BIO123 Lab Study Guide PDF

**Lab Exam I Study Guide** **\#1 Dialysis: Osmosis and Diffusion Lab** - Recall that the Fluid Mosaic Model uses a phospholipid bilayer as its foundation. In this bilayer, the polar phospholipid heads face out, and the nonpolar phospholipid tails avoid water by remaining in the inter...

**Lab Exam I Study Guide** **\#1 Dialysis: Osmosis and Diffusion Lab** - Recall that the Fluid Mosaic Model uses a phospholipid bilayer as its foundation. In this bilayer, the polar phospholipid heads face out, and the nonpolar phospholipid tails avoid water by remaining in the interior of the membrane. The membrane interior is nonpolar, so nonpolar molecules move across readily. - Water will flow from an area of high water potential to an area of low potential. - The speed at which diffusion occurs is influenced by the size, polarity, solubility, and especially by the concentration gradient of molecules. - Dialysis tubing has pores of a certain size, consequently, the size of a molecule is a determining factor in whether the molecule will be able to pass through dialysis tubing. Larger molecules may be too large to diffuse through the tubing.\ A great difference between the concentration of a substance outside of the dialysis tubing compared to its concentration inside the dialysis tubing is known as a steep concentration gradient. The steeper the concentration gradient, the faster diffusion will occur. - **Why does Iodine turns blue-black in the presence of starch?** - Diffusion is the movement of material from high concentration to low concentration. Osmosis is a specific type of diffusion. Osmosis specifically refers to the flow of a solvent (usually water) from high to low concentration. - Tonicity refers to solute concentration, but water concentration can be inferred from tonicity. When is the cell hypertonic? Hypotonic? And Isotonic? - Osmosis is the movement of a solvent from high to low concentration. - For our purposes in a lab, we can visualize the solute and the water in a beaker make up 100% of what is contained in the beaker. If we increase the amount of solute, the proportion of water would decrease. Solute concentration and water potential are inversely proportional. As solute increases, water potential decreases. - Water flows from high water potential to low water potential. - Tonicity refers to solute concentration, but water concentration can be inferred from tonicity. Solutes will not move through the dialysis membranes, but water will move through and will cause a change in the appearance of the cell. In a hypertonic environment, there is more solute and less water. Water will move from a higher concentration inside of the cell to a lower concentration outside of the cell, causing the cell to shrink. - As molecular weight increases, the rate of diffusion decreases. The solute that has the lowest molecular weight, it will move faster than the other substances. - Heat is the cause of the random pattern of the Brownian movement. - Tonicity refers to solute concentration, but water concentration can be inferred from tonicity. Hypertonic solutions cause cells to shrink because there is proportionally less water (and more solute) present in the environment than there is inside the cell. Through osmosis, the water would move from high to low concentration. Due to the cell wall, a plant cell would shrink, but a decrease in size would occur inside of the strong cell wall. - Diffusion is the movement of material from high to low concentration. This will occur until a uniform distribution of the material is present. - Permeability refers to the possibility that materials will move through a membrane. If a membrane allows some materials through but not others, it is called semi-permeable, or differentially permeable. - Just as the cell membrane is differentially permeable, dialysis tubing is differentially permeable. That shared property makes dialysis tubing a good model for a cell membrane. - Kinetic energy is the energy of movement. - Both the cell membrane and dialysis tubing exhibit semi-permeability. **Lab\#2 Enzyme Properties** **Catalase Enzyme (Peroxidase)** - The active site is part of the enzyme structure. - **How does Altering any of the following variables may make an enzyme function less than optimal?**pH, Temperature, Concentration of enzyme, Concentration of substrate - Recall that enzymes are an important class of protein. As such, the building blocks for enzymes are amino acids. - Enzymes speed up reactions by decreasing the energy expenditure necessary for the reaction to occur. - Enzymes speed up the rate of reaction. - Competitive inhibitors bind to the active site of an enzyme, while noncompetitive inhibitors bind to the enzyme at a location other than the active site. - Guaiacol is an indicator for enzymatic activity. It turns from colorless to Amber brown when peroxidase is active. - As the reaction rate increases, eventually all available substrate molecules will be bound to enzymes, or all available enzymes will be bound to substrate. The reaction will be substrate-limited or enzyme-limited. When all available molecules of either enzyme or substrate are bound, saturation occurs, and at this point the reaction rate will level off. To keep increasing the reaction rate, the levels of available substrate or enzyme must increase. In the above example, additional enzyme was added, so substrate must have been the limiting factor. - Although nonprotein enzymes exist, most are protein-based. - The suffix -ase is a reference to an enzyme. - Energy of activation is the energy requirement that a reaction must overcome to change substrate into product. - Denaturation refers to the irreversible destruction of the enzyme structure. **Lab\#3 Photosynthesis** - R~f~ = distance that the pigment moved divided by the distance from pigment origin to the solvent front. Chlorophyll a and chlorophyll b are primary photosynthetic pigments, while carotene and xanthophyll are accessory pigments. - Fluorescence occurs when an electron that has temporarily moved to an outer, higher-energy orbital falls back toward the atomic nucleus. When this occurs, the electron releases its energy as a photon. - Chlorophyll absorbs wavelengths of light that are used in photosynthesis. Wavelengths that are not used are reflected. - Chlorophyll is the primary photosynthetic pigment, as the energy it absorbed is directly used for photosynthesis. Xanthophyll, carotene, and phycobilin are accessory pigments. - Accessory pigments absorb a wider range of wavelengths of light compared to chlorophyll. Additionally, accessory pigments transfer their absorbed energy to chlorophyll. - When chlorophyll production stops as leaves die in fall, underlying accessory pigments are visible for a brief period of time as the trees shed their leaves. - Chromatography is the process of separating the components of a sample. - Carbon dioxide is a necessary ingredient for photosynthesis. - Photosynthesis produces glucose, which is a monomer. Glucose, as a monomer, can be assembled into different polymers, one of which is starch. - Without pigmentation in the form of chlorophyll, the plant would be unable to carry out photosynthesis and would be unable to survive. - As long as the light reactions occur, ATP and NADPH would be produced, water would be required, and oxygen would be released. If the dark reactions did not occur, carbon dioxide would not be fixed into glucose. - What happens when an electron falls to a lower energy level in the plant photosynthetic pigment. - Fluorescence occurs when an electron is released from a higher energy level. - Chlorophyll fluorescence is in red, other pigments undergo fluorescence in different colors. - Energy used in photosynthesis is channeled into the production of ATP, NADPH, and eventually glucose. - An additional light source is needed to visualize fluorescence. - Size and solubility will determine how quickly a pigment moves in chromatography. - The solvent is supposed to migrate up the paper, and as it does so it will carry the pigments with similar solubility with it. If the plant extract is below the solvent, pigments with a similar solubility to the solvent will dissolve. Since the solvent is nonpolar, the nonpolar pigments would dissolve. - formula20.mml= distance the pigment moved divided by distance the solvent moved. - Since the solvent is nonpolar, the nonpolar pigments will move farthest along with the solvent. Smaller molecules will move faster than larger molecules. - Don't contaminate the chromatography paper with your finger, only tough it from the side, because finger oils will be absorbed by the paper chromatogram and can alter the path of migration for the plant pigments.