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Target VII Identify and describe the functions of the component structures of the plasma membrane: phospholipid, integral protein, peripheral protein,

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Presentation on theme: "Target VII Identify and describe the functions of the component structures of the plasma membrane: phospholipid, integral protein, peripheral protein,"— Presentation transcript:

1 Target VII Identify and describe the functions of the component structures of the plasma membrane: phospholipid, integral protein, peripheral protein, cholesterol, hydrophilic head (polar), hydrophobic tails (non- polar), glycolipids, and glycoproteins.

2 The Cell Membrane Composed of macromolecules: phospholipids, proteins, and carbohydrates Is selectively permeable... Phospholipid bilayer is amphipathic –Hydrophobic hydrocarbon tails –Hydrophilic phosphate heads Structure and movement of cell membrane is described as the FLUID MOSAIC MODEL

3 I. FLUIDITY of Membrane A. Lipids and proteins move laterally within the membrane B. Fluidity depends upon a variety of factors: 1.Type of hydrocarbon tails 2.Temperature 3.Presence of cholesterol 4.Composition of lipids and proteins within the membrane (dynamic) 5.Whether membrane components are attached to ECM or cytoskeleton

4 I. FLUIDITY of Membrane C. Proper functioning of membrane depends upon membrane fluidity D.Fluidity can be altered by changing composition and quantity of proteins and/or lipids within membrane -->Adaptations of plants and smaller vertebrates to cold temperatures in winter

5 II. Mosaic: assortment of various proteins w/in membrane A.PROTEINS determine function(s) of membrane 1.Integral Proteins *transmembrane protein *describe the domain (portion) of the protein that is embedded within the membrane 2. Peripheral Proteins *If inside cell, held in place by cytoskeleton *If outside cell, held in place by Extracellular matrix (ECM) 3. One protein may have multiple functions OR several different proteins are required in a membrane to accomplish cellular tasks

6 Hydrophobic/philic Domains

7 II. Mosaic: assortment of various proteins w/in membrane B. Carbohydrates are located on the exterior surface of plasma membrane 1.Cells communicate with and recognize each other by the types of CHO on their exterior plasma membrane surface (ex: A, B, O blood types) 2.Oligosaccharides may be bound to lipids or proteins (oligo- = Few; ~15 monosaccharides) a. Glycolipidb. Glycoprotein


9 Target VIII Use representations, models, and/or data to analyze situations in which molecules move passively by diffusion, osmosis, or facilitated diffusion.

10 III. Movement Across Membranes A.Membrane is selectively permeable 1.What does selectively permeable mean? 2.Name examples of molecules that CAN pass thru cell membrane… WHY can they pass thru? 3.Name examples of molecules that CANNOT pass thru c.m WHY cant they? B.Functions of membrane proteins 1.Transport: water, ions, glucose 2.Enzyme Activity: cellular respiration, photosynthesis 3.Signal Transduction: bind protein hormone 4.Intercellular joining: tight &/or gap junctions, desmsomes 5.Cell to Cell Recognition: glycoproteins 6.Attach cell to ECM and/or cytoskeleton C.All transport proteins must be ________, because….

11 Membrane Protein Functions

12 IV. Passive Transport A.Movement of molecules down concentration gradient; from high [ ] to low [ ] B.Membrane must be permeable for molecules to diffuse C.Once equilibrium is reached, NET molecular movement is EQUAL both into and out of cell **molecules DO NOT stop moving** D.Diffusion HAPPENS (no energy required!) E.Diffusion of one type of molecule occurs independent of another molecule if theyre both permeable; direction of diffusion for each molecule depends upon [ ] of a particular molecule across membrane F. Can be: Diffusion, Facilitated Diffusion, Osmosis

