Cell Membrane Transport & Diffusion PDF

Review Particle Theory of Matter All matter made of small particles that are constantly randomly moving (Brownian motion) o Speed of particles (EK) increases with temperature ▪ e.g. smell of garbage in summer vs. winter Transport across the Cell Membrane concentration gradient → diffe...

Review Particle Theory of Matter All matter made of small particles that are constantly randomly moving (Brownian motion) o Speed of particles (EK) increases with temperature ▪ e.g. smell of garbage in summer vs. winter Transport across the Cell Membrane concentration gradient → difference in concentration ([ ]) across a membrane dynamic equilibrium → equal [ ] on either side → substances moving back & forth across membrane at equal rates, Equilibrium, but NO NET A GRADIENT no gradient. movement exists System is BALANCED Transport across the Cell Membrane - depends on size and polarity of substance CO2 exits easily through cell Proteins, carbohydrates, nucleic acids, and Repelled by the lipids hydrophobic tails Small, non-polar molecule will easily pass through. Important for metabolism.  Passive Transport ALWAYS DOWN the concentration gradient move from area of high [ ] to area of low [ ] doesn’t cost any energy NO ATP (energy) NEEDED 3 types 1. Diffusion net movement of particles from an area of high [] to low [] particles move randomly (Brownian Motion) diffusion driven entirely by EK the molecules possess non-polar, small molecules (O2, CO2) 2. Osmosis net movement of water from high [ ] to low [ ] water moves when solute can’t 3. Facilitated Diffusion many polar molecules & ions diffuse passively with help of transport proteins still passive because down a [ ] gradient a. Channel Proteins – have ex. aquaporins – allow entry of up to 3 hydrophilic channels that allow billion water molecules per second (in the kidneys – if we didn’t have aquaporins, we molecules/ions to cross would have to drink 50 gallons membrane of water a day b. Carrier Proteins – undergo ex. glucose transporter change in shape to pass – C6H12O6 passes through 50,000 × molecule through membrane faster than if diffusing on its own Tonicity - What happens when cells are placed in solution? Observe the effect of solution on cell volume Isotonic → equal [H2O] & solution [solute] → water will flow at same rate in both directions “equal” “over” “below or beneath” Hypertonic → relatively Hypotonic → relatively higher [solute] & lower lower [solute] & higher [H2O] [H2O]  Tonics and Animal Cells Tonics and Plant Cells Dialysis passage of material across semi-permeable membranes (dialysis tubing) address solute imbalances resulting from damaged kidney machine pumps blood out alongside membranes bathed in H2O and other solute mixtures waste material diffuses out, blood returned to the body. done multiple times a week Dialysis Diffusion & Osmosis Examples #1 A beaker contains a sealed pouch made of dialysis tubing. The tubing is permeable to water, but not to solutes. Identify: a. the missing % concentration in the bag b. the missing % concentration in the beaker c. whether the tube is hyper, hypo or isotonic to the surrounding solution d. indicate the flow of water Diffusion & Osmosis Examples #1 KEY A beaker contains a sealed pouch made of dialysis tubing. The tubing is permeable to water, but not to solutes. Identify: a. the missing % concentration in the bag b. the missing % concentration in the beaker c. whether the tube is hyper, hypo or isotonic to the surrounding solution d. indicate the flow of water a. 85% H2O in bag initially b. 50% H2O in beaker initially c. The bag is hypotonic compared to the surrounding solution d. Water would flow from the bag into the surrounding solution Diffusion & Osmosis Examples #2 The U-tube has sides A and B separated by a A B semipermeable membrane, m. The volumes of A and B are equal initially for each situation. Assuming that m is impermeable to starch, determine the % concentrations for the equilibrium state. m Initial At Equilibrium Side A: 6% glucose, 2% Starch Side A: Glucose _____, Starch ______ Side B: 2% glucose, no starch Side B: Glucose _____, Starch ______ Diffusion & Osmosis Examples #2 KEY A B The U-tube has sides A and B separated by a semipermeable membrane, m. The volumes of A and B are equal initially for each situation. Assuming that m is impermeable to starch, determine the % m concentrations for the equilibrium state. Initial At Equilibrium Side A: 6% glucose, 2% Starch Side A: Glucose _____, 2% 4%Starch ______ Side B: 2% glucose, no starch Side B: Glucose _____, 4%Starch ______ 0% Diffusion & Osmosis Experiments Iodine Diffusion via Egg Mass Change Potato