1 00:00:00,540 --> 00:00:02,310 [Instructor] Hi, we're back for part two 2 00:00:02,310 --> 00:00:04,890 of our bioenergetics lecture. 3 00:00:04,890 --> 00:00:09,030 We left off talking about how energy is produced 4 00:00:09,030 --> 00:00:10,440 by different reactions. 5 00:00:10,440 --> 00:00:15,440 And this slide is depicting some exergonic reactions 6 00:00:17,730 --> 00:00:19,410 and endergonic reactions. 7 00:00:19,410 --> 00:00:24,120 So if you recall, exergonic reactions produce energy, 8 00:00:24,120 --> 00:00:28,140 and endergonic reactions require energy 9 00:00:28,140 --> 00:00:32,310 to make them occur to produce more energy. 10 00:00:32,310 --> 00:00:37,310 So the blue gears are exergonic reactions, 11 00:00:37,950 --> 00:00:39,810 so they're gonna be producing energy 12 00:00:39,810 --> 00:00:44,700 to make these green reactions occur. 13 00:00:44,700 --> 00:00:48,750 And these green reactions are going to produce more energy. 14 00:00:48,750 --> 00:00:53,750 So in this case, we're eating some food, some carbohydrates, 15 00:00:54,210 --> 00:00:57,690 and that's producing ATP, 16 00:00:57,690 --> 00:00:59,440 which is going to then 17 00:01:00,390 --> 00:01:04,953 cause these other endergonic reactions to start. 18 00:01:11,430 --> 00:01:16,430 So the energy pathways that our body is capable 19 00:01:16,740 --> 00:01:21,630 of utilizing are aerobic, with oxygen, 20 00:01:21,630 --> 00:01:23,850 and anaerobic, without oxygen. 21 00:01:23,850 --> 00:01:26,940 So aerobic pathways are capable 22 00:01:26,940 --> 00:01:30,090 of generating large amounts of ATP, 23 00:01:30,090 --> 00:01:32,220 but it generates it slowly. 24 00:01:32,220 --> 00:01:35,070 And this aerobic respiration occurs 25 00:01:35,070 --> 00:01:37,440 within the mitochondria of our cells. 26 00:01:37,440 --> 00:01:39,900 And we can utilize all three macronutrients, 27 00:01:39,900 --> 00:01:41,280 carbs, proteins, and fats, 28 00:01:41,280 --> 00:01:45,990 as a fuel source for aerobic energy pathways. 29 00:01:45,990 --> 00:01:49,920 Anaerobic energy pathways generates smaller, 30 00:01:49,920 --> 00:01:52,230 limited quantities of ATP. 31 00:01:52,230 --> 00:01:56,580 However, the ATP is created really quickly, 32 00:01:56,580 --> 00:02:00,000 so this is if you need a sudden burst of energy. 33 00:02:00,000 --> 00:02:05,000 You're gonna use stores that are already made in your body. 34 00:02:06,810 --> 00:02:10,560 And you can only utilize carbohydrates 35 00:02:10,560 --> 00:02:14,310 as the fuel source for this anaerobic activity. 36 00:02:14,310 --> 00:02:16,230 This anaerobic respiration takes place 37 00:02:16,230 --> 00:02:18,423 within the cell sarcoplasm. 38 00:02:21,660 --> 00:02:24,090 The production of ATP occurs 39 00:02:24,090 --> 00:02:27,150 via three different metabolic pathways, 40 00:02:27,150 --> 00:02:28,980 and these pathways are activated 41 00:02:28,980 --> 00:02:31,500 at the beginning of muscle contraction. 42 00:02:31,500 --> 00:02:35,130 So as we start moving and using our muscles, 43 00:02:35,130 --> 00:02:38,190 our muscles require ATP to function. 44 00:02:38,190 --> 00:02:43,190 The first pathway is the phosphocreatine ATP pathway. 45 00:02:46,020 --> 00:02:49,293 So ATP is formed by breaking down phosphocreatine. 46 00:02:51,150 --> 00:02:54,630 The second pathway to form ATP 47 00:02:54,630 --> 00:02:59,430 is via the glycolytic pathway, glycolysis. 48 00:02:59,430 --> 00:03:03,090 And this is via the degradation of glucose, 49 00:03:03,090 --> 00:03:06,240 which is found in our blood, 50 00:03:06,240 --> 00:03:09,720 or glycogen, which is found in our muscles. 51 00:03:09,720 --> 00:03:12,330 And then the last metabolic pathway 52 00:03:12,330 --> 00:03:16,567 is the oxidative pathway to form ATP. 53 00:03:25,350 --> 00:03:30,350 ATP formed via the phosphocreatine pathway 54 00:03:30,570 --> 00:03:34,320 and glycolysis does not involve the use of oxygen. 55 00:03:34,320 --> 00:03:36,753 So these two pathways are anaerobic. 56 00:03:38,250 --> 00:03:42,600 ATP formed by oxidative processes 57 00:03:42,600 --> 00:03:46,680 is an aerobic metabolism and uses oxygen. 58 00:03:46,680 --> 00:03:50,670 And so this little diagram shows three different pathways, 59 00:03:50,670 --> 00:03:55,110 so the anaerobic pathway, the phosphagen system, 60 00:03:55,110 --> 00:03:56,763 and the glycolytic system. 61 00:03:58,890 --> 00:04:02,580 These are without oxygen, so they're fast-acting. 62 00:04:02,580 --> 00:04:04,530 And then the aerobic pathway, 63 00:04:04,530 --> 00:04:06,963 the oxidative pathway, is with oxygen. 64 00:04:10,890 --> 00:04:15,570 So the phosphagen system, the ATP-PC system, 65 00:04:15,570 --> 00:04:17,730 provides energy for muscle contraction 66 00:04:17,730 --> 00:04:19,050 at the start of exercise 67 00:04:19,050 --> 00:04:22,800 and during short, high-intensity activity. 