Cell membranes

Description

Degree MCBHD Mind Map on Cell membranes, created by Hannah Tribe on 04/25/2014.
Hannah Tribe
Mind Map by Hannah Tribe, updated more than 1 year ago
Hannah Tribe
Created by Hannah Tribe almost 11 years ago
24
1

Resource summary

Cell membranes
  1. Structure
    1. Lipid bi-layer

      Annotations:

      • Assymetric, fluid Electrically polarised to play a key role in transport
      1. Cholesterol
        1. Glycolipids
          1. AMPHIPATHIC

            Annotations:

            • BOTH hydrophobic and hydrophilic parts
            1. Carb component determines blood group
            2. Phospholipids
              1. Hydrophobic lipid tails
                1. Hydrophilic phosphate heads
                  1. AMPHIPATHIC
                    1. Can form liposomes

                      Annotations:

                      • Spherical vesicles which could be useful in delivery of drugs or DNA into a cell
                    2. Different classes have different prevalences on each side of membrance

                      Annotations:

                      • Assymetrical
                  2. Fluid
                    1. Constant lateral movement of lipids
                      1. Slow transverse movement of lipids

                        Annotations:

                        • Lipids are already in stable arrangement, would require Flippase enzyme to move lipids transversely
                        1. DEPENDS ON
                          1. Chain length

                            Annotations:

                            • longer = more bonds form between chains = more rigid
                            1. Saturation

                              Annotations:

                              • all saturated = more tightly packed.  unsaturated = bent chains = less tightly packed = more fluid
                              1. Cholesterol content

                                Annotations:

                                • increases fluidity TO AN EXTENT then decreases, as many straight cholesterol molecules will pack tightly = more rigidity
                                1. Spur Cell Anaemia

                                  Annotations:

                                  • Excess cholesterol in membranes of RBCs so they are more rigid. Have spurs on surface. Get stuck in capillaries
                          2. Synthesis
                            1. In lumen of ER

                              Annotations:

                              • then to Golgi then to destination
                              1. New phospholipids made on one side
                                1. Membrane bows

                                  Annotations:

                                  • Due to more phospholipids on one side than the other
                                  1. FLIPPASE

                                    Annotations:

                                    • enzyme transfers newly synthesised phospholipids onto other side so membrane straightens out
                              2. Apoptosis
                                1. Phosphatidylserine flips to outside of membrane
                                  1. = EAT ME signal
                                  2. By macrophages
                                  3. Proteins
                                    1. Peripheral
                                      1. On extracellular surface
                                        1. On cytosolic surface
                                          1. Non-covalent

                                            Annotations:

                                            • Not tightly associated
                                            1. Interact with integral proteins or polar lipid heads
                                            2. Integral
                                              1. Strong, non-covalent bonds
                                                1. Hydrophobic transmembrane domains

                                                  Annotations:

                                                  • Often alpha helices
                                                2. Lipid anchored
                                                  1. Covalently bonded
                                                    1. Important in signalling
                                                  2. Carbohydrates
                                                    1. Glycolipids
                                                      1. Glycoproteins
                                                        1. Always extracellular
                                                        2. Functions
                                                          1. Depend on structure

                                                            Annotations:

                                                            • and chemical composition
                                                            1. E.g. myelin

                                                              Annotations:

                                                              • High lipid content = good insulation
                                                              1. E.g. inner mitochondrial membrane

                                                                Annotations:

                                                                • high protein content = lots of transport of respiration molecules
                                                              2. Transport

                                                                Annotations:

                                                                • Passive or active
                                                                1. Permeability
                                                                  1. Lipid molecules and small uncharged polar molecules

                                                                    Annotations:

                                                                    • by diffusion
                                                                  2. Passive
                                                                    1. Antiporters/ Symporters

                                                                      Annotations:

                                                                      • = CO transporters Anti = opposite directions Sym = both in same direction
                                                                      1. E.g. GLUCOSE
                                                                        1. GLUT carriers

                                                                          Annotations:

                                                                          • 1 in all tissues 2 in liver and beta cells of pancreas 3 in all tissues 4 in muscle and fat cells 5 in small intestine
                                                                          1. Phosphorylated as transported

                                                                            Annotations:

                                                                            • To maintain concentration gradient
                                                                            1. Similar kinetics to enzymes
                                                                              1. Increasing no. of GLUT carriers increases uptake

                                                                                Annotations:

                                                                                • expression of GLUT 4 stimulated by insulin
                                                                          2. Active
                                                                            1. E.g. Na+ ions
                                                                              1. Antiporter with K+

                                                                                Annotations:

                                                                                • Na+/K+ ATPase pump
                                                                                1. Inhibited by digitalis (foxglove)
                                                                                  1. Na+ builds inside cell, so active pump is needed to remove it
                                                                                  2. Can help bring glucose in PASSIVELY

                                                                                    Annotations:

                                                                                    • SGLUT 1 and 2
                                                                                      1. Targeted in diarrhoea therapy
                                                                                2. Barrier
                                                                                  1. Separates reactions
                                                                                    1. Give specialised environments

                                                                                      Annotations:

                                                                                      • e.g. pH
                                                                                    2. Compartmentalisation
                                                                                      1. Proteins with specific sequences to specific destinations
                                                                                        1. Mutation = wrong sequence = wrong destination
                                                                                        2. Brings reactants together
                                                                                      2. Recognition/ Signalling
                                                                                        1. Receptors to hormones and neurotransmitters

                                                                                          Annotations:

                                                                                          • e.g. G Protein-coupled receptors
                                                                                          1. Glycolipids
                                                                                            1. Blood group antigens
                                                                                            2. Glycoproteins
                                                                                              1. E.g. selectins to bind lymphocytes
                                                                                            3. Endo/exocytosis
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