absorption in the intestine: the role of GLUT2"
184:. The four main kinds of passive transport are simple
435:
389:
345:
325:
265:
1272:. Harrow: Alpha Science Internat. pp. 140–148.
1142:
Chen, Lihong; Tuo, Biguang; Dong, Hui (2016-01-14).
49:. Unsourced material may be challenged and removed.
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464:by diffusing across the membrane of the pulmonary
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545:in the human body. There are many other types of
1495:
703:"5.2 Passive Transport - Biology 2e | OpenStax"
172:. The rate of passive transport depends on the
756:"5.3 Active Transport - Biology 2e | OpenStax"
1303:
1024:Dreyer, Ingo; Uozumi, Nobuyuki (2011-11-01).
1270:Elementary biophysics : an introduction
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456:and quickly diffuses across the membrane of
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1207:The Cell: A Molecular Approach. 2nd Edition
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1327:Mechanisms for chemical transport through
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300:{\displaystyle \langle r^{2}\rangle =2dDt}
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569:is that facilitated diffusion requires a
440:A biological example of diffusion is the
109:Learn how and when to remove this message
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615:in the kidneys are very small, and only
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448:within the human body. Upon inhalation,
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529:Example of facilitated diffusion: GLUT2
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16:Transport that does not require energy
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731:"5.2A: The Role of Passive Transport"
649:Osmosis is the net movement of water
319:). So to diffuse a distance of about
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225:Passive diffusion on a cell membrane.
1440:Non-specific, adsorptive pinocytosis
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47:adding citations to reliable sources
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1026:"Potassium channels in plant cells"
508:Depiction of facilitated diffusion.
311:being the number of dimensions and
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1247:Life : the science of biology
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436:Example of diffusion: Gas Exchange
156:, passive transport relies on the
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863:10.1021/acs.molpharmaceut.6b00613
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1003:10.1146/annurev.arplant.52.1.817
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887:Wagner, Peter D. (2015-01-01).
557:to facilitate its entry across
541:is absorbed into cells through
34:needs additional citations for
1203:"Transport of Small Molecules"
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663:, causing the cell to shrink.
376:{\displaystyle \sim x^{2}/2dD}
1:
1460:Receptor-mediated endocytosis
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543:Glucose transporter 2 (GLUT2)
383:, and the "average speed" is
1201:Cooper, Geoffrey M. (2000).
893:European Respiratory Journal
488:second law of thermodynamics
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158:second law of thermodynamics
7:
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125:Passive diffusion across a
10:
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1408:Secondary active transport
1268:Srivastava, P. K. (2005).
1094:Annual Review of Nutrition
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547:glucose transport proteins
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413:{\displaystyle \sim 2dD/x}
214:
203:Passive transport follows
144:to move substances across
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1222:Biology coloring workbook
906:10.1183/09031936.00039214
1403:Primary active transport
783:Skene, Keith R. (2015).
851:Molecular Pharmaceutics
591:Ultrafiltration (renal)
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140:that does not require
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475:Cellular respiration
452:is brought into the
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43:improve this article
1504:Transport phenomena
801:2015Entrp..17.5522S
678:Transport phenomena
444:that occurs during
148:. Instead of using
58:"Passive transport"
1509:Cellular processes
1349:mediated transport
1319:Membrane transport
735:Biology LibreTexts
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523:membrane potential
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462:circulatory system
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255:Speed of diffusion
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138:membrane transport
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1337:Passive transport
1161:10.3390/nu8010043
1036:(22): 4293–4303.
857:(11): 3816–3826.
810:10.3390/e17085522
607:generated by the
571:transport protein
332:{\displaystyle x}
134:Passive transport
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1514:Membrane biology
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971:. 25 April 2013
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202:
174:permeability
133:
132:
105:
96:
86:
79:
72:
65:
53:
41:Please help
36:verification
33:
1455:Potocytosis
1450:Pinocytosis
1427:Endocytosis
599:Filtration.
575:enterocytes
446:respiration
339:takes time
1519:Physiology
1498:Categories
1475:Exocytosis
1398:Antiporter
975:2020-12-06
950:2020-12-06
835:2020-12-06
766:2020-12-06
741:2020-12-06
713:2020-12-06
684:References
656:moves into
587:Filtration
581:Filtration
249:ATP energy
194:filtration
69:newspapers
1393:Symporter
1388:Uniporter
1170:2072-6643
1154:(1): 43.
1148:Nutrients
1114:0199-9885
1100:: 35–54.
1052:1742-4658
915:0903-1936
651:molecules
519:H ATPases
391:∼
347:∼
280:⟩
267:⟨
217:Diffusion
211:Diffusion
196:, and/or
186:diffusion
1370:Carriers
1365:Channels
1347:(or non-
1188:26784222
1122:18393659
1068:12814450
1060:21955642
1011:11337417
923:25323225
871:27611057
667:See also
661:move out
637:Tonicity
617:albumins
605:pressure
537:is when
486:and the
182:proteins
1418:Cytosis
1360:Osmosis
1251:105–110
1179:4728656
797:Bibcode
789:Entropy
633:Osmosis
627:Osmosis
539:glucose
521:alters
515:protons
458:alveoli
426:kinesin
198:osmosis
166:entropy
152:, like
83:scholar
1276:
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1228:
1186:
1176:
1168:
1120:
1112:
1066:
1058:
1050:
1009:
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913:
869:
450:oxygen
178:lipids
170:system
142:energy
85:
78:
71:
64:
56:
1064:S2CID
621:liver
454:lungs
307:with
90:JSTOR
76:books
1274:ISBN
1255:ISBN
1226:ISBN
1184:PMID
1166:ISSN
1118:PMID
1110:ISSN
1056:PMID
1048:ISSN
1007:PMID
919:PMID
911:ISSN
867:PMID
635:and
589:and
565:and
315:the
180:and
62:news
1174:PMC
1156:doi
1102:doi
1038:doi
1034:278
999:doi
901:doi
859:doi
805:doi
517:by
45:by
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295:t
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