00:04in order for us to use the molecules and00:07energy we get from food00:09we must transport them across cell00:11membranes transport of nutrients is00:15essential for all cells but we’ll use00:18cells in the small intestine to teach00:20the principles of membrane transport00:22let’s zoom into the surface of an00:26intestinal cell the plasma membrane is00:29selectively permeable some molecules can00:33move across it while others cannot00:35how do materials enter and leave cells00:41lipids such as these yellow molecules00:44can move freely across the lipid bilayer00:48notice that the lipid molecules move00:50down their concentration gradient from00:53where they are more concentrated to00:56where they are less concentrated this is00:58an example of simple diffusion diffusion01:01is a form of passive transport it does01:04not require energy from the cell but it01:07does depend on the concentration01:09gradient size in charge of the molecule01:12or ion01:13however most molecules cannot cross the01:17lipid bilayer instead molecules like the01:20sugar fructose move into intestinal01:23cells by facilitated diffusion moving01:26down their concentration gradient and01:28through transport proteins it also01:31differs because it acts only on specific01:34molecules and the transport proteins can01:37become saturated reducing the amount of01:40diffusion01:41however facilitated diffusion doesn’t01:44require energy from the cell so like01:47simple diffusion it’s a form of passive01:50transport the majority of water01:53molecules cross the plasma membrane by01:56facilitated diffusion also called01:58osmosis through specific protein02:01channels called aquaporins02:10some ions such as sodium and potassium02:13require transport against their02:16concentration gradients the sodium02:18potassium pump actively transports these02:21ions from where they are less02:23concentrated to where they are more02:25concentrated this process requires02:27energy from the cell and is known as02:30active transport energy from ATP is used02:34to move three sodium ions shown in red02:37out of the cell02:40and two potassium ions shown in blue02:43into the cell because the pump uses ATP02:47directly this type of transport is02:50called primary active transport02:53another type of active transport02:56secondary active transport also moves02:59chemicals against gradients it doesn’t03:02use ATP as a direct source of energy03:05instead it uses the downhill gradient03:08from one ion or molecule to drive the03:11uphill movement of another ion or03:13molecule for example sodium and glucose03:17move into the cell by secondary active03:19transport in a process called Co03:22transport or symport because both03:24substances are moving in the same03:26direction sodium ions move down their03:29concentration gradient created by the03:32sodium potassium pump but because03:34glucose concentrations inside the cell03:37can quickly exceed those outside the03:40cell glucose moves against its03:42concentration gradient03:49the cell moves larger materials such as03:52proteins from the intracellular fluid to03:55the extracellular fluid using vesicles03:58that fuse with the plasma membrane and04:00release their contents outside the cell04:03this process is called exocytosis and04:07endocytosis the plasma membrane pinches04:11in forming a vesicle that contains04:14material from outside the cell cells use04:18all these processes passive and active04:21transport exocytosis and endocytosis to04:26move materials across their membranes
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.
00:12Cell transport is the process of how things move in or out of the cell through the cell membrane00:19There are two broad categories of cell Transport00:23The first Category is passive transport, for a cell passive transport means00:28It’s an automatic process that doesn’t require any input of energy00:34for example00:36Diffusion is a passive process in which particles move either into or out of the cell from an area of higher00:43concentration to an area of lower concentration00:46The cell doesn’t use any energy when this happens00:51The second Category of cell Transport is active Transport00:56This is when particles move from an area of lower concentration to an area of higher concentration01:05when particles move against the concentration gradient01:08Energy is required often to allow protein pumps to assist in Particle Movement01:15why would the cell need to move particles from a low to high concentration and expend energy to do it01:24An Important example is seen in your heart muscle cells01:28In order for your heart to beat there are certain molecules that have to move from an area of low concentration01:35to an area of high concentration01:38for those cardiac muscle cells to work01:42So the main things to remember are passive transport happens automatically with no energy required01:49while active transport needs energy for it to occur01:56
The video transcripts may have typo errors but still can be understood.