Understanding Homeostasis at the Cellular Level

1. Understanding Homeostasis at the Cellular Level CELL THEORY AND STRUCTURE

2. What are the 3 parts of the Cell Theory? • All living things are made of cells • Cells are the basic unit of structure and function in an organism (basic unit of life) • Cells come from the reproduction of existing cells (cell division)

3. History of Cells & the Cell Theory • In 1665,Hooke is responsible for naming cells • In 1673, Leeuwenhoek was first to view living organisms in pond water • In 1838, Schleidenconcluded that all plants were made of cells • In 1839, Schwannconcluded that all animals were made of cells • In 1855, Virchowobserved, under the microscope, cells dividing and reasoned that all cells come from other pre-existing cells by cell division

4. Remember Endosymbiotic Theory • In 1970,Lynn Margulis, provided evidence that some organelles within cells were at one time free living cells themselves – this is called Endosymbiotic Theory • Chloroplasts and mitochondria were the organelles she pointed to as evidence of this theory • Chloroplast and Mitochondria have their own DNA which is different from the DNA of the cell

5. Number of Cells • Unicellular – composed of one cell • Ex: bacteria, yeast • Multicellular - composed of many cells that may organize • Ex: butterfly, flower

6. Prokaryotes • Have a nucleoid region contains the DNA (no nucleus) • Have a cell membrane & cell wall • Contain ribosomes to make proteins in their cytoplasm

7. Eukaryotic Cell Contain 3 basic cell structures: • Nucleus (containing DNA) • Cell Membrane • Cytoplasm with organelles • Organelles have specific functions

8. Two Main Types of Eukaryotic Cells Plant Cell Animal Cell

9. Lysosome • Contain digestive enzymes • Use Active Transport to trap and break down food an worn out cell parts

10. Nucleolus • Inside nucleus • Produces the ribosomes that make proteins

11. Smooth & Rough Endoplasmic Reticulum • Smooth ER - lacks ribosomes & detoxifies poisons and synthesizes lipids • Rough ER - has ribosomes on its surface & makes proteins to EXPORT

12. Mitochondria • Site of Cellular respiration – the capturing of energy from food • Breaks down glucose to produce energy ATP

13. Chloroplast Plant Cell Organelles • Process called photosynthesis occurs here

14. Cell wall Plant Cell • Made of cellulose • Found in plant cells

15. Vacuole Plant Cell Organelles • Have a large central vacuole

16. Animal Cell Organelles • Glycogen is stored in the cytoplasm of animal cells for food energy glycogen granule

17. Animal Cell Organelles • Near the nucleus in an animal cell • Help cell divide

18. Differences between plant cells and animal cells Animal cells Plant cells Relatively small in size Relatively large in size Irregular shape Regular shape No cell wall Cell wall present

19. Differences between Plant Cells and Animal Cells Animal cells Plant cells Vacuole small or absent Large central vacuole Glycogen as food storage Starch as food storage Nucleus at the center Nucleus near cell wall

20. The Cell Membrane

21. Outside of cell Carbohydrate chains Proteins Cell membrane Inside of cell (cytoplasm) Protein channel Lipid bilayer Cell or Plasma Membrane • Composed of double layer of phospholipids and proteins • Controls what enters or leaves the cell • Surrounds outside of ALL cells

22. Semipermeable Membrane • The cell membranes of all cells are selectively permeable • This means that some materials can pass easily through the membrane • Examples: H20, CO2 and O2 • This also means that some materials cannot pass easily through the membrane • Examples: glucose and salts

23. Cell Membrane Proteins • Proteins help move large molecules or aid in cell recognition • Peripheral proteins are attached on the surface (inner or outer) • Integral proteins are embedded completely through the membrane

24. Other Functions of Plasma Membrane • Provide a binding site for enzymes • Interlocking surfaces bind cells together (junctions) • Contains the cytoplasm (fluid in cell)

25. Phospholipids • Phospholipid bilayermakes up the cell membrane • Contains a polar head (attracts H2O) and 2 non-polar fatty acid tails (repels H2O) How is a phospholipid different from a triglyceride?

26. Fluid-Mosaic Model of the Cell Fluid: individual phospholipids and proteins can move side-to-side within the layer, like a liquid. Mosaic: the pattern produced by the scattered proteins on the surface of the cell when the membrane is viewed from above.

