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Cell Membrane

Cell Membrane. Cell Membrane?. Function?. Location?. Protection and support for the cell Regulation of what enters and exits the cell WHY? -Essential in order to maintain * homeostasis within the cell *maintaining normal internal conditions. Surrounding the cell.

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Cell Membrane

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  1. Cell Membrane

  2. Cell Membrane? Function? Location? Protection and support for the cell Regulation of what enters and exits the cell WHY? -Essential in order to maintain *homeostasis within the cell *maintaining normal internal conditions • Surrounding the cell

  3. Composition of Cell Membrane • Phospholipid Bilayer • Phospholipid: • Hydrophilic Head; “water-loving” • Hydrophobic Tail; “water-fearing” • Bilayer • Two-layers (of phospholipids)

  4. Composition of Cell Membrane • Proteins embedded throughout phospholipid bilayer • Integral Proteins: Span the width of the cell membrane • Peripheral Proteins: Located on one side of the cell membrane (or on the ‘periphery’) • A variety of different types of proteins within the cell membrane, each with different functions

  5. Composition • Cholesterol: another lipid that maintains the structural stability of the cell membrane • Carbohydrates: allow for cell-to-cell recognition; a “fingerprint” for each cell • Allows for the immune system to recognize ‘foreign’ cells and attack them • Attached to proteins or phospholipids on outside layer of cell membrane

  6. Fluid Mosaic Model • Break it down: • FLUID: The cell membrane is constantly moving due to the lipid “tails” on its interior; they “wiggle” • This means that the cell membrane is pliable • The cell membrane has the consistency of olive oil at body temp. • MOSAIC: Proteins of different types, randomly positioned throughout the membrane create a “mosaic” appearance The cell membrane is a constantly moving assemblage of parts.

  7. Cell Membrane Function • Transport of molecules from one side of the membrane to the other in order to maintain homeostasis within the cell. • Selectively Permeable: Only certain substances can move across the membrane while others cannot. • Small, non-charged molecules (H20, CO2, O2, etc.) can freely cross the cell membrane. • This is referred to as Passive Transport: molecules are ‘freely’ or ‘passively’ traveling through the cell membrane • This occurs through one of two ways: Diffusion or facilitated diffusion

  8. Passive Transport: Diffusion • No Energy is required • Diffusion: the movement of molecules from a higher concentration to a lower concentration until equilibrium is reached • Concentration: the amount of solute in the solvent • Solute: dissolved substance (in the solvent) • solvent: the liquid containing the dissolved substance • Equilibrium: occurs when the solute concentration is the same throughout the system; equal on both sides of the membrane

  9. Passive Transport: Facilitated Diffusion • A form of Passive Transport (so no energy required) • Facilitated Diffusion: Larger molecules (that are unable to passively cross the cell membrane) are “carried” through via a channel protein. • Specific protein channels carry specific types of molecules • For example: glucose is transported across the cell membrane via facilitated diffusion

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