Organic Molecules Essay Example

prepare for the next exercise, wash and dry each test tube. The upcoming exercise is called "Lugol's Test for Starch" and its objective is to determine if all carbohydrates are polysaccharides. According to the hypothesis, a carbohydrate reacts with the reagent and changes color if it is a polysaccharide. The variables in this experiment include: - Independent variable: The type of carbohydrate - Dependent variable: Color change. Water serves as the control in this experiment.

You will need the following materials:
- 4 mL of each solution (Water, Starch, Glucose, Maltose, Sucrose, Onion Juice, Potato slice, Milk)
- 8 test tubes
- 8 pipettes
- Lugol's reagent
- Test tube rack
- Dropper.

Follow these steps for the procedure:
1. Prepare the test tubes as instructed in the procedure for the Benedict's Test.
2. Add 4 mL of each solution to their respective test tube.
3. Record the initial color of each tube's contents in a data table.
4. Add 5 drops of Lugol's reagent to each tube, mix well and immediately record any color changes that occur without applying heat to the test tubes during this process.
5. Dispose of each test tube's contents down the sink and rinse with water before washing and drying them in preparation for the next exercise.

The subsequent exercise is titled "Proteins and Amino Acids" which aims to investigate whether all organic molecules contain peptide bonds.The hypothesis states that substances without proteins do not have peptide bonds. The variables in this experiment include protein identification and a control using water to observe color changes. The materials needed for the experiment are 4 mL of each solution (Distilled Water, Egg albumin, Potato starch, Glucose, Amino acid), 5 test tubes, 8 pipettes, Biuret Reagent,

a test tube rack, and a timer. The procedure involves obtaining five clean tubes numbered from 1 to 5 and adding the specified solutions to each tube while noting their original colors. Then, one dropperful of biuret reagent is added to each tube and gently mixed with the solution for two minutes. The results are recorded in a data table to determine if there is a color change indicating the presence of proteins. In addition to this protein test, Benedict's Test for Reducing Sugars is conducted by using water as a control for comparison. Different sugars such as glucose, maltose, sucrose,onion juice,potato slice,and milk react with Benedict's reagent due to their ketone or aldehyde groups being available.However,starch does not react with Benedict's reagent as it lacks reducing sugars.

The reactions to the Benedicts reagent were observed for different substances. Onion juice demonstrated a color change due to an available ketone or aldehyde group. Similarly, the potato slice turned yellow because it contained a reducing sugar. Milk also exhibited a yellow color due to the presence of an available aldehyde or ketone group. These results supported the hypothesis that any carbohydrate with an available ketone or aldehyde group would react with the reagent. Furthermore, the results aligned with the predictions, as starch and water did not react while the other solutions did.

Some discrepancies that may have influenced the lab are that the pipettes and dropper may not have been exact. Lugol’s Test for Starch:

a) The sugars starch and maltose reacted with the reagent because they contained polysaccharides.

b) Glucose, Sucrose, Onion Juice, the Potato slice, and the milk did not react with the reagent because they

did not contain polysaccharides.

c) Results for:

i. The onion juice reacted with the reagent and turned clear orange because it contained polysaccharides.

ii. The potato slice reacted with the reagent and turned dark orange because it also contained a polysaccharide.

iii. The milk also reacted with the reagent as a result of its polysaccharides.

d) Yes, the results for each test supported our hypothesis. Each carbohydrate with a polysaccharide reacted with the reagent and changed color.
e) The results of each test did not agree with my hypothesis. I predicted that all solutions, except water, would react with the reagent.

f) The results of each test did not agree with my predictions. I predicted that all solutions, except water, would react with the reagent.

g) The broken dropper could have caused a discrepancy.

Testing for Proteins 1. This experiment demonstrates that neither glucose nor starch have peptide bonds, amino acids, or polypeptides, as they were tested for proteins and did not contain the necessary components of proteins. 2. Water was included as a control to compare it to the other substances. 3. Both egg albumin and Unknown #3 reacted with Biuret, resulting in a purplish violet color change. This color change indicates the presence of polypeptides. 4.

Liquid potato starch, Amino Acid, Unknown # 1, and Unknown # 2 did not exhibit a reaction with Biuret, resulting in the absence of a violet color. The lack of reaction was due to the absence of polypeptides. In cases where the substances were not proteins, their color remained unchanged. However, if a color change occurred, it indicated the presence of polypeptides. The outcome

of the experiment aligned with my initial prediction as substances containing proteins did undergo a color change. Possible discrepancies could be attributed to variations in the volume of the biuret reagent dispensed using the dropper and insufficient agitation during the experiment.

The analysis and post-lab questions show that when two monosaccharide groups combine with an aldehyde group to create a disaccharide, Benedict's reagent does not react. On the other hand, the biuret reagent selectively reacts with certain solutions, such as those containing peptide bonds and proteins like egg albumin, but not with free amino acids like those in solution three. Regarding the unknown solutions, solution number two consists of starch, solution number one contains glucose, and solution number three contains an amino acid.When considering meal options for breakfast, lunch, and dinner, poultry, eggs, and fish are recommended sources of protein. Milk, pasta, and beans are good sources of carbohydrates. Butter, salmon, and avocadoes are suggested choices for healthy fats. Red meat provides nutrients such as iron, zinc,vitamin B,and protein.

Humans require at least two essential fatty acids that their bodies cannot produce on their own. These essential fatty acids not only provide energy but also help prevent deficiency.

In conclusion,the presence of an aldehyde group in the reaction between two monosaccharide groups affects the reactivity of the resulting disaccharide with Benedict's reagent.The biuret reagent specifically reacts with peptide bonds found in proteins like egg albumin,but not with free amino acids.

It is important to note that solution number two contains starch,solution number one contains glucose,and solution number three contains an amino acid. To ensure a balanced diet throughout the day,it is crucial to include protein sources like eggs,fish,and poultry.Additionally,it

is recommended to incorporate carbohydrates from sources such as milk,pasta,and beans.Furthermore,it is beneficial to include healthy fats like butter,salmon,and avocadoes.Red meats should also be included for their essential nutrients including iron,zinc,vitamin B,and protein.

Obtaining at least two essential fatty acids from the diet is crucial since they cannot be produced by the body.Fatty acids like Omega 3 offer energy and aid in preventing a deficiency of essential fatty acids.