1. Cell Size: is governed by several factors: The size of the cell is controlled by metabolic requirements.

2. DNA must be available to produce the enzymes and proteins needed for proper functioning. DNA must be available to produce the enzymes and proteins needed for proper functioning.

3. A too small cell will not have enough DNA to support life and a cell too large will need an enormous amount of DNA to carry on its functions.

4. Surface area to volume ratio: As the cell increases in size, the volume increases geometrically while the surface area increases arithmetically.

5. Eukaryotic cells cope with these problems in that they contain membrane bound organelles.

6. These organelles break up the volume of the cell performing distinct functions which cuts down on the raw materials needed.

7. Each part of the cell does not need the same material to function.

8. CytoskeletonCytoskeleton: contains microtubules and microfilaments. Cytoskeleton

9. Microtubules: straight hollow rods measuring about 25 nm. thick. Microtubules: straight hollow rods measuring about 25 nm. thick.

10.  They are constructed from a and b tubulin. They shape, support and help move organelles around the cell.

11.  They form centrioles, which are not found in plants. They have a "9 + 2 " pattern.

12. Microfilaments: are constructed of 2 interwoven pieces of actin about 7nm. in diameter.

13.  They function in muscle contraction, cytoplasmic streaming, ameboid movement, and changes in cell shape.  They function in muscle contraction, cytoplasmic streaming, ameboid movement, and changes in cell shape.

14. Cell Wall: From the cell membrane out the cell wall is as follows: Primary wall, secondary wall, and a sticky area between adjacent cells called the middle lamella

15. . In animal cells a fuzzy coat called the glycocalyx is found. This is made of sticky oligosaccharides that act as glue to keep the cells together.. In animal cells a fuzzy coat called the glycocalyx is found. This is made of sticky oligosaccharides that act as glue to keep the cells together.

16. Intercellular Junctions:

17. 1. Tight junctions. bind cells together in such a way that no material can pass through the intercellular spaces. Epithelial cells are held together by tight junctions.

18. 2. Desmosomes: These bind the cells together like rivets. They let material pass through the intracellular spaces.

19. 3. Gap Junctions: They connect cells but allow material to pass from one cell to another through the opening in the center of the joint. They are analogous to the plasmodesmata in plants. 3. Gap Junctions: They connect cells but allow material to pass from one cell to another through the opening in the center of the joint. They are analogous to the plasmodesmata in plants.

20. Cell Membrane Proteins: The proteins are of two types

21.  Integral ( passing through the width of the membrane, act as transport channels)  Integral ( passing through the width of the membrane, act as transport channels)

22.  Peripheral ( act as recognition sites ). These peripheral proteins contain carbohydrates to help in cell to cell recognition. These carbohydrates are called oligosaccharides.

23. If they bind to proteins they become glycoproteins, if they bind to lipids, they become glycolipids. If they bind to proteins they become glycoproteins, if they bind to lipids, they become glycolipids.

24.  Cholesterol molecules are found in animal membranes to help add support to its structure. The majority of the phospholipids contain unsaturated fatty acids to keep it fluid.  Cholesterol molecules are found in animal membranes to help add support to its structure. The majority of the phospholipids contain unsaturated fatty acids to keep it fluid.

25. Traffic of molecules across the membrane:

26. 1. Hydrophobic molecules (Hydrocarbons and Oxygen) can cross with ease because they can dissolve in the lipid bilayer.

27. 2. Small polar (uncharged) molecules will pass ( water and carbon dioxide).

28. 3. Large polar (uncharged) molecules will not pass ( sugar).

29. 4. Ions will not readily pass ( H+, Na+, Cl-).

30. Transport Proteins:

31. 1. Uniport - one molecule moves in only one direction.

32. 2. Symport - Two different molecules moving in only one direction.

33. 3. Antiport - Two molecules moving in opposite directions. These transport proteins work in the following ways:

34. provide a tunnel to allow material to flow through, bind to the substance and physically move it, they are specific for the substance they move. provide a tunnel to allow material to flow through, bind to the substance and physically move it, they are specific for the substance they move.

35. Diffusion and Passive Transport:

36. Concentration gradient: is a regular concentration change over a distance in a particular direction.

37. The net directional movement is away from the center of concentration.

38.  Diffusion is the net movement down the concentration gradient.

39. Diffusion is caused by the following natural occurrences: thermal motion ( movement caused by the loss of heat ), random molecular movement, and an increase in entropy of the system.

40. In a solution of many different substances each substance diffuses down its own concentration gradient independent of the others. In a solution of many different substances each substance diffuses down its own concentration gradient independent of the others.

41. Diffusion is a passive type of transport, it requires no additional energy to make it work. Diffusion is a passive type of transport, it requires no additional energy to make it work.

42.  Osmosis is diffusion of water across a biological membrane.

43. . Types of Aqueous Solutions:

44. 1.Hyperosmotic: solution with the greater concentration of solute ( salt water compared to fresh water).

45. 1. If a cell from a salt water fish is placed in a beaker of fresh water, the cell is said to be hyperosmotic to the water.

46. 1.2. Hypoosmotic: solution with a lesser concentration of solute ( fresh water compared to salt water).

47. 1.If a cell from a fresh water fish is placed into a beaker of salt water, the cell is said to be hypoosmotic to the water.

48. 1.3. Isosmotic: solutions of equal solute concentrations are said to be isosmotic.

49. 1.Water balance in a living cell:

50. 1.1. Cells placed in a hyperosmotic environment ( salt water) animal cells crenate (shrivel). Plant cells plasmolyze (shrivel).

51. 1.2. Cells placed in a hypoosmotic environment ( fresh water) animal cells lyse ( explode) and plant cell become turgid (firm).

52. 1.3. Cells placed in an isosmotic solution animal cells are normal, plant cells are flaccid (limp).

53.  Facilitated Diffusion: Passive form of transport caused by the help of carrier proteins specific for the molecules they transport.

54. Movement is always down the concentration gradient. Polar molecules and ions are usually moved in this fashion. Movement is always down the concentration gradient. Polar molecules and ions are usually moved in this fashion.

55.  Active Transport: Movement of molecules up the concentration gradient. The cell must expend its own energy to move the substances.

56.  Sodium-Potassium Pump: Antiport type molecule. It takes 3 sodium ions out of the cell for every 2 potassium ions it takes into the cell.

57. Since sodium is more abundant outside the cell and potassium inside the cell, the cell is working against the concentration gradient.

58. In order for the protein to work, it must be energized by ATP. In order for the protein to work, it must be energized by ATP.

59. As this occurs the cytoplasm generates an over all negative charge 2K as opposed to 3Na on the outside, giving the extracellular fluid a positive charge.

60.  Another example is a Proton pump that transports Hydrogen ions.

61. These are called electrogenic pumps, since they produce mild currents of electricity.

62. Chloroplasts and mitochondria use this to perform energy creating products from sunlight and macromolecules. Chloroplasts and mitochondria use this to perform energy creating products from sunlight and macromolecules..