Organic Molecules and Nutrition Notes

Learning Objectives

Test unknown samples for the presence of organic molecules, specifically sugars, starch, proteins, and lipids.
Understand the utilization of indicator chemicals to identify the presence of organic compounds within food samples.
Utilize and define key scientific terms, including:
    * Carbohydrates.
    * Proteins.
    * Lipids.
    * Biuret reagent.
    * Benedict\'s reagent.
    * Brown Paper test.
    * Iodine.
    * Positive and negative standards (controls).
Gain familiarity with the processes of planting, seeds, and germination.

Introduction to Organic Molecules and Macronutrients

Organic Molecules: Described as the "molecules of life," these are intricately involved in the structure, function, and regulation of cells, tissues, and entire organisms.
Macronutrients: Nutrients required by organisms to maintain health and execute essential physiological functions.
Chemical Composition: The three primary macronutrients—carbohydrates, proteins, and lipids—will always contain $\text{carbon (C)}$ and $\text{hydrogen (H)}$ .
Functional Relationship: The specific types of organic chemicals present in various body tissues are directly related to the unique functions of those tissues.
Category Descriptions:
    * Carbohydrates: These serve as the body’s primary energy source. Examples include starch and glucose. They are commonly found in foods such as grains, fruits, vegetables, and legumes.
    * Proteins: These are essential for the building, maintenance, and repair of tissues. They also facilitate the production of enzymes and hormones. Sources include both animal and plant-based foods.
    * Lipids: These function as an energy source, provide insulation for the body, protect vital organs, and assist in the absorption of certain vitamins. They are found in animal products and some vegetables.
Health Implications: A varied diet with appropriate balances of these three macronutrients is the key to optimal health and supporting diverse bodily needs.

Indicator Chemicals and Experimental Controls

Indicator Chemicals: Substances that signal a chemical change, most often through a change in color. These are used to detect the presence or absence of specific substances.
Standards/Controls: To accurately determine if a color change has occurred, a set of standards acts as an "answer key" for the experiment.
* Positive Control: This should yield an expected positive result. For instance, if testing for protein, the positive control must contain protein to show what a positive reaction looks like.
* Negative Control: This should yield an expected negative result. It ensures the experimenter knows what a sample looks like when the target substance (e.g., protein) is absent.

Activity #1: Setting Up the "Answer Key" (Standards)

Required Bench Supplies:
    * $6$ test tubes labeled $1$ to $6$ in a rack.
    * Large beaker.
    * Reagents: Benedict’s solution, Iodine dropper bottle, Biuret solution.
    * Solutions: Glucose, Starch, Protein, and a Distilled water squirt bottle.
    * One square of a brown paper bag.
Benedict’s Test for Simple Sugars:
    * Mechanism: Reacts with monosaccharides and some disaccharides, but requires heat to function.
    * Procedure:
        * Fill a large beaker $\frac{1}{2}$ way with distilled water; heat on a hot plate at high temperature.
        * Test Tube 1 (Positive): Add $2 imes \text{transfer pipets}$ of glucose solution.
        * Test Tube 2 (Negative): Add $2 imes \text{transfer pipets}$ of distilled water.
        * Add $2 imes \text{transfer pipets}$ of Benedict’s solution to both tubes.
        * Swirl to mix and place in a boiling water bath for $2 \text{ to } 5 \text{ mins}$ .
    * Results:
        * Positive: Color change ranging from green to yellow, orange, or red.
        * Negative: No color change (remains blue).
Iodine Test for Starch:
    * Procedure:
        * Test Tube 3 (Positive): Add $2 imes \text{transfer pipets}$ of starch solution.
        * Test Tube 4 (Negative): Add $2 imes \text{transfer pipets}$ of distilled water.
        * Add $1 \times \text{dropper full}$ of iodine to both tubes and swirl.
    * Results:
        * Positive: Iodine turns black.
Biuret Test for Protein:
    * Procedure:
        * Test Tube 5 (Positive): Add $2 imes \text{transfer pipets}$ of protein solution.
        * Test Tube 6 (Negative): Add $2 imes \text{transfer pipets}$ of distilled water.
        * Add $1 \times \text{transfer pipet}$ of Biuret solution to both tubes and swirl.
    * Results:
        * Positive: Solution color changes from blue to purple.
Test for Lipids (Brown Paper Test):
    * Rationale: Fats and oils do not evaporate from brown paper; they leave a translucent oily spot.
    * Procedure:
        * Place an equal drop of water and vegetable oil on different spots of a brown paper bag.
        * Wait $15 \text{ min}$ to evaluate.
    * Results:
        * Positive (Lipids): Oily spot remains.
        * Negative (Water): The spot evaporates.

