page_title: Membrane transport protein
section_title: 1: Channels/pores
hierarchical_section_title: Membrane transport protein / Types / 1: Channels/pores
caption_attribution_description: English: This picture represents symport. The yellow triangle shows the concentration gradient for the yellow circles while the green triangle shows the concentration gradient for the green circles and the purple rods are the transport protein bundle. The green circles are moving against their concentration gradient through a transport protein which requires energy while the yellow circles move down their concentration gradient which releases energy. The yellow circles produce more energy through chemiosmosis than what is required to move the green circles so the movement is coupled and some energy is cancelled out. One example is the lac permease which allows protons to go down its concentration gradient into the cell while also pumping lactose into the cell.
context_page_description: A membrane transport protein is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane. Transport proteins are integral transmembrane protein; that is they exist permanently within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion or active transport. The two main types of proteins involved in such transport are broadly categorized as either channels or carriers. The solute carriers and atypical SLCs are secondary active or facilitative transporters in humans. Collectively membrane transporters and channels are transportome. Transportomes govern cellular influx and efflux of not only ions and nutrients but drugs as well.
context_section_description: α-helical protein channels such as voltage-gated ion channel (VIC), ligand-gated ion channels(LGICs)
  β-barrel porins such as aquaporin
  channel-forming toxins, including colicins, diphtheria toxin, and others
  Nonribosomally synthesized channels such as gramicidin
  Holins; which function in export of enzymes that digest bacterial cell walls in an early step of cell lysis.
  Facilitated diffusion occurs in and out of the cell membrane via channels/pores and carriers/porters.
  Note:
  Channels:
  Channels are either in open state or closed state. When a channel is opened with a slight conformational switch, it is open to both environment simultaneously (extracellular and intracellular)
  Pores:
  Pores are continuously open to these both environment, because they do not undergo conformational changes. They are always open  and active.
caption: This picture represents symport. The yellow triangle shows the concentration gradient for the yellow circles while the green triangle shows the concentration gradient for the green circles and the purple rods are the transport protein bundle. The green circles are moving against their concentration gradient through a transport protein which requires energy while the yellow circles move down their concentration gradient which releases energy. The yellow circles produce more energy through chemiosmosis than what is required to move the green circles so the movement is coupled and some energy is cancelled out. One example is the lactose permease which allows protons to go down its concentration gradient into the cell while also pumping lactose into the cell.
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