Length Change Dialysis Tubing via Osmosis via Osmosis (Video) (Video) (Video) passive and active text 307 #1 – 7 transport transport workbook 27 – 30 Active Transport requires the cell to expend energy (uses ATP) solute may be “pumped” against (up) a [ ] gradient (from low to high [ ]) done by carrier proteins allows cells to maintain internal environment of solutes that differs from external environment 1. Protein Pumps each solute has its own pump a. Sodium-Potassium Pump + + animal cells NEED high [ ] of K and low [ ] of Na membrane helps keep these gradients by pumping Na+ OUT of the cell and K+ INTO the cell pumps 3 Na+ out for every 2 K+ in b. Proton Pump + actively transports H out of the cell co-transport → substance that has been pumped out can do work as it moves back across (H+ can couple with sucrose and bring it back into cell) 2. Exocytosis (Bulk Transport) “outside, cell” cells excrete molecules using vesicles (small membrane sacs) that fuse with membrane and release contents outside Cell membrane, Golgi and ER can all form vesicles 3. Endocytosis “within cell” cells take in molecules by forming new vesicles from cell membrane a. Phagocytosis (cell “eating”) “eating cell” used to bring in large materials to be digested may fuse with lysosomes White blood cells (macrophages) swallow bacteria b. Pinocytosis (cell “drinking”) “drinking, cell” cells take in droplets of fluid and small solutes/nutrients c. Receptor Mediated Endocytosis uses protein receptors in membrane identify, bind and bring specific materials into the cell passive and active text 307 #1 – 7 transport transport workbook 27 – 30 Plant Adaptations features / structures / behaviors of organisms to help them survive (and reproduce) in their env’t Physical Adaptation How does it help them survive? Darker leaves absorb more light; whereas leaves lighter in color will reflect more light Larger leaves ↑ SA to capture more light Waxy Cuticle Reduce water loss Thick Epidermis Reduce water loss Hairs Create a mini-windbreak that allows for a thick boundary layer of water vapor adjacent to plant 180px-Cap1033-botao1 Tropisms directional growth of a plant as determined by an environmental factor Positive tropism → grow toward the stimulus Negative tropism → grow away from the stimulus  “Turning” Types of Control systems to Tropism ensure survival Phototropism Gravitropism Thigmotropism Hydrotropism (nastic response) response response response to response to to water to light gravity contact Root tips negative moving Sunflower is a positive Closing of a highly gravitropism gravitropism towards phototropic carnivorous water plant - tracking Venus the movement shoots grow Flytrap leaf of the sun roots grow when it throughout the against gravity toward captures day. gravity prey  Types of Control systems to “Turning” Tropism ensure survival Phototropism Hydrotropism Gravitropism Thigmotropism (nastic response) response response response to gravity response to to water to light contact Root tips negative Closing of a moving Sunflower is a positive highly gravitropism carnivorous towards gravitropism phototropic Venus water plant - tracking the movement Flytrap leaf of the sun shoots grow roots grow when it throughout the against gravity toward captures day. gravity prey  Investigations of Phototropism Darwin & Darwin Growth but no Growth and covered the tip movement movement of emerging No growth nor movement cereal plant Confirmed that the tip was Growth and responsible for movement phototropism Boysen-Jensen proposed a chemical moving from tip is what allowed communication with area of elongation 1. cut tip and placed gelatin (allowed chemical to flow) 2. cut tip and inserted mica (did not allow chemical to flow) Chemical could still move to the Confirmed a chemical is tip present in the tip Went Confirmed that auxin is the chemical in the tip auxin is a hormone o a chemical compound made in one area and transported to another to stimulate the growth of new plant cells  Auxin moves away from the light Auxin spreads faster on the darker/shaded side Cells elongate on shaded size → causing uneven growth bending towards the light  Transport in Plants Plants must be able to move nutrients from the SOURCE (where they originate → leaves or storage bulbs) to the SINK (where nutrients are needed → meristem or roots)  Transport in the Xylem Begins with root pressure minerals enter root hairs via active transport H2O follows via osmosis Increases pressure in the xylem  Transport in the Xylem positive pressure (root pressure) pushes H2O up to small heights in the xylem H2O moves by “pushing” and “pulling” water moves through the plant Transport