1. Cell Transport Homeostasis Cell Membrane Vocabulary
Diffusion and Osmosis
Active vs. Passive Transport

2. Homeostasis
Homeostasis means maintaining a balance internally despite what is going on externally.
Organisms must adjust to changes in the environment in order to survive or they could die!

3. Homeostasis
For example, if it is below freezing outside, you must put on a heavy coat, gloves, double socks, a warm hat, ear muffs, and lots and lots of layers to maintain a healthy INTERNAL body temperature despite the EXTERNAL temperature

4. Homeostasis The Cell Membrane
What structure maintains homeostasis in our cells?
How does it maintain homeostasis?
How?
The Cell Membrane
By controlling the passage of molecules, such as water, salts, food particles, etc in and out of the cell.
(it regulates what enters and leaves)
Through passive transport, active transport and cell to cell communication!

5. The Cell Membrane The Cell Membrane is: A phospholipid bilayer
Two layers made of proteins and lipids
Phospholipid Structure:
Polar Head (hydrophilic—”water loving”)
Nonpolar Tails—(hydrophobic—”water fearing”)
Draw:
Polar Head
(hydrophillic)
Nonpolar Tails
(hydrophobic)

6. The Cell Membrane
Bilayer arrangement
Draw:

7. The Cell Membrane
The proteins embedded in the cell membrane help it to function properly
3 Types of Membrane Proteins
Transport — helps molecules enter or leave the cell
Marker — identify the cell
Receptor — allow cells to communicate

8. The Cell Membrane Transport Proteins Function as “gates/passageway”
Channel Protein
Transport Protein
Transport Proteins
Function as “gates/passageway”
Allow sugars, salts, etc to cross the membrane.
Special channel proteins:
Gated ion channels—gates that open/close
Carrier proteins—change shape to allow specific molecule to pass
Aquaporins - allow water to diffuse through (called osmosis)
Carrier Protein

9. The Cell Membrane Marker Proteins Cell’s “Name Tag”
Protein sticks out of phospholipid layer
Often has carbohydrates attached to outside end
Functions in cell identification to identify the cell to other cells and molecules
Important in
immunity—so various white blood cells in your body do not mistake your cells for foreign cells
- blood typing – so you can’t receive just any ol’ type of blood
Marker Protein

10. The Cell Membrane Receptor Proteins Function as “messenger/receiver”
Receive information from the environment (extracellular fluid, blood, interstitial fluid) and transmit that info to the inside of the cell
Protein has specific shape/charge to only allow certain molecules (like hormones) to bond
Triggers a response in cell
Receptor Protein

11. The Cell Membrane
Remember that these proteins are embedded or floating in the lipid bilayer.

12. The Cell Membrane The Cell Membrane is:
Selectively permeable/semipermeable
permeable means to let objects travel through
so if it is selectively or semi permeable it only allows SOME things through and not others

13. The Cell Membrane This represents a selectively permeable membrane.
It allows (selects) certain things to pass through it.
Is the membrane permeable to ?
Is the membrane permeable to ?

14. The Cell Membrane Molecules pass through the cell membrane through:
Passive Transport
Diffusion
Facilitated Diffusion
Osmosis
Active Transport
Vesicles
Pumps

15. Cell Transport Vocabulary
Molecule- the smallest unit of a compound/substance
Cannot be seen with the naked eye
1 drop of water has 16,700,000,000,000,000,000,000 molecules of H20
1 grain of salt has 120,000,000,000,000,000 molecules of salt

16. Cell Transport Vocabulary
Concentration Gradient-
an area of high concentration next to an area of low concentration
Low Concentration of Molecules
High Concentration of Molecules

17. Cell Transport Vocabulary
Equilibrium is when there is an EQUAL amount of molecules on each side of the membrane
There is no net movement
meaning, there is continuous
movement of molecules
back and forth through the membrane.

18. Passive Transport
Passive Transport is when molecules move from an area of HIGH concentration to an area of LOW concentration until equilibrium is reached.
Requires NO ENERGY!
Examples:
Diffusion
Osmosis
Facilitated Diffusion

19. Passive Transport
Diffusion - the process by which
molecules (“stuff”) spread from areas of high concentration, to areas of low concentration
Molecules are said to go “Down” or “with” the concentration gradient.
Requires no energy

20. What will happen when the gate is opened?
Where is the least concentration of cows?
Where is the greatest concentration of cows?

22. This process is called…
diffusion

23. Passive Transport Facilitated Diffusion
What does facilitate mean?
When substances move from high to low concentration (down the concentration gradient) using channel/carrier proteins located in membrane
Does not require energy

24. Facilitated Diffusion Animation
Click, hold, and drag slider to move forward, bckword, or slow down

25. Passive Transport A special type of diffusion is called osmosis
Osmosis- the process by which WATER molecules move from an area with a high concentration of water to an area of low concentration of water.
OR the “diffusion of water”
Requires no energy

26. Passive Transport
In Osmosis water will move in where there is a low concentration of SOLVENT, and a high concentration of SOLUTE
A solute = “stuff” (salt, glucose, food particles)
A solvent = “water”

28. Passive Transport There are three ways water can move in a solution:
Hypotonic- water moves INTO a cell and the cell swells (gets bigger)
Hypertonic – water moves OUT of a cell and the cell shrinks (gets smaller)
Isotonic- water moves into AND out of a cell at an equal rate (remember- molecules are constantly moving)

29. Passive Transport
Hypotonic -Describes a solution that is LESS CONCENTRATED (has less solute, more water)
When a cell is placed in a hypotonic solution, the cell will swell as water moves INTO the cell.

