BIO 251 Question and Answer Updated A+ Guaranteed Test

BIO 251 Question and Answer Updated A+ Guaranteed Test Name five fundamental characteristics shared by all living organism. -CORRECT ANSWERS-1. Cells 2. Energy consumption 3. Information 4. Replication 5. Evolutionary adaptation Describe the two components of cell theory. -CORRECT ANSWERS-1. All living things are made up of cell or cells. 2. Cells come from other cells. Define energy, and describe the major forms it can take. Understand in what way chemical bonds can be considered a form of energy. -CORRECT ANSWERS-Energy is the capacity to do work or to supply heat. Potential energy- may be stored. Kinetic energy- may be available in the form of motion. When chemical bonds are formed, energy is released. The internal energy of the system goes down Explain, both in mathematical terms and in plain English, how changes in entropy and potential energy determine whether or not a reaction is spontaneous. Understand under what conditions a nonspontaneous reaction can occur. -CORRECT ANSWERS-ΔG(ibbs free energy) = ΔH (enthalpy) - T ΔS (entropy) If ΔG is negative (big loss of potential energy, and/or big gain of disorder): the reaction is Exergonic (Exit of energy). SPONTANEOUS If ΔG is positive (big gain of potential energy, and/or big loss of disorder): the reaction is Endergonic (Input of energy). NOT SPONTANEOUS Explain and give examples of why proteins are essential to cell function. -CORRECT ANSWERS--Enzyme Catalysis (chemistry) -Cell receptors (signalling and immune response) -Transport (food uptake, e.g.) -Support (cell/organism structure) -Motion (muscles, flagella) -Regulation (gene expression) Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid. -CORRECT ANSWERS-Structure: Central carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom and in the 4th position, a side group (R-Group). The side chain is the chemical identity to the amino acid and extends out from the backbone, making it possible for them to interact with each other and with water. (Visual representation: slide 4) Sketch a nucleotide, label its three basic parts, and identify the 2', 3', and 5' carbons. -CORRECT ANSWERS-A nucleotide has a sugar or deoxyribose group, a phosphate that is attached on the 5' carbon and an organic nitrogenous base which is attached to the 3' carbon. Ribose has an -OH on the 2' carbon, Deoxyribose has a H' on the 2' carbon. Describe the primary, secondary, tertiary, and quaternary structures of RNA, and explain in what ways RNA differs from DNA. -CORRECT ANSWERS-RNA's primary structure consists of a sequence of nitrogencontaining bases that contain information in the form of a molecular code. Its secondary structure includes short double helixes and structures called hairpins that holds RNA strands together. Its tertiary and quaternary structures that fold secondary structures into complex shapes or hold different RNA strands together. RNA has Uracil instead of Thymine, it is single stranded, its ribose has an extra -OH group, and it acts as a transcript of DNA expression. Also, DNA does not have a tertiary and quaternary structure. Explain why and how the secondary structure of DNA allows organisms to store and copy information. - CORRECT ANSWERS-Complementary base pairing allows each strand of a DNA molecule to be copied exactly, producing two daughter molecules. DNA's primary structure serves as a mold or template for the synthesis of a complementary strand and DNA contains the information required for a copy of itself to be made Explain why RNA, and not DNA, was probably the first self-replicating molecule, and describe at least one piece of experimental evidence that supports this hypothesis. -CORRECT ANSWERS-To make a copy of itself, the first living organism had to provide a template that could be copied and catalyze polymerization reactions that would link monomers into a copy of that template. RNA is capable of both. One experimental evidence is by Wendy Johnston and David Bartel. They found that ribozymes isolated in each round are copied, the molecules that result are not identical in terms of their primary sequence because mutations were introduced during the copying step. By isolating the best enzyme and copying them in the next round, they continually selected ribozymes that were more efficient. This was to mimic the process of natural selection List the features shared by all carbohydrates. -CORRECT