1. Competencies
explain transport mechanisms in cells (diffusion osmosis,facilitated transport, active transport) STEM_BIO11/12-Ig-h-13
2. differentiate exocytosis and endocytosis - STEM_BIO11/12-Ig-h-14

2. Activity (15 mins)
Video on Cell Membrane and Transport
Guide Questions
1. What is cell membrane and its composition based on the video?
2. Initially, what is Cell Transport? Describe each type.
3. Why is Transport necessary in Cell?

3. Membrane Transport Passive Transport Active Transport
Motion of substances in and out of the cell
Cell membranes are Selectively permeable
Two Types of Transport Mechanisms:
Passive Transport
Active Transport

4. Membrane Transport
Passive transport is movement of molecules through the membrane in which no energy is required from the cell
Active transport requires energy expenditure by the cell

5. Types: A. Simple Diffusion – unassisted diffusion
1. Passive Movement – requires no energy
Types: 1. Diffusion – process of scattering molecules from an area of greater to a lesser concentration.
Types: A. Simple Diffusion – unassisted diffusion
1. Osmosis – movement of solvent materials
2. Dialysis – movement of solute materials.
B. Facilitated Diffusion – provides protein carriers as transport vehicle.
2. Filtration – process by which water and solute are forced thru a membrane by fluid or hydrostatic pressure

6. 2. Active Transport – when cells uses ATP supply to move substances across the membrane.
Types:
1. Solute Pumping – similar to facilitated diffusion that requires carriers that reversibly with substances to be transported across membrane.
2. Bulk Transport – some substances that cannot get through the plasma membrane in any other way are transported with the help of ATP into or out of cell.

7. Passive Transport
A process that does not require energy to move molecules from a HIGH to LOW concentration
Diffusion
Facilitated Diffusion

8. Diffusion is the movement of small particles across a selectively permeable membrane like the cell membrane until equilibrium is reached.
These particles move from an area of high concentration to an area of low concentration.
outside of cell
inside of cell

9. Diffusion is movement of solute molecules from high concentration to low concentration

10. 1. Passive Transport There are two types of diffusion Simple Diffusion
Facilitated Diffusion

11. 1. Passive Transport Simple Diffusion
Substances pass directly through the cell membrane
The cell membrane has limited permeability to small polar molecules, water, and ions
The motion of water across the membrane is known as osmosis

12. HIGH to LOW concentration
Diffusion
HIGH to LOW concentration

13. Semi-permeable membrane is permeable to water, but not to sugar
Osmosis is the diffusion of water through a selectively permeable membrane like the cell membrane
Water diffuses across a membrane from an area of high concentration to an area of low concentration.
Semi-permeable membrane is permeable to water, but not to sugar

15. Passive Transport Osmosis
Osmosis is the movement of water from an area of high to low concentration of water
movement of water toward an area of high solute concentration
in osmosis, only water is able to pass through the membrane
Osmosis moves water through aquaporins

18. Osmosis
Osmotic concentration is determined by the the concentration of all solutes in solution
Relative Osmotic Concentrations
Hypertonic solutions: have a higher relative solute concentration
Hypotonic solutions: have a lower relative solute concentration
Isotonic Solutions: have equal relative solute concentrations

19. 1. Passive Transport Facilitated Diffusion
Substances must pass through transported proteins to get through the cell membrane
The cell membrane is selectively permeable

20. Proteins that form channels (pores) are called protein channels
Facilitated Diffusion is the movement of larger molecules like glucose through the cell membrane – larger molecules must be “helped”
Proteins in the cell membrane form channels for large molecules to pass through
Proteins that form channels (pores) are called protein channels
outside of cell
inside of cell
Glucose molecules

21. Facilitated Diffusion
Selective permeability: integral membrane proteins allow the cell to be selective about what passes through the membrane.
Channel proteins have a polar interior allowing polar molecules to pass through.
Carrier proteins bind to a specific molecule to facilitate its passage.

