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

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. 2.A.3 – Organisms Must Exchange Matter With the Environment to Grow, Reproduce and Maintain Organization.
Surface area-to-volume ratios affect a cell’s 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

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 6s2 and the formula for volume is s3 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?
40µm
20µm
30µm
10µm

6. Cells lining the kidneys are cuboidal
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 (N2, O2,) 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
CO2, O2, 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?
Cells must not need those molecules or ions
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 Peripheral – temporarily attached Integral
Attachment sites
Enzymes
Signaling
Electron carriers (ETC)
Integral
Transport channels (ex.)
Receptors for communication (ex.)
Attachment (ex.)

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) = Ψp + Ψs
Ψp – pressure potential (atmospheric pressure)
Ψs – solute potential (osmotic pressure)
The Ψp of atmosphere at sea level = 0 MPa
The Ψs of pure water = 0 MPa
Pure water at sea level = 0 MPa

31. Solute Potential Solute Potential (Ψs ) = - iCRT
i – ionization constant
C – Concentration in Moles
R – pressure constant ( literbars/mole-K)
T – temperature in Kelvin (273 + oC)
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 (Ψp)
MPa (Ψs)
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
Medium
Water Potential (MPa)
Air (50% humidity)
-100.0
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 (Ψs)
Soil or root?

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

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

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?
highered.mcgraw-hill.com

47. Hydrostatic Pressure Pressure created by blood - (Ψp)
Glomerulus of the kidney - dialysis

48. Moving Molecules Against a Gradient
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 molecule’s energy
Plants: proton ‘pump’

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

54. Exocytosis/Endocytosis
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 LDL’s from blood; recessive
Cholesterol molecules as LDL’s

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