68 00:04:22,800 --> 00:04:24,420 So when you're sprinting 69 00:04:24,420 --> 00:04:26,310 or running quickly across the street, 70 00:04:26,310 --> 00:04:31,310 it's something that is a very fast movement 71 00:04:31,650 --> 00:04:33,753 that doesn't last a long time. 72 00:04:34,710 --> 00:04:39,710 And this reaction is a really simple one-enzyme reaction. 73 00:04:43,050 --> 00:04:46,080 The phosphagen system is the quickest way 74 00:04:46,080 --> 00:04:49,200 for our body to generate ATP. 75 00:04:49,200 --> 00:04:54,200 This phosphagen system takes creatine phosphate, 76 00:04:55,170 --> 00:04:57,330 which is stored in our skeletal muscles, 77 00:04:57,330 --> 00:05:02,167 and it donates a phosphate to ADP to produce ATP. 78 00:05:03,450 --> 00:05:05,703 So the pathway has two components. 79 00:05:07,410 --> 00:05:09,600 There's molecules of ATP. 80 00:05:09,600 --> 00:05:12,843 So you can see here, here's our creatine phosphate, 81 00:05:14,160 --> 00:05:18,540 and an enzyme, creatine kinase, splits the molecule 82 00:05:18,540 --> 00:05:21,543 into two components, creatine and phosphate. 83 00:05:22,470 --> 00:05:26,700 And then the ATP bond is broken, 84 00:05:26,700 --> 00:05:30,870 so breaking ATP into ADP. 85 00:05:30,870 --> 00:05:34,420 And the creatine phosphate 86 00:05:36,510 --> 00:05:41,510 adds a phosphate to the ADP to make ATP. 87 00:05:44,010 --> 00:05:48,060 And this reaction is for short-term, 88 00:05:48,060 --> 00:05:49,620 high-intensity exercise. 89 00:05:49,620 --> 00:05:51,810 And this is for activities 90 00:05:51,810 --> 00:05:53,730 that are lasting less than five seconds 91 00:05:53,730 --> 00:05:58,650 because we quickly deplete any of the creatine phosphate 92 00:05:58,650 --> 00:06:02,523 and the stored ATP in our system to produce it. 93 00:06:05,970 --> 00:06:09,120 The second pathway is glycolysis, 94 00:06:09,120 --> 00:06:14,120 and this is also an anaerobic, without oxygen, process. 95 00:06:14,160 --> 00:06:16,830 Glycolysis consists of the breakdown 96 00:06:16,830 --> 00:06:20,070 of glucose, which is in the blood, 97 00:06:20,070 --> 00:06:25,070 or muscle glycogen, to form two molecules of pyruvate acid 98 00:06:26,880 --> 00:06:30,090 or lactic acid if no O2 is present. 99 00:06:30,090 --> 00:06:31,650 So I'll show you this on another slide, 100 00:06:31,650 --> 00:06:33,540 so hopefully it'll make sense. 101 00:06:33,540 --> 00:06:34,680 There's a series 102 00:06:34,680 --> 00:06:37,980 of enzymatically catalyzed coupled reactions, 103 00:06:37,980 --> 00:06:40,830 so the whole series of steps which occur 104 00:06:40,830 --> 00:06:43,860 in the sarcoplasm of the muscle cells. 105 00:06:43,860 --> 00:06:48,673 And glycolysis produces a net gain of two molecules of ATP 106 00:06:49,830 --> 00:06:52,230 and two molecules of pyruvic 107 00:06:52,230 --> 00:06:55,293 or lactic acid per glucose molecule. 108 00:06:56,760 --> 00:06:59,130 The energy-investment phase 109 00:06:59,130 --> 00:07:03,273 to kind of get the system going requires two ATPs to start. 110 00:07:04,170 --> 00:07:09,170 The energy-generation phase produces actually four ATP, 111 00:07:09,660 --> 00:07:14,283 but because you use two at the start, it's a net of two ATP. 112 00:07:21,720 --> 00:07:26,400 So to summarize the energy investment phase of glycolysis, 113 00:07:26,400 --> 00:07:30,120 which is part one, there's five different reactions, 114 00:07:30,120 --> 00:07:34,050 and these five reactions are gonna require the utilization 115 00:07:34,050 --> 00:07:38,610 of ATP to continue to proceed through them. 116 00:07:38,610 --> 00:07:41,550 So what I'd like you to understand is 117 00:07:41,550 --> 00:07:44,940 that in the energy-investment phase of glycolysis, 118 00:07:44,940 --> 00:07:48,063 two ATP are used. 119 00:07:51,000 --> 00:07:56,000 During this energy investment phase, 120 00:07:56,340 --> 00:07:59,670 as I said earlier, two ATP are used, 121 00:07:59,670 --> 00:08:04,670 and then that can allow the glycolysis pathway 122 00:08:05,130 --> 00:08:08,460 to continue into the energy generation phase. 123 00:08:08,460 --> 00:08:12,960 This phase requires hydrogen molecules, 124 00:08:12,960 --> 00:08:17,960 and so these hydrogen molecules need to be transported. 125 00:08:18,780 --> 00:08:20,913 And they're transported via NAD and FAD. 126 00:08:22,800 --> 00:08:27,120 So the NAD is gonna accept one hydrogen, 127 00:08:27,120 --> 00:08:30,060 and it's gonna convert it into NADH. 128 00:08:30,060 --> 00:08:33,060 So there needs to be adequate amounts 129 00:08:33,060 --> 00:08:35,700 of NAD within the system 130 00:08:35,700 --> 00:08:38,700 to be able to accept the hydrogen atoms 131 00:08:38,700 --> 00:08:40,683 to continue the process. 132 00:08:46,140 --> 00:08:51,140 So this schematic depicts the whole process of glycolysis, 133 00:08:52,530 --> 00:08:55,950 the energy-investment phase requiring two ATP 134 00:08:55,950 --> 00:08:57,720 and the energy-generation phase, 135 00:08:57,720 --> 00:09:00,300 which is producing four ATP. 136 00:09:00,300 --> 00:09:05,300 The energy-investment phase needs two ATP to get it going. 