Cell Membrane

Descrição

components and functionality of a cell membrane
Julia Castellani
Mapa Mental por Julia Castellani, atualizado more than 1 year ago
Julia Castellani
Criado por Julia Castellani aproximadamente 9 anos atrás
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Resumo de Recurso

Cell Membrane
  1. Functions
    1. Separates cytoplasm from environment
      1. controls the traffic of molecules(**selectively permeable**)
        1. recognized by other cells, hormones, and antibodies
        2. Membrane Lipids
          1. Phospholipids

            Anotações:

            • most abundant lipids in membrane
            • amphipathic (hydrophobic & hydrophillic regions)
            • Functions: -form layers on surface of water -determine fluidity at lower temps (varying degrees of unsaturation in tails)
            1. Glycolipids

              Anotações:

              • like phospholipids, but with sugars attached at head
              • Found only on outside layer of plasma membrane
              • Functions: -protect cell surface -act as recognition sites -help cells stick to surfaces
              1. Cholesterol

                Anotações:

                • small, flat, ringed steroid between phospholipid molecules
                • Functions: -decrease membrane fluidity -decrease membrane permeability -make membranes tougher
              2. Membrane Proteins
                1. Functions
                  1. Enzymes
                    1. Transport
                      1. Receptors
                        1. Formation of Junctions
                          1. Cell-Cell Recognition
                            1. Attachment to extracellular matrix
                            2. Properties
                              1. Amphipathic
                                1. move around in membrane
                                  1. some protrude on both sides of membrane
                                  2. Eg) Globular Proteins ('Potato"), Glycoprotein
                                  3. Membrane Transport
                                    1. Passive Trasport
                                      1. Simple Diffusion (high-low concentration)
                                        1. Non-polar solutes

                                          Anotações:

                                          • cross easily (eg oxygen, hydrocarbons)
                                          • smaller molecules cross faster
                                          1. Polar solutes

                                            Anotações:

                                            • small ones (eg Carbon Dioxide, Water) cross easily
                                            • larger molecules (eg sugars) won't pass readily
                                            • Ions pass hardly at all
                                          2. Facilitated Diffusion (high-low concentration of solute)

                                            Anotações:

                                            • polar solutes and ions are helped by transport proteins
                                            • solute is moving across a membrane from high-low concentration
                                            1. carrier proteins

                                              Anotações:

                                              • bind to a solute and physically move them across membranes
                                              • very specific
                                              1. channel proteins

                                                Anotações:

                                                • provide a hydrophilic channel for ions
                                                • less specific
                                            2. Active Transport

                                              Anotações:

                                              • molecules move against concentration gradient (low-high)
                                              • Requires transport protein and energy input (eg Sodium / Potassium pump)
                                              1. Eg) Sodium-Potassium pump

                                                Anotações:

                                                • -found in plasma membrane
                                                • same carrier transports sodium and potassium ions across  membrane in opposite directions
                                                • 3 sodium ions out for every 2 potassium ions in
                                                • pump is "electrogenic" (produces a change in electrical charge) because it creates a membrane potential
                                                • uses ATP as energy
                                                1. Molecules move against concentration gradient
                                                  1. requires transport proteins and energy
                                                  2. Co-Transport Systems
                                                    1. Ion pump works together with another protein transporter

                                                      Anotações:

                                                      • Eg) glucose pump
                                                    2. Regulated Transport

                                                      Anotações:

                                                      • can be PASSIVE or ACTIVE
                                                      • involves the movement of molecules through specialized channels
                                                      1. Voltage Gated Channels

                                                        Anotações:

                                                        • -closed when electric potential is high (polarized) -open when potential is low (depolarized)
                                                        1. Ligand Gated Channels

                                                          Anotações:

                                                          • -closed when concentration of molecule is low -open when concentration is high
                                                      2. Transport of Large Molecules
                                                        1. Endocytosis
                                                          1. Phagocytosis (uptake of solids)
                                                            1. Pinocytosis (uptake of fluids)
                                                              1. Receptor-mediated endocytosis (specific uptake of proteins)
                                                              2. Exocytosis
                                                                1. reverse of endocytosis

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