This week in AP Biology, we started off with learning a little bit about water’s properties and specific heat, then delved deeper into the complicated world of proteins. Proteins are responsible for all life activities of the cell.
Water is special and is considered most like a “universal solvent” because not only does it exist in all 3 phases (liquid, solid and gas) at normal terrestrial conditions, but its solid form is less dense than its liquid form. This is because the hydrogen bonds are an ideal distance away from each other, as well as having very high surface tension.
Next, we focused on proteins. Proteins are made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. From these elements, amino acids are created to make up monomers inside of polymers. From what scientists know right now, there are only 21 amino acids. Every amino acid has a different function within the protein due to the different structure of the R group. The directionality of the amino acid is determined from the amino group to the carboxyl group (on opposite ends of the structure). There are 4 different types of structure within the protein.
First, there is the Primary structure. The primary structure is a peptide chain made up of amino acids bonded by peptide bonds, or covalent bonds (the strongest).
Then there is Secondary structure. This includes regular repeated 3D structures found in all polypeptide chains, with hydrogen bonding between atoms in the Carbon-Nitrogen backbone. The two different forms are the alpha helix and beta pleated sheet.
Tertiary structure is the next level up, including a 3D shape of a particular polypeptide chain (conformation). This comes from interactions between the R group atoms with other R group atoms and their environments in the cell.
Quaternary structure is the 3D shape of any protein that is made of more than one polypeptide chain, and is the only optional level of the structures. It is the overall appearance when multiple chains form a functional protein.
When proteins “denature”, it means the conformation of the structure has been altered, so therefore the function of the protein will also be altered.
ENZYMES
After learning about proteins, we discussed enzymes. Enzymes (proteins) are responsible for the reactions within the body. Most reactions occur spontaneously by bumping into each other. This requires a certain amount of activation energy, which is why if the molecules are moving faster, there will be more reactions. If the molecules are moving slower, there will be less. Introducing heat speeds up the system and therefore the reactions.
The energy can be divided into to categories; catabolic and anabolic. Catabolic is when bonds are broken down, while anabolic is when bonds are built.
Each enzyme has an active site that fits a specific substrate – this is known as the lock and key model. “Induced fit” is when the enzyme hugs the substrate tightly. The rate of enzyme reactions with their substrate is dependent on the concentration of the substrate and the enzyme, as well as the temperature. Another factor is the types of inhibitors that can appear; you can have competitive or noncompetitive/allosteric inhibitors that prevent reactions.
LABS
Finally, we did two labs that assisted in our understanding of proteins and enzyme reactions. The first we did was pretty fun, when all we did was create cheese curds from milk and vinegar and poach an egg (ours was perfect). This lab showed us how we can put chemical reactions into real life scenarios. The second lab we did was more relevant, and showed us how the process of substrate and enzyme reactions occurred. We did this in three stages, also looking at what happens when you add in inhibitors.
This week, we studied more of big idea #2, which talks about energy in order to maintain homeostasis. Now that we’ve studied the energy aspect, I am expecting to look more into maintaining homeostasis next week.
Links
AP Biology 