137 00:09:06,480 --> 00:09:10,770 The one ATP is needed to get the glucose 138 00:09:10,770 --> 00:09:13,290 from the blood into the cell 139 00:09:13,290 --> 00:09:18,290 to start having the cell be able to utilize that glucose. 140 00:09:18,360 --> 00:09:22,053 The energy generation phase is producing four ATP. 141 00:09:23,010 --> 00:09:26,250 However, because we use two at the beginning, 142 00:09:26,250 --> 00:09:30,273 the net that glycolysis produces is two ATP. 143 00:09:31,740 --> 00:09:36,740 Because NAD accepted the hydrogen atom, 144 00:09:36,810 --> 00:09:39,480 there were two NAD in this process. 145 00:09:39,480 --> 00:09:44,310 And so there are two NADH produced. 146 00:09:44,310 --> 00:09:47,250 The NADH will go on 147 00:09:47,250 --> 00:09:52,250 to become pyruvate or lactate molecules. 148 00:09:53,280 --> 00:09:56,100 So the net production for glycolysis, 149 00:09:56,100 --> 00:09:58,770 what you need to know is 150 00:09:58,770 --> 00:10:03,770 if there is one glucose molecule to start the process, 151 00:10:03,840 --> 00:10:07,560 the output is going to be two pyruvate 152 00:10:07,560 --> 00:10:12,560 or two lactate molecules, two ATP, and two NADH. 153 00:10:17,250 --> 00:10:21,120 If oxygen is available within the system, 154 00:10:21,120 --> 00:10:23,433 so if it's an aerobic system, 155 00:10:24,480 --> 00:10:27,210 the hydrogens from the NADH can be shuttled 156 00:10:27,210 --> 00:10:29,430 into the mitochondria of the cell, 157 00:10:29,430 --> 00:10:34,110 which will get into the aerobic production of ATP. 158 00:10:34,110 --> 00:10:35,670 If oxygen is not available, 159 00:10:35,670 --> 00:10:38,520 so if it's an aerobic process, 160 00:10:38,520 --> 00:10:42,090 the hydrogens can't be accepted in the mitochondria. 161 00:10:42,090 --> 00:10:46,200 So pyruvic acid will take that hydrogen 162 00:10:46,200 --> 00:10:48,093 and form lactic acid. 163 00:10:55,020 --> 00:10:57,960 Here is a very busy picture 164 00:10:57,960 --> 00:11:02,610 of the whole process of glycolysis. 165 00:11:02,610 --> 00:11:05,620 And on the left-hand side of the screen 166 00:11:06,540 --> 00:11:11,190 are the written words to describe the process. 167 00:11:11,190 --> 00:11:14,400 And on the right-hand side is just a diagram. 168 00:11:14,400 --> 00:11:18,510 So you can see here glucose 169 00:11:18,510 --> 00:11:22,500 up at the tippy-top is in the blood, 170 00:11:22,500 --> 00:11:27,500 and that is being used to go into the cell. 171 00:11:28,320 --> 00:11:31,980 So one ATP is used to get that glucose into the cell. 172 00:11:31,980 --> 00:11:36,167 And then we have our series of cellular changes 173 00:11:37,710 --> 00:11:41,880 and reactions of changing glucose 6-phosphate 174 00:11:41,880 --> 00:11:43,830 to fructose 6-phosphate. 175 00:11:43,830 --> 00:11:48,830 Another ATP is used to produce fructose 1,6 biphosphate. 176 00:11:50,670 --> 00:11:54,930 And in this case, 177 00:11:54,930 --> 00:11:59,930 we now proceed through the energy-investment phase 178 00:12:00,240 --> 00:12:02,883 to the energy-generation phase. 179 00:12:04,080 --> 00:12:07,420 The energy-investment phase 180 00:12:08,700 --> 00:12:11,040 is a series of five steps, 181 00:12:11,040 --> 00:12:15,120 and the net result of the series 182 00:12:15,120 --> 00:12:19,470 of the first investment phase, five steps, is the production 183 00:12:19,470 --> 00:12:24,470 of two glyceraldehyde 3-phosphate molecules. 184 00:12:24,840 --> 00:12:27,240 So one glucose molecule 185 00:12:27,240 --> 00:12:32,240 will produce two glyceraldehyde 3-phosphates. 186 00:12:32,400 --> 00:12:37,400 And this begins the second part of glycolysis, phase two, 187 00:12:38,520 --> 00:12:41,340 which is the energy-generation phase. 188 00:12:41,340 --> 00:12:44,020 This series of reactions 189 00:12:45,180 --> 00:12:48,600 are a total of five additional reactions. 190 00:12:48,600 --> 00:12:52,140 And the net result 191 00:12:52,140 --> 00:12:55,680 of this second phase of glycolysis 192 00:12:55,680 --> 00:13:00,680 is the production of two ATPs 193 00:13:01,050 --> 00:13:06,000 per glyceraldehyde 3-phosphates 194 00:13:06,000 --> 00:13:08,763 and two pyruvate molecules. 195 00:13:10,680 --> 00:13:14,790 This is where the NADH becomes important 196 00:13:14,790 --> 00:13:16,260 or NED becomes important 197 00:13:16,260 --> 00:13:21,044 because for this second phase of glycolysis to proceed, 198 00:13:21,044 --> 00:13:23,193 NAD needs to accept a hydrogen. 199 00:13:24,030 --> 00:13:27,180 Otherwise the whole process stops here 200 00:13:27,180 --> 00:13:30,000 at the end of the investment phase. 201 00:13:30,000 --> 00:13:33,810 So NAD needs to be present to accept that hydrogen 202 00:13:33,810 --> 00:13:37,200 for this series of the remaining five 203 00:13:37,200 --> 00:13:42,200 enzymatically generated reactions to proceed. 204 00:13:43,500 --> 00:13:47,010 So NAD is gonna accept one hydrogen, 205 00:13:47,010 --> 00:13:48,963 and it's gonna convert to NADH. 206 00:13:52,170 --> 00:13:57,170 The ATP is going to be produced along the way, 207 00:13:57,990 --> 00:14:00,573 and then pyruvate will be formed. 