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Active Transport Mechanisms

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Active Transport Mechanisms Chapter 3: Cell Biology AP1 Chapter 3 1 I. Fxns of a cell • Cell – the basic unit of all living things (the smallest part of a living organism in our case humans) • Shared Characteristics – Plasma Membrane • Outer boundary of the cell though which the cell interacts with its external environment – Nucleus • Directs activities of the cell – Cytoplasm • Most cell activities occur here – Organelles • Perform specific fxns in cell AP1 Chapter 3 2 4 major fxns of cells I. Fxns of a cell A. Cell metabolism & e+ use: – Metabolic rxns in the cell e+ is released to accomplish cell activities & maintain Body Temp. B. Synthesis of Molecules – Can prod proteins, nucleic acids, lipids – Cell’s fxn & characteristics are determined by the molecules they prod C. Communication – Cells prod & respond to chemical & e+ signals wh/ allows them to communicate w/each other – * Neuron to a muscle = contraction or relaxation D. Reproduction & inheritance – Cell holds the genome. It determines structure & fxnl characteristics of that cell. – Cells can prod new cells – Gametes transmit genetic info. AP1 Chapter 3 3 III. Plasma Membrane AP1 Chapter 3 4 III. Plasma Membrane • Outer most component of the Make-up: cell • 45-50% Lipids • Fxns as a boundary to • 45-50% Proteins separate inside from outside of • 4-8% Carbohydrates the cell (intra vs extra cellular) • Encloses and supports the cell’s contents • Attaches the cell to the extracellular environment or to other cells • Cell’s ability to recognize & communicate with each other occurs via the plasma membrane • Determines what moves into ot • Membrane potential: electrical out of the cell (therefore the charge difference across the contents inside the cell can be PM resulting from the cell’s different from what is outside). regulation of movement into and out of the cell AP1 Chapter 3 5 • Terminology – Intracellular: (Intra- Inside) inside the cell – Extracellular: (Extra- Outside) outside of the cell – Intercellular: (Inter- Between) from 1 cell to another – Glycoproteins: carb’s + proteins – Glycolipids: Carb’s + Lipids – Membrane Potential: result of uneven distribution of ions on the inside verses the outside of the cell • Glycocalyx: III. PlasmaMembrane – Collection of glycoproteins, glycolipids, and carb’s that lies on the outer surface of the plasma membrane 6 IV. Membrane Lipids AP1 Chapter 3 7 • Phospholipids (PL’s): – Predominant lipid in membrane – Bipolar: • Hydrophilic “head” is water loving and polar and faces both surfaces (inner & outer) • Hydrophobic “tail” is water hating and non-polar and crowd together between the heads • Cholesterol – Makes up 1/3 of the membrane and lie btwn PL’s – Helps to limit PL’s mvmt providing stability for the PM – It is also bipolar and the “tail” is embedded in head while the IV. Membrane Lipids IV. ring is embedded in the tails AP1 Chapter 3 8 IV. Membrane Lipids • *Fluid Mosaic Model* – The lipid bilayer is mobile with things floating w/in it – Consequences of this: a) Important for molecule distribution in the membrane b) Slight damage can be repaired because the PL’s will move to cover it c) It enables two different membranes to fuse with each other AP1 Chapter 3 9 V. Membrane Proteins A. Marker Molecules B. Attachment Proteins C. Transport Proteins D. Receptor Proteins E. Enzymes AP1 Chapter 3 10 V. Membrane Proteins (MP) • Many fxns of the plasma membrane are determined by the combination of membrane proteins present. • The ability of these proteins to fxn properly is determined by their 3-D shape • There are 2 major types: 1. Integral/Intrinsic • (Transmembrane) contain hydrophobic and hydrophilic regions to match the phospholipids characteristics & location 2. Peripheral/Extrinsic • Surface proteins on inner or outer surface. • Can be bound to an integral protein or the phospholipids head • There are 5 major classes of MP’s AP1 Chapter 3 11 12 V. Enzymes V. Receptors linked to B G-proteins Proteins Receptors linked to IV. Receptor IV. A channel proteins ATP powered C pump Proteins Antiporter 3 AP1 Chapter c III.Transport Carrier Symporter 5 major classes of 5 classes major Membrane proteins Membrane b B Proteins Uniporter a Ligand-gated ii channel b Gated Proteins Channel II. Attachment II. Voltage-gated Channel i channel A Proteins Non-gated a Channel I.Marker molecules Membrane Proteins: I. Marker Molecules • Glycoproteins or glycolipids that allow for cells to identify other cells or other molecules • Important because cells aren’t isolated and must function as a whole for normal body function. • May be integral or peripheral proteins • Ex/ immune cells AP1 Chapter 3 13 Membrane Proteins: II. Attachment Proteins • Integral proteins that may attach to intracellular molecules. • Integrins can also function in cellular communication. AP1 Chapter 3 14 Membrane Proteins: III. Transport Proteins All exhibit 3 characteristics 1. Specificity – Each binds to & transports only 1 types of molecule/ion 2. Competition – Closely