1. Cell Transport

2. Cell Membrane: Function: Maintain homeostasis.
This is also called equilibrium.
Allow passage of some molecules while preventing the passage of others
This is called being “Selectively permeable” or “semi-permeable”

3. Semipermeable Membrane
The Plasma Membrane
4/20/2017
Semipermeable Membrane
Small molecules and larger hydrophobic molecules move through easily.
e.g. O2, CO2, H2O
G. Podgorski, Biol. 1010

4. Semipermeable Membrane
The Plasma Membrane
4/20/2017
Semipermeable Membrane
Ions-hydrophilic molecules larger than water, and large molecules such as proteins do not cannot pass through the membrane without help.
G. Podgorski, Biol. 1010

5. Membrane structure: Composed of a phospholipid bilayer
Have a phosphate head which is polar- does react with water
Have a fatty acid (lipid) tail that is non-polar- does not react with water
Together these make up the membrane

6. The outside of the membrane is hydrophobic- which means it does react with water
The inside of the membrane is hydrophilic- which means it does not react with water

7. Contains proteins within its structure
Integral proteins (transport proteins)- which allow the passage of molecules to large too pass through the membrane without help
Peripheral proteins- aid in signaling for the cell to communicate with other cells

8. Cell Structure:
Make up a metaphor for the phosphate heads of the membrane and the lipid tails of the membrane.
The cell’s structure allows it to maintain homeostasis in different situations.

9. Concentration Gradient
Concentration gradients occur when there is a higher amount of solutes in one area of solution then in another.
Molecules will tend to travel from areas of high concentration to areas of lower concentrations

10. Passive transport Molecules flow with or down a concentration gradient
No energy required
Two types:
Diffusion
Ex. Osmosis
Facilitated Diffusion

11. Diffusion

12. Facilitated Diffusion
Diffusion for molecules that are not lipid soluble or are too large to pass through the membrane.
Carrier proteins change shape to aid these molecules across the membrane
No Energy Required.
Example: Glucose, Fructose

13. Osmosis
Diffusion involving water moving from high solute concentrations to low solute concentration.
Water can move freely across the membrane
No energy required.

14. Osmosis There are three different types of osmotic solutions:
Hypotonic
isotonic
Hypertonic

15. Hypotonic Solution Higher concentration of solutes within the cell
More free water outside the cell
Water moves into the cell
The cell becomes swells or gets larger
Hypo Hippo- it gets big and swells.

16. Hypertonic Solution Higher concentration of solute outside the cell
More free water in the cell
Water moves out of the cell
Cell shrinks

17. Isotonic solution Solutions are equal between the two areas
Water moves both directions to keep the solutions at an equilibrium.

18. What will happen to water in the cell?

19. Three different Osmotic Solutions
Hypotonic- higher concentration of solutes in the cell
Hypertonic- higher amount of water inside the cell
Isotonic – equal amount of solutes inside and outside the cell

20. Example- Plants:
In a hypotonic solution plant cell’s membrane is pushed against the cell wall
Turgor Pressure
In a hypertonic solution a plant cell’s membrane will shrink within the cell wall
Plasmolysis
Causes wilting when plants dehydrate

21. Turgor Pressure Plant cell become engorged with water
Gives plant the stiffness in their stem

22. Plasmolysis Plant cell membrane shrinks from the cell wall
Causes plant to wilt.

23. Active Transport
Molecules are transported against the concentration gradient by proteins
Requires energy (ATP)
Example: Sodium-Potassium Pump
A protein that transfer Na+ and K+ ions up the gradient
Cell has a high Na+ concentration outside the cell and a high K+ concentration inside the cell

24. Active transport Enodcytosis: Exocytosis:
cells engulf substances that are too large to enter the cell by passing through the cell membrane
cellular wastes are removed from sacs at the cell’s surface

25. Exocytosis- moving things out.
The Plasma Membrane
4/20/2017
Exocytosis- moving things out.
Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.
This is how many hormones are secreted and how nerve cells communicate with one another.
copyright cmassengale
G. Podgorski, Biol. 1010

26. The Plasma Membrane
Exocytosis
4/20/2017
Exocytic vesicle immediately after fusion with plasma membrane.
copyright cmassengale
G. Podgorski, Biol. 1010

27. The Plasma Membrane
4/20/2017
Large molecules move materials into the cell by one of three forms of endocytosis.
copyright cmassengale
G. Podgorski, Biol. 1010

28. Pinocytosis- Most common form of endocytosis.
The Plasma Membrane
4/20/2017
Pinocytosis-
Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.
G. Podgorski, Biol. 1010

29. Pinocytosis- Cell forms an invagination
The Plasma Membrane
4/20/2017
Pinocytosis-
Cell forms an invagination
Materials dissolve in water to be brought into cell
Called “Cell Drinking”
copyright cmassengale
G. Podgorski, Biol. 1010

30. Example of Pinocytosis
The Plasma Membrane
4/20/2017
Example of Pinocytosis
Transport across a capillary cell (blue).
mature transport vesicle
pinocytic vesicles forming
copyright cmassengale
G. Podgorski, Biol. 1010

31. Receptor-Mediated Endocytosis
The Plasma Membrane
4/20/2017
Receptor-Mediated Endocytosis
Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.
copyright cmassengale
G. Podgorski, Biol. 1010

32. copyright cmassengale

33. Endocytosis – Phagocytosis
The Plasma Membrane
4/20/2017
Endocytosis – Phagocytosis
Used to engulf large particles such as food, bacteria, etc. into vesicles
Called “Cell Eating”
copyright cmassengale
G. Podgorski, Biol. 1010

34. The Plasma Membrane
4/20/2017
Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
copyright cmassengale
G. Podgorski, Biol. 1010

35. So to review the three types of Endocytosis are:
Phagocytosis
Pinocytosis
Receptor mediated Endocytosis.

36. The Plasma Membrane
4/20/2017
Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane.
copyright cmassengale
Inside Cell
Cell environment
G. Podgorski, Biol. 1010

37. What are the three different types of active transport?
Protein pumps
Endocytosis
Exocytosis

38. Cell Transport
Passive transport: molecules travel along the concentration gradient
No energy required
Active Transport: molecules are transported against the concentration gradient
energy required