208 00:14:01,770 --> 00:14:05,190 If oxygen is available, 209 00:14:05,190 --> 00:14:10,190 these hydrogens from the NADH can be shuttled 210 00:14:13,860 --> 00:14:15,900 to the mitochondria of the cell 211 00:14:15,900 --> 00:14:19,020 to contribute to aerobic production of ATP. 212 00:14:19,020 --> 00:14:21,390 If oxygen is not available, 213 00:14:21,390 --> 00:14:24,810 if it's an anaerobic activity, 214 00:14:24,810 --> 00:14:26,850 the hydrogens cannot be accepted 215 00:14:26,850 --> 00:14:28,890 or moved into the mitochondria. 216 00:14:28,890 --> 00:14:32,610 So the pyruvic acid, pyruvate, 217 00:14:32,610 --> 00:14:37,500 will transform to pyruvic acid, 218 00:14:37,500 --> 00:14:42,500 and if there is lactate dehydrogenase present, an enzyme, 219 00:14:43,350 --> 00:14:47,583 this can convert the pyruvic acid to lactic acid. 220 00:14:49,290 --> 00:14:54,187 And this conversion to lactic acid 221 00:14:55,590 --> 00:15:00,590 generates an NAD, which now can go back up 222 00:15:00,870 --> 00:15:05,813 to the top of the beginning of phase-two glycolysis 223 00:15:08,940 --> 00:15:11,643 to allow glycolysis to continue. 224 00:15:13,080 --> 00:15:17,490 To summarize, the energy investment phase is a series 225 00:15:17,490 --> 00:15:20,460 of five reactions using two ATP 226 00:15:20,460 --> 00:15:25,460 and producing two glyceraldehyde 3-phosphates. 227 00:15:27,000 --> 00:15:31,053 The phase two of glycolysis, the energy-generation phase, 228 00:15:32,340 --> 00:15:37,340 proceeds through, if NAD is present, to accept a hydrogen. 229 00:15:39,540 --> 00:15:44,540 And then those next remaining steps, six to 10, 230 00:15:46,110 --> 00:15:49,290 it's like a 10-step process for glycolysis. 231 00:15:49,290 --> 00:15:54,290 So step six to 10 are the energy-generation phase. 232 00:15:55,470 --> 00:15:57,333 Two ATP will be produced. 233 00:15:58,410 --> 00:16:00,093 Pyruvate will be produced. 234 00:16:01,170 --> 00:16:06,170 If oxygen is not present, lactic acid will be produced. 235 00:16:08,190 --> 00:16:10,500 If oxygen is present, 236 00:16:10,500 --> 00:16:15,500 the hydrogen from the NADH will go to the mitochondria. 237 00:16:15,720 --> 00:16:19,260 Both of those processes at the end 238 00:16:19,260 --> 00:16:21,840 will allow glycolysis to continue. 239 00:16:21,840 --> 00:16:26,433 So when NAD takes the hydrogen and becomes NADH, 240 00:16:28,530 --> 00:16:31,920 we need at the end of the glycolytic process, 241 00:16:31,920 --> 00:16:35,640 we need to get rid of that hydrogen, and there's two ways. 242 00:16:35,640 --> 00:16:38,940 So if oxygen's present or if oxygen is not present, 243 00:16:38,940 --> 00:16:41,880 either way, a hydrogen will be given up, 244 00:16:41,880 --> 00:16:46,880 producing NAD to allow the cycle to continue. 245 00:16:56,370 --> 00:17:00,240 After the 10-step glycolysis process, 246 00:17:00,240 --> 00:17:03,210 two pyruvate molecules are formed. 247 00:17:03,210 --> 00:17:07,383 So one glucose molecule will produce two pyruvates. 248 00:17:08,250 --> 00:17:11,793 One glucose molecule will also produce two NADH. 249 00:17:13,290 --> 00:17:17,850 So the end product of glycolysis is this production 250 00:17:17,850 --> 00:17:19,830 of the two pyruvate molecules. 251 00:17:19,830 --> 00:17:24,150 These pyruvates in the presence of oxygen will move 252 00:17:24,150 --> 00:17:29,040 into the mitochondria, where they undergo further oxidation. 253 00:17:29,040 --> 00:17:33,300 So you could see here is the pyruvate sitting out 254 00:17:33,300 --> 00:17:34,980 in the cytoplasm. 255 00:17:34,980 --> 00:17:38,700 With oxygen, it can move into the mitochondria, 256 00:17:38,700 --> 00:17:43,700 where it reacts and transforms into acetyl-CoA. 257 00:17:43,890 --> 00:17:47,430 This acetyl-CoA then moves 258 00:17:47,430 --> 00:17:51,600 into another process called the Krebs cycle, 259 00:17:51,600 --> 00:17:55,833 or it's also known as the citric acid cycle. 260 00:17:57,300 --> 00:18:00,780 So here is the citric acid cycle, 261 00:18:00,780 --> 00:18:03,120 and there's a series of processes 262 00:18:03,120 --> 00:18:06,990 that occur within this cycle. 263 00:18:06,990 --> 00:18:11,990 So one turn of this cycle one time around 264 00:18:13,140 --> 00:18:16,470 will produce three NADH. 265 00:18:16,470 --> 00:18:21,120 So here's a production of NAD accepting a hydrogen. 266 00:18:21,120 --> 00:18:22,680 So there's an NADH. 267 00:18:22,680 --> 00:18:26,400 Here's another NAD accepting a hydrogen, another NADH. 268 00:18:26,400 --> 00:18:31,400 And here's another NAD accepting a hydrogen for a third NADH 269 00:18:32,760 --> 00:18:37,740 It also produces one FADH over here. 270 00:18:37,740 --> 00:18:40,893 FAD, if you recall, can also accept hydrogen. 