1. Obtaining Ions, Nutrients and Water
Cellular Transport
Obtaining Ions, Nutrients and Water

2. Plasma (Cell) Membrane
semipermeable membranes regulate cell interaction with surroundings

3. small openings (pores) allow certain molecules to penetrate cell but denies others making it semi
Small black molecules allowed through
Large red molecules NOT allowed through
WHY?

4. 2 layers = 1 plasma membrane
Plasma membrane is composed of a phospholipid bilayer (two layers of phospholipids or lipids with phosphates)
2 layers = 1 plasma membrane

5. Phospholipids composed of:
lipids (fats): glycerol group and two fatty acid straight tails
Nonpolar / hydrophobic (water-fearing), can’t dissolve in water, found in interior of plasma membrane
Phosphate head
Lipid tails

6. phosphate group: phosphate (PO4)
Polar / hydrophilic (water-loving) globular heads, form outside of membrane (can be exterior or interior side of cell)
Can dissolve in water, allows plasma membrane of cell to interact with watery environment of cell.
Phosphate head
Lipid tail

7. properties of phospholipids do NOT allow water-soluble molecules to move through membrane easily.

8. H2O soluble
H2O soluble

9. Proteins embedded within membrane move about in a fluid fashion
Fluid mosaic model explains how structural properties of plasma membrane allow lipids & proteins to move freely in membrane
Mosaic: something consisting of variety of components

10. Plasma membrane also contains:
Transport proteins: allow substances or waste materials to move through plasma membrane
Proteins & carbohydrates: stick out from cell and help cells identify each other
Proteins: give cell flexibility
Carbohydrates: act as identifier of cell type

11. Homeostasis
Cell constantly interacts with environment & has to respond to external conditions to maintain homeostasis
Increase in heat makes temperature rise
99.0ºF
98.8ºF
98.6ºF
Cell will seek to cool itself down
Homeostasis at work!

12. Eating a bag of chips will cause cell to respond to new salty condition

13. Cell membranes maintain homeostasis by regulating passage of materials into and out of the cell:
Passive Transport – no energy required to move solute or solvent from high to low concentration (down concentration gradient)
Active Transport – energy required to move solute from low to high concentration (against concentration gradient)
Outside Cell (16)
Inside Cell (4)

14. concentration gradient = difference in amount of substance present inside the cell versus outside the cell
outside
inside

15. Molecules will freely flow from high concentration to low concentration

16. Concentration Gradient
Pathway from high to low concentration is concentration gradient
Eventual point where concentration is equal = equilibrium (particles still randomly move but equal in/out)
Concentration Gradient
High Concentration
Low Concentration

17. Passive Transport Three methods:
Simple diffusion – particles (solutes)
Osmosis – diffusion of water (solvent)
Carrier-facilitated diffusion – particles (solutes) with protein assistance

18. Simple Diffusion
Simple diffusion – free movement of ions & molecules through protein channels in membrane
Outside cell
Inside cell

19. Simple Diffusion – the homemade animation

20. Osmosis Osmosis – free movement or diffusion of solvent (water) ONLY
Note how the red sugar particles stay put.
Only the blue water molecules move.

21. Osmosis– the homemade animation

22. three types of solutions that determine direction of water :
isotonic solution
hypotonic solution
hypertonic solution

23. Isotonic Solution
concentration of water on outside of cell is same as on inside of cell
Cells do not experience overall osmosis (or diffusion)
retain their normal shape,
Still random movement for an overall net gain of 0

24. ISOTONIC SOLUTION 90% H2O 10% particles (inside cell) 90% H2O
(outside cell)
ISOTONIC SOLUTION

25. Hypotonic Solution
concentration of water is higher outside cell than concentration of water inside cell.
Cells experience osmosis (and diffusion)
water moves into cell
cell swells and will burst if animal cell but will not burst if plant cell due to cell wall

26. Diffusion of particles
30% H2O
70% particles
(inside cell)
Osmosis of water
Diffusion of particles
70% H2O
30% particles
(outside cell)
HYPOTONIC SOLUTION

27. Hypertonic Solution
concentration of water is higher inside cell than concentration outside cell.
Cells experience osmosis (and diffusion)
water moves out of cell
Cells shrink
Plant wilts because of a decrease in pressure on cell wall

28. Diffusion of particles
55% H2O
45% particles
(inside cell)
Osmosis of water
Diffusion of particles
45% H2O
55% particles
(outside cell)
HYPERTONIC SOLUTION

29. Hypertonic vs. Isotonic vs. Hypotonic Solutions
Higher solute OUTSIDE
Equal solute
Higher solute INSIDE
Higher water INSIDE
Equal water
Higher water OUTSIDE
Water moves OUT
No net movement
Water moves IN
Cell SHRINKS
Normal
Cell SWELLS

30. Hypertonic vs. Isotonic vs. Hypotonic Solutions

31. Hypertonic vs. Isotonic vs. Hypotonic Solutions

32. Hypertonic vs. Isotonic vs. Hypotonic Solutions

33. Diffusion and Osmosis are Simultaneous!
Often times, diffusion of large particles can’t happen or happen fast enough
Water will diffuse via osmosis to regulate concentration (PERCENTAGES)
Outside cell is 50% solute, 50% water
Inside cell is 10% solute, 90% water
Solute is too big to move. Will we die? No. Water will move to get concentration equal

34. Particles Can’t Move What will Happen?
90% H2O
10% particles
(inside cell)
50% H2O
50% particles
(outside cell)
Hint: look at water % only. Where will the water go?

35. Diffusion of particles
Question1: Which way will the particles move?
outside
Question 2: Which way will the water move?
20% H2O
80% particles
(inside cell)
inside
Osmosis of water
Diffusion of particles
80% H2O
20% particles
(outside cell)

36. Analyze the following picture. What will happen?
DIFFUSION
OSMOSIS

37. Analyze the following picture. What will happen?

38. Carrier-Facilitated Diffusion
free movement of larger molecules with aid (help) of a transport/carrier protein
Large solutes (sugars, amino acids) are too big to go through plasma membrane unaided

39. Facilitated Diffusion – the homemade animation

40. ACTIVE TRANSPORT
Needs energy (ATP) to move particles across plasma membrane
Three types:
Active transport – small molecules AGAINST concentration gradient (from low to high)
Endocytosis – large molecules being engulfed by plasma membrane into vesicles
Exocytosis – large molecules being expelled out by vesicles out of plasma membrane

41. Active Transport
Requires energy (ATP) to move materials against gradient (low to high concentration)
carrier protein allows specific molecule or ion to bind
Example: sodium/potassium (Na/K) pump
ATP changes shape of protein to move molecule or ion across plasma membrane
ATP

42. Endocytosis
cell surrounds material with a portion of its plasma membrane and forms a vesicle
Vesicle moves particle inside cell for digestion
Bacteria, food
Phagocytosis – large, solid particles
Pinocytosis – small, liquid particles

43. Active Transport of People
STARRING
train as the CELL
platform as the
EXTRACELLULAR SPACE
people as the PARTICLES
conductors as the ATP

44. Exocytosis
Vesicle brings material to cell membrane & expels (secretes) it
Wastes, hormones

47. Passive vs. Active Overview

49. The End