27. Solubility of the Membrane • Materials that are soluble in lipids can pass through the cell membrane easily • Ex: Oxygen, carbon dioxide, and water

28. Cell Transport Mechanisms Passive Transport Active Transport Does require cellular energy Types: Membrane Pumps Endocytosis Exocytosis • Does not require cellular energy • Types: • Simple Diffusion • Osmosis • Facilitated Diffusion

29. Passive Transport

30. Simple Diffusion • Movement of materials from a region of high concentration to a region of low concentration • Materials are moving down/with their concentration gradient • Example: Oxygen diffusing into a cell and carbon dioxide diffusing out using kinetic energy

31. Simple Diffusion

32. Osmosis • Osmosis is the passive transport (diffusion) of water across a membrane • Moves from a region of HIGH water potential (low solute) to a region of LOW water potential (high solute)

33. Osmosis • The purpose of osmosis is to balance out the concentration of materials between the environment inside of the cell and the environment outside the cell • Water moves because the other materials cannot • This allows the cell to be in equilibrium - balance

34. Types of Solutions a Cell May be Found In • Solution - a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent). • Examples – salt water or glucose solutions; solutes are salt or glucose, solvent is water • Types of solutions: • Isotonic • Hypotonic • Hypertonic

35. Isotonic Solution 10% NaCL90% H2O ENVIRONMENT CELL 10% NaCL 90% H2O Q: What is the direction of water movement in an isotonic solution? A: No net movement (water molecules moving equally back and forth)

36. Hypotonic Solution ENVIRONMENT 10% NaCL90% H2O CELL 20% NaCL 80% H2O Q: What is the direction of water movement in a hypotonic solution? A: Water moves into the cell

37. Hypertonic Solution ENVIRONMENT 15% NaCL85% H2O CELL 5% NaCL 95% H2O Q: What is the direction of water movement in a hypertonic solution? A: Water moves out of the cell.

38. Hypertonic or Hypotonic? • Hypotonic solution will result in cytolysis – cell bursts from build up of water inside cell • Hypertonic solution will result in plasmolysis – cell membrane pulls away from the cell wall in plant, fungal or bacterial cells • Plant cells prefer a hypotonic environment • Animal cells prefer an isotonic environment

39. Label the pictures: hypotonic, hypertonic, isotonic

40. Facilitated Diffusion • Uses transport proteins to move materials from high to low concentration • Examples: Glucose or amino acidsmoving from blood stream into a cell.

41. Active Transport

42. Proteins and Cell Membrane Function • Types of Membrane Proteins: • Structural • Cell recognition • Communication • Transport: • Channel proteins are embedded in the cell membrane & have a pore for materials to cross • Carrier proteins can change shape to move material from one side of the membrane to the other

43. Channel Proteins Channel proteins act as bridges to allow materials to pass across the membrane

44. Carrier Proteins Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer

45. Protein Pumps • Cells need a steady supply of sodium (Na+), potassium (K+), calcium (Ca2+) and hydrogen (H+) in order to function correctly • Protein pumps that span the cell membrane are powered by ATP and supply these materials to the cell on demand • This requires a steady supply of ATP • Materials are moving from and area of low concentration to an area of high concentration • They are moving up/against their concentration gradient

46. Sodium Potassium Pump 3 Na+ pumped out for every 2 K+ pumped in

47. Types of Active Transport using Vesicles • Q: What is a vesicle? • A: A small bubble within a cell surrounded in its own lipid bilayer. • Q: What is the function of a vesicle? • A: Vesicles are involved in: • Metabolism • Transport of materials • Enzyme storage • Types of active transport using vesicles: • Exocytosis • Endocytosis

48. Exocytosis Exocytosis -using a vesicle to move big stuff out of the cell

49. Exocytosis • How it works: • Vesicle is formed around some sort of material made by the cell (like proteins or hormones) • Vesicle is released and travels toward cell membrane • Vesicle fuses with cell membrane • Vesicle expels materials to the outside of the cell membrane

50. Endocytosis • Large amount of materials move into the cell by one of two forms of endocytosis: • Pinocytosis- • Materials dissolve in water to be brought into cell • Called “Cell Drinking” • Phagocytosis - Used to engulf large particles such as food, bacteria, etc. into vesicles. • Called “Cell Eating” • White blood cells eat foreign substances in your body this way