271 00:18:44,160 --> 00:18:45,960 Another important phosphate 272 00:18:45,960 --> 00:18:49,353 is this guanosine triphosphate here. 273 00:18:50,400 --> 00:18:54,060 Guanosine diphosphate can also accept a phosphate 274 00:18:54,060 --> 00:18:58,110 to form GTP, and we'll talk a little bit about that later. 275 00:18:58,110 --> 00:19:03,110 But GTP can also be used to produce ATP. 276 00:19:06,180 --> 00:19:10,260 Aerobic ATP production occurs inside the mitochondria. 277 00:19:10,260 --> 00:19:15,060 So if you recall, that pyruvate moves into the mitochondria. 278 00:19:15,060 --> 00:19:18,570 Two cooperative metabolic pathways occur. 279 00:19:18,570 --> 00:19:20,310 One is the Krebs cycle, 280 00:19:20,310 --> 00:19:24,120 which we discussed on the prior slide. 281 00:19:24,120 --> 00:19:29,120 The Krebs cycle will generate two acetyl-CoAs 282 00:19:30,108 --> 00:19:35,108 and will be oxidized in the Krebs cycle. 283 00:19:35,310 --> 00:19:36,660 The other metabolic pathway 284 00:19:36,660 --> 00:19:38,880 is the electronic transport chain, 285 00:19:38,880 --> 00:19:43,880 and this chain is the process of oxidative phosphorylation, 286 00:19:45,420 --> 00:19:48,093 which is the process of ATP formation. 287 00:19:50,040 --> 00:19:51,480 The Krebs cycle, 288 00:19:51,480 --> 00:19:55,293 it's more commonly now called the citric acid cycle. 289 00:19:56,220 --> 00:19:59,670 And this citric acid cycle completes the oxidation, 290 00:19:59,670 --> 00:20:01,890 or the removal of hydrogen, 291 00:20:01,890 --> 00:20:04,200 of carbohydrates, fats, and proteins, 292 00:20:04,200 --> 00:20:08,100 so our food macronutrients, 293 00:20:08,100 --> 00:20:11,430 using NAD and FAD as the hydrogen carriers. 294 00:20:11,430 --> 00:20:16,430 So recall we need to mobilize hydrogen molecules, 295 00:20:18,240 --> 00:20:23,043 and NAD and FAD are the molecules 296 00:20:24,360 --> 00:20:27,450 that can accept these hydrogens. 297 00:20:27,450 --> 00:20:31,050 The hydrogens contain the potential energy 298 00:20:31,050 --> 00:20:32,160 in the food molecules. 299 00:20:32,160 --> 00:20:34,560 So the hydrogens are really, really important 300 00:20:34,560 --> 00:20:38,820 as are the structures that are needed to carry the hydrogens 301 00:20:38,820 --> 00:20:42,603 to make these cycles continue. 302 00:20:43,740 --> 00:20:47,790 The potential energy of hydrogen can be used 303 00:20:47,790 --> 00:20:49,650 in the electron transport chain 304 00:20:49,650 --> 00:20:54,650 to combine ADP plus phosphate to reform into ATP. 305 00:20:55,200 --> 00:20:57,420 And this process of aerobic production 306 00:20:57,420 --> 00:21:00,063 of ATP is oxidative phosphorylation. 307 00:21:06,690 --> 00:21:11,043 Here's another schematic of the citric acid cycle. 308 00:21:13,290 --> 00:21:15,030 So important things to know, 309 00:21:15,030 --> 00:21:17,160 again, just to summarize this, 310 00:21:17,160 --> 00:21:22,160 pyruvate enters into the mitochondria and forms acetyl-CoA. 311 00:21:25,110 --> 00:21:27,730 Acetyl-CoA then 312 00:21:28,950 --> 00:21:33,210 is formed into citrate, 313 00:21:33,210 --> 00:21:38,210 and this is why this cycle is called the citric acid cycle, 314 00:21:38,700 --> 00:21:42,960 because that's the main structure 315 00:21:42,960 --> 00:21:45,723 that starts this Krebs cycle. 316 00:21:48,960 --> 00:21:53,960 The oxidation of pyruvate from glycolysis 317 00:21:54,690 --> 00:21:59,690 starts this whole enzymatically catalyzed cycle. 318 00:22:02,070 --> 00:22:07,070 Hydrogens are bound to NAD and FAD and GDP. 319 00:22:14,280 --> 00:22:19,280 One full turn of this Krebs cycle will produce three NADH, 320 00:22:20,490 --> 00:22:21,750 and I showed you in the other slide. 321 00:22:21,750 --> 00:22:23,340 So here's an NADH. 322 00:22:23,340 --> 00:22:25,110 Here's another NADH. 323 00:22:25,110 --> 00:22:27,540 Here's another, and an FADH. 324 00:22:27,540 --> 00:22:30,420 So you get three NADH and one FADH. 325 00:22:31,470 --> 00:22:36,470 At the end of the cycle, oxaloacetate is formed. 326 00:22:36,480 --> 00:22:40,353 This is a substrate that binds with the acetyl-CoA, 327 00:22:41,220 --> 00:22:44,960 and this binding of oxaloacetate 328 00:22:44,960 --> 00:22:48,303 to acetyl-CoA is what forms the citrate. 329 00:22:54,090 --> 00:22:56,370 To go back to the beginning 330 00:22:56,370 --> 00:23:01,370 where we had glucose in the blood entering into the cell, 331 00:23:01,470 --> 00:23:04,950 each molecule of glucose results 332 00:23:04,950 --> 00:23:07,140 in two turns of the Krebs cycle. 333 00:23:07,140 --> 00:23:08,103 Why is that? 334 00:23:08,940 --> 00:23:10,413 So think for a moment. 335 00:23:12,570 --> 00:23:14,520 It's two turns of the Krebs cycle 336 00:23:14,520 --> 00:23:19,200 because at the end of glycolysis, two pyruvate are formed. 337 00:23:19,200 --> 00:23:23,310 So two pyruvate will enter into the mitochondria, 338 00:23:23,310 --> 00:23:25,230 and each of those pyruvates 339 00:23:25,230 --> 00:23:28,053 will start up a citric acid cycle. 