30. Passive Transport Hypotonic (continued) -
there is more solvent/less solute on the outside of the cell that the inside
The solvent (water) moves to an area of low solvent (water) concentration
The cell could burst (lyse)

31. Passive Transport
Hypertonic-- describes a solution that is MORE CONCENTRATED (has more solute, less water)
When a cell is placed in a hypertonic solution, water moves out of a cell and the cell shrinks (gets smaller)

32. Passive Transport Hypertonic (continued)
There is less solvent/more solute on the outside on the cell than the inside
The solvent (water) moves to an area of low solvent (water) outside

33. Passive Transport
Isotonic – describes a solution that is of EQUAL concentration to another
water moves into and out of the cell at an equal rate(remember – molecules are constantly moving)
No change in the size of the cell will be observed
The concentration of solvent and solute on the inside of the cell is equal to the concentration of solvent and solute on the outside of the cell

34. Practice Draw arrows to show the flow of water
Label at the top if the solution is isotonic, hypotonic or hypertonic

35. 100% distilled water Where is the greatest concentration of solvent?
Outside of the bag
Which way does the
water move?
Into the Bag
What type of solution is this?
100% distilled water
Hypotonic
selectively permeable membrane

36. 80% distilled water Where is the greatest concentration of solvent?
10% salt
90% water
In the bag
Which way does the water move?
Out of the bag
What type of solution is this?
80% distilled water
Hypertonic
selectively permeable membrane

37. 80% distilled water What happens to the bag?
90 % solvent
10% salt
80% distilled water
selectively permeable membrane

38. 80% distilled water What happens to the bag?
90 % solvent
10% salt
80% distilled water
selectively permeable membrane

39. 80% distilled water What happens to the bag?
90 % solvent
10% salt
80% distilled water
selectively permeable membrane

40. 80% distilled water What happens to the bag? The bag shrinks.
90 % solvent
10% salt
80% distilled water
selectively permeable membrane

41. Passive Transport Recap!
requires no energy
moves from high concentrations to low concentrations
Moves down the concentration gradient
Includes diffusion, facilitated diffusion and osmosis

42. Active Transport
When molecules are forced from a low concentration to a high concentration they must use active transport
Cells must transport certain amino acids, sugars, etc. into their cytoplasm from the surrounding fluid.
Some of these substances, however, are already in higher concentrations inside versus outside.
This requires energy!

43. Active Transport Opposite of Passive Transport
Forces molecules to go against the concentration gradient
Energy is provided by the ATP made in the mitochondria

44. Active Transport
Pumps allow molecules to travel against their concentration gradient
1. Sodium/Potassium Pump
For example, the sodium/potassium pump actively transports sodium molecules and potassium molecules through the cell membrane
Requires energy

45. Active Transport Na+ pumped out of a cell K+ pumped into a cell
Important because it prevents cells from bursting by lowering the sodium inside causing less water to enter through osmosis.

46. Sodium Potassium Pump

48. Proton Pump
Proton (H+) pump – forces protons out of a membrane enclosed space (organelle or cell), often to create a proton gradient down which the protons can flow back in
Why would the cell “waste” energy on a proton pump? *Because the cell needs isolated areas of the cell with different pH for particular functions; ex) lysosomes – have proton pumps to maintain a pH=5
*Because the cell only uses one ATP to pump a proton out, and that proton can be used in co-transport

49. Pumps
Co-transport – process cells use to bring large molecules, such as sugars, into a cell with a minimum amount of energy used; usually a proton and a sugar enter a double tunneled protein at the same time; the tunnel only “works” when both molecules are present

50. Active Transport
Vesicles can transport molecules across the cell membrane through:
Endocytosis- moving INTO the cell
Pinocytosis – moving a liquid into a cell
Phagocytosis – moving a solid into a cell

51. Types of Endocytosis Pinocytosis (drinking) Phagocytosis (eating)
Pinocytosis: * a process where very large (too big to go through the plasma membrane) particles are "sucked in" to a cell, forming a vacuole * "cell drinking"--uses energy (active transport)
4) Phagocytosis: * a process where a cell engulfs large undissolved particles, forming a vacuole * "cell eating"--uses energy (active transport)
Pinocytosis (drinking) Phagocytosis (eating)

53. Active Transport Exocytosis- moving OUT of the cell
Excretion – moving waste out of the cell after something is digested by a lysosome
Secretion – moving a cell product (like glucose or insulin) out of a cell

54. Active Transport Recap!
Opposite of Passive Transport
Molecules go against the concentration gradient (from low to high concentration)
Energy is provided by the ATP made in the mitochondria
Active transport can involve pumps or vesicles
Requires energy