1. The Cell (Plasma) Membrane
The cell membrane is made up of three organic parts: lipids, proteins, and carbohydrates. It has many parts but is still very flexible: a fluid mosaic model.

3. The Cell (Plasma) Membrane
Made of a phospholipid bilayer a double layer of lipids

6. The Cell (Plasma) Membrane
Proteins serve as channels or pumps “doors” that things can pass through

7. Transport proteins provide larger openings in the plasma membrane through which particles can pass…

8. The Cell (Plasma) Membrane
Carbohydrates act like chemical “ID tags” how cells recognize one another

9. Why is the cell membrane so important?
The membrane provides structure and controls what enters and leaves the cell.

11. Why is the cell membrane so important?
The cell membrane is said to be semipermeable, or selectively permeable, because some substances can pass through easily while others cannot.
It regulates homeostasis between the solutions on each side of the membrane.

12. Solutions, Solutes, and Concentration
A solution is a mixture of two or more substances.
Solutes are the substances dissolved in a solution.
Example: In a solution of Kool-aid, our solutes are Kool-aid mix and sugar.

13. Solutions, Solutes, and Concentration
Concentration refers to the amount of solutes dissolved in a solution.
One packet of Kool-aid mix dissolved in a glass of water is more concentrated, while one packet of Kool-aid mix dissolved in a gallon of water is less concentrated.

14. Passive Cell Transport
In passive transport, no energy is required. There are three kinds of passive transport:
Diffusion
Osmosis
Facilitated diffusion

15. Passive Cell Transport
In passive transport, no energy is required. There are three kinds of passive transport:
Diffusion
Osmosis
Facilitated diffusion

16. Passive Cell Transport: Diffusion
Diffusion is the movement of molecules from areas of to
concentration.
HIGH
LOW

18. Passive Cell Transport: Diffusion
If a substance CAN cross the membrane, it tends to move towards the area where it is LESS concentrated until the two areas reach EQUILIBRIUM (equal concentrations).
Think of people filling up a movie theater

20. Passive Cell Transport: Osmosis
Osmosis is the diffusion of WATER through a semi-permeable membrane.
Water also moves from areas of HIGH to LOW concentrations (think of a waterfall).
If a solute is too large to diffuse, water molecules will diffuse instead until the two solutions reach equilibrium.

21. Osmosis: movement (diffusion) of water / solvent

22. Passive Cell Transport: Facilitated Diffusion
Facilitated diffusion occurs when protein “doors” in the cell membrane help larger molecules move across the membrane.
Still passive transport because solutes move from high to low concentration gradients.

23. Passive, aided diffusion
A form of passive transport using transport proteins
Passive, aided diffusion

24. Passive Transport
When molecules move with the concentration gradient, it means molecules move from HIGH to LOW concentrations. This does not require energy (ATP). Think of a waterfall.
Is it easy or hard for water to flow down a waterfall? Does it take a lot of energy?

26. Types of Solutions
Hypertonic- concentration of solute outside of cell is greater than inside of cell, water flows out, cell shrivels

27. Types of Solutions
Hypotonic- concentration of solute inside cell is greater than outside of cell, water flows in, cell swells

28. Types of Solutions
Isotonic- concentration of solution is the same inside and outside of cell, water flows equally in and out, cell remains same size

31. A:
Hypertonic

32. B:
Hypotonic

33. C:
Isotonic

34. Active Cell Transport
In active transport, energy IS required.

35. Active Cell Transport
Protein pumps within the membrane “pump” molecules and solutes such as calcium, sodium, and potassium across membranes.
Changes in the shape of the protein allow molecules to move in specific directions.

36. Active Cell Transport
Endocytosis is the process of creating “pockets” in the membrane which are then pinched off and taken inside the cell.
Exocytosis is opposite process --- vacuoles within the cell merge with the cell membrane and deposit their contents outside of the cell.

37. Active Cell Transport
When cells move molecules against the concentration gradient, it means molecules move from LOW to HIGH concentrations. This does require energy (ATP). Think of paddling upstream, or trying to go up a waterfall.

39. Active Cell Transport
A lot of the energy used our cells is devoted to active transport – we need certain concentrations of molecules in order for specific parts of our bodies to function. For example, unequal concentrations of Na+ and K+ ions help our nerve cells function.

40. Active Cell Transport
Therefore, both passive and active transport help us maintain homeostasis.

41. Chemical Energy and ATP
A T P (adenosine triphosphate) is the main chemical compound in cells that stores and releases energy

42. How does it work? ADP is ATP with one less phosphate
Energy is stored in the bond between the three phosphates
ATP must lose a phosphate to become ADP

43. How does it work?
When the phosphate bond is broken, energy is released
Like breaking a glow stick or a hot/cold pack

44. How does it work?
*[ATP] breaks down to [ADP + Phosphate] and releases energy to carry out life processes

45. Why do we need ATP? ATP is “energy currency” in the cell
When ATP breaks down into ADP, it provides energy for cellular processes:
Making proteins
Energy for photosynthesis
Active transport

46. Why do we need ATP? Our cells store a limited amount of ATP
only enough for a short period of activity
cells regenerate ATP from ADP as needed
***like recharging and using a cell phone