1. Transport Across Membranes
Image from:
2.4

2. Importance of Transport
intake of nutrients
removal of wastes
communication with environment & other cells
blocking entry of harmful substances
Cell membrane is selectively permeable.

3. Passive Transport
the movement of materials across the cell membrane without the use of chemical energy (ATP)
movement is due to diffusion

4. Diffusion
the net movement of a substance from an area of higher to an area of lower concentration until a state of dynamic equilibrium
Image from:

5. Simple Diffusion substances move unassisted
small non-polar molecules, small uncharged polar molecules
larger molecules & ions need assistance
Image from:
small non-polar molecules (O2, CO2, steroid hormones, some drugs) and small polar molecules (H2O, glycerol)

6. Facilitated Diffusion
diffusion across membrane assisted by integral membrane proteins called transport proteins
channel proteins form hydrophilic pathways for water & ions; ion channels are usually voltage-gated
carrier proteins usually have specificity

7. Facililated Diffusion
Image from:

8. Carrier Proteins
Image from:

9. Osmosis the diffusion of water across a membrane
water follows concentration gradient until equilibrium

10. Osmosis
direction of osmosis changes depending on type of solution surrounding the cell:
isotonic solution
hypotonic solution
hypertonic solution

11. Cell in Isotonic Solution
The Plasma Membrane
11/24/2018
Cell in Isotonic Solution
10% NaCL 90% H2O
ENVIRONMENT
CELL
NO NET MOVEMENT
10% NaCL
90% H2O
What is the direction of water movement?
equilibrium
The cell is at _______________. 11
G. Podgorski, Biol. 1010 11

12. Cell in Hypotonic Solution
The Plasma Membrane
11/24/2018
Cell in Hypotonic Solution
10% NaCL 90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement? 12
G. Podgorski, Biol. 1010 12

13. Cell in Hypertonic Solution
The Plasma Membrane
11/24/2018
Cell in Hypertonic Solution
15% NaCL 85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement? 13
G. Podgorski, Biol. 1010 13

14. Animal Cells Prefer Isotonic Environments
Image from:

15. Red Blood Cells
Image from:

16. Plant Cells Prefer Hypotonic Environments

17. Active Transport
Image from:

18. Active Transport
the movement of materials against the concentration gradient (from low to high concentrations)
requires cellular energy (ATP)

19. Primary Active Transport
pumps move positively charged ions (H+, Ca2+, Na+, K+) across membranes
creates electrochemical gradient
Image from:

20. Secondary Active Transport
uses gradient established by a primary active transport pump
Image from:

21. Bulk Transport
movement of larger substances across a cellular membrane
requires energy (ATP)
exocytosis & endocytosis

22. Endocytosis
Image from:

23. Exocytosis Neurotransmitters
Image from:
Neurotransmitters