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Cycling of Matter in Living Systems 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. - Louis Pasteur (1822-1895) developed a swan-neck flask and through experiments disproved abiogenesis once and for all (p.259) - Biogenesis – the theory that living organisms could only come from other living organisms - Rudolf Virchow (1821-1902) Abiotic – non-living Biotic - living 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) studying plant cells observed a nucleus in all cells 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 Assignment - Page 265 #1-6 (copy question or complete sentences) Cells and Technology - Simple microscopes used only one lens and were used early in science - Compound Light microscopes first designed by Janssen (1580-1638) had two lens and can magnify to 2000x - Electron Microscopes use a beam of electrons instead of light and can magnify up to 1.2 million times - 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 - 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 Assignment: Label the parts of a microscope (p. 508) Lab – take 2 different slides and sketch the samples on low, medium and high power. 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 - 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 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 - 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 Assignment - Page 276 #1-5 (copy question or complete sentences) Finish p. 286 key terms and hand in. Read pages 277 –281 *In your notes sketch the cell and label the parts of the cell** “BOTH ANIMAL and PLANT” do: p. 286 – key terms p. 284 #1- 6 p. 285 (b, e, i, k) Cell Structure The 3 main parts of a cell are: 1. Cell membrane 2. Cytoplasm 3. Nucleus Cell Membrane - composed of a double layer of phospholipids – bilayer (p. 293) - proteins and other molecules are embedded between and attached to the phospholipids - the phospholipid has a head and a tail (p. 291) - the top end is hydrophilic – ‘water-loving’ - 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 - some proteins may act as attachment sites for messenger molecules like hormones. - the molecules that make up membranes are thought to be in constant motion – fluid-mosaic model - Carbohydrates – sugars attached to the membrane’s outer surface are involved with cell-to-cell communication - are thin flexible and semi-permeable Assignment: p. 286 #1-12 (copy questions) Transport Across Cell Membranes Brownian motion – particles are in constant motion – the motion is random, in a straight line Passive Transport - Molecules move without using energy - 3 types: 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 equilibrium occurs. o occurs faster the higher the temperature o always moves with the concentration gradient (from high to low concentration), faster the greater the difference in concentration o oxygen and carbon dioxide easily diffuse through cell membranes 2. Osmosis - is the diffusion of water from a higher concentration to a lower concentration through a cell membrane o Hypotonic solutions lose water- they have more water and less solute than surrounding solution o Hyper tonic solutions gain water – they have less water and more solute than the surrounding solution o Isotonic solutions are at equilibrium with their surroundings 3. 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 o transport proteins are membrane proteins that help move molecules across the membrane o are highly specific – only recognize certain molecules o always occurs with the diffusion gradient Active Transport - requires energy - may move molecules against the concentration gradient - moves larger molecules Endocytosis (p. 304) - 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 - pinocytosis –when cells ‘drink’ taking in droplets of fluid - membrane proteins assist in this process – receptormediated endocytosis – eg cholesterol Exocytosis (p. 305) - 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 Assignment: p. 316 – key terms Read pages 306 – 307 Questions pg 307 #1- 4 (copy question) p. 316 – key terms 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 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 - 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 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 - 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 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 - 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 - 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 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. In mature plants most xylem cells are dead They form hollow tubes consisting only of cell walls The cells are connected end to end – xylem vessels Phloem cells transport the sugars produced during photosynthesis from the leaves to all parts of the plant Phloem vessels are living cells. Assignment: p. 330 #1 p. 340 #1 p. 350 – key terms 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 - root pressure is the turgor pressure inside the root xylem - this pressure only accounts the movement of water a few meters up a plant - transpiration from the leaves pulls the water up Sugar - sugars produced by photosynthesis provide energy for the whole plant - Phloem vessels transport the sugars throughout the plant 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 light more photosynthesis - the chemicals found to cause plants to grow toward the light are auxins produced in the growing tips of some plants 2. Gravitropism - is a plant’s growth response to the force of gravity - plant stems grow away from the pull of gravity called negative gravitropism. - roots show positive gravitropism 3. Nastic Response - response by plants to touch Assignment: p. 348 #1 - 3 p. 349 (b, c, e, h, i, o) p. 350 #1-3, 6 - 8 (copy questions) Cell Size and Function As an efficient, open system, the cell must be able to carry out all of the life processes. To ensure access to oxygen and nutrients, cells must minimize the distance over which substances diffuse. There is an upper limit on cell size. The relative magnitude (size) of a cell’s surface area to its volume is called its surface area-to-volume ratio. A very large cell with a very low surface area-to-volume ratio could either starve to death or be poisoned from the build up of its waste – such a cell would not survive. Thus, the higher the surface area-to-volume ratio, the more transport is possible across the cell membrane. Multi-cellular organisms (such as humans) have millions of cells. These organisms grow by adding more cells instead of simply growing larger cells (small cells are more efficient). Cell Life 1. Cell Growth 90% of a cell’s life is spent growing growth phase is called interphase during growth the cell produces organelles and cytoplasm rate of cell growth varies depending upon type of cell Metabolism is the changing of food into usable energy cells are constantly adjusting to changing conditions in order to maintain a balance. This is called homeostasis. cells in higher level organisms specialize to perform one specific task (e.g. muscle cells) 2. Division of Cells – Mitosis 10% of life is spent dividing as cells get larger, the surface area to volume ratio becomes too large and cells have difficulty feeding themselves Mitosis = division of the DNA two daughter (identical) cells are formed from the mother cell Mitosis or Cell Division There are 5 stages of the life of a cell 1. Interphase – cell grows 2. Prophase nuclear membrane disappears chromosomes condense and become visible 3. Metaphase duplicated chromosomes line up on both sides of the cell 4. Anaphase individual chromosomes move to each end 5. Telophase the cell begins to divide nuclear membranes reforms around chromosomes two identical daughter cells are produced Assignment: p. 356 #1-7, 9, 11, 14, 15, 17, 19, 20 Complete sentences or Copy question first.