Cellular Transport And the Cell Cycle

1. Cellular Transport And the Cell Cycle

2. Diffusion • Diffusion is the movement of particles from a region of high concentration to an area of lower concentration • At all temperatures above absolute zero, the individual atoms that constitute any substance are always in movement. The amount of this movement is what constitutes temperature itself.

3. Particles of a substance will move from a region of high concentration to a region of lower concentration. The difference in concentration of atoms is know as a concentration gradient As particles move in a given area, an equilibrium is reached where the space between the particles becomes fairly uniform. This equal distribution of atoms is called dynamic equilibrium Diffusion Cont.

4. Selective Permeability • Membranes are selectively permeable, or semi-permeable which means that only some substances can pass through, but not others. • It’s kind of like a screen door..

5. Membrane Structure and Function

6. Membrane Function • Membranes organize the chemical activities of cells. • The outer plasma membrane • forms a boundary between a living cell and its surroundings • Exhibits selective permeability • Controls traffic of molecules in and out

7. Membrane Function • Internal membranes provide structural order for metabolism • Form the cell's organelles • Compartmentalize chemical reactions

8. Fluid Mosaic Model of the PM • A membrane is a mosaic • Proteins and other molecules are embedded in a framework of phospholipids • A membrane is fluid • Most protein and phospholipid molecules can move laterally

9. Membrane Structure Phospholipid Phospholipids are the major structural component of membranes.

10. Membrane Structure All membranes are phospholipid bilayers with embedded proteins. Phospholipid Bilayer Label the: Hydrophilic heads Hydrophobic tails

11. Plasma Membrane • Made up of two layers of phospholipids • Controls what moves into and out of the cell • Selectively permeable

12. Embedded in the bilayer are proteins • Most of the membrane’s functions are accomplished by the embedded proteins. • Integral proteins span the membrane • Peripheral proteins are on one side or the other of the membrane

13. Passive Transport • Transport (diffusion) of particles across the membrane without the use of energy by the cell • Particles move from a region of high concentration to a region of low concentration across the concentration gradient

14. Passive transport by proteins Facilitated Diffusion - Transport of materials across the plasma membrane with the aid of channel proteins • Common method for moving sugars and amino acids across membranes • Driven by a concentration gradient (substances on both sides of the membrane are trying to reach equal concentration)

15. Passive Transport • Video

16. What is Osmosis? • Osmosis – Diffusion of water across a selectively permeable membrane • The plasma membrane does not limit the diffusion of water • Water moves freely through proteins called aquaporins • In a cell, water always tries to reach an equal concentration on both sides of the membrane

17. What Controls Osmosis? • Concentration gradient - Unequal distribution of particles

18. Cells in an Isotonic Solution • Isotonic Solution – when the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside of the cell • Equal movement of water into and out of the cell, cell stays the same size

19. Cells in a hypotonic solution • Hypotonic solution – when the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell • Water is pulled into the cell, the cell swells and the internal pressure increases

20. Cells in a hypertonic solution • Hypertonic Solution – where the concentration of dissolved substances outside the cell is higher than the concentration inside the cell. • Water moves out of the cell, the cell shrinks, and internal pressure decreases

21. Water moves into a cell placed in a ___________________ solution. • Osmotic • Hypertonic • Isotonic • Hypotonic

22. Water moves out of a cell if it is placed in a _______________ solution • Hypotonic • Hypertonic • Isotonic • Passive

23. A cell moves particles from a region of lesser concentration to a region of greater concentration by _________________. • Facilitated Diffusion • Passive Transport • Osmosis • Active Transport

24. If a cell is placed in salt water, water leaves the cell by _____________. • Osmosis • Diffusion • Active transport • Phagocytosis

25. After viewing the recipe above, explain the role of osmosis in making pickles. Be ready to share your answers!

26. Active Transport • Cells can move particles from a region of low concentration to a region of high concentration, but it takes ! • Active Transport – movement of materials through a membrane against the concentration gradient energy

27. Active Transport Cont. • Proteins in the cell membrane (Carrier proteins) bind with particles of the substance. When the right molecule binds to the right carrier protein, ATP allows the carrier protein to change shape so that the particle can be moved to the other side of the membrane

28. Examples of Active transport

29. Transport of Large Particles • Some cells can take in large molecules, groups of molecules, or even whole cells • Endocytosis – process by which a cell engulfs a material and forms a vacuole inside of the cell • Exocytosis – expulsion or secretion of materials from the cell • Used to get rid of waste, secrete hormones • Both endocytosis and exocytosis require cellular energy (Active transport)

30. Endocytosis

31. Exocytosis

32. Endocytosis and Exotytosis • Use the play dough to model the processes of endocytosis and exocytosis. Be able to explain the process. When you have finished, wait for Mrs. Johnson to come and check your work and hear your explanation.

