https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/membrane-transport/v/introduction-to-passive-and-active-transport 2023-09-14T11:22:40.102153098Z Introduction to passive and active transport Active transport requires energy to move substances against a concentration or electrical gradient, like a canoeist paddling upstream. Passive transport, on the other hand, does not require energy as substances move along their gradient, similar to a canoeist drifting downstream. The sodium-potassium pump is a key example of active transport. Sal Khan video https://cdn.kastatic.org/googleusercontent/fdWO9Yuei6p31qnT761hfXD49OujsJrLlCUkyOZ9fqqBliHjpxCgUmtZzli5EqJlXRbf1Jwzc8Zps-EiJpi5IDvW Introduction to passive and active transport Active transport requires energy to move substances against a concentration or electrical gradient, like a canoeist paddling upstream. Passive transport, on the other hand, does not require energy as substances move along their gradient, similar to a canoeist drifting downstream. The sodium-potassium pump is a key example of active transport. https://cdn.kastatic.org/ka-youtube-converted/TsoAA7zOyj8.mp4/TsoAA7zOyj8.mp4 486 Membrane transport mechanisms https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/membrane-transport/e/membrane-transport 2025-11-24T20:40:43.982882282Z Membrane transport Test your knowledge of membrane transport! Megan Cohn exercise https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/facilitated-diffusion/a/hs-active-transport-review 2021-04-29T07:49:58Z Active transport review article https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/membrane-transport/v/passive-transport-and-selective-permeability 2022-11-16T04:22:43.7414897Z Passive transport and selective permeability Passive transport describes the movement of substances across a cell membrane down their concentration gradients, which does not require energy. Cell membranes are selectively permeable, so only certain substances can passively diffuse directly across the membrane. These substances include small, nonpolar molecules such as carbon dioxide and molecular oxygen. video https://cdn.kastatic.org/googleusercontent/aflva8hc3VykpA-t2fWCghsKpvcIakEAdPPJOTwP3HeVdxtMbxM0GNE4l_kqNWUVdd1gDPxVopl7GKfAqSqfHVXg Passive transport and selective permeability Passive transport describes the movement of substances across a cell membrane down their concentration gradients, which does not require energy. Cell membranes are selectively permeable, so only certain substances can passively diffuse directly across the membrane. These substances include small, nonpolar molecules such as carbon dioxide and molecular oxygen. https://cdn.kastatic.org/ka-youtube-converted/jQN07Hvq6WI.mp4/jQN07Hvq6WI.mp4 420 Membrane transport mechanisms https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/membrane-transport/a/hs-passive-transport-review 2021-04-29T07:58:54Z Passive transport review article https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/mechanisms-of-transport-tonicity-and-osmoregulation/v/osmosis 2024-05-06T19:22:43.24334365Z Osmosis Osmosis is a process where water molecules move from an area of low solute concentration to high solute concentration through a semipermeable membrane. This movement can be influenced by factors like solute size and charge. Understanding osmosis helps us grasp how cells maintain balance and control their internal environment. Sal Khan video https://cdn.kastatic.org/googleusercontent/5zu_ewQLVv3K9YYdURQ6En-3UA3eyDo-0dRBO5hg88GHbmgIfSeBEKAUNuEPQOBPiPQxNK0Y36qXLMUFn9hiRNSl Osmosis Osmosis is a process where water molecules move from an area of low solute concentration to high solute concentration through a semipermeable membrane. This movement can be influenced by factors like solute size and charge. Understanding osmosis helps us grasp how cells maintain balance and control their internal environment. https://cdn.kastatic.org/ka-youtube-converted/rCNlG_j_gSM.mp4/rCNlG_j_gSM.mp4 484 Membrane transport mechanisms https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/mechanisms-of-transport-tonicity-and-osmoregulation/a/osmosis 2024-01-19T18:25:11.349624553Z Osmosis and tonicity Osmosis and tonicity. Hypertonic, isotonic, and hypotonic solutions and their effect on cells. article https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/facilitated-diffusion/v/sodium-potassium-pump-video 2023-04-04T21:01:09.417661961Z Sodium potassium pump The sodium-potassium pump is a trans-membrane protein that helps establish the resting membrane potential of cells, particularly neurons. In a process that requires ATP, the pump moves three sodium ions out of the cell for every two potassium ions it brings in. This contributes to the electric potential difference between the inside and outside of the cell. Sal Khan video https://cdn.kastatic.org/googleusercontent/Y0aAqx-V-2fUBSS5Q82FyCBplRx6bXTe14eT7-rRH4zOoTn5frmrhoeXVDiCs6ZB5E2ikKTpnnd0KAIXMIx07lI Sodium potassium pump The sodium-potassium pump is a trans-membrane protein that helps establish the resting membrane potential of cells, particularly neurons. In a process that requires ATP, the pump moves three sodium ions out of the cell for every two potassium ions it brings in. This contributes to the electric potential difference between the inside and outside of the