Objective: 1. Identify and describe each of the characteristics of water and explain why that characteristic is important to living things

Transcription

1 Why is Water Important to life? Objective: 1. Identify and describe each of the characteristics of water and explain why that characteristic is important to living things

2 Living things are ~75% water. Water can absorb and store large amounts of energy (good insulator) Water allows organisms to control their temperature and transport substances (homeostasis)

3 1. Transports substances in and out of cells/around body 2. Recognizes foreign material 3. Communicates with other cells

4 1. Cohesion-(High surface tension) 2. Adhesion- (capillary action) 3. High heat of vaporization 4. Resists temperature change 5. Expands when it freezes 6. Universal solvent

5 Cohesion the attraction of water to itself Because water is a polar molecule, it easily attracts other water molecules. Surface tension Attraction of water molecules to one another causes it to act like a stretched film over the surface of the water.

6 Attraction of water to other substances The clinging of one substance to another. Capillary action movement of water up thin tubes Example plants and the movement of water against gravity!

7 It takes a lot of energy to make water evaporate. Importance: evaporative cooling as water evaporates, the surface of the liquid that remains behind cools down When sweat evaporates from skin, it draws away the heat to help cool the body. Homeostasis!

8 Water changes its temperature less when it absorbs or loses a given amount of heat. Significance Homeostasis -beneficial in helping to maintain body temperature as well Coastal areas a large body of water can absorb and store a huge amount of heat from the sun in the daytime and during the summer. At night and during the winter, the gradually cooling water can warm up the air. Example: Chicago and Lake Michigan

9 Water is less dense as a solid than a liquid, so ice floats in liquid water. When water freezes, it expands because the hydrogen bonds keep the molecules at arm s length and create a crystalline structure. Important in the fitness of the environment. If ice sank, bodies of water would freeze solid, making life impossible.

10 Solution a mixture in which all of the components are evenly distributed. Solvent dissolves the solute (water) Solute the substance that is dissolved Likes dissolve Likes Water can easily dissolve other polar substances. Nonpolar substances do not dissolve in water. Oil and water.

11 1. Explain how water is used to transport materials through a cell. 2. Predict the way water will move in three typical environmental solutions: hypertonic, hypotonic, and isotonic.

12 ocell Membrane controls what enters and leaves the cell oselectively Permeable (Semi-Permeable) oallows some materials into the cell while keeping other materials out ouseful in maintaining homeostasis (a constant internal environment.) omade of a phospholipid bilayer ostructure is a fluid mosaic- meaning can move/is flexible and consists of many things other than phospholipids like proteins and cholesterol.

13 ocells are omade up mostly of water and are surrounded by a watery environment ocytoplasm and its external environment are made up of many different solute particles dissolved in water. othe concentration of a solution is the mass of a solute in a given volume of solution. oin a solution, molecules move constantly colliding and spreading out. ohttp://highered.mcgrawhill.com/sites/ /student_view0/chapter2/animation how_diffu sion_works.html

14 o2 Mechanisms cells use to move materials: Passive transport does not require energy from the cell Diffusion is a type of passive transport Osmosis is a type of diffusion Active transport requires energy from the cell endocytosis cells move substances into the cell Exocytosis- cells move substances out of the cell

15 odiffusion the tendency of molecules to move from areas of high concentration (a lot of solute particles) to areas of low concentration (fewer solute particles.) oused to help maintain homeostasis. oeventually the molecules will reach equilibrium where the two concentrations are equal on both sides or in both areas. odiffusion of molecules across the cell membrane is a process that does not require energy. opassive transport omolecules move down a concentration gradient (from high to low concentration.) ohttp://

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17 othe diffusion of water through a selectively permeable membrane owater moves from areas of high to low concentration. oconcentration = mass of solute in a given volume of soultion oin a solution ohigh water = Low solutes olow water = High solutes owater will move across the membrane until the concentrations are equal on each side

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19 1) Isotonic o o Solutes and water are equal inside and outside of the cell. No net movement of water - water moves in and out of the cell in equal amounts.

20 2) Hypotonic o o o Low solute concentration (High water) outside of the cell. More water outside than inside the cell. Causes water to move into the cell.

21 owater entering the cell causes an increase in turgor (osmotic) pressure on the membrane. oplants can withstand this increase because they have cell walls. oanimal cells do not have cell walls, and they run the risk of bursting Lysis. osome animal cells have special organelles contractile vacuoles that pump excess water from their cells.

22 3) Hypertonic o o o High solute concentration (low water) outside of the cell. More water inside the cell than outside the cell. Causes water to move out of the cell.

23 oplasmolysis the loss of water from a cell oresults in the drop of osmotic pressure oin plant cells, the central vacuole shrinks, loses support, and begins to wilt. ohttp:// xt_from=pl&index=29 ohttp:// oanimal cells can eventually shrink and die.

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25 Label the following solutions as isotonic, hypertonic, or hypotonic. 1. A cell with 97% water is placed into an environment with 100% water. A. Hypotonic 2. A cell shrinks and becomes weak. A. Hypertonic 3. A plant cell develops turgor pressure. A. Hypotonic 4. A fresh water cell (97% water) lives in a pond that is 97% water. A. Isotonic 5. A fresh water cell (97% water) is placed into the ocean (88% water.) A. Hypertonic 6. An animal cell bursts. A. Hypotonic