Membrane Transport Activity

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in order for us to use the molecules and
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energy we get from food
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we must transport them across cell
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membranes transport of nutrients is
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essential for all cells but we’ll use
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cells in the small intestine to teach
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the principles of membrane transport
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let’s zoom into the surface of an
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intestinal cell the plasma membrane is
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selectively permeable some molecules can
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move across it while others cannot
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how do materials enter and leave cells
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lipids such as these yellow molecules
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can move freely across the lipid bilayer
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notice that the lipid molecules move
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down their concentration gradient from
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where they are more concentrated to
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where they are less concentrated this is
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an example of simple diffusion diffusion
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is a form of passive transport it does
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not require energy from the cell but it
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does depend on the concentration
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gradient size in charge of the molecule
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or ion
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however most molecules cannot cross the
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lipid bilayer instead molecules like the
01:20
sugar fructose move into intestinal
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cells by facilitated diffusion moving
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down their concentration gradient and
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through transport proteins it also
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differs because it acts only on specific
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molecules and the transport proteins can
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become saturated reducing the amount of
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diffusion
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however facilitated diffusion doesn’t
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require energy from the cell so like
01:47
simple diffusion it’s a form of passive
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transport the majority of water
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molecules cross the plasma membrane by
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facilitated diffusion also called
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osmosis through specific protein
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channels called aquaporins
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some ions such as sodium and potassium
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require transport against their
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concentration gradients the sodium
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potassium pump actively transports these
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ions from where they are less
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concentrated to where they are more
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concentrated this process requires
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energy from the cell and is known as
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active transport energy from ATP is used
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to move three sodium ions shown in red
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out of the cell
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and two potassium ions shown in blue
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into the cell because the pump uses ATP
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directly this type of transport is
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called primary active transport
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another type of active transport
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secondary active transport also moves
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chemicals against gradients it doesn’t
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use ATP as a direct source of energy
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instead it uses the downhill gradient
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from one ion or molecule to drive the
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uphill movement of another ion or
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molecule for example sodium and glucose
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move into the cell by secondary active
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transport in a process called Co
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transport or symport because both
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substances are moving in the same
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direction sodium ions move down their
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concentration gradient created by the
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sodium potassium pump but because
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glucose concentrations inside the cell
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can quickly exceed those outside the
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cell glucose moves against its
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concentration gradient
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the cell moves larger materials such as
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proteins from the intracellular fluid to
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the extracellular fluid using vesicles
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that fuse with the plasma membrane and
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release their contents outside the cell
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this process is called exocytosis and
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endocytosis the plasma membrane pinches
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in forming a vesicle that contains
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material from outside the cell cells use
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all these processes passive and active
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transport exocytosis and endocytosis to
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move materials across their membranes

Biology: Cell Transport

How do things move across the cell membrane, either in or out? This animation shows two broad categories of how things pass into or out of a cell: passive transport and active transport. Passive transport is automatic; no input of energy is required. For example, diffusion is a passive process in which particles move either into or out of the cell from an area of higher concentration to an area of lower concentration. Active transport, on the other hand, is when particles move from an area of lower concentration to an area of higher concentration. Because particles are moving against the concentration gradient, energy is required. After viewing this video, the viewer will be able to: • List the two broad categories of cell transport • Describe the difference between active and passive transport.

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Cell transport is the process of how things move in or out of the cell through the cell membrane
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There are two broad categories of cell Transport
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The first Category is passive transport, for a cell passive transport means
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It’s an automatic process that doesn’t require any input of energy
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for example
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Diffusion is a passive process in which particles move either into or out of the cell from an area of higher
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concentration to an area of lower concentration
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The cell doesn’t use any energy when this happens
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The second Category of cell Transport is active Transport
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This is when particles move from an area of lower concentration to an area of higher concentration
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when particles move against the concentration gradient
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Energy is required often to allow protein pumps to assist in Particle Movement
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why would the cell need to move particles from a low to high concentration and expend energy to do it
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An Important example is seen in your heart muscle cells
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In order for your heart to beat there are certain molecules that have to move from an area of low concentration
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to an area of high concentration
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for those cardiac muscle cells to work
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So the main things to remember are passive transport happens automatically with no energy required
01:49
while active transport needs energy for it to occur
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Action Potential in the Neuron

The video transcripts may have typo errors but still can be understood.