Unit 2 Reflection

This unit was about molecules. One of our first themes was matter, in which we learned about atoms, the basic unit of matter; elements, pure substances made of a single type of atom; compounds and molecules, which are formed by more than one element; and ionic, covalent, and hydrogen bonds. Another theme was water, which is polar, very attractive, and a good solvent. Also, we learned about acids, which are less than 7 on the pH scale, and bases, which are greater than 7 on the pH scale.

We also learned about macromolecules such as carbohydrates, lipids, proteins, and nucleic acids. Carbohydrates are rings of carbon, hydrogen, and oxygen, and can be monosaccharides (one-ringed), disaccharides (two-ringed), or polysaccharides (many rings). They are used as a main source of energy. Lipids are long chains of fatty acids, which can be saturated or unsaturated, and are mostly nonpolar. Some lipids, such as phospholipids, have a hydrophilic head and hydrophobic fatty acid tail. Lipids store energy, make up cell membranes, and make hormones. Proteins are made of amino acids, and can be structural proteins, which support the body, or enzymes, which speed up chemical reactions by lowering their activation energy. Nucleic acids are made of nucleotides, which are made of a sugar, phosphate group, and a nitrogen base. Nucleotides bond together in one strand to make RNA, or in two strands to make DNA, a blueprint for making proteins. ATP, another nucleic acid, is an energy transferring molecule.

We also learned that proteins (and enzymes, since enzymes are proteins), have four levels of structure and an optimal environment, which includes temperature and pH. If an enzyme is kept in an unoptimal environment for a long time, it may become denatured.

We did many labs during this unit. From these labs, I learned more about the information covered in the vodcast. For example, in our sugar lab, I learned that monosaccharides are often sweeter than disaccharides and polysaccharides. In our cheese lab, I learned that curdling agents, which are an enzyme, have an optimal environment of acidic and hot.

While many of our labs were successes and incredibly productive, the cheese lab was a setback because our data was not accurate, and did not support our claim because we made some errors during the experiment. A topic that was confusing at first was protein structure. At first, I did not understand the differences between primary and secondary structure, but now I understand that primary is the bonds between amino acids that keep them in a chain, and secondary is the bonds between amino acids that aren't necessary next to each other.



From these experiences, I learned about matter, types of bonds, properties of water, the functions and structures of different macromolecules, and enzyme structure. I also learned proper experiment procedure, and how to better follow instructions, which makes me a better student now.

I would like to learn more about different types of proteins. Since there are a limited number of amino acids, there must also be a limited number of proteins. How do the amino acids in a protein affect the protein's function? Do all proteins that have the same structure have the same function? Is the type of protein determined by the primary structure of the protein, or by all four structure?

Sweetness Lab Analysis

In this lab, we asked the question "how does the structure of a carbohydrate affect its taste?" We found that while the sweetness of monosaccharides and disaccharides varies between different carbohydrates, both monosaccharides and disaccharides are ultimately sweeter than polysaccharides. This is shown by the degree of sweetness, rated on a scale from 0 to 200, of each carbohydrate. Starch and cellulose, the two polysaccharides, both received a 0, while the monosaccharides and disaccharides all received scores higher than 0. Because monosaccharides and disaccharides received higher scores than polysaccharides, this shows that monosaccharides and disaccharides were considered sweeter than polysaccharides.



Carbohydrate structure might affect how carbohydrates are used by cells in that carbohydrates with simpler structures might be easier to use. Since polysaccharides are long chains of monosaccharides, cells might need to break down polysaccharides in order to obtain the energy, which would take longer than using a monosaccharide, which doesn't need to be broken down. Because of this, monosaccharides and disaccharides might be used for an instant boost of energy, while polysaccharides might be used for a steady amount of energy.

All of our testers gave each sample the same rating. However, this might have been because we discussed how sweet we thought each carbohydrate was before settling on a degree of sweetness number. The ratings could be different because some people may eat more sweets than others and so they cannot accurately judge sweetness since everything they eat is sweet. They could also be different because some people didn't drink water between each carbohydrate. Finally, the ratings could be different because different people could perceive carbohydrates as sweeter or less sweet than they actually are.

According to Daniel Gritzer's article, Flavor Science: How We Taste Sweet, Sour, Salty, and More, our tongues detect tastes using protein receptors. When a sweet molecule touches a sweet protein receptor, it sends a signal to our brain that says there is a sweet molecule. Because of this, tasters could rank sweetness differently because their tongues are different. Since we are all different people, it is very likely that our tongues are different and that we taste things differently. It is also probable that our protein receptors are different, or that our brains don't register the signals given by the protein receptors in the same way.

What is Biology? Collage

Jean Lab Conclusion

In this lab, we asked the question "what concentration of bleach is best to fade the color out of new denim material in 10 minutes without visible damage to the fabric?" We found that 25% bleach fades the most color out of denim jeans without fabric damage. Both 100% bleach and 50% bleach, although they faded the jeans more than 25% bleach, caused fabric damage to the denim squares. When ranking the amount of color removal for each concentration on bleach on a scale of one to ten, 25% bleach had a score of 2 for color removal. All lower concentrations of bleach had lower scores for color removal and the same score for fabric damage. Our results are also supported by the scientific method, since we followed all steps of the scientific method in our experiment. This data supports our claim because it explicitly says that 25% bleach creates the most faded jeans without fabric damage.

From left to right: 0% bleach, 12.5% bleach, 25% bleach, 50% bleach, and 100% bleach.

While our hypothesis was mostly supported by our data, there could have been errors due to a few mistakes we made in our experiment. First of all, since we gathered scissors, rulers, and markers before collecting the jeans, we were left with scrap pieces of jeans. These scrap pieces were from different jeans, and some were originally lighter than others. Because some squares were lighter than others, they may have skewed the results to be favorable towards their concentration of bleach, when, in reality, they had little color to begin with. Second, some jean squares were left in their bleach solutions for a bit longer than others. This was because it took some time to take the squares out of the petri dishes. This may have affected our data in that the time in bleach was not constant, and so the results of the experiment are inaccurate. Finally, instead of submerging the squares in petri dishes of water, we submerged them in a beaker of water. Since most of the bleach from the squares ended up in the water in the beaker, we may have unintentionally bleached some squares longer than others. This affected our data in the same way the before error did. Due to these errors, in future experiments I would recommend having more materials, so that no group is stuck with scraps. I would also recommend making the written procedures clearer, as some instructions were vague and confused our group.

This lab was done to demonstrate which concentration of bleach would fade jeans the most. This lab was also done to experience the scientific method, and see how well our group would do as a group. From this lab, I learned how to work with others in order to achieve a conclusion to an experiment, which helps me understand the scientific method. Based on my experience from this lab, I can now apply the scientific method to other experiments in the future.