340 00:23:29,190 --> 00:23:31,770 The primary function of the citric acid cycle 341 00:23:31,770 --> 00:23:33,750 is to remove hydrogens 342 00:23:33,750 --> 00:23:37,230 and the energy associated with those hydrogens. 343 00:23:37,230 --> 00:23:40,410 NAD and FAD pick up the hydrogens 344 00:23:40,410 --> 00:23:43,560 and convert to NADH and FADH. 345 00:23:43,560 --> 00:23:47,763 For each turn of these two Krebs cycles, 346 00:23:48,810 --> 00:23:50,520 three molecules of NADH 347 00:23:50,520 --> 00:23:53,370 and one molecule of FADH are formed. 348 00:23:53,370 --> 00:23:57,660 So there's a net then of six NADH 349 00:23:57,660 --> 00:24:01,023 and two FADH per glucose. 350 00:24:02,370 --> 00:24:06,030 For each NADH, enough energy is available 351 00:24:06,030 --> 00:24:09,090 to produce 2 1/2 ATPs. 352 00:24:09,090 --> 00:24:12,360 For each FADH, enough energy is available 353 00:24:12,360 --> 00:24:15,153 to produce 1 1/2 ATPs. 354 00:24:16,530 --> 00:24:18,783 I've put this little table here. 355 00:24:19,740 --> 00:24:23,370 For two turns of the Krebs cycle, which occurs 356 00:24:23,370 --> 00:24:28,370 because one glucose molecule produces two pyruvates, 357 00:24:28,590 --> 00:24:31,710 which are going to enter the mitochondria 358 00:24:31,710 --> 00:24:35,523 and cause two turns of the Krebs cycle, 359 00:24:37,410 --> 00:24:39,840 and with two turns of the Krebs cycle, 360 00:24:39,840 --> 00:24:43,860 we're gonna have six NADH and two FADH, 361 00:24:43,860 --> 00:24:48,040 yielding 18 ATP molecules 362 00:24:49,800 --> 00:24:51,603 for the citric acid cycle. 363 00:24:53,790 --> 00:24:55,860 Now the guanosine triphosphate, 364 00:24:55,860 --> 00:24:57,990 which I talked about earlier, 365 00:24:57,990 --> 00:25:00,870 is another high-energy compound formed 366 00:25:00,870 --> 00:25:02,523 through the Krebs cycle process. 367 00:25:03,600 --> 00:25:07,650 This GTP can transfer its phosphate group to ADP 368 00:25:07,650 --> 00:25:11,070 to form another ATP. 369 00:25:11,070 --> 00:25:15,703 So GTP contributes one ATP 370 00:25:16,770 --> 00:25:19,140 per turn of the Krebs cycle. 371 00:25:19,140 --> 00:25:22,650 As we know, there are two turns to the Krebs cycle 372 00:25:22,650 --> 00:25:24,810 for every molecule of glucose. 373 00:25:24,810 --> 00:25:29,810 So GTP will produce a net of two ATP. 374 00:25:31,980 --> 00:25:35,880 Therefore for two turns of the Krebs cycle, 375 00:25:35,880 --> 00:25:39,990 we are going to produce 20 ATPs. 376 00:25:45,780 --> 00:25:50,640 After the citric acid cycle has completed its two turns, 377 00:25:50,640 --> 00:25:54,360 we have those three NADH and one FADH, 378 00:25:54,360 --> 00:25:57,090 and these are taken to the electron transport chain 379 00:25:57,090 --> 00:26:02,090 to re-phosphorylate ADP to ATP to make more energy. 380 00:26:02,310 --> 00:26:04,800 So electrons are removed from hydrogen atoms 381 00:26:04,800 --> 00:26:07,770 and are passed down a series of electron carriers, 382 00:26:07,770 --> 00:26:09,600 or cytochromes. 383 00:26:09,600 --> 00:26:11,310 During the passage of these electrons 384 00:26:11,310 --> 00:26:12,630 down the cytochrome chain, 385 00:26:12,630 --> 00:26:17,630 energy is released to re-phosphorylate ADP to ATP 386 00:26:17,940 --> 00:26:19,863 at three different sites. 387 00:26:25,110 --> 00:26:28,800 Here's an image of the electron transport chain. 388 00:26:28,800 --> 00:26:33,060 Oxidation of compounds in the electron transport chain 389 00:26:33,060 --> 00:26:36,390 coupled with the phosphorylation of ATP is referred to 390 00:26:36,390 --> 00:26:39,120 as oxidative phosphorylation. 391 00:26:39,120 --> 00:26:43,680 The FADH and NADH molecules produced from glycolysis 392 00:26:43,680 --> 00:26:45,600 and the Krebs cycle donate protons 393 00:26:45,600 --> 00:26:48,240 and electrons to the electron transport chain. 394 00:26:48,240 --> 00:26:50,790 And at specific steps along the chain, 395 00:26:50,790 --> 00:26:52,590 sufficient free energy is released 396 00:26:52,590 --> 00:26:56,070 to phosphorylate ATP molecules from ADP and phosphate. 397 00:26:56,070 --> 00:26:57,720 You can see over here, 398 00:26:57,720 --> 00:27:01,110 here's our NADH releasing its hydrogen. 399 00:27:01,110 --> 00:27:03,900 Here's our FADH releasing its hydrogen. 400 00:27:03,900 --> 00:27:07,997 Here's our hydrogen coming back in to combine 401 00:27:11,070 --> 00:27:15,690 and work to produce ATP 402 00:27:15,690 --> 00:27:18,633 from the ADP and phosphate. 403 00:27:22,590 --> 00:27:25,830 To summarize how many ATPs are produced 404 00:27:25,830 --> 00:27:28,830 during glycolysis and the Krebs cycle, 405 00:27:28,830 --> 00:27:33,330 we need to look at each of these cycles individually 406 00:27:33,330 --> 00:27:37,683 and remember that in glycolysis, two NADH were formed, 407 00:27:38,580 --> 00:27:43,140 and for each NADH, 2 1/2 ATPs are produced. 408 00:27:43,140 --> 00:27:47,433 So if there's two NADHs, there's gonna be five ATPs. 409 00:27:48,510 --> 00:27:51,030 What we also need to remember, 410 00:27:51,030 --> 00:27:52,953 and we didn't talk about this yet, 411 00:27:54,840 --> 00:27:59,550 the process of glycolysis depends 412 00:27:59,550 --> 00:28:04,550 on whether the body's using glucose or glycogen. 