related substances may bind to the same binding site & the one w/ greater [ ] or higher affinity is more readily moved across the PM 3. Saturation – Movement is limited by the # of transport proteins rate will eventually plateau because the # of proteins are going at AP1 Chapter 3 their maximum rate 15 Membrane Proteins: III. Transport Proteins A. Channel Proteins • Form passageways through the plasma membranes that have both hydrophobic and hydrophilic regions. B. Carrier Proteins • Move larger ions or molecules across the membrane, when bound it changes shape to allow it to move from one side of the membrane to the other then return to its original shape to work again. C. ATP-powered pumps • Moves ions or molecules across the membrane using ATP. AP1 Chapter 3 16 Membrane Proteins: III. Transport Proteins A. Channel Proteins a. Non -gated Channels • Always open responsible for the permeability of the plasma membrane when the cell membrane at rest. b. Gated Channels • Can be opened or closed i. Ligand Gated – Small molecules must bind in order to open or close the channel ii. Voltage Gated – Change in voltage across the plasma membrane causes the gate to open AP1 Chapter 3 17 Membrane Proteins: III. Transport Proteins B. Carrier Proteins a. Uniporter • Movement of 1 ion or molecule across the plasma membrane. b. Symporter • Movement of 2 ions or molecules in the same direction (into the cell or out of the cell). c. Antiporter • Movement of 2 ions or molecules in opposite directions (one in and one out or vise versa). AP1 Chapter 3 18 Membrane Proteins: III. Transport Proteins C. Sodium-Potassium Pump • These have 2 binding sites. One is for the molecule to be moved the other is for ATP • Breakdown of ATP releases e+ ∆ing shape of the “pump” protein which moves the molecule across the membrane AP1 Chapter 3 19 Membrane Proteins: IV. Receptor Proteins • Proteins or glycoproteins in the plasma membrane that have an exposed receptor site on the outer cell surface which can attach to specific chemical signals. • Many are part of an intercellular communication system that coordinates cell activities. AP1 Chapter 3 20 Membrane Proteins: IV. Receptor Proteins A. Receptor linked to channel proteins – These help form ligand- gated channels & when bound it changes the channels shape to move ions B. Receptors linked to G- protein complexes – Uses a second messenger system, binding of the receptor externally causes to the cell internally • 3 ways α can stimulate a cellular response 1. Intracellular chemical signals 2. Opening channels in the plasma membrane 3. Activation of enzymes AP1 Chapter 3 associated with the plasma membrane 21 Membrane Proteins: V. Enzymes • These may work on the inner or outer surface of the plasma membrane. • Some are always active but others are activated by things like GPCR’s AP1 Chapter 3 22 VI. Movement through the plasma membrane AP1 Chapter 3 23 V. Mvmt thru the PM • Inside of the cell: – Enzymes other proteins, glycogen, high potassium concentration • Outside of the cell: – High concentration of sodium, calcium, & chloride • The cell has to be able to bring in nutrients inside and get waste products out without changing the cell’s volume, because too much can cause the cell the rupture (causing cell death) or to shrivel (also causing cell death). • Movement 1. Molecules that are lipid soluble or very small water soluble molecules will freely go across the plasma membrane. 2. Large lipid soluble molecules and water soluble molecules can’t pass through the plasma membrane and may need to use transport proteins. 3. Larger water soluble molecules or whole cells may be moved by vesicles. AP1 Chapter 3 24 Membrane transport mechanisms A. Passive Transport Mechanisms B. Active Transport Mechanisms • No energy required to • Energy required to move move molecules from one molecules from one side side of the membrane to of the membrane to another another AP1 Chapter 3 25 Membrane transport mechanisms Passive Transport Mechanisms Active Transport Mechanisms A. Diffusion A. Active Transport B. Osmosis B. Secondary Active C. Facilitated Diffusion Transport C. Vesicular Transport a. Endocytosis b. Exocytosis AP1 Chapter 3 26 Passive Transport Mechanisms A. Diffusion: – Movement of solutes from an area of high concentration to an area of low concentration – Concentration gradient: concentration difference between 2 points divided by the distance between the 2 points, – Rate of Diffusion 1. Magnitude of the concentration gradient 2. Temperature of the solution 3. Size of the diffusion molecules 4. Viscosity of the solvent 27 AP1 Chapter 3 Passive Transport Mechanisms B. Osmosis – Diffusion of water across a selectively permeable membrane – Will allow water but not all solutes with in the water – Important because it can influence a cell’s function when water moves. – Osmotic Pressure: • Force required to prevent water movement across a selectively permeable barrier via osmosis 1) Isosmotic 2) Hyperosmotic Concentration 3) Hyposmotic of solutions AP1 Chapter 3 28 Passive Transport Mechanisms B.
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