About Cell Membranes1.All cells have a cell membrane2.Functions: a.Controls what enters and exits the cell to maintain an internal balance called homeostasis TEM picture of a b.Provides protection and real cell membrane. support for the cell
About Cell Membranes (continued)3.Structure of cell membraneLipid Bilayer -2 layers of phospholipids a.Phosphate head is polar (hydrophilic or water Phospholipid loving) b.Fatty acid tails non-polar (hydrophobic or water fearing) c.Proteins embedded in Lipid Bilayer membrane
Polar heads Fluid Mosaic love water Model of the & dissolve. cell membrane Non-polar Membrane move tails hide from water. Carbohydrate cell markersProteins
About Cell Membranes (continued)• 4. Cell membranes have pores (holes) in it a.Selectively permeable: Allows some molecules in and keeps other molecules out b.The structure helps it be selective! Pores
About Cell Membranes (continued)• 5. Size (macro or micro), charge (+ or -) and solubility (lipid-soluble or not) affect a molecule’s ability to cross the cell membrane. In general, small noncharged, lipid-soluble molecules easily cross the cell membranes Pores
Structure of the Cell Membrane Outside of cell Carbohydrate Proteins chains Lipid Bilayer Transport Protein Phospholipids Inside of cell Animations (cytoplasm) of membraneGo to structureSection:
•Animations of ActiveTypes of Cellular Transport Transport & Passive Transport Weeee!!• Passive Transport ! cell doesn’t use energy 1. Diffusion high 2. Facilitated Diffusion 3. Osmosis low Tonicity Water Potential This is gonna• Active Transport be hard work!! high cell does use energy low
Types of Cellular Transport• Bulk Transport 1. Endocytosis Phagocystosis Pinocytosis Receptor-mediated 2. Exocytosis
Passive Transport• cell uses no energy• molecules move randomly• Molecules spread out from an area of high concentration to an area of low concentration.• (HighLow)• Three types:
3 Types of Passive Transport1. Diffusion2. Facilitative Diffusion – diffusion with the help of transport proteins ,3. Osmosis – diffusion of water
Passive Transport: Simple Diffusion A 1. Diffusion1. Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low)• Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm
Passive Transport: 1. Diffusion• Occurs in liquid or gas mediumDiffusion of a solute within a solvent is affected by several factors: Temperature Pressure Density of the solvent Concentration Gradient Solubility of the solute http://bio.winona.edu/berg/Free.htm
Passive Transport: 2. Facilitated Diffusion2. Facilitated diffusion: diffusion of specific particles through membrane transport proteins to help them move through the cell membrane a. Transport Proteins are specific – they “select” only certain molecules to cross the membrane b. Transports larger or charged molecules c. Concentration gradient required – can’t transport from low to high concentration d. Energy not needed e. Rate of transport reaches a maximum when all membrane transport proteins are used up (saturated) f. Membrane transport proteins are sensitive to inhibitors that can cause them not to function
Passive Transport: 2. Facilitated Diffusion A BThere are 2 types of membrane transport proteins involved:Channel proteins – contain tunnels/openings that serve as passageways of Facilitated molecules Diffusion diffusion (LipidCarrier proteins – undergo (Channel Bilayer) temporary binding to the Protein) molecule it carries resulting in conformational change that moves the molecule through the membrane Carrier Protein
Passive Transport: 2. Facilitated Diffusion Glucose moleculesCellular Transport From a- High High Concentration • Channel Proteins animations Cell Membrane Protein Low Concentration Low channel Transport Through a Go to ProteinSection:
Passive Transport: Osmosis 3. Osmosis animation• 3.Osmosis: diffusion of water through a selectively permeable membrane •Water moves freely through pores. •Solute (green) to large to move across.
The water molecules will continue to cross the semi-permeablemembrane until an equilibrium is reached, where the two solutionsare of equal concentration.
Passive Transport: 3. OsmosisWater is found inside and outside of the cell, separated by a semi-permeable membraneThe presence of different solutes in the water solutions in and out of the cell means concentration of water on both sides is different.Water Potential – term for movement of water molecules as it undergoes osmosis- The measure of the difference between the “force” that pushes water molecules and the “force” exerted by the membrane
Passive Transport: 3. OsmosisWater solution with less solute (more diluted solution because of more water) = higher water potentialWater solution with more solute (more concentrated solution) = lower water potentialWater Potential Gradient - when 2 solutions of different water potentials are separated by a semipermeable membrane, thus allowing osmosis to occurOsmotic Pressure – “force” that moves water molecules through a semi- permeable membrane
Passive Transport: 3. Osmosis Tonicity – strength of a solution in relation to osmosis 3 Types: Isotonic Hypotonic Hypertonic Remember: Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.