413 00:28:05,940 --> 00:28:07,770 And if it's using glucose, 414 00:28:07,770 --> 00:28:11,103 which is the process we have talked about so far, 415 00:28:12,060 --> 00:28:16,560 the energy-investment phase requires two ATPs. 416 00:28:16,560 --> 00:28:21,150 So the net is two ATPs are produced. 417 00:28:21,150 --> 00:28:24,420 So the energy investment phase is two ATPs. 418 00:28:24,420 --> 00:28:27,750 One ATP is used to get that glucose 419 00:28:27,750 --> 00:28:30,180 from the blood into the cell. 420 00:28:30,180 --> 00:28:32,220 And then in the energy-generation phase, 421 00:28:32,220 --> 00:28:34,080 four ATP are produced. 422 00:28:34,080 --> 00:28:38,070 So four produced minus two used is a net of two. 423 00:28:38,070 --> 00:28:40,440 If the body's using glycogen, 424 00:28:40,440 --> 00:28:45,440 which is already within the muscle cell, 425 00:28:46,830 --> 00:28:49,740 you don't need to use an ATP 426 00:28:49,740 --> 00:28:54,740 to transport that sugar substrate into the muscle. 427 00:28:56,310 --> 00:28:57,480 It's already in there. 428 00:28:57,480 --> 00:28:59,820 So we don't need to use that one ATP. 429 00:28:59,820 --> 00:29:03,300 So only one ATP is used 430 00:29:03,300 --> 00:29:07,380 in the energy-generation phase if we're utilizing glycogen. 431 00:29:07,380 --> 00:29:10,170 And then four ATP are produced 432 00:29:10,170 --> 00:29:12,180 in the energy-generation phase. 433 00:29:12,180 --> 00:29:15,570 So four minus one is three ATP. 434 00:29:15,570 --> 00:29:17,340 So just thinking about that 435 00:29:17,340 --> 00:29:19,200 and understanding the difference of the glucose 436 00:29:19,200 --> 00:29:20,313 versus the glycogen. 437 00:29:21,870 --> 00:29:24,030 Two NADH are formed during the conversion 438 00:29:24,030 --> 00:29:25,773 of pyruvate to acetyl-CoA. 439 00:29:26,700 --> 00:29:29,220 And so there's four, five more ATP 440 00:29:29,220 --> 00:29:31,623 during our citric acid cycle. 441 00:29:32,820 --> 00:29:35,910 For each turn of the citric acid cycle, 442 00:29:35,910 --> 00:29:38,160 there are three NADH, 443 00:29:38,160 --> 00:29:42,090 and you recall that there are two turns 444 00:29:42,090 --> 00:29:44,040 per glucose molecule. 445 00:29:44,040 --> 00:29:48,480 So the net result of our citric acid cycle 446 00:29:48,480 --> 00:29:53,480 are six NADH, two FADH, and two GTPs. 447 00:29:54,720 --> 00:29:57,517 So we're gonna get 15 ATP from the NADH, 448 00:29:57,517 --> 00:30:02,517 three ATP from FADH, and two ATP from the GTP. 449 00:30:05,850 --> 00:30:09,480 The overall total ATP from carbohydrates then, 450 00:30:09,480 --> 00:30:11,580 starting with glucose in the muscle 451 00:30:11,580 --> 00:30:14,430 and brain cells, yields 36 ATP. 452 00:30:14,430 --> 00:30:18,840 Starting with glycogen in the muscle, yields 37 ATP 453 00:30:18,840 --> 00:30:21,120 because we didn't use one ATP 454 00:30:21,120 --> 00:30:24,390 at the beginning of the glycolysis phase. 455 00:30:24,390 --> 00:30:26,670 If we are starting with glucose in the liver, kidney, 456 00:30:26,670 --> 00:30:29,857 and cardiac cells, we're gonna get 38 ATP. 457 00:30:30,840 --> 00:30:34,080 If we are starting with glycogen in the liver, kidney, 458 00:30:34,080 --> 00:30:37,057 and cardiac cells, we're gonna yield 39 ATP. 459 00:30:38,070 --> 00:30:42,150 However, the net result for glucose is really 32, 460 00:30:42,150 --> 00:30:45,933 and glycogen, 33, due to different ATP uses. 461 00:30:53,190 --> 00:30:55,860 This image here gives a nice overview 462 00:30:55,860 --> 00:30:59,580 of all of the different systems that are used 463 00:30:59,580 --> 00:31:03,750 to metabolize fats, carbs, or proteins. 464 00:31:03,750 --> 00:31:06,600 So far, we have been talking just about glucose 465 00:31:06,600 --> 00:31:10,800 and glycogen, carbohydrates, looking at glycolysis, 466 00:31:10,800 --> 00:31:13,020 and then the citric acid cycle 467 00:31:13,020 --> 00:31:15,630 and then the electron transport chain. 468 00:31:15,630 --> 00:31:19,020 Aerobic respiration or mitochondrial respiration, 469 00:31:19,020 --> 00:31:20,790 the production of ATP molecules 470 00:31:20,790 --> 00:31:25,080 in this pathway using fats is the greatest, 471 00:31:25,080 --> 00:31:30,080 but it's way slower than either the phosphagen system 472 00:31:30,840 --> 00:31:33,210 or the glycolytic system. 473 00:31:33,210 --> 00:31:36,000 Remember that all three of these macronutrients, though, 474 00:31:36,000 --> 00:31:40,323 serve as fuel substrate for the manufacturer of energy. 475 00:31:43,350 --> 00:31:48,350 Fat oxidation, lipid oxidation, is an important source 476 00:31:48,450 --> 00:31:51,750 of free energy for ATP production. 477 00:31:51,750 --> 00:31:55,713 And the primary source of lipids are free fatty acids. 