33. Active Transport • Video

34. Release of waste or large cell products from inside to outside of cell _____________________. • Endocytosis • Exocytosis • Osmosis • Facilitated Diffusion

35. Type of cell transport which requires energy from the cell. • Osmosis • Facilitated Diffusion • Active Transport • Passive Transport

36. Active Transport is to carrier protein as _____________ is to channel protein. • Osmosis • Endocytosis • Exocytosis • Facilitated Diffusion

37. When cell engulfs a large particle and forms a vacuole inside the cell _____________________. • Endocytosis • Exocytosis • Osmosis • Facilitated Diffusion

38. Term for “cell eating” • Osmosis • Exocytosis • Pinocytosis • Phagocytosis

39. Cells come in different sizes • Red blood Cells = 8 µm • Some nerve cells can be up to 1mm in length • The yolk of an Ostrich egg measures 8cm • Most living cells are between 2 and 200 µm • Given the wide range of cell sizes, why can’t most organisms be just one giant cell?

40. What limits cell size? • Diffusion • Diffusion is fast and efficient over short distances but slow and inefficient over larger distances • a mitochondrion at the center of a hypothetical cell with a diameter of 20 cm would have to wait months before receiving molecules entering the cell

41. What limits cell size? cont. • DNA • The nucleus contains blueprints for the cell’s proteins (proteins are used throughout the cell by the organelles) • There is a limit as to how quickly the DNA (blueprints) can be copied • The cell can’t survive unless there is enough DNA to support the protein needs of the cell • Some large single celled organisms have developed more than 1 nucleus

42. What limits cell size? Cont. • Surface area to volume ratio • As cell size increases, its volume increases faster than its surface area • If cell size doubles, the cell would require eight times more nutrients and would have eight times more waste to excrete. The surface area would increase only by a factor of four. The plasma membrane would not have enough surface area for nutrients, waste and oxygen to diffuse through

43. 1cm 1cm 2cm 2cm 4cm 4cm Surface area to volume ratio Surface area = 6cm2 Volume = 1cm3 Surface area = 24cm2 Volume = 8cm3 Surface area = ?? Volume = ?? Refer to PS lab 8.1 pg 209

44. Cell Size • Video

45. The structure most responsible for maintaining cell homeostasis is the ___________. • Cytoplasm • Mitochondria • Cell Wall • Plasma Membrane

46. As a cell grows, its ___________ increases more than its ___________. • Length, volume • Width, surface area • Volume, surface area • None of these

47. Which of the following explain why a cell’s size is limited? • Volume increases faster than surface area • Surface area increases faster than volume • Homeostasis is disrupted by a cell that is too large • Both a and c

48. Limits to cell Size summary…. -The cell membrane controls what moves in and out of the cell…homeostasis -The cell membrane represents the surface area of the cell -Small cells have a greater surface area to volume ratio than larger cells…which is good. -If cells get too large: - they can’t make enough proteinto keep the cell running -diffusion is too slow so the cell won’t be able to get what it needs (food and waste) -the surface area to volume ratio decreases, which decreases the ability of the plasma membrane to do its job for the cell (the cell can’t get in enough food, oxygen… or get rid of enough waste, CO2) -Many different types of cells have found ways to become large by developing adaptations that increase their SA to V ratio and amount of DNA

49. Cell Reproduction

50. Cell Reproduction (video clip) • The cell theory states: all cells come from preexisting cells • We know that all organisms grow and change • Throughout our lives, worn-out tissues are repaired or replace by new cells • All of this occurs through Cell Division • The process by which new cells are produced from one cell • Results in two cells that are identical to the parent cell