in the Xylem because of… Transpiration Evaporation of H2O through leaf stomata & bark lenticels creates a pull of water and dissolved minerals up the xylem dependent on temp ↑ temp ↑ evaporation ↑ movement in xylem  Transport in the Xylem Cohesion attraction of H2O to each other (due to H bonding) Adhesion attraction of H2O molecules to other substances (like the inside of the xylem) → cohesion & adhesion help H2O pull itself up the plant Transport in the Phloem leaves (site of photosynthesis) are the source places where sugars are used are known as the sink phloem tissue is essential to transport of sugar from leaves to rest of plant for cellular respiration  Pressure Flow Theory Do not copy in leaf, phloem becomes loaded as companion cells use carrier proteins & active transport to take in sugar from photosynthesis water moves into sieve cells by osmosis ↑ water pressure inside sieve cells pushes water & sugars through phloem to rest of plant Surface Area to Volume ratio Let’s think about this for a second… (DO NOT COPY) - rate at which a substance moves in a cell is 0.02 μm/s - how long for it to move halfway across a cell that is 100 μm in diameter? (2 500 s or 42 min) - how long for it to move halfway across a cell that is 0.25 m in diameter (e.g. basketball)? (6 250 000 s or 72 days!) What’s the problem? Cell Size and Function once inside the cell, all materials move by diffusion diffusion over long distances is slow & inefficient o Risking cell death when cell cannot quickly remove waste from and bring nutrients into cell There is an upper limit on cell size o Cells prefer to divide rather than growing Image from: Schmoller, Kurt & Skotheim, Jan. (2015). The Biosynthetic Basis of Cell Size Control. Trends in Cell Biology. 25. 10.1016/j.tcb.2015.10.006. Relationship between Surface Area and Volume HIGH surface area means lots of places for materials to enter and leave o Large membrane surface equates to more material movement (rate of material exchange) Lots of folds LOW volume, means that once inside, nutrients get to where they are needed quickly o Larger cells need more energy to sustain essential functions (rate of metabolism) Surface Area to Volume Ratio ratio of external surface area to volume (SA:VOL) SA V higher the number, the more efficient the cell, greater chances for survival o Nutrients reach the places they need to quickly → processes can happen SA:VOL& Cell Size/Number 2(5x5) + 2(5x5) + 2(5x5) = [2(1x1) + 2(1x1) + 2(1x1)] x 53 2(1x1) + 2(1x1) + 2(1x1) = 1x1x1 5x5x5 5x5x5 6/1 150/125 750/125 Relationship of SA:VOL & Cell Shape High SA:VOL for cells with o flattened shapes (i.e. not a sphere) o lots of folding of membrane (i.e. wavy, reticulated)  many smaller, flatter, wavy cells are more efficient than a few larger, round cells Cells and tissues that are specialized for gas or material exchanges will increase their surface area to optimize material transfer Examples → villi line the intestines for nutrient absorption → plant roots have root hairs both have high SA:V Calculating SA to Vol Ratio SA for a cube = (L x W) x 6 Volume for a cube = (L x W x H) divide SA by Vol to compare cells with different proportions When a cell grows, VOLUME (units3) increases faster than SURFACE AREA (units2) SA leading to a decreased SA:Vol ratio V  Example Determine the surface area to volume ratio of a rectangular prism cell with a length of 13.0 μm, a width of 12.0 μm, and a height of 11.0 μm. SA = 2(l x w) + 2(l x h) + 2 (w x h) = Volume = l x w x h = SA:V = Example Determine the surface area to volume ratio of a rectangular prism cell with a length of 13.0 μm, a width of 12.0 μm, and a height of 11.0 μm. SA = 2(l x w) + 2(l x h) + 2 (w x h) = 2(13x12) + 2(13x11) + 2(12x11) = 862 μm2 Volume = l x w x h = 13x12x11 = 1716 μm3 SA:V = 862/1716 = 0.502 chapter 8 315 a-j text review 316 #1 – 11  Surface Area Playdough 1. Take a chunk of dough about as large as your fist. Make your dough into a cube shape, approximately square on all sides. 2. Using a permanent marker, label each of the three dimensions of the cube with a “W” (for “width”), “L” (for “length”) or a “H” (for height). On either side of each letter, put a dash to show the direction of the dimension on that side of the cube. 3. Place your labeled cube of dough on a table or desk with the side marked for height pointing up and down (the dashes should be vertical). Use a ruler to measure the three dimensions you labeled on the cube (length, width and height). What are the measurements of the cube? Write these down on a scrap sheet of paper. 