ANSWERS-A molecule made up of a bunch of carbon, hydrogen, and oxygen. These atoms are arranged in a few specific ways: they have a carbon atom that's bonded to a carbonyl group (>C=O), several hydroxyl functional groups (-OH), and many C-H bonds. Sketch several representative monosaccharides, illustrating three ways in which monosaccharides can differ from one another. -CORRECT ANSWERS-Monosaccharide have a carbonyl group at various locations , several hydroxyl functional groups at various locations, and many carbon-hydrogen (C-H) bonds (energy). Linear form, ring form, alpha vs beta form. Give examples of the four major functions that carbohydrates can perform in cells (raw materials, structure, cell identity, and chemical energy storage). -CORRECT ANSWERS-Raw materials: Sugars frequently furnish the raw "carbon skeletons" that are used as a building blocks in the synthesis of important molecules. Amino acids use sugars as a starting point. Structure: Cellulose and chitin, along with modified polysaccharide peptidoglycan, are key to structural compounds. They form fibers that give cells and organisms strength and elasticity. Cell identity: Enormous number of structurally distinct monosaccharides make it possible for an enormous number of unique oligosaccharides to exist. As a result, each cell type and each species can display a unique identity Chemical energy storage: Kinetic energy in sunlight is converted to chemical energy stored in bonds of carbohydrates by photosynthesis. Sketch a phospholipid's molecular structure, and explain why phospholipids spontaneously form bilayers in water. -CORRECT ANSWERS-Phospholipids have polar ends and nonpolar tails. The hydrophobic tails on the phospholipid molecules react with one another, and are repelled by water. The polar head groups on the phospholipids are hydrophilic and react with water. For these reasons, the phospholipids organize themselves in such a way as to maximize the hydrophobic and hydrophilic interactions. The form that accomplishes this the best is a bilayer. Predict which way a certain substance will diffuse, given its concentration on either side of a selectively permeable membrane. -CORRECT ANSWERS-If a solution is hypertonic (the solution surrounding the cell has higher concentration of solutes) water will rush out of the cell, shrinking it. If a solution is hypotonic, (the solution surrounding the cell has less concentration of solutes) water will rush into the cell, enlarging it. If a solution is isotonic, (the concentration of solute is the same inside and outside the cell) the water stays as is. Describe at least three ways in which membrane proteins can help substances cross a cell membrane. - CORRECT ANSWERS-1. Carrier proteins are in the phospholipid bilayer (the membrane) and they transport large molecules: glucose and amino acids via the proteins by changing the shape of them to make them more easy to transport. 2. Channel proteins: Used for ions (as the membrane is polar and so cannot transport charged particles), and they can be gated and so selected about what they allow through the protein. 3. Active Transport: Using ATP (energy) to move from a low to a high concentration of solutes (with other diffusion it is from high to low diffusion) it transports molecules using carrier proteins, the only difference is the direction e.g. from a high or a low concentration. 4. Fluid mosaic model: Due to the phospholipids in the bilayer and the fluid like consistancy of the membrane, small non polar (non charged particles/molecules) can move through the membrane unaided. Define the difference between passive transport and active transport, and give examples of each. - CORRECT ANSWERS--Passive transport- movement is determined by concentration, movement from high to low. Doesn't require any energy. Oxygen and water and get into cells easily (Diffusion of oxygen into an aerobically respiring cell). -Active transport- Moving substances across a membrane against their concentration gradients (high to low). Requires energy (ATP). Example: a cell uses energy to pump out a substance already present in the extracellular fluid in concentrations higher than inside the cell Explain what molecular "zip codes" are and how they function. -CORRECT ANSWERS-Molecular "zip codes" determines where a protein should be delivered. Inside cells, materials are transported to their destinations with the help of