* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Outline
Survey
Document related concepts
Cell encapsulation wikipedia , lookup
P-type ATPase wikipedia , lookup
Mechanosensitive channels wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Cell nucleus wikipedia , lookup
Theories of general anaesthetic action wikipedia , lookup
Magnesium transporter wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
SNARE (protein) wikipedia , lookup
Ethanol-induced non-lamellar phases in phospholipids wikipedia , lookup
Lipid bilayer wikipedia , lookup
Membrane potential wikipedia , lookup
Cytokinesis wikipedia , lookup
Model lipid bilayer wikipedia , lookup
Signal transduction wikipedia , lookup
List of types of proteins wikipedia , lookup
Transcript
Cell Biology: Membrane structure and function Membranes consist largely of phospholipid and protein molecules Outline 1. Key concepts 2. Cell Membrane General 3. Movement across cell membrane 4. Conclusions Key Concepts: 1. Membranes consist largely of phospholipid and protein molecules 2. Organelles are membrane-bound compartments inside eukaryotic cells 3. Diffusion is the movement of ions from a region of higher concentration to one of lesser concentration Key Concepts: 4.Osmosis is the movement of water across a selectively permeable membrane to a region where its concentration is lower 5.Some membrane proteins function in passive transport whereas some function in active transport Cell Membrane General Cell membrane consists of a bilayer of phospholipids and embedded proteins Transport proteins span the bilayer Open channels, gated channels, carriers, and pumps Receptor proteins receive chemical signals Recognition proteins are used for identification Membrane system Membrane system The Nuclear Envelope 1. 2. Double-membrane system Pores allow exchange The Endoplasmic Reticulum Protein and Lipid Synthesis Golgi Bodies and Vesicles Phospholipids bilayer Phospholipid Bilayer arrangement of lipids Plasma Membrane Bilayer of phospholipids Hydrophilic phosphate *head* Hydrophobic *tails* of fatty acids Fluid Mosaic Model Specialized proteins and enzymes embedded in the membrane Movement across cell membrane 1. Passive transport a. simple diffusion b. osmosis c. facilitated diffusion 2. Energy-requiring transport a. active transport b. exocytosis c. endocytosis Passive Transport Movement of substances across a membrane, going down a gradient of concentration, pressure, or electrical charge. Does not require the cell to expend energy. 1. Simple diffusion: Net movement of particles down a concentration gradient. Small, nonpolar molecules (e.g. O2, CO2) can get through the phospholipid bilayer by simple diffusion. Diffusion doesn’t have to have a membrane (perfume). Passive Transport 2. Osmosis: Diffusion of water across a differentially permeable membrane – that is, a membrane that is more permeable to water than to dissolved molecules (e.g. sugars, salt). (always need a membrane) water moves from an area with fewer solutes to an area with higher solutes. 3. Facilitated diffusion: Diffusion of (normally watersoluble) molecules through a channel or carrier protein. For example, glucose (large non-polar molecule) across cell membrane by channel protein. Only down a concentration gradient and no energy required How Substances Cross Cell Membranes Diffusion Movement of substance from a region where it is more concentrated to a region where it is less concentrated Factors Influencing the Rate and Direction of Diffusion Concentration Until gradient equilibrium is reached Molecular Small size molecules move faster Temperature Faster Electric at higher temperatures or Pressure gradient Electrical Pressure charge difference across membrane differences Osmosis Effect of solute concentration on water movement Passive Transport (Facilitated Diffusion) Solute transport through transport protein Movement From higher to lower concentration No energy use Energy-requiring Transport Movement of substances across a membrane, usually against a concentration gradient, using cellular energy. 1. Active transport: movement of small molecules or charged ions through membrane – carried by carrier protein using ATP. Sodium (Na+)-potassium(K+) pump: sodium pumped out of a cell and potassium pumped into a cell Energy-requiring Transport 2. Endocytosis: Movement of large particles, including large molecules or entire microorganisms, into a cell by engulfing extracellular material, as the plasma membrane forms membrane-bound sacs that enter the cytoplasm. a. Phagocytosis - “cell eating”, engulf solid materials b. Pinocytosis – “cell drinking”, liquid substance 3. Exocytosis: Movement of materials out of a cell by enclosing the material in a membranous sac that moves to the cell surface, fuses with the plasma membrane, and opens to the outside, allowing its contents to diffuse away. (Golgi apparatus vesicle moves out) Active Transport ATP needed Movement is against the concentration gradient Sodium-potassium pump Calcium pump Active Transport a. A transport protein, Ca++ and an ATP b. Transport protein binds ATP and Ca++ c. E from ATP change the shape of protein and moves the ion across the membrane d. The carrier release the ion and the remnants of the ATP )ADP and P) and back to original shape Exocytosis and Endocytosis Exocytosis Vesicle moves to cell surface and fuses with plasma membrane Endocytosis Substances move in when plasma membrane balloons inward Phagocytosis Form of endocytosis Cell engulfs microbes, large particles, and cellular debris Amoebas and white blood cell In Conclusion 1. The plasma membrane maintains the cell as a separate entity 2. Proteins carry out most of cell membrane functions 3. Membranes divide the cytoplasm into functional compartments called organelles 4. Cell membrane is a bilayer of lipids with proteins embedded In Conclusion 5. Osmosis is the diffusion of water across a selectively permeable membrane in response to concentration gradients 6. Small non-polar molecules diffuse across the membrane’s bilayer 7. Passive transport allows movement down a concentration gradient In Conclusion 8. Active transport pumps a solute across the membrane against the concentration gradient using ATP 9. Exocytosis entails movement of a vesicle to the plasma membrane and release of particles 10. Endocytosis entails the plasma membrane folding in to engulf particles