1. Molecular (cell) transport
Material Exchange and Osmosis

2. Material exchange
Cell transport: movement of particles across membrane
Takes place because cells are trying to maintain homeostasis

3. Exchanged Materials What materials are exchanged?
WATER – MOST IMPORTANT
Oxygen, Carbon Dioxide
Ions – Na+, Mg+, Ca+, H+, Cl-, K+
Hormones (to transmit messages)
Nutrients enter (sugars & amino acids)
Wastes must exit (Ammonium)

4. Cell Membrane
Membrane composed of a Phospholipid bilayer with proteins & carbohydrates interspersed
Lipids & proteins cause membrane to be fluid, not rigid

5. The fluid mosaic model Fluid = all the parts move around
Mosaic = made of many different parts

6. Components of cell membrane
Lipid: Main component of cell membrane

7. Carbohydrates (Sugars)
Act as ID tags
Attached to phospholipids and proteins

8. Membrane Proteins Signaling Receptors – receiving signals
Transport – move molecules across the membrane
Channels – act as doorways
Glycoproteins – act as ID tags
Enzymes - biological catalysts
Attachment - sticks to other cells

9. Cell membrane: Phospholipid bilayer
Phosphate heads: polar, hydrophilic
Fatty acid tails: nonpolar, hydrophobic
Heads arrange themselves on the outside & tails arrange themselves on the inside

10. Cell membrane as a barrier
Causes membrane to be Selectively permeable: only certain molecules are allowed to pass through
Small, nonpolar molecules like nitrogen & oxygen gas pass through easily.
Ions (like H+ and Ca2+) are repelled by nonpolar tail and cannot cross membrane
Nonpolar O2
Larger ions
Polar molecules
You shall not pass

11. 2 types of cell transport
Passive transport Active transport

12. Passive transport
Molecules move across the cell membrane from an area of higher concentration to an area of lower concentration
Does not require cells to expend energy
Three types:
Diffusion
Facilitated Diffusion
Osmosis

13. Diffusion
The movement of molecules from an area of HIGHER concentration to an area of LOWER concentration until it reaches EQUILIBRIUM
Molecules move down a concentration gradient (from high to low)
Concentration: amount of molecules in a given area
Concentration gradient: difference in the amount of molecules in a given area

14. Facilitated diffusion
Movement of small molecules across a membrane with the help of proteins
Channel Proteins
Carrier Proteins

15. OSMOSIS Diffusion of water molecules
Water does this to balance relative concentration of molecules
Therefore depends on solutions on both sides of membrane
Cell membranes are completely permeable to water with the help of aquaporins

16. Direction of osmosis is due to the concentration of the solutions
Tonicity
Direction of osmosis is due to the concentration of the solutions
Amount of solutes = tonicity

17. Isotonic
Isotonic Solution: concentration of solute inside and outside the cell are equal
No NET movement of water

18. hypertonic
Hypertonic Solution: concentration of solute outside the cell is higher than concentration inside the cell.
HYPER = MORE STUFF
Water will flow out of cell

19. hypotonic
Hypotonic Solution: concentration of solute outside the cell is lower than the concentration in the cytoplasm.
HYPO = NO STUFF
Water will flow into cell
“In Hypo, cell will be Hippo”

20. Isotonic: Cell will retain its normal shape!

21. Hypertonic: Cell will SHRINK!

22. Hypotonic: Cell will SWELL!

23. Movement of Materials Through the Cell Membrane

25. Active Transport
Molecules move across the membrane from an area of lower concentration to an area of higher concentration
Requires cells to expend energy
Three types:
Transport Proteins
Exocytosis
Endocytosis

26. Transport Proteins
Actively pump small molecules and ions across the cell membrane

27. Exocytosis removal of waste materials from cell Larger molecules
Vesicles made by the cell fuse with the cell membrane
releasing their contents into the external environment

28. Exocytosis

29. Endocytosis
Taking material into the cell by formation of a pocket of the cell membrane to make a vesicle
Pinocytosis: vesicle contains fluids (cell drinking)
Phagocytosis: vesicle contain large particles (cell eating)

30. Endocytosis

31. Active transport