1. Homeostasis and Transport

2. The Cell Membrane
Balanced internal condition of cell is called homeostasis/equilibrium
Maintained by plasma membrane
controlling what enters & leaves the cell

3. Semipermeable Membrane
The Plasma Membrane
11/13/2018
Semipermeable Membrane
Selectively permeable
Small molecules move through easily.
O2, CO2, H2O
G. Podgorski, Biol. 1010

4. Jobs of The Cell Membrane
Protective barrier
Regulate transport
Communication
Anchoring sites for filaments of cytoskeleton

5. Passive Transport

6. Passive Transport
The movement of substances across the membrane without any input of energy is known as passive transport
Types of passive transport are:
Diffusion Osmosis Facilitated Diffusion

7. What is Diffusion?
Small molecules can pass through the cell membrane = diffusion.
Diffusion happens because molecules move from higher concentration to an area of lower concentration.
Diffusion is passive transport because it does not require energy.

8. Why do molecules move?
Kinetic energy keeps molecules in constant motion .
The rate of diffusion depends on temperature, size of the molecule, and type of molecule diffusing.
Diffusion is faster at higher temperatures
Smaller molecules move faster

9. Why does diffusion happen?
The difference in the concentration of molecules across a membrane is called a concentration gradient.
Diffusion occurs down a concentration gradient.

10. Diffusion
When equilibrium is reached - molecules will continue to move equally back and forth across a membrane.

11. Osmosis
Osmosis occurs from an area of high water concentration (less solute) to an area of lower water concentration (more solute).
Water moves down its concentration gradient and does not require energy.
Water moves across a membrane in one direction until equilibrium is reached.

12. Osmosis Water is the universal solvent for all living organisms.
Osmosis is the movement of water across a membrane.

13. Facilitated Diffusion
Facilitated diffusion is a type of passive transport that allows substances to cross membranes with the assistance of special transport proteins.
Some molecules such as glucose need help across a cell membrane.

14. Facilitated Diffusion
The channel proteins are regulated by the cell and are either open or closed to control the passage of substances into and out of the cell.
Carrier proteins bind to specific molecules, change shape and then deposit the molecules across the membrane.

15. Facilitated Diffusion
The Plasma Membrane
11/13/2018
Facilitated Diffusion
Some Carrier proteins do not extend through the membrane. They are called peripheral proteins.
They bond and drag molecules through the lipid bilayer and release them on the opposite side.
G. Podgorski, Biol. 1010

16. Types of Solutions

17. Hypertonic Solutions Solute concentration outside the cell is higher
(solution=less pure water/ cell=more pure water)
Water diffuses out of the cell until equilibrium is reached
Cells will shrink and die if too much water is lost…called plasmolysis.
Plant cells become flaccid (wilt).

18. Hypotonic Solutions Solute concentration is greater inside the cell
(solution= more pure water/ cell= less pure water)
Water moves into the cell until equilibrium is reached
Animal cells swell and burst if they take in too much water this is called cytolysis
Plant cells become turgid.
Turgor pressure in plant cells helps them keep their shape
Plant cells do best in hypotonic solutions

19. Paramecium Paramecium live in fresh water.
Maintain homeostasis through their contractile vacuole.
The contractile vacuole pumps water out so he does not burst.

20. Isotonic Solution
Concentration of solutes are the same inside and outside of cell
Water moves into and out of cell at an equal rate so there is no net movement of water.
Animal cells do best in isotonic solutions.

21. The Three types of Solutions
The Plasma Membrane
11/13/2018
The Three types of Solutions
Hypertonic Solution
Isotonic Solution
Hypotonic Solution
NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
PLASMOLYSIS
CYTOLYSIS
G. Podgorski, Biol. 1010

22. Plants prefer Hypotonic Solutions: Turgor Pressure

23. Animals prefer isotonic solutions
The Plasma Membrane
11/13/2018
Animals prefer isotonic solutions
Isotonic
Hypertonic
Hypotonic
G. Podgorski, Biol. 1010

24. Active Transport

25. Active Transport
Active transport is the movement of molecules up/against their concentration gradient from an area of lower to higher concentration using energy (ATP).
May involve transport proteins.
Used to move ions such as Na+ and K+ across the cell membrane.

26. Sodium Potassium Pump
The sodium-potassium pump ships Na+ outside the cell and K+ inside the cell, against their concentration gradients.
3 Na+ are pumped out of the cell while 2 K+ are pumped into the cell.
ATP drives the energy.

27. Sodium Potassium Pump The Plasma Membrane 11/13/2018
G. Podgorski, Biol. 1010

28. Moving the “Big Stuff”

29. Two types of Endocytosis
Endocytosis “ENTER” is the movement of large particles into a cell.
The two types of endocytosis are:
Phagocytosis
Pinocytosis

30. Phagocytosis “Cell Eating”
Pseudopod surrounds the particle.
Membrane pouch encloses the material and pinches off inside the cell making a vesicle.
Vesicle can fuse with lysosomes or release their contents in the cytoplasm.
Used by amoeba to feed and white blood cells to kill bacteria.

31. Phagocytosis

32. Phagocytosis
The Plasma Membrane
11/13/2018
Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
G. Podgorski, Biol. 1010

33. Phagocytosis about to occur
The Plasma Membrane
11/13/2018
Phagocytosis about to occur
G. Podgorski, Biol. 1010

34. Pinocytosis “Cell Drinking”
Cell membrane surrounds fluid droplets
Fluids taken into membrane-bound vesicle.

35. Exocytosis
Large molecules that are manufactured in the cell are released through the cell membrane.

36. Exocytosis
This is how many hormones are secreted and how nerve cells communicate with one another.

37. The End