Membrane transport: Difference between revisions
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Transport across the membrane can be divided into 2 sub-divisions, macrotransfer, which is the bulk movement of molecules across the [[Cell membrane|cell membrane]], and microtransfer, which is the movement of 1 or a few molecules across the membrane. Examples of macrotransfer include exocytosis and endocytosis. Microtransfer includes both passive transport and active transport, both use a range of different membrane transport proteins. | Transport across the membrane can be divided into 2 sub-divisions, macrotransfer, which is the bulk movement of molecules across the [[Cell membrane|cell membrane]], and microtransfer, which is the movement of 1 or a few molecules across the membrane. Examples of macrotransfer include exocytosis and endocytosis. Microtransfer includes both passive transport and active transport, both use a range of different membrane transport proteins. | ||
Membrane transport occurs through the use of membrane transport [[Proteins|proteins]]. Without these, membranes would only be permeable to some gases and small molecules <ref>Lodish H et al. (2012) Molecular Cell Biology, 6th Edition, New York: WH Freeman. pg.473</ref>, due to the semi-permeability phospholipid bilayer structure of the membrane. There are two types of <span style="line-height: 1.5em;">Transport proteins, these are [[Carrier proteins|Carrier (Transporter) Proteins]] and [[Channel proteins|Channel Proteins. ]]</span> | Membrane transport occurs through the use of membrane transport [[Proteins|proteins]]. Without these, membranes would only be permeable to some gases and small molecules <ref>Lodish H et al. (2012) Molecular Cell Biology, 6th Edition, New York: WH Freeman. pg.473</ref>, due to the semi-permeability phospholipid bilayer structure of the membrane. There are two types of <span style="line-height: 1.5em;">Transport proteins, these are [[Carrier proteins|Carrier (Transporter) Proteins]] and [[Channel proteins|Channel Proteins. ]]</span> | ||
< | === <span style="line-height: 1.5em;">[[Channel proteins|Channel proteins]]</span>Carrier Proteins === | ||
<span style="line-height: 1.5em;">[[Channel proteins|The former is an active process as it requires ]][[ATP|ATP]]</span><span style="line-height: 1.5em;">.</span> [[ATP-powered pumps|ATP-powered pumps]] use energy from [[ATP|ATP]] [[Hydrolysis|hydrolysis]] in order to move [[Ions|ions]] or [[Molecules|molecules]] against their concentration gradient. However<span style="line-height: 1.5em;"> Channel Proteins are passive as they allow the </span><span style="line-height: 1.5em;">movement of ions through the membrane down their concentration gradient </span><ref>Alberts B., Johnson A., Lewis J., Raff M., Roberts K., Walter P. (2008) Molecular Biology of The Cell, 5th Edition, New York: Garland Science.</ref>. | <span style="line-height: 1.5em;">[[Channel proteins|The former is an active process as it requires ]][[ATP|ATP]]</span><span style="line-height: 1.5em;">.</span> [[ATP-powered pumps|ATP-powered pumps]] use energy from [[ATP|ATP]] [[Hydrolysis|hydrolysis]] in order to move [[Ions|ions]] or [[Molecules|molecules]] against their concentration gradient. However<span style="line-height: 1.5em;"> Channel Proteins are passive as they allow the </span><span style="line-height: 1.5em;">movement of ions through the membrane down their concentration gradient </span><ref>Alberts B., Johnson A., Lewis J., Raff M., Roberts K., Walter P. (2008) Molecular Biology of The Cell, 5th Edition, New York: Garland Science.</ref>. | ||
Transporters are split into three g<span style="line-height: 1.5em;">roups; </span>[[Uniporters|Uniporters]]<span style="line-height: 1.5em;">, which transport a single molecule down a concentration gradient, </span>[[Symporters|Symporters]]<span style="line-height: 1.5em;">, which transport a molecule against its concentration gradient through the transport of other molecules down their [[Electrochemical gradient|electrochemical gradient (same direction of travel across membrane), and ]]</span>[[Antiporters|Antiporters]]<span style="line-height: 1.5em;">, which also use the transport of other molecules down their electrochemical gradient to transport other molecules (opposite directions of travel of molecules across the membrane) </span><ref>Lodish H et al. (2012) Molecular Cell Biology, 6th Edition, New York: WH Freeman. pg.475</ref><span style="line-height: 1.5em;">. Symporters and Antiporters are also known as co-transporters due to the aided movement of two or more differing molecules simultaneously. | Transporters are split into three g<span style="line-height: 1.5em;">roups; </span>[[Uniporters|Uniporters]]<span style="line-height: 1.5em;">, which transport a single molecule down a concentration gradient, </span>[[Symporters|Symporters]]<span style="line-height: 1.5em;">, which transport a molecule against its concentration gradient through the transport of other molecules down their [[Electrochemical gradient|electrochemical gradient (same direction of travel across membrane), and ]]</span>[[Antiporters|Antiporters]]<span style="line-height: 1.5em;">, which also use the transport of other molecules down their electrochemical gradient to transport other molecules (opposite directions of travel of molecules across the membrane) </span><ref>Lodish H et al. (2012) Molecular Cell Biology, 6th Edition, New York: WH Freeman. pg.475</ref><span style="line-height: 1.5em;">. Symporters and Antiporters are also known as co-transporters due to the aided movement of two or more differing molecules simultaneously.</span> | ||
