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Terms Active transport Amphipathic Aquaporin Concentration gradient Co-transport Diffusion Electrochemical gradient Endocytosis Exocytosis Facilitated.

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Presentation on theme: "Terms Active transport Amphipathic Aquaporin Concentration gradient Co-transport Diffusion Electrochemical gradient Endocytosis Exocytosis Facilitated."— Presentation transcript:

1 Terms Active transport Amphipathic Aquaporin Concentration gradient Co-transport Diffusion Electrochemical gradient Endocytosis Exocytosis Facilitated diffusion Flaccid Fluid mosaic model Gated channel Glycolipid Glycoprotein Hypertonic Hypotonic Integral protein Ion channel

2 Isotonic Ligand Membrane potential Osmoregulation Osmosis Osmotic potential Passive transport Peripheral protein Phagocytosis Pinocytosis Plasmolysis Proton pump Receptor-mediated endocytosis Selectively permeable Sodium-potassium pump Tonicity Transport protein Turgid

3 Surface area-to-volume ratios affect a cells ability to exchange materials. –As cells increase in volume, the relative surface area decreases and demand for material resources increases; more cellular structures are necessary to adequately exchange materials and energy with the environment. Limits cell size. Ex. Root hairs, alveoli cells, villi, microvilli 2.A.3 – Organisms Must Exchange Matter With the Environment to Grow, Reproduce and Maintain Organization.

4 The surface area of the plasma membrane must be large enough to adequately exchange materials; smaller cells have a more favorable surface-area-to- volume ratio for exchange of materials with the environment.

5 SA/V Practice Problems Simple cuboidal epithelial cells lines the ducts of certain exocrine glands. Various materials are transported into or out of the cells by diffusion. The formula for the surface area of a cube is 6s 2 and the formula for volume is s 3 where s = length of the side of the cube. Which of the following cube- shaped cells would be most efficient in removing wastes by diffusion? 10µm 20µm30µm 40µm

6 Cells lining the kidneys are cuboidal. What is the SA/V of a kidney cell with a side length of 3.5µm? What would be the SA/V if cell (b) had a side that is 2.7µm? Which cell (a or b) would have an easier time with diffusion? What is the SA/V of a spherical liver cell with a diameter of 9.2µm?

7 2.B.1 – Cell Membranes Are Selectively Permeable Due to Their Structure Cell membranes separate the internal from the external environment The fluid mosaic model explains selective permeability of the membrane –Cell membranes consist of phospholipids, proteins, cholesterol, glycoproteins and glycolipids –Phospholipids have both hydrophobic and hydrophilic regions; fatty acids are oriented towards the middle and phosphate portions are oriented to the outsides

8 2.B.1 continued: –Embedded proteins can be hydrophilic with charged and polar side groups, or hydrophobic with nonpolar side groups. –Small, uncharged molecules (N 2, O 2,) and small hydrophobic molecules pass freely across the membrane; hydrophilic and ions move across through embedded channel and transport proteins. Water moves across through the membrane and through aquaporin proteins.


10 Semi or Selectively Permeable CO 2, O 2, steroid hormones enter cells easily; conclusion? The membrane must be mostly made of _______ Ions (Na +, Cl -, Ca ++ ) proteins and larger molecules (glucose) move more slowly or not at all; conclusion? 1.Cells must not need those molecules or ions 2.The membrane must have (?) that enables that stuff to get in/out

11 Membrane Model Amphipathic - ? Phospholipids bilayer

12 Fluid Mosaic Model Proteins and shape determine the function of the cell Aquaporins

13 Membrane Proteins Integral –Transport channels (ex.) –Receptors for communication (ex.) –Attachment (ex.) Peripheral – temporarily attached Attachment sites Enzymes Signaling Electron carriers (ETC)


15 Membrane Carbohydrates Glycolipids – oligosaccharides –Attached to lipids –Cell attachment forming tissues –Self recognition Antigens – A, B, O blood types

16 Membrane Carbohydrates Glycoproteins – oligosaccharides attached to proteins –Antibodies (MHC) –Mucin –Collagen –Hormones – ex. FSH


18 Kinetic Energy Molecules are in constant motion Kinetic energy is free energy (usable) The greater the kinetic (free) energy, the ___ molecules can move. Molecules move ___ a concentration ___.

19 Movement Across the Membrane Passive Transport – molecules have enough free energy –Diffusion –Osmosis –Facilitated diffusion –Hydrostatic pressure/dialysis Active transport – against a concentration gradient –Pumps (proteins) –Endo/exocytosis

20 2.B.2 – Growth and Dynamic Homeostasis Are Maintained By the Constant Movement of Molecules Across the Membrane. Passive transport requires no cellular energy; movement of molecules from high to low concentration –Facilitated diffusion through proteins Ex. Glucose, Na+/K+ –Hypertonic, hypotonic, isotonic

21 Diffusion Kinetic (free) energy of molecules –Down a concentration gradient until equilibrium –Higher kinetic (free) energy = faster movement Gases; small, uncharged molecules –In solution**- membranes moist –SA/V of lungs is ?

