Chapter 4 Study Guide Intro to Biology

Study Guide – Chapter 4 How Cells Obtain Energy 1. Explain what metabolic pathways are Metabolic pathway is a series of chemical reactions that take starting material and modify it step-by-step through a series of intermediates, eventually yielding a final product. Each reaction requires an enzyme to catalyze. The pathway takes in one or more starting molecules and, through a series of intermediates, converts them into products. Metabolic pathways can be broadly divided into two categories based on their effects. 2. Explain the difference between kinetic and potential energy - Potential energy is the type of energy that stored in an object due to its position and has the potential to do work Kinetic energy is the type of energy associated with motion. 3. Discuss how enzymes function as molecular catalysts Enzymes are the molecules that catalyze biochemical reactions. Most enzymes are proteins and perform the critical task of lowering the activation energies of chemical reactions inside the cell. Most of the reactions critical to a living cell happen too slowly at normal temperatures to be of any use to the cell. Without enzymes to speed up these reactions, life could not persist. Thus, the enzyme is a biological catalyst that accelerates a chemical reaction without altering its equilibrium. 4. Explain how ATP is used by the cell as an energy source - ATP is the energy currency of the cell, filling any energy need. It is a relatively small simple molecule, safe short-term storage product. ATP has the potential for a quick burst of energy that can be harnessed to perform cellular work. ATP can recharge once energy is spent. 5. Describe the overall result in terms of molecules produced of the breakdown of glucose by glycolysis Glucose is the source of almost all energy used by cells. Glycolysis is the first step in the breakdown of glucose to extract energy for cell metabolism. Glycolysis takes place in the cytoplasm of most prokaryotic and all eukaryotic cells. Overall, glycolysis produces two pyruvate molecules, a net gain of two ATP molecules, and two NADH molecules. 6. Describe the location and overall outcome of the citric acid cycle The citric acid cycle takes place in the matrix of the mitochondria. The overall outcome of citric acid cycle products: - CO2 is released from cells and bodies as a waste product. - ATP can be used for energy by the cell. - NADH and FADH2 go to the electron transport chain for the production of more ATP. 7. Describe the location and overall outcome of electron transport chain/oxidative phosphorylation - - Electron Transport Chain/Oxidative phosphorylation is the production of ATP by the transfer of electrons down the electron transport chain to create an H+ gradient that is used by ATP synthase to add phosphate groups to ADP molecules. It occurs at the inner mitochondrial membranes. The overall outcome: + Electrons from NADH and FADH2 dropped off at the electron transport chain. + Electrons get transferred down the electron transport chain to lower energy levels. This releases energy which is used to pump H+ across to the inter-membrane space, creating an H+ gradient. + In chemiosmosis, H+ ions returned through ATP synthase. This drives the addition of phosphate group (Pi) to join ADP molecules to make ATP. 8. Which of the following is not true about enzymes? a. They are consumed by the reactions they catalyze. b. They are usually made of amino acids. c. They lower the activation energy of chemical reactions. d. Each one is specific to the particular substrate(s)to which it binds. 9. Energy is stored long-term in the bonds of _____ and used short-term to perform work from a(n) _____molecule .a. ATP : glucose b. an anabolic molecule : catabolic molecule c. glucose : ATP d. a catabolic molecule : anabolic molecule 10. The energy currency used by cells is _____. a. ATP b. ADP c. AMP d. adenosine 11. The glucose that enters the glycolysis pathway is split into two molecules of _________. a. ATP b. phosphate c. NADH d. pyruvate 12. What do the electrons added to NAD+ do? a. They become part of a fermentation pathway. b. They go to another pathway for ATP production. c. They energize the entry of the acetyl group intothe citric acid cycle. d. They are converted into NADP. 13. Chemiosmosis involves a. the movement of electrons across the cell membrane b. the movement of hydrogen atoms across a mitochondrial membrane c. the movement of hydrogen ions across a mitochondrial membrane d. the movement of glucose through the cell membrane 14. Which of the following fermentation methods can occur in animal skeletal muscles? a. lactic acid fermentation b. alcohol fermentation c. mixed acid fermentation d. propionic fermentation 15. Does physical exercise to increase muscle mass involve anabolic and/or catabolic processes? Give evidence for your answer. Physical exercise to increase muscle mass does involve both anabolic and catabolic processes because the presence of glycogen in muscle cells as a source of glucose allows ATP to be produced during the exercise. The body cells break down sugars to provide ATP to do the work necessary for exercise, such as muscle contractions. This is catabolism. Muscle cells also must repair muscle tissue damaged by exercise by building new muscle. 16. Both prokaryotic and eukaryotic organisms carry out some form of glycolysis. How does that fact support or not support the assertion that glycolysis is one of the oldest metabolic pathways? “Both prokaryotic and eukaryotic organisms carry out some form of glycolysis”. Because nearly all of the energy used by living things comes to them in the bonds of sugar, glucose, and glycolysis is the first step in the breakdown of glucose to extract energy for cell metabolism. Glycolysis takes place in the cytoplasm of most prokaryotic and all eukaryotic cells. This fact supports the assertion that glycolysis is one of the oldest metabolic pathways because if glycolysis evolved relatively late, it likely would not be as universal in organisms as it is. It probably evolved in very primitive organisms and persisted, with the addition of other pathways of carbohydrate metabolism that evolved later. 17. We inhale oxygen when we breathe and exhale carbon dioxide. What is the oxygen used for and where does the carbon dioxide come from? Oxygen is used for respiration and releases carbon dioxide. Because when we inhale, air enters the lungs, and oxygen from the air moves in the lungs. Then the heart pumps this oxygen-rich blood from the lungs to your cells. When the oxygen-rich blood gets to the cells, the cells receive the oxygen and release the carbon dioxide. 18. When muscle cells run out of oxygen, what happens to the potential for energy extraction from sugars and what pathways do the cell use? When running out of oxygen, oxidative phosphorylation and the citric acid cycle stop, so ATP is no longer generated through this mechanism, which extracts the greatest amount of energy from a sugar molecule. Also, NADH accumulates, preventing glycolysis from going forward because of an absence of NAD+. Lactic acid fermentation uses the electrons in NADH to generate lactic acid from pyruvate, which allows glycolysis to continue, and then a smaller amount of ATP can be generated by the cell.