To remain alive the cell needs FOODName two examplesName the material that also enters a cell & is used asa SOLVENTGLUCOSEAMINO ACIDSWATERSalts are also needed in plant cells,for exampleNITRATES
Active Transport Passive Transport• Requires energy • No energy requiredActive Transport vs. PassiveTransport
Active Transport Passive Transport• From lower concentrationto higher concentration(against gradient)• From higher concentrationto lower concentration (withgradient)
Active Transport Passive Transport• Exocytosis• Endocytosis• Phagocytosis• Pinocytosis• Ion Pumps• Diffusion• Osmosis• Facilitated DiffusionActive Transport v. PassiveTransport
Description of diffusion• ‘The movement of a substancefrom a concentrated solution to a dilute solutionUntilequilibrium isreached.
A diffusion gradientThe molecules are more densely packed onthe left and so they tend to diffuse into thespace on the right. This is a diffusion gradientDiffusion gradient7
The concentration ofoxygen molecules isgreater outside the cellthan insideSo the oxygenmoleculesdiffuse into the cellDiffusion of oxygen into a cell9Because the cell is using up oxygen, theconcentration of oxygen inside the cell isalways lower then the concentrationoutside.
Concentration gradient. The greater the difference inconcentration between two areas, the faster the rate ofdiffusion.
RAISING THE TEMPERATURE GIVES THE MOLECULES MOREKINETIC ENERGY, AND THUS THEY SPREAD OUT FROM THEAREA OF HIGH CONCENTRATION AT A FASTER RATE
The rate of diffusion depends on:4. surface area• the greater the surface area, the faster the diffusion•Larger surface area separating two regions results in afaster rate of diffusion
5. Distance separating the two areas – “shortdiffusion path”.The shorter the distance, the faster the rate of diffusion.The rate of diffusion depends on:
How long could the people haveremained alive in the water?On the night of the Titanic sinking, the temperature of thesalt water was likely around 28° F(-2 °C). The human bodyloses heat to the water about 30 times faster than it does tothe air. When the core body temperature falls to approximately (31°C), adecrease in consciousness occurs. If the core temperature cools to below 86°F(30°C) then heart failure becomes a major concern, as it is the most commoncause of hypothermia-related deaths. The people in the -2 °C water above thesinking Titanic would have had anywhere from several minutes to an hour tolive, depending on their physical condition and how much they flailed. Somepeople in the water might have believed that swimming would help their bodyto generate heat. In reality, people who swam or moved around a lot wouldhave lost heat 35-50% faster and been susceptible to exhaustion. There wereeven several people who died from hypothermia in the Titanic lifeboats,because they were open and gave no protection against thecold. Regulations have since been put in place that requirelifeboats to be fully or partially enclosed.
*allows smallmolecules (water) topass through it* does not allow largermolecules to passthrough (glucose).* kind of molecularsievelower water potential. higher water potential.
WATER POTENTIAL quantifies the tendencyof WATER to leave a system due to OSMOSIS/Gravity or MECHANICAL PRESSURE+water => +water potential‘The movement of waterfrom a dilute solution to a concentrated solution across a partially permeablemembrane.TWO CONDITIONSa partially permeable membrane.a difference in concentrationOSMOSIS
Osmotic concentration relates to theamount of dissolved solutes in asolutionhigh osmotic concentration low osmotic concentrationInsoluble molecules do not affect the osmotic concentration(concentrated) (dilute)
Isotonic solutions have the same osmoticconcentration as the cytoplasm of the cellexternal solutionblood cellNo NET osmosisCell just not change
Hypertonic solutions have a higherosmotic concentration than the cytoplasmof the cellexternal solutionblood cellNET osmosis out of the cellCauses animal cells to shrink
Hypotonic solutions have a lower osmoticconcentration than the cytoplasm of the cellexternal solutionNET osmosis into the cellblood cellCan cause animal cells to burst
Osmosis in red onion cellsIsotonic solutionIncipientplasmolysisosmosisHypertonic solutionFull plasmolysisosmosisCauses a plant to wiltHypotonic solutionTurgorCell wall exerts an inward pressureosmosis
CELL needs water/O2/ salts and needs to release CO2 by•DIFFUSION (+ - ) gases/ concentrated substance• Depends on * concentration gradient the bigger, the faster* thickness of the membrane the thinner, the faster* surface area the greater, the faster* size of the molecules the smaller, the faster* ENDOCYTOSIS (Fagocytosis and Pinocytosis) - EXOCYTOSIS* ACTIVE TRANSPORT (from - concentration + concentration) => ENERGYIt moves a solute against a concentration gradient•OSMOSIS => * Partially Permeable MEMBRANE* diffusion of solvent (WATER) molecules from +diluted to+concentratedHow substancesget in and out of cells