Activity #2: Testing Food Samples

Objective: Analyze commonly eaten foods to determine nutrient content.
Methodology: Solid food samples are blended into liquid form for easier testing.
Experimental Steps:
    1. Form a hypothesis regarding which organic compounds will be present in specific foods (Protein Shake, Hamburger, Tuna, Milk, Refried Beans, Peanut Butter, Wheat Pasta, Cottage Cheese).
    2. Use $3$ clean test tubes and $1$ piece of brown paper for each food sample.
    3. Follow the procedures established in Activity #1 to test for simple sugars, starch, proteins, and lipids.
    4. Compare findings with the standard controls saved from Activity #1.

Plant Growth Observations and Brassica rapa Genetics

Purpose: The study of Mendelian Genetics and observing stages of plant growth over the semester.
Species Identification: Brassica rapa, a relative of mustard known for blooming in the spring.
Development of "Fast Plants":
    * Developed by Dr. Williams at the University of Wisconsin.
    * Created for research and classroom use to allow a complete life cycle study within a single semester.
    * Selective Breeding: Through a process spanning $20 \text{ years}$ , Dr. Williams reduced the seed life cycle from $6 \text{ months}$ to just $5 \text{ weeks}$ .
Seed Characteristics:
* Seeds contain all necessary instructions and food (carbohydrates, oils, or proteins) to grow a plant before photosynthesis begins.
* Historical Case Study: Russian scientists successfully grew fertile plants from $30,000\text{-year-old}$ seeds found in fossilized squirrel burrows in Siberian permafrost.
Germination Definition: The growth of a plant embryo following a resting state, fueled by harnessed stored energy.
Germination Trigger: For many seeds, water acts as the "switch." As the seed absorbs water, cells enlarge, and the seed coat cracks.

Planting Procedure

Preparation: Obtain a green pot filled with moistened soil from the bin.
Labeling: Use label tape and a marker to indicate the lab section and an initial for identification.
Seeding: Sprinkle a "pinch" of Brassica seeds on top of the soil. They do not require deep planting.
Initial Watering: Use a water squirt bottle to moisten the top of the seeds, which helps push them down and triggers germination.
Placement: Place the pot on the light bench under the designated lab section label.

Questions and Discussion (Worksheet Content)

Q: What are the 3 main organic molecules we will be studying in this lab?
* A: Proteins, Lipids, Carbohydrates.
Q: And what are these molecules mainly composed of?
* A: Carbon and Hydrogen.
Q: What are the 3 main organic molecules' primary function in the cell?
* A: Regulation of cells.
Q: Testing for sugar—Which test tube will be used for the positive control? Negative Control?
* A: Negative will be blue; positive will turn a reddish brown.
Q: What color is the Benedict's solution?
* A: Blue.
Q: If the color of the solution did not change at all then is the solution positive or negative?
* A: Negative.
Q: What ingredient is in the test tube that tested positive for glucose?
* A: Distilled water (Note: The student response here is incorrect; glucose solution is the positive ingredient).
Q: Which test tube tested negative for glucose?
* A: Tube 2.
Q: Based on the results of the Benedict's test, glucose belongs to which group?
* A: Simple Sugars.
Q: Testing for starch—What ingredient is in the positive and negative control?
* A: Positive—starch solution; Negative—distilled water.
Q: What color is the iodine solution?
* A: Black (Note: student is describing the positive result color; iodine is naturally brownish-yellow).
Q: Which tube was positive for starch? Which was negative?
* A: Tube 3 (Positive); Tube 4 (Negative).
Q: Testing for protein—What ingredient is in the positive and negative control?
* A: Positive—Protein Solution; Negative—distilled water.
Q: What color is the Biuret solution?
* A: Blue.
Q: Testing for lipids—Describe the immediate effect of oil on brown paper.
* A: The water stays and the oil spreads.
Q: Which sample spot is positive for lipids? Which is negative?
* A: Oil (Positive); $H_2O$ (Negative).
Q: At what point does the plant become independent of stored energy reserves and dependent on light?
* A: Germination.
Q: List 3 foods you eat that are seeds or contain them.
* A: Strawberries, Cucumbers, Watermelon.
Q: What quality of seeds makes them a good food source for us?
* A: They have healthy fats and nutrients.