13 V. Facilitated Diffusion A. Help polar and charged molecules across membrane thru transport (integral) proteins 1. Recall transport proteins are specific to molecules they move (like enzyme/substrate specificity) 2. Transport proteins can be saturated therefore, they have a maximum rate of moving stuff due to limited # of proteins within membrane 3. Transport proteins can be inhibited 4. Catalyze physical movement of stuff that would not be able to cross membrane B.Molecules move down concentration gradient C.AQUAPORINS: transport protein for water D.GATED CHANNELS: stimulus (electrical or chemical), cause opening & closing --> stimulus causes change of protein shape

14 V. Facilitated Diffusion E.Examples of gated channels: Ligand-gated Voltage-gated Mechanically-gated

15 VI. Osmosis (a type of passive transport) A.Movement of WATER from high [water] to low [water] B.Water follows solutes… water moves from area of low [solute] to area of high [solutes] C.Direction of water movement depends upon [ ] of water and solutes across a membrane between a cell and solution (environment) D.Osmosis and Cells Animal Cell Plant Cell

16 Plant & Animal Cell Osmosis Review A.hypotonic solution -->low [solute] in solution compared to cell animal cell: lysed plant cell: turgid B. HYPERTONIC solution: -->high [solute] in solutionn compared to cell animal cell: crenate plant cell: plasmolysed C. ISOTONIC solution: =[solute] in solution & cell animal cell: normal plant cell: flaccid

17 Osmosis

18 VI. Osmosis Water balance for Osmoregulators 1.In cells WITHOUT cell walls (animals, protists) MUST control amount of water entering and leaving cell if not in an environment that is isotonic to cell = osmoregulate Osmoregulators use ENERGY to maintain internal osmotic balance different from the surrounding environment example: Paramecium contractile vacuoleParamecium contractile vacuole -->The pond in which the Paramecium lives is ______ to the cell, so water moves ______ and cell has to use energy to pump water ______ the cell

19 Paramecium Contractile Vacuole

20 VI. Osmosis Water balance for Osmoregulators 2. In cells WITH cell walls (plants, fungi, bacteria) Cells prefer to be in a HYPOTONIC solution because water enters cells and pressure of extra water in vacuole pushes against cell walls. The water pressure in the vacuole is exterted onto and by nearby cells which makes cells TURGID - very firm so plant structures (stems, leaves) stand upright :) In isotonic solution cells lack adequate push from water in nearby cells…FLACCID-plants wilt, droop:| In hypertonic solution, cell wall NOT an advantage, cell shrinks and plasma membrane pulls away from cell wall…PLASMOLYSIS - lethal to cell :(

21 Target IX Use representations, models, and/or data to analyze situations in which molecules move actively to establish concentration gradients across a membrane or move large molecules into or out of a cell (endocytosis and exocytosis).

22 Co-Transport

23 VII. CO-TRANSPORT (active transport) SYMPORT (Active, Indirect) ANTIPORT (Active, Direct) Hyperlink to Animation

24 How do macromolecules enter or exit cells? How do large quantities of substances enter or exit cells? There are FOUR ways!

25 IIX. EXOCYTOSISEXOCYTOSIS A. Secrete large molecules out of cell B. Cellular vesicles fuse with plasma membrane C. Process of fusion repairs / replaces cell membrane D. Process deposits proteins from inside surface of vessicle membrane to outer surface of cell membrane b/c vesicle turned inside out as it becomes part of plasma membrane E. Therefore, exocytosis ensures the plasma membrane will display its characteristic CELL SURFACE proteins which dictate membrane function

26 IX. ENDOCYTOSIS A. Phagocytosis: cell eatingPhagocytosis More animationsanimations B. Pinocytosis: cell drinkingPinocytosis Another animation of pinocytosisanimation of pinocytosis X. Receptor Mediated Endocytosis -->Intake of specific molecules, regardless of their concentration, due to specificity and affinity of ligand (binding molecule) to its ligand-receptor protein on cell surface -->Example Animation: Cholesterol MetabolismCholesterol Metabolism

27 X. Receptor-Mediated Endocytosis

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