Cycling of Matter in Living Systems

1. Unit 3 Cycling of Matter in Living Systems

2. Life from Life • -Spontaneous generation or abiogenesis –Aristotle - living organisms arose spontaneously from nonliving matter was believed for 2000 years. • - Francesco Redi (1626-1697) tested this theory with experiments – disproved abiogenesis • - With the discovery of microorganisms abiogenesis was once again accepted.

3. Life from Life (continued) • - Louis Pasteur (1822-1895) developed a swan-neck flask and through experiments disproved abiogenesis once and for all. • -  Biogenesis – the theory that living organisms could only come from other living organisms Rudolf Virchow (1821-1902)

4. Developing the Cell Theory • - Robert Hooke (1635-1703) looking at cork cells under a microscope coined the term ‘cells’ • Antony van Leeuwenhoek (1632-1723) first person to describe single celled organisms - Theodor Schwann (1810-1882) studying animal cells and Matthias Schleiden (1804-1881)

5. The Cell Theory • 1. All organisms are composed of one or more cells • 2. The cell is the smallest functional unit of life • 3. All cells are produced from other cells • Work Page 265 Questions 1- 5

6. Cells and Technology • - Simple microscopes used only one lens and were used early in science • Electron microscopes use a beam of electrons instead of light and can magnify up to 1.2 million times • - Compound Light microscopes first designed by Zacharias Janssen (1580-1638) had two lens and can magnify to 2000x

7. Cells and Technology continued • Transmission electron microscope (TEM) gives a two dimensional image Scanning electron microscope (SEM) sweeps a beam of electrons over the surface to create a three dimensional image

8. Cells and Technology continued • - Confocal laser scanning microscope (CLSM) is used on thicker specimens, a laser beam is used to collect images on different planes and a computer puts the images together • - Scanning Tunnelling microscope (STM) has greater magnifying power and is used to view things like DNA

9. A Molecular World • - the genetic information in a cell is contained in the DNA molecules • - DNA subunits consist of 4 bases • o   Adenine – A • o   Cytosine – C • o   Guanine – G • o   Thymine – T

10. A Molecular World (continued) • -The order of these bases are different in every gene • Gene sequencing involves mapping the order of the gene’s bases • - Human Genome Project (HGP) was an international project to sequence all 30 000 to 40 000 human genes • -  One of the ways researchers learn more about cancer causing genes is to determine their sequences

11. Why are viruses and prions not considered living or a functional unit of life?

12. Culturing Cells • Cell culturing is a valuable technique in cancer and cell research • Isolated cells are placed in test tubes or petri dishes and supplied with all the nutrients they need for growth

13. Culturing Cells (continued) • -The generations of cells that result are called cell lines -Stem cells are cells that can divide to produce all other types of specialized cells. Most of the cells in a one week old embryo are stem cells. Most adult stem cells are in bone marrow, where new blood cells are produced Work Page 276

14. Cell Membrane • -  composed of a double layer of phospholipids – bilayer • -   proteins and other molecules are embedded between and attached to the phospholipids • -   the phospholipid has a head and a tail • the head end is hydrophilic – ‘water-loving’

15. Cell Membrane (continued) • -  the tail end is hydrophobic – ‘water-fearing’ (do not dissolve readily in water) • -  the two tail ends point to the middle – shielded from the water • -  the heads point toward the water • -  the embedded proteins move substances across the membrane and carry out chemical reactions

16. Cell Membrane (continued) •  some proteins may act as attachment sites for messenger molecules - hormones • the molecules that make up membranes are thought to be in constant motion – fluid-mosaic model • carbohydrates – sugars attached to the membranes outer surface are involved with cell-to-cell communication • are thin flexible and semi-permeable

17. Transport Across Cell Membranes • Brownian motion • particles are in constant motion • the motion is random • movement is always in a straight line • Passive Transport • molecules move without using energy • 3 types:

18. Transport Across Cell Membranes (continued) • 1.  Diffusion – net movement of molecules from an area of high concentration to an area of lower concentration • o   diffusion may occur across cell membranes • o   ends when an equilibrium occurs. • o   occurs faster the higher the temperature • o   always moves with the concentration gradient, faster the greater the difference in concentration • oxygen and carbon dioxide easily diffuse through cell membranes

19. Transport Across Cell Membranes (continued) • 1.  Osmosis • - is the diffusion of water from a higher concentration to a lower concentration through a cell membrane • ohypotonic solutions lose water- they have more water and less solute than surrounding solution • ohypertonic solutions gain water – they have less water and more solute than the surrounding solution • isotonic solutions are at equilibrium with their surroundings

