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7-3: Cell Boundaries

7-3: Cell Boundaries. CELL MEMBRANE The cell membrane regulates what enters and also leaves the cell and also provides protection and support. The cell membrane is made up of two phospholipid layers called a lipid bilayer.

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7-3: Cell Boundaries

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  1. 7-3: Cell Boundaries CELL MEMBRANE • The cell membrane regulates what enters and also leaves the cell and also provides protection and support. • The cell membrane is made up of two phospholipid layers called a lipid bilayer. • Scientists refer to it as a “fluid mosaic model” that contains different molecules.

  2. CELL WALL • Many cells also produce a strong supporting layer around the membrane known as the cell wall. • Cell walls may be present in plants, protists, fungi, and many prokaryotes. • The main function of the cell wall is to provide support and protection for the cell.

  3. CELL WALL

  4. DIFFUSION THROUGH CELL BOUNDARIES • In a solution, particles move constantly. They will collide into one another and tend to spread out randomly. • Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. • This process will continue until equilibrium is reached. Particles will still continue to move. • No energy is required by the cell.

  5. Osmosis is the diffusion of water through a selectively permeable membrane. • Selectively permeable membrane means that some substances can pass and some cannot.

  6. There are 3 effects of Osmosis on the cell: • Isotonic: The concentration is the same on both sides of the cell. (Normal Cell) • Hypertonic: The solution, in which the cell is in, is of higher solute concentration than the cell. (Skinny Cell) • Hypotonic: The solution, in which the cell is in, is of lower solute concentration than the cell. (Swollen Cell)

  7. FACILITATED DIFFUSION • Sometimes in a cell there are certain molecules that cross the selective permeable membrane that are too large for it to happen by osmosis. • The process that helps large molecules pass the membrane in a cell is called facilitated diffusion. • This happens when protein molecules act as channels for large molecules to pass from one side of the membrane to the other side. • No energy is required by the cell.

  8. ACTIVE TRANSPORT • A process in which the cell does require energy to transport materials across the cell membrane is called Active Transport. • This is the movement of molecules against the concentration differences. • Types of active transport consist of: • Endocytosis= this occurs by infoldings, or pockets, of the cell membrane.

  9. Phagocytosis= “cell eating” extensions of the cytoplasm surround a particle and package it within a cell a food vacuole. • Pinocytosis= tiny pockets form along the cell membrane, fill with liquid and then pinch off to form vacuoles within the cell. Exocytosis= this is the removal of contents from the cell. Contractile vacuoles are examples of exocytosis.

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