L07 GRQs - 7th GRQS UNC Chapel Hill Bio101 PDF

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7th GRQS UNC Chapel Hill Bio101...

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Cellular Respiration Guided Reading Qs (Dot he s ebe f or et heMa s t e r i ngAs s i gnme nt . ) (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? Refresh: glycolysis = the breaking down of glucose and is the first stage of cellular respiration, where 1 glucose molecule goes through 9 reactions that conclude with 2 pyruvate molecules (and also results in 2 ATP) -Substrate level phosphorylation: the formation of ATP by an enzyme directly transferring a phosphate group to ADP from an organic molecule (ex: one of the intermediates in glycolysis or the citric acid cycle) -In glycolysis, 2 ATP are made from phosphorylation

How many pyruvates form in glycolysis? _2____ . Each pyruvate has how many carbons? _3 (Glucose molecules has 6 carbons, so no carbon is created nor destroyed) __ Electrons are passed to _NAD+________ which is reduced to become NADH. How many NADH form from glycolysis? _2! (+ 2 H+)_ (These will hold/shuttle electrons to the third stage.)

2. Stage 2: Pyruvate Oxidation and Citric Acid Cycle. *Pyruvate itself does not enter the 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 (first step in which CO2 is released) ______ 2.Electrons reduce NAD+ to form _NADH_______ 3.A coenzyme called _coenzyme A___________ joins the two-carbon compound to form _acetyl coenzyme A (aka acetyl CoA) _________. (Citric Acid Cycle): 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_____. FAD is also reduced

to form one _FADH2__________. Substrate level phosphorylation forms _4?? Including Stages 1 and 2 of cellular respiration____ 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 Phosphoryation: Stages 1 and 2 only produced a total (net gain) of _4 (2 from one occurrence of glycolysis, and then each of the 2 pyruvate formed goes through a process which each creates 1, for a total of 2)__ ATP per glucose molecule so far. (A total of 32 can be made.) **note: the energy captured by both NADH and FADH2 (both of which now have high-energy electrons) in stage 1 and stage 2 is what is used to phosphorylate ADP to ATP in this stage (aka why it is called oxidative phosphorylation) Electron transport proteins (electron carriers) and ATP synthase are located where? _membrane of the mitochondria_________ Follow the electrons in Fig 6.9 as they are oxidized from NADH and FADH2. What ultimately happens to those electrons? The electrons which are brought in by NADH and FADH2, both of which GOT those electrons from being reduced in stages 1 and 2 of cellular respiration, are delivered to the electron transport chain. Electron carriers transport them across the membrane. Eventually these electrons are what REDUCE oxygen when ½ O2 joins with 2H+ to make water Besides passing electrons to each other through an electron transport chain, what else do these proteins do? (Follow green arrows). These proteins also serve as membrane transport proteins to pump H+ across the membrane (AGAINST its concentration gradient. This is active transport and powered by the energy released from electron transfers at each stage of the electron transport chain. 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! The H+ ions are stored in the intermembrane of the mitochondria. Once they are pumped by the proteins from the inner membrane into the intermembrane space, they cannot return. Therefore, the intermembrane space is hypertonic in its concentration compared to the inner and outer membranes which surround it. This inability for the H+ ions to move along their concentration gradient creates high potential energy that is “stored”. Now, ATP synthesis can take place. ATP Synthase is a remarkable molecular motor that is embedded in the inner mitochondrial membrane and that is powered by the hydrogen concentration gradient through chemiosmosis. ATP Synthase is the ONLY place that hydrogen ions can move back across the inner membrane. ATP synthase can be thought of like a water wheel driven by the flow of water, except it’s the flow of hydrogen ions. ATP synthase’s activation by the hydrogen ions causes it to at the bottom half, perform phosphorylation and turn ADP & a phosphate group into ATP!!

4. Scientific Thinking:

What is the difference (in terms of metabolic activity and organelles) between white fat and brown fat? White fat: little metabolic activity Brown fat: actively burns energy. Brown fat keeps us warm Brown fat burns fuel and produces heat but does not produce _ATP______. (As we would expect during cellular respiration). The Hydrogen ions that usually should not be able to move anywhere, instead, are able to flow in and out of membranes as their concentration gradient would want. Since there is no stored potential energy to power the ATP synthase, no ATP is created and all the energy from the burning of fuel molecules would be released as heat. 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? The PET scans told the scientists that brown fat may be present in most people (experiment done on males), and when activated by cold, the brown fat of lean individuals 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 shown to be activated by cold weather, which makes sense because its initial purpose for infants is to keep them warm by only producing heat energy and not ATP, so it does the same thing in adults – produces heat energy without ATP Lean people (BMI less than 25) have more brown fat than overweight people. False – the scientists found that people who were lean typically had more active brown fat but not necessarily less of it How might this new information be applied to weight loss? Scientists predict that finding new ways to activate brown fat in people would result in burning calories by doing nothing at a rapid rate. 5. How much ATP is gained from one glucose molecule during: a.Glycolysis? _2____ b.Citric Acid Cycle? __1 for each pyruvate, and there are 2 pyruvates, so 2 from one glucose___ 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, regardless of oxidative phosphorylation. If it is blocked by a poison, ATP can still be created through glycolysis and the citric acid cycle 6. Fill in the blanks. Fe r me nt a t i onPa t hwa ys( Ana e r obi c ) 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?

Muscle cells use lactic acid fermentation when the need for ATP outpaces or goes faster than the delivery of oxygen through the blood stream 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 6.12 A and B. What are the differences between lactic acid fermentation and alcohol fermentation? Lactic acid fermentation: the 2 pyruvate formed through glycolysis then become 2 lactate Alcohol fermentation: the 2 pyruvate formed through glycolysis then become 2 ethanol and ALSO releases CO2 What do you think you would need to make beer/wine? Yeast – yeast are single celled fungi that normally use aerobic respiration to process their food but also can survive in anaerobic conditions. Yeasts convert pyruvate to ethanol and CO2 and recycle their NADH back to NAD+ 9. Without digging into any details of Modules 6.14, use figure 6.14 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: has glucose polymers so many different types of it can be hydrolyzed to form glucose Fats: obtain many hydrogen atoms (recall shape of fats) and thus many energy rich electrons aka it has a lot of stored energy to power the process. It then converts glycerol to G3P, one of the intermediates in glycolysis. Fatty acids are broken down into things that enter the citric acid cycle as CoA. Proteins: can be used for fuel but not as commonly. To be oxidized as fuel proteins must first be digested into their amino acids. Typically, cells use these amino acids to make their own proteins. But enzymes can convert excess amino acids to intermediates of glycolysis or the citric acid cycle, and their energy is then harvested by cellular respiration....