Essential idea: Membranes control the composition of cells by active and passive transport.
The image above is a piece of artwork inspired by the complexity of an E. Coli. Complexity in cell structure is much greater in Eukaryotes and this only possible through the compartmentalisation and the selective transport membranes allow.
Understandings, applications and skills:
| 1.4.U1 | Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport. |
| 1.4.U2 | The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. |
| 1.4.U3 | Vesicles move materials within cells. |
| 1.4.A1 | Structure and function of sodium–potassium pumps for active transport and potassium channels for facilitated diffusion in axons. |
| 1.4.A2 | Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis. |
| 1.4.S1 | Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2) [Osmosis experiments are a useful opportunity to stress the need for accurate mass and volume measurements in scientific experiments.] |
[Text in square brackets indicates guidance notes]
Starters
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A fast paced introduction to membrane transport by Hank Green from Crash Course
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A rap by Mr W to introduce you to how water moves in and out of cells
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Presentation and notes
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The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.
Vocabulary
Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.
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Labs
Bubbles - modelling membranes
Investigate membranes structure and transport using bubbles from Ms Purdy. Extension: can you use your equipment to model endosymbiosis and exocytosis? Osmosis Observing plasmolysis and turgor in plant cells by Practical Biology 1.4.S1 Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2) - ideas and links given in the presentation Quick quiz
Quick quiz Use the BioK Quick Quiz on 1.4 Membrane transport (as directed) to check your understanding of the topic.
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Nature of science:
Experimental design—accurate quantitative measurement in osmosis experiments are essential. (3.1) (covered by the practical and processing of data)
Weblinks
Membrane transport
Video on vesicles move materials within cells by Stephanie Castle Video on Endocytosis and Exocytosis by Stephanie Castle Membrane transport by Wisconsin online Cellular transport by Interactive concepts in biochemistry Cell transport tutorials and notes by National Louis University Membrane Structure and Transport and Membrane Dynamics & Communication plus quizzes to test your learning by Biocoach Molecules move across the cell membrane by Sunamas Inc. Diffusion, osmosis and facilitated diffusion The cell: passive transport diffusion by Wisconsin online How diffusion works by McGraw and Hill Passive transport: filtration and facilitated diffusion by Wisconsin online How osmosis works by McGraw Hill Osmosis animation by St. Olaf College Isotonic equilibrium by Carnegie Mellon Facilitated diffusion by St. Olaf College Facilitated diffusion by Northland Community and Technical College Passive transport by W H Freeman Lifewire Active transport Cotransport by McGraw and Hill Sodium-potassium exchange pump by McGraw and Hill Proton pump by McGraw and Hill Examples of active transport, uniports, symports, antiports (e.g. resting potential in neurones) by St. Olaf College Vesicle transport Macromolecules by Lifewire from W H Freeman Endoplasmic reticulum and Golgi apparatus by W H Freeman Lifewire Vesicle budding and fusing by Sunamas Inc Lysosomes by McGraw and Hill Endocytosis and exocytosis by McGraw and Hill Phagocytosis (endocytosis) by McGraw and Hill Endocytosis of LDL by Candlelight productions Directing Traffic: How Vesicles Transport Cargo - learn more about vesicles and see them in action on this learn.genetics tutorial Protein synthesis and exocytosis by St. Olaf College Plasmolysis Plasmolysis of red onion epidermis as seen under a light microscope |
Interesting extras
Liposomes are artificial vesicles which are used to transport drugs around the body and deliver them to specific cells. To find out more about this medical use of membranes use the links below:
Liposomes tutorial and animation Video introduction from Encapsula Nanosciences (below) Fun and clever rap from the Stanford Biologists Play a game
Against the gradient uses your knowledge of the different modes of membrane transport to solve puzzles |