20. Transport Across Cell Membranes (continued) • 1.  Facilitated Diffusion • o   glucose, ions and other substances too big to diffuse through the cell membrane must have a way to get into the cells • otransport proteins are membrane proteins that help move molecules across the membrane • o   are highly specific – only recognize certain molecules • always occurs with the diffusion gradient

21. Transport Across Cell Membranes (continued) • Active Transport  • requires energy • may move molecules against the concentration gradient • moves larger molecules

22. Transport Across Cell Membranes (continued) • Endocytosis • process that moves substances into a cell that cannot be moved by other methods •  the cell membrane folds in forming a pocket enclosing the molecule • this pinches off as a vacuole or vesicle • phagocytosis – when cell ‘eat’ large particles, eg amoeba eating or white blood cells engulfing bacteria

23. Transport Across Cell Membranes (continued) • pinocytosis –when cells ‘drink’ taking in droplets of fluid • membrane proteins assist in this process – receptor-mediated endocytosis – eg cholesterol

24. Transport Across Cell Membranes (continued) • Exocytosis • allows the materials stored in vesicles to exit the cell • opposite to endocytosis • very important to cells that specialize in the secretion of cell products – hormones and enzymes

25. Plant Cells • cells in the leaves of plants are designed to carry out different functions • the main purpose is photosynthesis –during which energy from sunlight, carbon dioxide from the air and water from the soil are combined to make glucose • glucose is important energy source for both plants and animals

26. Cellular Organization • multicellular organisms have: • 1.    a larger size • 2.    a variety of specialized cells • 3.    an ability to thrive in a broader range of environments • all of these demand organization • within a cell different functions are preformed by organelles • groups of specialized cells are called tissues

27. Cellular Organization (continued) • groups of tissues that work together for one purpose are called organs • organs working together form organ systems and many organ systems create an organism

28. Gas Exchange in Plants • the stomata in surface cells of the leaves allow gas exchange to occur • carbon dioxide, oxygen and water move in and out by diffusion • these gases then circulate to other cells through the spaces in the spongy layer

29. Gas Exchange in Plants (continued) • in woody plants lens shaped openings perforate the bark allowing direct gas exchange between the environment and the living cells just under the bark • during cellular respiration plant cells consume oxygen and produce carbon dioxide and water • during photosynthesis plants consume carbon dioxide and water and produce oxygen as waste

30. Water Loss by Plants • transpiration is the evaporation of water from the leaves of plants • water diffuses out of the stomata • guard cells can change their shape to stop the loss of water on hot days thus preventing the plants from dying due to dehydration

31. Water Loss by Plants (continued) • water moves in and out of the guard cells by osmosis • when water moves in the cells swell due to increased pressure – turgor pressure • the swollen guard cells change shape opening the stomata

32. Water Loss by Plants (continued) • when water decreases in the guard cells the cells deflate and the stomata closes   - stomata open during the day and close at night - in desert plants the stomata only open at night

33. Water Transport in Plants • Vascular plants have a system of vessels that transport water, minerals and sugars throughout the plant. • Xylem and phloem are the specialized tissues that make up the transport system • Xylem tissue transports water and minerals from the soil to the leaves

34. Water Transport in Plants (continued) • In mature plants most xylem cells are dead • They form hollow tubes consisting only of cell walls • The cells are connected end to end – xylemvessels

35. Water Transport in Plants (continued) • Phloem cells transport the sugars produced during photosynthesis from the leaves to all parts of the plant • Phloem vessels are living cells

36. Water • cohesion is the tendency for water molecules to stick together • this helps explain water moving upward in xylem vessels • adhesion is the tendency of water molecules to stick to other surfaces – the clinging of xylem sap to the xylem walls helps to prevent the sap from falling back down to the roots

37. Water (continued) • root pressure is the turgor pressure inside to root xylem • this pressure only accounts the movement of water a few meters up a plant • transpiration from the leaves pulls the water up

38. Sugars • sugars produced by photosynthesis in the palisade and spongy cell provide energy for the whole plant • phloem vessels transport the sugars throughout the plant

39. Plant Control Systems • 1.       Phototropism • the growth of a plant towards light is called phototropism • this maximizes the amount of light absorbed by plants • more lights more photosynthesis • the chemicals found to cause plants to grow toward the light are auxins produced in the growing tips of some plants

40. Plant Control Systems (continued) • 2.       Gravitropism • is a plant growth response to the force of gravity • plant stems grow away from the pull of gravity – negative gravitropism • roots show positive gravitropism • auxins also explain the growth of the plant in gravitropism

41. Plant Control Systems (continued) • 3.    Nastic Response • response by plants to touch • eg Venus Fly Trap, Mimosa