Membrane Transport 1 - Video Tutorials & Practice Problems
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Membrane Transport 1
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There are a variety of ways that membrane transport could be accomplished, and the simplest among these is simple diffusion, which Onley occurs with non polar compounds because they must enter the non polar environment of the membrane. However, it's worth noting that water is a major exception here, as it is a very polar molecule. However, it's small enough that it can still cross the membrane through simple diffusion. Facilitated diffusion uses channels and carriers that have specificity for particular. Saul you. Now it is worth noting that water actually moves via facilitated diffusion as well as simple diffusion. And it's moved through channels called Aqua Porn's. And this is because even though water can move by facilitated diffusion, it doesn't actually move fast enough for the various biological processes that necessitate water crossing the membrane. So it actually also moves through these channels called Aqua Porn's, And here we have an example of a protein channel, and the basic idea of a channel is it just carries molecules in one direction, and it is basically just, um, like an open tube in the membrane so molecules will just go through the channel. Some channels are gated, so they can have a gating mechanism, something to close off the channel. This will only occur on one side of the channel, and what's important is channels are very specific. They're they're designed to carry just one type of salute. However, because they do carry salutes, water tends to move in conjunction with salute of interest through the channel. Oftentimes these air ions that are moving through and so water will associate with the ions, and they'll all move through the channel together. That said, aqua por ins are channels that specifically bring in water and not other stuff. Now, in addition to channels, there are also these carriers and carriers will move. We'll move substances across the membrane, and they can actually go in both directions. However they because this is a Phyllis facilitated diffusion process, they only move solid roots down their concentration greeting. So a nice example of this is glucose transporter and glucose transporter. While it can transport glucose in both directions, it tends to Onley move it in one direction, down its concentration radiant and uhh! In a very clever way. Cells sort of trick the concentration Grady int to ensure that glucose through this transporter is always moving into the cell, and the way it does that is whenever glucose enters the cell, it's actually very quickly converted to glucose six phosphate that you see right here. So because glucose is converted to this other molecule that maintains a low internal glucose concentration and a higher external glucose concentration because technically, the glucose in the cell is actually Glucose six phosphate, which is a molecule we're going to talk about at length later when we talk about cellular respiration. So, um, the basic idea here is that thes carriers also use facilitated diffusion to move molecules, uh, across the membrane. However, um, the thes carriers can actually move the molecules in either direction, and the direction is determined again by the, uh, electrochemical Grady int of salute. Now, these simple diffusion and facilitated diffusion represent forms of passive transport, meaning that no energy is required for this transport to occur. It happens passively, the opposite being active transport, which requires energy. And actually there's two types of active transport. There is primary active transport, which directly uses ATP to move salutes against their concentration, radiance, and generally these are found as pumps and pumps play a big role in maintaining specific electric chemical radiance across the membrane, which is really important in neuroscience and also really important for cellular respiration. And something again we're gonna talk about at great length. So to really good examples of these primary active transporters, specifically pumps are the sodium potassium pump, also called Enoch at pus. Occasionally and these pumps move the I M. Sodium and potassium across the membrane. They pump out, they pump three so Diem's and to potassium at the expense of you can see one ATP right there. Another really good example of a pump is thes pumps that we're gonna take a look at later and cellular respiration and these air proton pumps, and they play a crucial role in ATP synthesis. So due to the electron transport chain, these pumps will actually pump hydrogen ions into the the inter membrane space of the mitochondria. And then this, um, this electrochemical Grady int that is created, which is also called the Proton Motive Force. This electrical chemical radiant will drive ATP synthesis, which is an enzyme that produces a teepee from ADP and inorganic phosphate. Um, as it transports hydrogen ions or protons down they're electrochemical Grady int So passive transport does not use energy and passive transport comes in the form of simple diffusion and facilitated to fusion and primary. Active transport uses energy directly in the form of ATP. Now let's turn the page and talk about secondary active transport.