March 2, 2017 Biology I CSI Worksheet 6 1. List the four components of cellular respiration, where it occurs in the cell, and list major products consumed and produced in each step. i. Hint: Think about reactants that enter each step, products that leave each step; CO2, ATP, and electron carrier production; the role of oxygen; the role of the hydrogen ion gradient; and the role of ATP hydrolysis. a. Glycolysis: Requires 2 ATP to get started, produced 4 ATP and NADH, the glucose is turned into 2 pyruvate molecules for every glucose atom. Glycolysis occurs in the cytoplasm of eukaryotes and prokaryotes. b. Pyruvate processing: Pyruvate is processed to release one molecule of carbon dioxide, and the remaining two carbons are used to form the compound acetyl CoA, NADH is also produced. Occurs in the matrix of the mitochondria or the cytoplasm of the prokaryotes. c. Citric acid cycle: Acetyl CoA is oxidized to two molecules of carbon dioxide, 3 NADH, an ATP and FADH2 is produced, the cycle runs twice for each glucose molecule oxidized. Occurs in the matrix of the mitochondria or the cytoplasm of prokaryotes. d. Electron transport and oxidative phosphorylation: Electrons from NADH and FADH2 move through a series of proteins called the electron transport chain (ETC). The energy released in this reaction is used to create a protein gradient across a membrane; there becomes a positive charge in the inner membrane of the mitochondria. This chemical potential energy is changed into kinetic energy in the ATP synthase protein. This process is known as oxidative phosphorylation. Oxygen is used and water is produced. 2. Label the fermentation diagram Fermentation occurs when there is no oxygen available to produce ATP. There is less ATP production and instead of carbon dioxide being a waste product, lactate is the waste product, which produces lactic acid.
3. Describe and illustrate what happens in the Calvin cycle and its role in photosynthesis. The Calvin cycle reduces carbon dioxide to glucose. The enzyme rubisco is essential to this reaction. It uses CO2 to go to a 3-carbon sugar. Then through the use of ATP and the reducing power of NADPH, two of the 3-phosphoglycerates combine to form glucose-3-phosphate. These are the steps that are also found in the reactions of glycolysis. Finally rubisco needs to be regenerated. It is regenerated from glucose-3-phosphate. Then the cycle begins again. 4. What happens in Photosystem II? Excited electrons from the antenna complex resonate energy to the reaction center. From there pheophytin is reduced by electrons in photosystem II. Plastoquinone (PQ) receives electrons from photosystem II and carries them across the lumen side of the thylakoid and delivers them to more electronegative molecules in the cytochrome complex. Hydrogen is stripped from the molecules on the stroma side and dropped off to the lumen side to create a high chemical potential energy. This potential energy of the hydrogen concentration is used in the ATP synthase molecule to form ATP. Very similar to the ETC in cellular respiration.
5. What happens in Photosystem I? Pigments in the antenna complex absorb photons and pass the energy to the photosystem I reaction center. Electrons are excited from the energy, the reaction center pigments are oxidized. The highenergy electrons are passed through a series of carriers inside the photosystem, then to a molecule called ferredoxin, and then to the enzyme NADP + reductase. NADP + reductase transfers two electrons to NADP + to form NADPH. This has a similar function as NADH and FADH2 produced by the citric acid cycle. NADPH allows cells to reduce carbon dioxide to carbohydrates in the Calvin cycle. 6. Define and illustrate the Z-scheme. The Z-scheme is a model for how Photosystems II and I interact. The model proposes that electrons from water are first energized by photosystem II to generate ATP and then energized again by photosystem I to reduce NADP + to NADPH.
7. What is the C4 pathway? The C4 pathway is in mesophyll cells that contain PEP carboxylase. A 3-carbon compound is fixed to PEP carboxylase to create a four carbon organic acid. The C4 pathway increases the carbon dioxide concentration. This helps improve the efficiency of the Calvin cycle. This helps the efficiency of rubisco in the Calvin cycle. It can react with either O2 or CO2, depending on concentration levels. The C4 pathway helps increase the CO2 concentration in cells that perform the Calvin cycle to increase the efficiency of the enzyme rubisco. Feedback inhibition pathways also allow for very precise control of respiration. 8. What are CAM plants and what happens inside of them? CAM occurs in plants that regularly keep their stoma closed on hot, dry days and open them on cool nights. Much like the C4 pathway the CAM pathway creates higher concentrations of carbon dioxide. The difference is that carbon dioxide is stored at night and used during the day. 9. Provide an example of a catabolic pathway and an anabolic pathway. Catabolic reactions degrade macromolecules into monomers by splitting bonds, e.g. heating a protein until it denatures into its amino acid constituents is a catabolic reaction where peptide bonds are split. Anabolic reactions synthesize macromolecules from monomers by forming bonds, e.g. a ribosome building a polypeptide chain from its amino acid constituents is performing an anabolic reaction. 10. Consider the NADH formed during glycolysis. What is the final acceptor for its electrons during fermentation? What is the final acceptor for its electrons during anaerobic respiration? Acetaldehyde during alcohol fermentation, pyruvate during lactic acid fermentation, oxygen during aerobic respiration.
11. If the following redox reaction occurred, which compound would be oxidized? Which reduced? C! H! O! + NAD! C! H! O! + NADH + H! OXIDIZED REDUCED 12. What effect would an absence of oxygen have on the process of oxidative phosphorylation? Oxidative phosphorylation would eventually stop entirely, resulting in no ATP production by this process. Without oxygen to pull electrons down the electron transport chain, H + would not be pumped into the mitochondrion s intermembrane space and chemiosmosis would not occur. 13. How do the reactant molecules of photosynthesis reach the chloroplasts in leaves? CO2 enters the leaves via stomata, and water enters the plant via roots and is carried to the leaves through veins. 14. Write a short definition of each word: a. Cytokinesis- The division of the cytoplasm to form two separate daughter cells immediately after telophase b. Chromosome- A long, threadlike DNA molecule and its associated proteins (histones) c. Chromatin- The complex of DNA and proteins that makes up a chromosome in eukaryotic organisms d. Sister Chromatids- Replicated strands of the same chromosome, joined together by cohesion, which is loaded, at the highest levels, at the centromere e. Nucleosome- The beads on a string ; a segment of DNA wound around 8 histones f. Histone- The small protein that binds to the DNA, contributing to the chromatin structure g. Centromere- The central region that joins two sister chromatids h. Centrosome- The microtubule organizing center present in the cytoplasm
15. In the light reactions, what is the initial electron donor? At the end of the light reactions, where are the electrons? The ATP would end up outside the thylakoid. The thylakoids were able to make ATP in the dark because the researchers set up an artificial proton concentration gradient across the thylakoid membrane; thus, the light reactions were not necessary to establish the H + gradient required for ATP synthesis by ATP synthase.
16. Draw the phases of mitosis. 17. Which of the following conditions will most likely prevent a cell from passing the G1 checkpoint? c. DNA is damaged 18. Many cancers are due to the failure of cells to properly regulate the checkpoint during the cell cycle. d. G1