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NOTES – The Cell Membrane

NOTES – The Cell Membrane. All Cells Have a Cell Membrane. Cells are the basic units of structure and function in living things, which means, they have all the characteristics of life

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NOTES – The Cell Membrane

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  1. NOTES – The Cell Membrane

  2. All Cells Have a Cell Membrane • Cells are the basic units of structure and function in living things, which means, they have all the characteristics of life • The cell membrane allows the cell to adjust to its environment by using energy to control what comes in and what goes out • By doing this the cell maintains homeostasis, or a stable internal environment, which it needs to survive

  3. What are cell parts made of? • Proteins (C,H,O,N,S) – building materials, messengers, speed things up • Lipids (C,H,O) – store energy, form membranes, insulation • Carbohydrates (C,H,O) – energy source for cells, building material • Nucleic Acids (C,H,O,N,P) – store and carry information • Water (H2O) • 97% of an organism’s body weight is the elements C,H,O,N Organic Molecules

  4. Why does the cell need to control what comes in and what goes out? • The cell needs to keep a certain amount of substances in its cytoplasm • The cell has to take in what it needs and let out what it doesn’t need

  5. Cell Membrane Structure

  6. Structure of the Cell Membrane • The cell membrane is arranged in a bi-layer • There are 2 layers of phospholipids • A phospholipid is made up of a phosphate head (polar) and a lipid tail (non-polar) • There are protein molecules spread throughout cell membrane • Cholesterol molecules are found in the middle of the bi-layer

  7. Function of Individual Parts • Phospholipids: make up a majority of the flexible inner and outer layer of the cell membrane • The phosphate head is polar (charged) and is attracted to water (hydrophilic) • The lipid tail is non polar (no charge) and is not attracted to water (hydrophobic) • Protein molecules: act as a gates that let certain substances in and out, also act as cell identifiers • Cholesterol: keeps the lipid tails from sticking together

  8. Cell Membrane Structure Cholesterol Protein Molecules Phospholipid

  9. Fluid Mosaic Model • The Cell Membrane is often described as a Fluid Mosaic because • A. The membrane moves in a fluid-like motion • B. The membrane is made up of many different parts like an art mosaic

  10. Selective Permeability • The cell membrane is selectively permeable, which means it allows some substances to pass through while holding other substances back

  11. What are solutions and how do they affect cells? • Cells are filled with solution and surrounded by solution • A solution is a mixture of solvent (water) and a solute (salt, sugar, calcium, etc.) • Cytoplasm is a solution of water and many different solutes (amino acids, oxygen, carbon dioxide, sugars, proteins, organelles, etc.)

  12. Concentration is the amount of solute in a certain amount of solvent • High concentration means there is a lot of solute compared to the amount of solvent (Ex. Strong Kool Aid – 4 Tsp sugar to 8 oz water) • Low concentration means there is a little solute compared to the amount of solvent (Ex. Weak Kool Aid – 1 Tsp sugar to 8 oz water)

  13. What are the three types of solutions?When you compare the solution outside of a cell to the inside of the cell (cytoplasm), there are 3 possibilities: • Hypotonic Solution – has a lower concentration of solute than the cytoplasm of the cell

  14. What are the three types of solutions?When you compare the solution outside of a cell to the inside of the cell (cytoplasm), there are 3 possibilities: • Isotonic Solution – has an equal concentration of solute to the cytoplasm of the cell

  15. What are the three types of solutions?When you compare the solution outside of a cell to the inside of the cell (cytoplasm), there are 3 possibilities: • Hypertonic Solution – has a higher concentration of solute than the cytoplasm of the cell

  16. Comparing Concentration of the Cytoplasm to the Concentration of the Solution Outside of the Cell • The outside has a lower concentration than Cell A (hypotonic) • The outside has a higher concentration than Cell B (hypertonic) • The outside has an equal concentration to Cell C (isotonic)

  17. Where will substances move? • If nothing prevents them from doing so, substances in solution will always move from areas of high concentration to areas of low concentration

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