Lesson 7 GRQs Cellular Respiration PDF

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Lesson 7 GRQs Cellular Respiration - process, reactants, products, etc....

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Cellular Respiration Guided Reading Qs (Do these before the Mastering Assignment.) (Reading: 6.7 – 6.14) *Note: this chapter can be dense at times. Follow the questions as you usually do to see my expectations for where you should be spending your time. Tip: Watch the BioFlix animation in the Study Area of Mastering in this chapter. Then, put it on mute and see if you can narrate it! Reading Objectives: • Describe the inputs and outputs of each three stages of aerobic respiration and compare each stage for amount of ATP made and location in the cell. • Explain why oxygen is necessary and what happens when oxygen is not available. • Explain why lactic acid or ethyl alcohol is sometimes an output of cellular respiration. 1. Stage 1 Glycolysis: (We will be sticking to overviews, i.e. I am interested in you knowing fig 6.7 A and B but NOT 6.7C). Fig 6.7A is a simplification because there are actually nine reactions all performed by various enzymes represented by the arrow. What is substrate level phosphorylation and how many ATP form in glycolysis by this? Substrate level phosphorylation is the formation of ATP by an enzyme directly transferring a phosphate group to ADP from an organic molecule. This produces 2 ATP. How many pyruvates form in glycolysis? 2 pyruvate . Each pyruvate has how many carbons? 3 carbons Electrons are passed to NAD+ which is reduced to become NADH. How many NADH form from glycolysis? 2 molecules of NADH (These will hold/shuttle electrons to the third stage.)

2. Stage 2: Pyruvate Oxidation and Citric Acid Cycle. What three mini steps occur as each pyruvate is “groomed” before the citric acid cycle-1. Pyruvate loses a carbon which is released in the form of CO2 2. Electrons reduce NAD+ to form NADH 3. A coenzyme called coenzyme A joins the two-carbon compound to form acetyl coenzyme A (acetyl CoA) As a two-carbon acetyl coA enters the citric acid cycle a series of reactions begin. Ultimately, the two carbons are released in the form of CO2. Electrons from the intermediate reactions are reduced NAD+ to form how many NADH? 3 NADH molecules. FAD is also reduced to form one FADH2. Substrate level phosphorylation forms 4 ATP. *Remember that we split glucose into two pyruvates, so everything you see in Fig 6.8 and 6.9A would be doubled. Don’t worry about Figure 6.9B. 3. Stage 3: Oxidative Phosphorylation: Stages 1 and 2 only produced a total (net gain) of 4 ATP per glucose molecule so far. (A total of 32 can be made.) Electron transport proteins (electron carriers) and ATP synthase are located where? The membrane of the mitochondria 1

Follow the electrons in Fig 6.9 as they are oxidized from NADH and FADH 2. What ultimately happens to those electrons? The electrons brought in by NADH and FADH2 from being reduced in stages 1 and 2 in cellular respiration are now being delivered to the electron transport chain. Electron carriers transport them across the membrane and eventually they reduce oxygen to make water. Besides passing electrons to each other through an electron transport chain, what else do these proteins do? (Follow green arrows). They pump hydrogen ions across the membrane (against the concentration gradient) Describe the significance of the gradient of H+? How do the H+ relate to ATP formation? Be sure to use the words chemiosmosis and ATP synthase in your answer! This high concentration gradient in the intermembrane space stores potential energy. Through the process of chemiosmosis, a hydrogen ion concentration gradient powers ATP synthase in the mitochondrial membrane and is the only place hydrogen ions can move across their membrane again. As the ions flow down the concentration gradient, they move into binding sites that cause the rotor portion of ATP synthase to spin and then turns an internal rod, which activate sites that phosphorylate ADP into ATP.

4. Scientific Thinking [6.12]: What is the difference (in terms of metabolic activity and organelles) between white fat and brown fat? Brown fat: actively burns energy and produce heat White fat: little metabolic activity Brown fat, burns fuel and produces heat but does not produce ATP. (As we would expect during cellular respiration). Up until recently, we thought only human infants had brown fat. What did the PET scans tell the scientists about the presence of brown fat in adult males? In adult females? PET scans told us that brown fat may be present in most people and when activated by the cold, the brown fat of lean people is more active and burns more calories than it does in obese people. True or false? Explain your answers. • Brown fat is activated to become metabolically active in hot weather. False – brown fat has been proven to activate in colder weather since it produces heat energy • Lean people (BMI less than 25) have more brown fat than overweight people. False – scientists found that leaner people typically had more active brown fat compared to obese people not necessarily more. How might this new information be applied to weight loss?

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Scientists predict finding new ways to activate brown fat in people can result in burning calories at a faster rate.

5. How much ATP is gained from one glucose molecule during: a. Glycolysis? 2 b. Citric Acid Cycle? 2 c. Oxidative phosphorylation? (about) 28 Some poisons block oxidative phosphorylation, yet a small amount of ATP can be made in the presence of these poisons. Explain. ATP is still created in the first two stages of cellular respiration so even without oxidative phosphorylation, ATP can still be produced during glycolysis and the citric acid cycle.

6. Fill in the blanks. Fer Fermentation mentation Pathways (Anaerobic) Anaerobic pathways operate when oxygen is absent (or limited). Glycolysis is the first stage to yield 2 ATP, 2 pyruvate, and 2 electrons, In the absence of oxygen, the reduced coenzyme used in glycolysis, acetyl CoA cannot donate its electrons to the electron transfer chain. Once it is oxidized, we call it NAD+.

7. Why do our muscle cells sometimes use lactic acid fermentation? Our muscle cells sometimes use lactic acid fermentation when the demand for ATP goes faster than the delivery of oxygen through our bloodstream. What is “regenerated” during the process that can then be used again for glycolysis? NAD+ is regenerated. NADH is oxidized back into NAD+ as pyruvate is reduced to lactate. 8. Examine fig 6.14A and B. What are the differences between lactic acid fermentation and alcohol fermentation? Lactic acid fermentation has the 2 pyruvate formed through glycolysis become 2 lactate while the alcohol has the 2 pyruvate become 2 ethanol and releases CO2. What do you think you would need to make beer/wine? You need yeast to convert the pyruvate into ethanol and CO2 and recycle NADH into NAD+. 9. Without digging into any details of Modules 6.16, use figure 6.16 to explain why food with components other than glucose can be resources for making ATP. For example, how do proteins and fats make ATP? Carbohydrates: glucose polymers so many types can be hydrolyzed to form glucose Fats: obtain hydrogen atoms and many energy rich electrons to power the process. It converts glycerol into G3P which are one of the intermediates in glycolysis. These fatty acids are broken down into things that enter the citric acid cycle as CoA. Proteins: must be digested into their amino acids and then enzymes can convert excess amino acids into intermediates of glycolysis or the citric acid cycle and their energy is harvested by cellular respiration

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