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Biology 12: Biochemistry (Chapter 2)

Text:

Vocabulary:

Acid, Hydrogen Bonding, pH, solvent, temperature regulator, lubricant, dissociation, polarity, hydrophilic, hydrophobic, buffer

Goals:

1. Describe the characteristics of water and its role in biological systems

-Describe the role of water as a solvent, temperature regulator and lubricant

-Describe how the polarity of the water molecule results in hydrogen bonding

2. Describe the role of acids, bases and buffers in biological systems in the human body

-Differentiate between acids, bases and buffers

-Describe the importance of pH to biological systems in the human body

Part A: Water

1. Properties of Water Molecules

-The images of Mars’ Istok crater right highlight water erosion tracks made 500,000 years ago.

-Why is NASA so obsessed with finding evidence of water on other planets?

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-Just in case you’ve forgotten, label the water molecule right. Include charges!

-Water is a polar molecule (no, it isn’t from the Arctic). What does this mean? Hint: What do the arrows in the water molecule diagram above represent?

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*This website provides a great overview of water molecules: http://www.johnkyrk.com/H2O.html

-Examine the image right. What is occurring here?

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2. Importance of Water

-The polar nature of water molecules and H bonding affect the characteristics of water that are important to life:

a) Cohesion

-Why can you overfill a glass of water to a certain point without it overflowing?

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b) Adhesion

-Why does a meniscus form in a test tube?

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c) Surface Tension

-What is going on with the Jaguar right?

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-Explain how each of the characteristics of water above function in moving water through trees.

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d) Water Moderates Temperature

-What is the difference between heat and temperature?

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-The graph right illustrates an experiment designed to test the relative heating and cooling of water and soil. Which container contained the water? How do you know this?

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-How is the moderating effect of water important to living organisms?

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e) Water Density

-Why does ice float?

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-What would be some consequences of ice sinking if it froze?

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f) Water is the Solvent of Life

-Examine the diagram below. Identify and define the solvent, solute and solution.

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-The cytoplasm in our cells is an aqueous solution. What does this mean?

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-What happens when a solute like sodium chloride is dissolved in water?

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-What is the difference between hydrophilic and hydrophobic substances?

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-Gecko toe pads are super-hydrophobic as air bubbles are trapped between toe hairs. This results in water being repelled and the gecko being able to stick to surfaces even in damp conditions. Scientists have used this principle to develop Gecko Tape!

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-Use the cartoon right to explain the idea “Like dissolves like”.

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*Refer to the website below for more information: http://www.chemistryland.com/CHM107/Water/ WaterTutorial.htm

Part B: Acids, Bases and Buffers

-Examine the image right. What does dissociate mean?

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-Examine the beakers right. How would you describe the solutions created by the dissociation of the compounds in water?

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*Have a look at the following website to explore this idea in more detail: http://www.johnkyrk.com/H2O.html

-If you had to describe how acidic or basic lemon juice is, how would you do that? What does this description mean?

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-How much more acidic is lemon juice than human blood?

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-What is the difference in H+ ions between grapefruit and seawater?

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-Use the enzyme images right to explain the importance of pH to living organisms.

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-How is the pH in our bodies kept at an appropriate level?

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-Below are two examples of buffers in your body:

1. Phosphate buffer is found in the internal fluids of all cells.

H2PO4 H+ + HPO4 2-

2. Bicarbonate buffering system in blood maintains a constant plasma pH.

Part C: Acid Precipitation

-Remember back to Science 10, what is acid precipitation and causes it?

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-One of the negative effects of acid precipitation is ocean acidification:

-CO2 dissolves in the top layers of the ocean, mixing with H2O to create H2O3 (carbonic acid). This decreases the concentration of CO3

2- ions which are required by coral and other organisms to produce their skeletons.

-An increase in ocean pH can also cause coral’s photosynthetic partner to leave, resulting in coral bleaching and the death of coral reefs.

*View Acid Test: The Global Challenge of Ocean Acidification for more information.

*Complete Connecting the Concepts 1-25. 25 will be discussed in class and 2 you will explain to your peers.

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