</span | |||
< | === <span style="line-height: 1.5em;" />Channel Proteins === | ||
Channel can either form aqueous pores in which specific solutes pass through the bilayer <ref>Alberts, B., et al. (2007) Molecular Biology of the Cell. 5th Edition. New York:Garland Science.</ref> or become gated. Pore or ungated channel proteins allow the movement of molecules such as water across cell membrane while gated channels require some signal in order to be activated and opened. Voltage-gated Sodium and Potassiun channels are critical for neuronal and muscle communication. The influx of Sodium ions and efflux of Potassium ions generates action potential underlying the delivery of neuronal information and muscle contraction. | Channel can either form aqueous pores in which specific solutes pass through the bilayer <ref>Alberts, B., et al. (2007) Molecular Biology of the Cell. 5th Edition. New York:Garland Science.</ref> or become gated. Pore or ungated channel proteins allow the movement of molecules such as water across cell membrane while gated channels require some signal in order to be activated and opened. Voltage-gated Sodium and Potassiun channels are critical for neuronal and muscle communication. The influx of Sodium ions and efflux of Potassium ions generates action potential underlying the delivery of neuronal information and muscle contraction.<br> | ||
=== References === | |||
<references /><br> | <references /><br> | ||
Revision as of 06:24, 4 December 2015
Transport across the membrane can be divided into 2 sub-divisions, macrotransfer, which is the bulk movement of molecules across the cell membrane, and microtransfer, which is the movement of 1 or a few molecules across the membrane. Examples of macrotransfer include exocytosis and endocytosis. Microtransfer includes both passive transport and active transport, both use a range of different membrane transport proteins.
Membrane transport occurs through the use of membrane transport proteins. Without these, membranes would only be permeable to some gases and small molecules [1], due to the semi-permeability phospholipid bilayer structure of the membrane. There are two types of Transport proteins, these are Carrier (Transporter) Proteins and Channel Proteins.
Channel proteinsCarrier Proteins
The former is an active process as it requires ATP. ATP-powered pumps use energy from ATP hydrolysis in order to move ions or molecules against their concentration gradient. However Channel Proteins are passive as they allow the movement of ions through the membrane down their concentration gradient [2].
Transporters are split into three groups; Uniporters, which transport a single molecule down a concentration gradient, Symporters, which transport a molecule against its concentration gradient through the transport of other molecules down their electrochemical gradient (same direction of travel across membrane), and Antiporters, which also use the transport of other molecules down their electrochemical gradient to transport other molecules (opposite directions of travel of molecules across the membrane) [3]. Symporters and Antiporters are also known as co-transporters due to the aided movement of two or more differing molecules simultaneously.
Channel Proteins
Channel can either form aqueous pores in which specific solutes pass through the bilayer [4] or become gated. Pore or ungated channel proteins allow the movement of molecules such as water across cell membrane while gated channels require some signal in order to be activated and opened. Voltage-gated Sodium and Potassiun channels are critical for neuronal and muscle communication. The influx of Sodium ions and efflux of Potassium ions generates action potential underlying the delivery of neuronal information and muscle contraction.
References
- ↑ Lodish H et al. (2012) Molecular Cell Biology, 6th Edition, New York: WH Freeman. pg.473
- ↑ Alberts B., Johnson A., Lewis J., Raff M., Roberts K., Walter P. (2008) Molecular Biology of The Cell, 5th Edition, New York: Garland Science.
- ↑ Lodish H et al. (2012) Molecular Cell Biology, 6th Edition, New York: WH Freeman. pg.475
- ↑ Alberts, B., et al. (2007) Molecular Biology of the Cell. 5th Edition. New York:Garland Science.