1. Homeostasis and Transport

2. What is homeostasis?
Homeostasis is defined as the stable internal conditions of living organisms.

3. What helps us maintain this balance?
Homeostasis is maintained by adjusting to our changing internal environments.
These adjustments are conducted by our cells.

5. Homeostasis
Our cells move molecules in and out of the cell across the membrane to maintain the desired balance.
Thermostat example

7. Two methods of transportation?
There are two methods that are used to transport molecules across the membrane
Passive transport
Active transport

8. Passive transport
Passive transport is used by cells to move molecules across the membrane WITHOUT USING ANY ENERGY from the cell.
There are three ways cells use passive transport
Diffusion
Osmosis
Facilitated diffusion

10. Diffusion
Diffusion- is the movement of molecules from an area of higher concentration to an area of lower concentration.

12. Diffusion
Molecules move DOWN THE CONCENTRATION GRADIENT from areas of higher concentration to lower in order to maintain homeostasis.
This is referred to as simple diffusion

14. Equilibrium
Without any outside influence diffusion will result in the concentration of molecules being the same throughout. This is equilibrium.
Sugar in a beaker example

17. Osmosis
Osmosis - is the process in which water diffuses across a membrane from an area of higher concentration to an area of lower concentration.
Requires no energy.

18. Osmosis
There are three different ways you can refer to a solution, all three influence the direction water will move
Hypotonic
Hypertonic
Isotonic

19. Direction of osmosis
Hypotonic situation exists when water enters the cell
This causes water to move into the cell due to the concentration gradient

21. Osmosis Hypertonic situation exists when water leaves the cell
This causes water to move outside of the cell

23. Osmosis
An Isotonic solution exists when the concentration of solutes inside the cell equal that of outside the cell
This situation results in NO net movement of water

26. Cells in hypotonic environments
Some organisms have special adaptations to help with osmosis problems
EX: paramecia
Contractile vacuole helps rid the cell of excess water by using energy to pump the water out.

27. Plant Cells
Cells expand and fill with water; the pressure exerted on cell wall is called turgor pressure

28. Water leaving the cell and reducing the pressure inside the cell is plasmolysis.
Reason for wilting plants

29. Facilitated diffusion
Facilitated diffusion occurs when a concentration gradient exists but the molecules are too large to get across the membrane.

31. Carrier proteins
Carrier proteins help these molecules across the membrane

33. Ion Channels
Ion Channels move ions such as Na+ (sodium), K+ (potassium), Ca2+ (calcium), and Cl- (chloride).
An ion channel is specific to the substance being moved. For example calcium ion channels will only move calcium ions.

34. Ion Channels
Ion channels are made of proteins in the
bi-layer.

35. Ion Channels Some channels stay open all the time.
Some channels open and close in response to certain stimuli
Stretching of the membrane
Electrical signals
Chemicals in cytosol

36. Active Transport

37. What is active transport?
Active transport is the process of moving molecules across the cell membrane against the concentration gradient
Moving molecules low concentration to high concentration.

38. Three main types of active transport
Cell membrane pumps
Endocytosis
Exocytosis

39. Membrane pump
Membrane pumps are carrier proteins located in the cell membrane that use energy to pump molecules against the concentration gradient.

40. One example of a membrane pump is a sodium potassium pump.
This pump moves potassium into the cell and sodium out of the cell.
Pumps Na+, K+ against the concentration gradient
Uses ATP to accomplish this

42. Exocytosis The second type of active transport is called exocytosis
Exocytosis is the reverse of endocytosis
Vesicle fuse with the membrane and release contents to the external environment

45. Endocytosis
The process by which cells ingest external fluid, macromolecules and large particles.
A vesicle is formed around the materials that are ingested ( a lipid bi-layer)
Two main types of endocytosis
Pinocytosis
Phagocytosis

47. Pinocytosis
Pinocytosis is the form of endocytosis involved with the transport of fluids and solutes across the membrane
A vesicle is formed in this process

48. Phagocytosis
This form of endocytosis is the process of bringing large particles or whole cells across the membrane.
Many unicellular organisms feed by phagocytosis

50. Phagocytes
Phagocytes are cells that ingest viruses and bacteria into the cell
Lysosomes then fuse with the vesicle containing the bacteria or virus and digest it before it can harm the animal