1. Cellular Transport

2. About the Plasma Membrane
All cells have a cell membrane
surrounds the cytoplasm of a cell and controls what enters and exits.
they consist of two layers of phospholipids, arranged into sheets, called a bilayer.

3. polar “head” region and two nonpolar “tails.”
the heads are hydrophilic (water-loving) while the tails are hydrophobic (water- fearing).
The middle section, made up of fatty acids, is nonpolar and hydrophobic

4. The physical properties of this middle section determine how easily different substances may move across the membrane!!!
What molecules can pass across the membrane?
small, nonpolar molecules ---example 02 and CO2
What molecules can’t pass across the membrane?
Ions an large, polar molecules –K+, Cl-, and sugar

5. QUESTION
Which of the following should pass MOST easily through the plasma membrane?
A. a protein
B. a small lipid
C. a sodium ion
D. a water molecule

6. The physical properties of this middle section determine how easily different substances may move across the membrane!!!
What molecules can pass across the membrane?
small, nonpolar molecules ---examples: 02 and CO2
What molecules can’t pass across the membrane?
Ions, large molecules, polar molecules –examples: K+, Cl-, sugar, and H2O

7. Proteins throughout the membrane
help to stabilize and shape the membrane
allow the cell to be recognized by other cells
act as receptors to which hormones and other molecules
help to transport ions and polar molecules
EXAMPLE: Water molecule needs a protein called aquaporin
NOTE: carbohydrates can attach to membrane proteins or lipids, creating glycoproteins and glycolipids. These act as "self-markers" for body cells, so that the immune system does not attack them.

8. QUESTION
Proteins are made up of different amino acids. The R group of an amino acid gives it specific properties, making it small or large, polar or nonpolar. Where are the nonpolar amino acids in an aquaporin protein most likely to be found? A. along the inner tube of the channel B. in a band around the outside of the channel C. on the end of the protein that faces the cytoplasm D. on the end of the protein that faces the extracellular fluid

9. QUESTION
The tongue is lined with taste buds, which detect the components of food and relay this information to the brain. What type of membrane protein do taste bud cells rely on, and how do they help these cells carry out their function? Cells of the taste buds contain receptors for substances in foods. When a chemical in food binds to a receptor, this type of membrane protein causes changes in the cell that result in a signal being sent to the brain.

10. Structure of the Plasma Membrane
Outside of cell
Carbohydrate
chains
Proteins
Lipid
Bilayer
Transport
Protein
Phospholipids
Inside of cell
(cytoplasm)
Animations
of membrane structure
Go to Section:

11. Passive Transport
DID YOU KNOW? The plasma membrane is an area of constant movement as molecules are shuttled back and forth in a variety of ways. SOOO…what is the movement of these molecules driven by? ANSWER: concentration gradient When a dissolved substance is more concentrated in one area compared to another area (adjacent to)

12. Remember that Cells…
Maintain a constant internal environment (or homeostasis)
Respond to the concentration gradient of the environment by moving molecules across membranes to either balance inside and outside concentrations (i.e. equilibrium) or to stockpile more

13. Types of Passive Transport
does NOT require any energy input to occur
Simple Diffusion
Facilitated Diffusion
Osmosis
Animations of Active Transport & Passive Transport
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low
Weeee!!!

14. Simple Diffusion Animation
Diffusion (simple)
What is diffusion?
Movement of molecules “down” the concentration gradient. That is, more concentrated region to the less-concentrated regions. (High to Low)
continues until all molecules are evenly spaced (equilibrium is reached)

15. Diffusion continued…..
Click here for diffusion animated explanation

16. Diffusion (facilitated)
Recall that large molecules, charged ions, and polar molecules do not readily cross the phospholipid bilayer.
What is facilitated diffusion?
diffusion of specific particles through transport proteins found in the membrane
Transport Proteins are specific – they “select” only certain molecules to cross the membrane
Transports larger or charged molecules

17. Facilitated diffusion continued……
Diffusion of bigger molecules (but still smaller than particles) through channel proteins
Click here for facilitated diffusion explanation

18. Facilitated diffusion continued……
Glucose
molecules
Cellular Transport From a-
High
High Concentration
Channel Proteins animations
Cell Membrane
Low Concentration
Protein
channel
Low
Transport Protein
Through a 
Go to Section:

19. Facilitated diffusion (Channel Protein)
Simple Diffusion (Lipid Bilayer)

20. QUESTION Which is NOT an example of passive transport?
Carbon dioxide in a capillary crosses the alveoli membranes of the lungs.
B. Oxygen dissolved in the blood crosses the phospholipid portion of the membrane of a red blood cell.
C. Glucose molecules are transported by a carrier protein until its concentration on both sides of the membrane is equal.
D. Sodium ions move through a protein channel until there is a higher concentration in extracellular fluid than the cytoplasm.