cell. https://cdn.kastatic.org/ka-youtube-converted/vh166DKxYiM.mp4/vh166DKxYiM.mp4 438 Membrane transport mechanisms https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/facilitated-diffusion/v/facilitated-diffusion 2023-04-04T21:01:09.417661961Z Facilitated diffusion Facilitated diffusion is a type of passive transport that uses specialized proteins, such as channel proteins and carrier proteins, to help molecules move across a cell membrane. In this process, molecules can move down their concentration gradient without requiring any energy input from the cell. video https://cdn.kastatic.org/googleusercontent/j3iz6FxjluOP1LA1JOB3dwfz7toKRngFRsx4MunfxU-UA7746u8LxYDbVz3PXE9-cSl-r8QtLmDFPWbBUkea_rc Facilitated diffusion Facilitated diffusion is a type of passive transport that uses specialized proteins, such as channel proteins and carrier proteins, to help molecules move across a cell membrane. In this process, molecules can move down their concentration gradient without requiring any energy input from the cell. https://cdn.kastatic.org/ka-youtube-converted/8HlVy__J8XA.mp4/8HlVy__J8XA.mp4 395 Membrane transport mechanisms https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/facilitated-diffusion/e/facilitated-diffusion 2025-11-24T20:40:43.982882282Z Facilitated diffusion Test your knowledge of facilitated diffusion! Megan Cohn exercise https://www.khanacademy.org/science/grade-11-biology-snc-aligned/x58c107ba92d3f0b2:domain-d-cells-and-sub-cellular-organelles/x58c107ba92d3f0b2:membrane-transport-mechanisms/v/passive-transport-by-facilitated-diffusion 2023-08-14T21:12:46.061619254Z Passive Transport by Facilitated Diffusion Explore the process of passive transport in cells, when a substances moves along its concentration gradient, traveling from an area of higher concentration to an area of lower concentration. Learn about the function of the phospholipid bilayer, along with the hydrophilic heads and hydrophobic tails, in this process. Understand how facilitated diffusion employs chloride channels to transport ions from the cell's exterior to its interior, all without expending any energy. Raja Narayan video https://cdn.kastatic.org/googleusercontent/uFcZ2M9BQ3YAYqz4XInaItUcdJToxXxWOyqEMKm0HbbBtdUGuzIYLdsSkeYlj0SMf6FeIa6lgFgEOb62CAW-XE1c Passive Transport by Facilitated Diffusion Explore the process of passive transport in cells, when a substances moves along its concentration gradient, traveling from an area of higher concentration to an area of lower concentration. Learn about the function of the phospholipid bilayer, along with the hydrophilic heads and hydrophobic tails, in this process. Understand how facilitated diffusion employs chloride channels to transport ions from the cell's exterior to its interior, all without expending any energy. https://cdn.kastatic.org/ka-youtube-converted/ZAbrCJxk8fs.mp4/ZAbrCJxk8fs.mp4 316 Membrane transport mechanisms https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/membrane-transport/v/endocytosis-phagocytosis-and-pinocytosis 2022-11-16T04:22:43.7414897Z Endocytosis, phagocytosis, and pinocytosis Phagocytosis is the process by which a cell engulfs and internalizes a large particle, such as a bacterium, by extending its membrane around it. Pinocytosis is similar, but instead the cell engulfs droplets of extracellular fluid, taking in any dissolved substances within. Both phagocytosis and pinocytosis are forms of endocytosis. video https://cdn.kastatic.org/googleusercontent/J8korir2x9DjX2wj95SlH6A9y_Hy794t_Q-kdp8TiZzvS570svKHMapJKtc1E3QcFaY1lNZdfWw6gU8r_nVAdOij Endocytosis, phagocytosis, and pinocytosis Phagocytosis is the process by which a cell engulfs and internalizes a large particle, such as a bacterium, by extending its membrane around it. Pinocytosis is similar, but instead the cell engulfs droplets of extracellular fluid, taking in any dissolved substances within. Both phagocytosis and pinocytosis are forms of endocytosis. https://cdn.kastatic.org/ka-youtube-converted/QspmZf_yWyU.mp4/QspmZf_yWyU.mp4 278 Membrane transport mechanisms https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/membrane-transport/a/bulk-transport 2025-01-07T20:24:30.121144203Z Bulk transport Endocytosis and exocytosis. Phagocytosis, pinocytosis, and receptor-mediated endocytosis. article https://www.khanacademy.org/science/ap-biology/cell-structure-and-function/membrane-transport/v/exocytosis 2022-11-16T04:22:43.7414897Z Exocytosis Exocytosis is a form of bulk transport during which large numbers of molecules are transported out of the cell. In exocytosis, a vesicle (a small, membrane-bound compartment) containing the molecules to be released fuses with the cell membrane, and the contents of the vesicle are expelled. Exocytosis is important for the transport of neurotransmitters. video https://cdn.kastatic.org/googleusercontent/_aV5PG_I6CMsjjgJE0Gjlk9Mjkbps-pMSXOV0NxjxHNkp2ukUfcJGDYmHMD6xEMAFMrfiHChopf_TSYDChxHQVxj Exocytosis Exocytosis is a form of bulk transport during which large numbers of molecules are transported out of the cell. In exocytosis, a vesicle (a small, membrane-bound compartment) containing the molecules to be released fuses with the cell membrane, and the contents of the vesicle are expelled. Exocytosis is important for the transport of neurotransmitters. https://cdn.kastatic.org/ka-youtube-converted/VOzV4d0HKis.mp4/VOzV4d0HKis.mp4 257 Membrane transport mechanisms