22 Osmosis Diffusion of water through a semi-permeable membrane Cells are a solution, in a solution Compare solutions: –Hypertonic/hyperosmotic –Hypotonic/hypoosmotic –Isotonic/isoosmotic **Important to understand concentration gradient Water moves from hypotonic to hypertonic



25 Time

26 Water Potential Measurement of the Potential of Water to Move Through a Membrane Useful for Mathematically Predicting Which Way Water Will Flow

27 Water Potential What is potential ? Water Potential = ? Water flows from high water potential to low water potential till _____(?)*** Water potential is expressed as Psi (Ψ) Psi is measured in MPa, atm, or bar –Car tire = 32 psi, 0.2 Mpa –Sea level = 14.5 psi, 0.0MPa, 1 atm, 1 bar, 760mm Hg

28 Water Potential Water Movement Force Down a hill Garden hose Fresh to salty Straw

29 Water Potential = Pressure Potential + Solute Potential Pressure potential: ( p ) –Positive pressure, pushing like a hose –Negative pressure; sucking like a straw Major factor moving water through plants Solute potential: ( s) –Reduction in water potential due to the presence of dissolved solutes Solutes take up space in the water (dilutes pure water) Solutions have lower water potential than pure water

30 Water Potential Water potential (Ψ) = Ψ p + Ψ s –Ψ p – pressure potential (atmospheric pressure) –Ψ s – solute potential (osmotic pressure) The Ψ p of atmosphere at sea level = 0 MPa The Ψ s of pure water = 0 MPa –Pure water at sea level = 0 MPa

31 Solute Potential Solute Potential (Ψ s ) = - iCRT –i – ionization constant –C – Concentration in Moles –R – pressure constant ( literbars/mole-K) –T – temperature in Kelvin (273 + o C) I = number of ions that will ionize –Glucose = 1 –NaCl = 2 (Na +, Cl - )

32 Calculating Solute Potential ( s) s = - iCRT Ex. A 1.0 M sugar 22° C under standard atmospheric conditions: s = -(1)(1.0M)( L · bar )(295K) M · K s = bars

33 Adding solute to water lowers its water potential –Solute molecules take up space –Ex. 0.1 M solution = MPa –A 0.1 M solution at sea level: 0 MPa (Ψ p ) MPa (Ψ s ) MPa = Ψ Ψp = 0 +Ψs = 0


35 Problem : A student calculates that the water potential of a solution inside a bag is: s = bar, p = 0 bar And the water potential of the solution surrounding the bag is s = bar, p = 0 bar. –In which direction will the water flow? Inside = bar; outside = bar Water will flow into the bag. This occurs because there are more solute molecules inside the bag (therefore a value further away from zero) than outside in the solution.

36 ? ? ? Plasmolysis

37 Plant Transport Concepts: Water potential Active transport

38 Water Potential Values MediumWater Potential (MPa) Air (50% humidity) Air (90% humidity)-13.0 Leaf-1.5 Stem- 0.7 Root- 0.4 Soil- 0.1 Saturated soil+ 2.0

39 Water Potential in Plants


41 Water moves from soil into root cells because the cells have lower water potential due to the (Ψ s ) Soil or root?

42 To maintain solute potential in their cells, plants use cotransport *Cotransport molecules are proteins Proton Pumps

43 Real life scenario: what happens with salt water intrusion or over-fertilization? Cell has More/Less water potential than soil? Cell Soil Plasmolysis - cells lose water, become flaccid

44 Additional Water Absorption by Roots SA/V increased by: –Root hairs –Mycorrhizae - 90% of terrestrial plants

45 Increase rate of water uptake –Integral proteins in the membrane –Congenital diabetes insipidus (?) – mutation Aquaporins

46 Facilitated Diffusion Glucose moves faster through membranes than diffusion can account for (?) Diffusion through proteins –May require a receptor –Insulin/glucose – what is diabetes?

47 Hydrostatic Pressure Pressure created by blood - (Ψ p ) Glomerulus of the kidney - dialysis

48 Active Transport Moving Molecules Against a Gradient Ions Large Molecules

49 Cell Membrane Ions, polar molecules, large molecules move slowly or not at all Integral proteins enable movement of specific molecules across the membrane –Shape determines function –Protein shape is sensitive to change (homeostasis)

50 2.B.2 Active transport requires free energy (ATP) –Establish and maintain concentration gradients –Moves molecules and ions –Needs membrane proteins Endocytosis and exocytosis move large molecules (use of vesicles)

51 Active Transport Nerve cells: –Na+ K+ ion pump –Membrane potential - difference in electrical charge across a membrane – Electrochemical gradient –Costs the cells ___(?)

52 Co-Transport Passing of molecules against their concentration gradient using energy from another molecules energy Plants: proton pump

53 Channel protein Carrier protein Down the concentration gradient Against the concentration gradient

54 Exocytosis/Endocytosis Exocytosis: –Secretion –Secretory vesicle Endocytosis: –Phagocytosis –Pinocytosis –Receptor-mediated endocytosis

55 Phagocytosis Phagocytosis - Pseudopodia engulf food items – macrophages Pinocytosis – cell drinking; invagination

56 Receptor-Mediated Endocytosis Receptor proteins on the membrane –Hypercholesterolemia = lack protein to take up LDLs from blood; recessive –Cholesterol molecules as LDLs

57 2.B.1 Cell walls create a structural boundary, as well as a permeability barrier for some substances –Most organisms have cell walls (Plants - cellulose; fungi - chitin, prokaryotes – peptidoglycans)

58 Water potential = pressure potential + solute potential

59 ? ? ?

60 Dialysis Tubing Experiment

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