21. Now we’ll focus on water movement because it moves more freely than other molecules
Notice the sugar molecules are too big to pass through the membrane but water is not

22. Osmosis What is osmosis?
diffusion of water through a selectively permeable membrane
Water moves from high to low concentrations
Water moves freely through pores.
Solute (green dots) to large to move across.
Osmosis animation

23. Osmosis on Life
Water is so small and there is so much of it the cell can’t control it’s movement through the cell membrane. SO, under what conditions can affect a cell by osmosis?
………. lets see how different conditions (isotonic/hypotonic/hypertonic) affect the cell

24. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
Isotonic Solution
Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

25. Isotonic solution Water moves equally in BOTH directions
Therefore, cell size does not change
* Note the cell is also isotonic compared to the solution around it

26. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
Hypertonic Solution
Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)
shrinks
Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

27. Hypertonic solution
Water moves outside of the cell, toward higher solute concentration
Cell size shrinks
* Note the cell is hypotonic compared to the solution around it

28. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

29. Hypotonic solution
Water moves inside of cell, toward higher solute concentration
Cell size increases
* Note the cell is hypertonic compared to the solution around it

30. How will you remember? Think hypo-hippo
A cell in a hypo- environment will swell like a big fat hippo!

31. B C A What type of solution are these cells in? Hypertonic Isotonic
Hypotonic

32. Review Hypertonic Higher solute concentration outside the cell
Hypotonic
Lower solute concentration outside the cell
Water moves in
Cell size increases
E.g. Diluted solution
Isotonic
Same solute concentration
Water moves in and out
No change in cell size
Hypertonic
Higher solute concentration outside the cell
Water moves out
Cell size decreases
E.g. Strong salt solution

33. Types of Active Transport
sodium potassium pump Active Transport using proteins)
Sodium / Potassium Pumps
---transport proteins that require energy to do work
---are important in nerve responses. Animation: The Nerve Impulse
--- 3 Na+ out and 2 K+ in
Protein changes shape to move molecules: this requires energy!

34. Types of Active Transport Endocytosis and Exocytosis
2. Endocytosis: taking bulky material into a cell
Uses energy
Cell membrane in-folds around food particle
Think pac-man
This is how white blood cells eat bacteria!
Types of endocytosis:
Phagocytosis (takes in large particle) “cell eating”
Pinocytosis (takes in liquid) “cell drinking”
Receptor-mediated endocytosis

35. Types of Active Transport
3. Exocytosis: Forces material out of cell in bulk
cell “pooping”
membrane surrounding the material fuses with cell membrane
Cell changes shape – requires energy
Endocytosis & Exocytosis animations

36. Endocytosis (in) & Exocytosis (out)

37. SUMMARY: Types of Cellular Transport
Animations of Active Transport & Passive Transport
SUMMARY: Types of Cellular Transport
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Passive Transport
cell doesn’t use energy
Diffusion
Facilitated Diffusion
Osmosis
Active Transport
cell does use energy
Sodium-Potassium Pump
Endocytosis
Exocytosis
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low
This is gonna be hard work!!

38. Summary Passive Transport Similarities Active Transport
No energy required
Movement down the gradient
Diffusion, osmosis, facilitated diffusion
Maintains equilibrium
Movement through channel proteins
Movement of small ions & molecules
Maintains homeostasis
Requires ATP
Movement against gradient
Ion pump or endo/exocytosis
Movement of large particles
Stockpiles materials (extra’s)

39. Passive transport Active transport
____________ required
Movement from _________________area of concentration
Molecules move __________ concentration gradient
3 Examples
Requires ___________
Movement from __________________area of concentration
Molecules move ____________concentration gradient
3 Examples

40. Passive transport Active transport
No energy required
Movement from high to low area of concentration
Molecules move down concentration gradient
Examples
Diffusion
Osmosis
Facilitated diffusion
Requires energy
Movement from low to high area of concentration
Molecules move against concentration gradient
Examples
Sodium-potassium ion pump
Endocytosis
Exocytosis