4. Now you are ready to change the shape of your dough by squishing it. Put a flat surface, such as a book or a hard binder, on top of the dough cube. Slowly press down on the dough while keeping the corners square (i.e., straight) as you go by patting in from the sides with your hands. Stop pressing down when it looks like the dough has changed shape a little. How does the dough look now? What shape is it? 5. Again, use a ruler to measure the three dimensions you labeled on the dough. What are the measurements of the dough now? Write these down. What do you notice? Specialization limits placed on size b/c as ↑ size, SA:Vol ↓ Large, multicellular organisms solve this in 3 ways: 1. make cells smaller (↑ SA:Vol) 2. cells specialized for jobs 3. Interdependence – cells support each other in survival  Do not copy Organization whole organisms are organized into a hierarchy of structure (organizes and streamlines life functions) Levels of Organization of an Organism living entity made of interacting inter-dependent systems 01 03 Cells Organs Basic building Groups of tissues that work together to block of life. 02 do a specific 04 fucntion. Tissues Organ Systems Groups of similar Groups of organs that cells that function work together to do a together. specific function.  Plant Organ Systems Shoot system Root system everything above – mostly below ground ground, captures energy – obtains water, nutrients & anchors plant  Plant Organs plant Flowers: reproduction Stem/Shoot: support, transport, energy capture Leaves: gas exchange, energy capture/photosynthesis Roots: obtain water, nutrients, support Leaf Tissues - be able to identify tissue from image Palisade (e.g. text p 321 & 325) and describe its function Mesophyll Dermal/Cuticle → packed → outer layer of vertically, many non-woody chloroplasts, plants primary site of → one cell layer photosynthesis thick → protective Vascular → layer that is transport tissue, transparent to tube-like veins transmit light transport water & → waxy cuticle nutrients (present in limits from roots, stems and water loss leaves) Spongy Mesophyll → round and loosely packed, gas exchange Meristem → unspecialized cells located throughout the organism buds of leaves and flowers or tips of roots and shoots → site of cell division where the cells begin to specialize Cells (Specialized Cells in the Leaf) plants photosynthesize (not animal cells) 6 CO2 (g) + 6 H2O (l) + energy → C6H12O6 (s) + 6 O2 (g) plants also undergo cellular respiration (as do animal cells) C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) + energy Stomata “mouth” → holes on underside of leaf where CO2, H2O and O2 enter and exit leaf → open or close to regulate water loss and gas exchange → typically open during day, closed at night Guard Cells → open or close stomata → lots of water in guard cells (turgid) causes them to swell and stomata to open → less water in guard cells (flaccid) causes them to deflate and stomata to close Turgor Pressure → pressure applied by water in a cell Specialized Cells in the Plant Xylem → non-living cells at maturity → conducts water & minerals from root to leaves → one-way transport → Bulk flow due to negative pressure Phloem → formed from long sieve tubes (no nuclei) which are connected to companion cells (nuclei) → transports sugary sap and water from leaves to other parts of plant → osmosis or turgor pressure  Other Specialized Structures Lenticels → plants with bark have lens shaped pores Root Hairs → growths on root to ↑ SA and ↑ absorption Pollen → male gametes (reproductive cells) of plant Seeds → embryonic plant enclosed in protective coating Needles → retain H2O in coniferous tree The Cell Membrane (Plasma Membrane) makes up cell phospholipid channel carrier protein protein carbohydrate membranes and organelle membranes semi-permeable or selectively permeable cholesterol Mosaic → made of transport/transmembrane proteins different part integral protein hydrophilic head Phospholipids are the Proteins help transport materials, hydrophobic tail main structure Carbohydrates act to and are receptors recognize & bind Cholesterol keeps the substances fatty acids mobile Phospholipid Bilayer phospholipids have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) fatty acid tail causes phospholipids to arrange in bilayers (heads facing towards extracellular fluid and cytoplasm) Fluid- Mosaic Model of the Cell Membrane Fluid Flexible and made of small, movable, components Why is a cell considered an open system? To maintain homeostasis, a cell must: obtain or make all materials needed obtain energy from the environment control the movement of matter and energy in and out of the cell role is to maintain equilibrium membrane text 296 #1 – 4 properties cell membrane workbook 27 diagram