If the concentration of solute (salt) is equal on both sides, the water willmove back in forth but it wont have any result on the overall amount ofwater on either side."ISO" means the same
"HYPO" means less In this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell, causing it to swell. The cell will gain water and grow larger. As osmosis continues, osmotic pressure builds up inside the cell causing cell lysis.In plant cells, the vacuoles will fill and the plant becomes stiff and rigid.The pressure exerted by the water molecule is called TURGORPRESSURE, and the phenomenon TURGIDITY. The turgor pressure inplants will not result in cell lysis as the cell wall keeps the plant frombursting.TURGIDITY is important in maintaining the firm and erect position of aplant.
"HYPER" means moreIn this case there are more solute (salt) molecules outside the cell, whichcauses the water to be sucked in that direction.Causes cells to shrink and lose shape because of water loss.In plant cells, the central vacuole loses water and the cells shrink, causingwilting (plasmolysis). In animal cells, the cells also shrink.In both cases, the cell may die.
Active Transport•cell uses energy (ATP or Adenosine Triphosphate)•actively moves molecules to where they are needed•Movement of molecules against concentration gradient(concentration gradient not required)•Movement from an area of low concentration to anarea of high concentration (Low High)•Transport proteins are highly specific•Involves carrier proteins (like facilitated diffusion) oftencalled pumps because they use energy to movemolecules against a concentration gradient
SodiumExample: Sodium Potassium Pumps-Potassium Pumps (Active Transport using proteins)are important in nerveresponses. Theytransfer Na and Kions in and out of thenerve and musclecells. Protein changes shape to move molecules: this requires energy!
Types of Bulk Transport1. Endocytosis: taking bulky material that can’t use transport proteins (like macromolecules) into a cell • Uses energy • Cell membrane in-folds around the macromolecule to be transported • 3 Types: Phagocytosis Pinocytosis Receptor-mediated Endocytosis
Types of Bulk Transport Phagocytosis – “cell eating” - Process by which cells take in large particles by infolding the cell membrane to form endocytotic vesicles Ex. WBC capture and kill invading bacteria
Types of Bulk Transport Pinocytosis – “cell drinking” - Process of taking in fluids into the cell by invagination of the cell membrane. Any solute or small particles in the fluid will be moved into the cell.
Types of Bulk TransportReceptor-mediated Endocytosis – “cell drinking”- Compared to pinocytosis, is very specific. The plasma membrane becomes indented and forms a pit. The pit lined with receptor proteins picks specific molecules from its surroundings. The pit will close and pinch off to form a vesicle which will carry the molecules inside the cytoplasm.
Types of Active Transport2. Exocytosis: Forces Endocytosis & Exocytosis material out of cell in animations bulk • membrane surrounding the material fuses with cell membrane • Cell changes shape – requires energy • EX: Hormones or wastes released from cell
Effects of Osmosis on Life• Osmosis- diffusion of water through a selectively permeable membrane• Water is so small and there is so much of it the cell can’t control it’s movement through the cell membrane.
• Osmosis Animations for Hypotonic Solution isotonic, hypertonic, and hypotonic solutionsHypotonic: The solution has a lower concentration ofsolutes and a higher concentration of water thaninside the cell. (Low solute; High water)Result: Water moves from the solution to inside thecell): Cell Swells and bursts open (cytolysis)!
• Osmosis Animations for Hypertonic Solution isotonic, hypertonic, and hypotonic solutionsHypertonic: The solution has a higher concentrationof solutes and a lower concentration of water thaninside the cell. (High solute; Low water) shrinksResult: Water moves from inside the cell into thesolution: Cell shrinks (Plasmolysis)!
• Osmosis Animations for Isotonic Solution isotonic, hypertonic, and hypotonic solutionsIsotonic: The concentration of solutes in the solutionis equal to the concentration of solutes inside the cell.Result: Water moves equally in both directions andthe cell remains same size! (Dynamic Equilibrium)
What type of solution are these cells in ? A B C Hypertonic Isotonic Hypotonic
How Organisms Deal • Paramecium (protist) removing excess water with Osmotic Pressure video•Bacteria and plants have cell walls that prevent themfrom over-expanding. In plants the pressure exerted onthe cell wall is called tugor pressure.•A protist like paramecium has contractile vacuoles thatcollect water flowing in and pump it out to prevent themfrom over-expanding.•Salt water fish pump salt out of their specialized gills sothey do not dehydrate.•Animal cells are bathed in blood. Kidneys keep theblood isotonic by remove excess salt and water.
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