2. 7-3 Cell Boundaries A cells survival depends on its ability to maintain homeostasis and get nutrients Homeostasis – dissolved substances are equal inside and outside the cell Cell Membrane Regulates what enters and leaves the cell Selective Permeability – the cell membrane allows some molecules into the cell while keeping others out Made of a phospholipid bilayer – two layers of phospholipids Phospholipid – lipids with a phosphate head and fatty acid tails

3. Phosphate head Fatty acid tail

4. The two fatty acid tails repel water and the phosphate heads don’t Water soluble molecules will not easily move through the membrane because they are stopped by the fatty acid tails

5. Fluid Mosaic Model Fluid because the membrane is flexible Mosaic because proteins, carbohydrates, lipids, embedded in it Transport Proteins Span the entire membrane Allow needed substances or waste materials to move through plasma membrane

7. Passive Transport Passive Transport – no energy is required to move particles across membranes by diffusion 3 Types of Passive Transport 1.Diffusion 2.Osmosis 3.Facilitated Diffusion

8. Diffusion Diffusion – net movement of particles from an area of high to low concentration Diffusion is a slow process because it relies on the random motion of molecules Dynamic Equilibrium – concentration of solutes is equal inside and outside the cell Concentration Gradient – difference in concentration of a substance across space Because molecules diffuse from an area of high to low concentration, they move with the gradient, and does not require the cell to use energy Diffusion will continue until there is no concentration gradient

9. 3 Factors That Affect Diffusion 1.Concentration – the more concentrated the substance, the more rapidly diffusion occurs 2.Temperature – increase temperature increase diffusion 3.Pressure – increase pressure increase diffusion

10. Osmosis Osmosis – the diffusion of water across a selectively permeable membrane from an area of high to low concentration Water flows to the side of the membrane where the water concentration is lower

11. Osmosis Sugar molecules

12. 3 Types of Solutions Cells Can Be In 1.Isotonic Solution The concentration of dissolved substances is the same inside and outside the cell Most solutions injected into the body are isotonic, so that cells are not damaged by the loss or gain of water The concentration of dissolved substances is in equilibrium so the cell is in homeostasis 12% H 2 O 88% NaCl 12% H 2 O

13. 2. Hypotonic Solution The concentration of dissolved substances is lower outside the cell A cell placed in a hypotonic solution, osmosis will cause water to move through the plasma membrane into the cell As water diffuses in the cell swells Cytolysis – cell swelling This is what causes plants to be firm 20% H 2 O 80% NaCl 10% NaCl 90% H 2 O

14. 3. Hypertonic Solution The concentration of dissolved substance is higher outside the cell If a cell is placed in a hypertonic solution, osmosis will cause water to leave the cell Cell will shrivel Plasmolysis – cell shrinking This is what causes plants to wilt 60% H 2 O 40% NaCl 50% NaCl 50% H 2 O

16. The cytoplasm and central vacuole shrink. The plasma membrane moves away from the wall

18. Facilitated Diffusion Cell membranes have protein channels that act as carriers, making it easy for certain molecules to cross Facilitated Diffusion – transport materials across the cell membrane by means of transport proteins from high to low concentration Common in the movement of sugars and amino acids

19. Copyright Pearson Prentice Hall Facilitated Diffusion Protein channel Glucose molecules

21. Active Transport Materials move from low to high concentration – against concentration gradient Requires energy

22. Molecule to be carried Active Transport

24. Endocytosis – A cell surrounds and takes in material from its environment. (pac-man) Phagocytosis – large solid particles taken in by endocytosis Pinocytosis – liquid particles taken in by endocytosis Exocytosis – material is released from cell. Cell excretes

25. Copyright Pearson Prentice Hall Endocytosis A process in which a cell surrounds and takes in material from its environment It is engulfed 2 Types of Endocytosis 1.Phagocytosis – large solid particles taken in 2.Pinocytosis – liquid particles taken in Exocytosis Material is released from the cell Cell excretes

27. 7-4 The Diversity of Cellular Life

28. Cell Differentiation The differences among living things arise from the ways in which cells are specialized to perform certain tasks Animal cells are specialized in many ways….

29. Red blood cells transport oxygen.

30. Cells in the pancreas produce proteins.

31. Muscle cells allow movement.

32. Guard cells in plants control the opening and closing of the stomata which allows CO 2, oxygen, water, and other gases

33. Levels of Organization The levels of organization in a multicellular organism are… Individual cells Tissues – a group of similar cells Organs – groups of tissues that work together Organ systems – a group of organs that work together

34. Levels of Organization Smooth muscle tissue Muscle cell Stomach Digestive system

35. Copyright Pearson Prentice Hall 10–1 Cell Growth

36. Surface Area to Volume Ratio Cells come in a variety of sizes Range from 2-200µm Why can’t most organisms be just one giant cell? You know the plasma membrane allows a steady supply of nutrients to enter cell and allows wastes to leave Diffusion becomes slow and inefficient as the distances become larger Cells would die before nutrients could reach them The cell cannot survive unless there is enough DNA to support the protein needs of the cell

37. Surface area to volume ratio As cell size increases its volume increases much faster than its surface area If cell size doubled the cell would require more nutrients and have more waste but the surface area would not have increased enough to get the nutrients and get rid of waste, so the cell would starve

38. Limits to Cell Growth