Ap Bio

Topics: Oxygen, Water, Chemical bond Pages: 6 (1300 words) Published: October 8, 2013
Name: ______________________________________Date: ________________________

Student Exploration: Dehydration Synthesis

Vocabulary: carbohydrate, chemical formula, dehydration synthesis, disaccharide, glucose, hydrolysis, monosaccharide, polysaccharide, valence

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

1. If you exercise on a hot day, you need to worry about dehydration. In this context, what do you think dehydration means? When you are exercising in the heat you will sweat a lot. The sweat is water leaving your body trying to cool you down. If you don’t rehydrate yourself you could become dehydrated.

2. Astronauts and backpackers often bring dehydrated food. What do you think dehydrated food is? Dehydrated food is food that has had all of the water removed from it.

Gizmo Warm-up
What do rice, potatoes, and sugar have in common? They are all foods rich in carbohydrates. Carbohydrates are an important energy source for your body. The basic building block of most carbohydrate compounds is the molecule glucose. Using the Dehydration Synthesis Gizmo™, you will learn about the structure of a glucose molecule and how glucose molecules can be joined together to make larger carbohydrate molecules.

To begin, select the CREATE GLUCOSE tab.

1. Look at the chemical formula for glucose. How many carbon (C), hydrogen (H), and oxygen (O) atoms are found in a molecule of glucose?C:6 H:12 O:6

2. Turn on Show chemical structure. Each black sphere represents a carbon, hydrogen, or oxygen atom. The lines connecting the spheres represent chemical bonds.

A. How many black spheres are in the diagram? 24

B. How does this relate to the number of carbon, hydrogen, and oxygen atoms in the chemical formula for glucose? It is the same number as all of the carbons, hydrogens, and oxygens added up.

|Activity A: |Get the Gizmo ready: |[pic] | | |Be sure the CREATE GLUCOSE tab is still selected. | | |Build a glucose molecule | | |

Introduction: Each element tends to form a certain number of chemical bonds. This value is the valence of the element. For example, a carbon atom has a valence of four.

Goal: Construct a molecule of glucose.

1. Identify: The structure of a water molecule (H2O) can be written as H-O-H, with each dash representing a chemical bond. Count the number of bonds the oxygen and hydrogen atoms form in a water molecule.

A. What is the valence of oxygen? 2
B. What is the valence of hydrogen? 1

2. Build a model: Use the carbon, oxygen, and hydrogen atoms from the Atoms box to build a glucose molecule on the empty hexagon in the building region. Use the chemical structure in the lower right as a guide, and pay attention to the valence of each atom as you build.

Once you think you have correctly constructed the glucose molecule, click Check. If necessary, continue to modify your molecule until it is correct.

3. Make a diagram: Congratulations, you have completed a molecule of glucose! Click the COPY SCREEN button to take a snapshot of your completed molecule. Paste the image into a blank document and label the image “Glucose.” [pic]

4. Explain: How did the valence of each element help you determine the structure of the glucose molecule? The valence numbers told how many bonds could be formed, so I knew where to put each molecule.

5. Make connections: Carbon forms the backbone of every major type of biological molecule, including carbohydrates, fats, proteins, and nucleic acids. How does carbon’s high valence relate to its ability to form these large and complex biomolecules?

Carbon has a valence of four. That way it can bond...
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