22. Channel Proteins Channel proteins include:
- ion channels allow the passage of ions (charged atoms or molecules) which are associated with water
- gated channels are opened or closed in response to a stimulus
the stimulus may be chemical or electrical

23. Fig. 5.10
ion channels

24. Channel Proteins
Ion channels allow the passage of ions (charged atoms or molecules) across the membrane
A concentration gradient of ions across the membrane creates a membrane potential
a membrane potential is a charge difference between the two sides of the membrane

25. Fig. 5.10
ion channels + + + + + + + + + +

26. Carrier Proteins
Carrier proteins bind to a specific molecule to facilitate its passage.

27. Click

28. Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel.
Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode.
Isotonic Solutions: contain the same concentration of solute as another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.

30. Interactive Red Blood Cell
Click

31. Organisms can maintain osmotic balance in different ways:
1. Some cells use extrusion in which water is ejected through contractile vacuoles.
2. Isosmotic regulation involves keeping cells isotonic with their environment.
3. Plant cells use turgor pressure to push the cell membrane against the cell wall and keep the cell rigid.

32. B. Active Transport
Active transport is the movement of molecules from LOW to HIGH concentration.
Energy is required as molecules must be pumped against the concentration gradient.
Proteins that work as pumps are called protein pumps.
Ex: Body cells must pump carbon dioxide out into the surrounding blood vessels to be carried to the lungs for exhale. Blood vessels are high in carbon dioxide compared to the cells, so energy is required to move the carbon dioxide across the cell membrane from LOW to HIGH concentration.
outside of cell
inside of cell
Carbon Dioxide molecules

34. ANALOGY: ENERGY NEEDED: Active Transport NO ENERGY NEEDED: Diffusion
Osmosis
Facilitated Diffusion
ENERGY NEEDED:
Active Transport

36. 2. Active Transport Active transport
Requires energy – ATP is used directly or indirectly to fuel active transport
Able to moves substances against the concentration gradient - from low to high concentration
allows cells to store concentrated substances
Requires the use of carrier proteins

37. Active Transport Carrier proteins used in active transport include:
-uniporters – move one molecule at a time
-symporters – move two molecules in the same direction
-antiporters – move two molecules in opposite directions

38. 1. Solute Pumping Sodium-potassium (Na+-K+) pump
An active transport antiport mechanism
Uses an antiporter to move 3 Na+ out of the cell and 2 K+ into the cell
ATP energy is used to change the conformation of the carrier protein
The affinity of the carrier protein for either Na+ or K+ changes so the ions can be carried across the membrane

39. Active Transport Sodium-potassium (Na+-K+) pump
Used by animal cells to maintain a high internal concentration of K+ ions and a low internal concentration of Na+ ions
Maintains a concentration gradient that is used to power many other important physiological process

40. Fig

41. Fig

42. Fig

44. Active Transport Coupled transport
Uses the energy released when a molecule moves by diffusion to supply energy to active transport of a different molecule
A symporter is used
Glucose-Na+ symporter captures the energy from Na+ diffusion to move glucose against a concentration gradient

46. 2. Bulk Transport Bulk transport of substances is accomplished by
1. Endocytosis – movement of substances into the cell
2. Exocytosis – movement of materials out of the cell

47. Ex: White Blood Cells, which are part of the immune system, surround and engulf bacteria by endocytosis.

48. Bulk Transport
Endocytosis occurs when the plasma membrane envelops food particles and liquids.
1. phagocytosis – the cell takes in particulate matter
2. pinocytosis – the cell takes in only fluid
3. receptor-mediated endocytosis – specific molecules are taken in after they bind to a receptor

52. Bulk Transport
Exocytosis occurs when material is discharged from the cell.
Vesicles in the cytoplasm fuse with the cell membrane and release their contents to the exterior of the cell
Used in plants to export cell wall material
Used in animals to secrete hormones, neurotransmitters, digestive enzymes

54. (10mins) Application:
1. What did you learn today?
2. How do you relate the Cell Transport to real life situation? Make an analogy