molecular "zip codes." Describe the structural and functional importance of the cytoskeleton. -CORRECT ANSWERS-This provides a structural framework within the cell, and plays a role in cell division, movement, and transport. Explain the dynamic nature of the cell. -CORRECT ANSWERS--Lots of chemical reactions occur each second -Molecules constantly enter and exit across the plasma membrane -Products move along protein fibers The cytoskeleton continually grows and shrinks Understand the relationship between exergonic and endergonic reactions and ATP. -CORRECT ANSWERS-ATP catalyzes endergonic reactions. Example: ADP + Pi --> ATP In exergonic reactions, ATP is released. Example: ATP --> ADP + Pi Describe the four components of cellular respiration. Part 1. -CORRECT ANSWERS-Glycolysis: -starts by using ATP. -Glucose is phosphorylated to form glucose-6-phosphate. -An enzyme rearranges this to fructose-6-phosphate. -A phosphate group is added, making fructose-1,6-biphosphate. -2 ATP used before any ATP is produced -NAD+ molecules are reduced -2 ATP produced -Final reaction in the sequence produces another 2 ATP For each molecule of glucose processed, the net yield is 2 NADH, 2 ATP, 2 Pyruvate. Takes place in the cytosol. Describe the four components of cellular respiration. Part 2. -CORRECT ANSWERS-Pyruvate Processing: -Pyruvate reacts with a compound called coenzyme-A (CoA). -CoA acts as a coenzyme by transferring an acetyl group to a substrate -Pyruvate reacts with CoA to produce acetyl CoA NADH produced. Takes place in the cytosol. Describe the four components of cellular respiration. Part 3. -CORRECT ANSWERS-Krebs/Citric Acid Cycle: -Acetyl-CoA reacts with 4-carbon oxaloacetate to from 6-carbon citric acid -Two of the 6-carbons of the citric acid leave as CO2 3 NADH, 1 FADH2, 1 ATP. Takes place in the mitochondrial matrix. Describe the four components of cellular respiration. Part 4. -CORRECT ANSWERS-Electron Transport Chain: -NADH and FADH2 is oxidized to NAD+ and FADH -The electrons released by the NADH and the FADH2 is carried from one complex to another by molecule ubiquinone and cytochrome c. -Hydrogen that is also released by the oxidized NADH is pumped from the matrix, through the complex, to the intermembrane -Hydrogen protons runs the ATP synthase. The ATP synthase takes ADP and one inorganic phosphate molecule (Pi). The ATP synthase puts the ADP and the Pi together to make ATP. -The electrons are moved from one complex to another, then they are added to 2 hydrogens and 1/2O2 to make H2O. ~29 ATP Explain how cellular respiration and fermentation are regulated. -CORRECT ANSWERS-Feedback inhibition. If ATP concentrations are high, the reaction rate is lowered. ATP acts as an allosteric regulator in this case. Describe how fermentation operates in the absence of the electron transport chain. -CORRECT ANSWERS-Humans: Pyruvate accepts electrons from NADH. This process, called lactic acid fermentation forms lactate and regenerates NAD+. 2 ATP, 2 NAD+ (regenerated). Yeast: Glycolysis is used to metabolize sugar by enzymatically converting pyruvate to 2-carbon compound acetaldehyde. 2 CO2, 2 ATP, 2 NAD+ (regenerated). Explain the energy flow and conversion of photosynthesis. -CORRECT ANSWERS-1. Sunlight hits chlorophyll. When light is absorbed, electrons enter an excited state. 2A. If the excited electrons fall back into its ground state, some of the absorbed energy is released as heat and the rest as light (electro magnetic radiation). This is known as fluorescence. 2B. When a red or blue photon hits a pigment molecule in the antenna complex, the energy is absorbed and an electron enters an excited state. The energy is then passed to a nearby chlorophyl molecule and another electron is excited. This is known as resonance. 3. At the reaction center, excited electrons are transferred to a specialized chlorophyll molecule that acts as an electron acceptor. When this molecule becomes reduced, the energy transformation event that started with the absorption of light become permanent. Electromagnetic energy is transformed to chemical energy. The redox reaction that occurs results in the production of chemical energy from sunlight. 4. Electrons bind to pheophytin. The reduction of pheophytin completes the energy transformation step that started with the absorption of light in the antenna complex. Electrons that reach pheophytin are passed to an ETC in the thylakoid membrane.