478 00:31:57,270 --> 00:32:00,150 The activation of the sympathetic nervous system brought on 479 00:32:00,150 --> 00:32:03,180 by stressors provides a signal to begin the breakdown 480 00:32:03,180 --> 00:32:05,910 of stored triglycerides in our muscles 481 00:32:05,910 --> 00:32:08,433 or in our adipose tissue. 482 00:32:09,480 --> 00:32:14,480 Beta-oxidation, or the breakdown of our free fatty acids 483 00:32:14,670 --> 00:32:17,043 into two carbon fragments, 484 00:32:18,480 --> 00:32:23,010 involves usually three different stages. 485 00:32:23,010 --> 00:32:24,780 The first is the activation 486 00:32:24,780 --> 00:32:28,710 of the free fatty acids in the cytosol 487 00:32:28,710 --> 00:32:33,270 and a series of enzymatic processes 488 00:32:33,270 --> 00:32:38,270 and then the transport of the activated free fatty acids 489 00:32:38,490 --> 00:32:43,490 into the mitochondria via a carnitine shuttle, 490 00:32:43,590 --> 00:32:48,590 and then the beta oxidation in the mitochondrial matrix. 491 00:32:49,110 --> 00:32:53,310 Each beta oxidation sequence removes a two-carbon segment 492 00:32:53,310 --> 00:32:56,850 that results in the manufacturer of one acetyl-CoA. 493 00:32:56,850 --> 00:32:59,193 And we already know what acetyl-CoA can do. 494 00:33:00,030 --> 00:33:04,770 And it also simultaneously removes electrons and hydrogen, 495 00:33:04,770 --> 00:33:09,360 reducing NAD and FAD to NADH and FADH. 496 00:33:09,360 --> 00:33:10,710 Again, we know what they do. 497 00:33:10,710 --> 00:33:13,530 They can all work to produce ATP. 498 00:33:13,530 --> 00:33:16,020 So this is a schematic here with the activation 499 00:33:16,020 --> 00:33:18,360 of the free fatty acids in phase one 500 00:33:18,360 --> 00:33:22,480 and then the transport of the free fatty acids 501 00:33:24,810 --> 00:33:27,150 via the mitochondrial shuttle 502 00:33:27,150 --> 00:33:30,660 and beta-oxidation proper in this matrix, 503 00:33:30,660 --> 00:33:32,520 producing acetyl-CoA. 504 00:33:32,520 --> 00:33:37,083 And then acetyl-CoA will go into the Krebs cycle. 505 00:33:38,195 --> 00:33:43,140 FADs and NADs will go into the electron transport chain, 506 00:33:43,140 --> 00:33:47,040 and then we will have complete palmitate degradation, 507 00:33:47,040 --> 00:33:49,743 which we're gonna talk about on the upcoming slides. 508 00:33:55,230 --> 00:33:59,280 Palmitate is the most common free fatty acid utilized 509 00:33:59,280 --> 00:34:01,920 by our body to produce energy. 510 00:34:01,920 --> 00:34:05,730 However, there are others, and they vary in length, 511 00:34:05,730 --> 00:34:09,030 and the net ATP yield will vary from structure to structure. 512 00:34:09,030 --> 00:34:10,920 But we're gonna focus on palmitate 513 00:34:10,920 --> 00:34:13,080 because it is the most common. 514 00:34:13,080 --> 00:34:18,080 And to oxidize these lipids into energy, 515 00:34:21,330 --> 00:34:24,060 as I said on the other states' slide, 516 00:34:24,060 --> 00:34:25,980 there's three different steps, 517 00:34:25,980 --> 00:34:28,320 and the first is that the free fatty acids, 518 00:34:28,320 --> 00:34:31,140 they need to be activated. 519 00:34:31,140 --> 00:34:33,750 And they need to be shuttled into the mitochondria, 520 00:34:33,750 --> 00:34:36,240 which requires energy 'cause free fatty acids 521 00:34:36,240 --> 00:34:38,910 can't penetrate the biologic membranes. 522 00:34:38,910 --> 00:34:41,790 So they have to cross the membrane 523 00:34:41,790 --> 00:34:46,023 with a specific process which requires two ATPs. 524 00:34:48,420 --> 00:34:52,590 Once the fatty acid is inside the mitochondrial matrix, 525 00:34:52,590 --> 00:34:57,590 beta-oxidation occurs by cleaving two carbons every cycle 526 00:34:57,870 --> 00:34:59,130 to form acetyl-CoA. 527 00:34:59,130 --> 00:35:02,790 So palmitate is a 16-carbon structure. 528 00:35:02,790 --> 00:35:07,740 So two carbons 529 00:35:07,740 --> 00:35:11,823 every cycle will yield eight cycles, 530 00:35:17,300 --> 00:35:18,133 and this will result in the production of eight acetyl-CoA. 531 00:35:21,240 --> 00:35:25,653 This cleaving of the two-carbon fragments 532 00:35:27,180 --> 00:35:32,180 from the 16-carbon structure occurs seven different times. 533 00:35:32,640 --> 00:35:35,940 So the beta-oxidation sequence must occur seven times 534 00:35:35,940 --> 00:35:39,090 to yield eight two-carbon fragments. 535 00:35:39,090 --> 00:35:44,090 During this seven beta-oxidation sequences, 536 00:35:45,720 --> 00:35:50,163 seven NADH are formed, and seven FADH are formed. 537 00:35:51,780 --> 00:35:56,340 You can see the total number of ATP formed 538 00:35:56,340 --> 00:36:01,340 from one palmitate free fatty acid. 539 00:36:03,990 --> 00:36:08,820 So there's a lot of ATP formed when we use fats 540 00:36:08,820 --> 00:36:13,593 as our nutrient for energy. 541 00:36:22,050 --> 00:36:26,160 Our final macronutrient to talk about is protein. 542 00:36:26,160 --> 00:36:29,730 Proteins are a substrate that can be catabolized. 543 00:36:29,730 --> 00:36:32,910 They do provide the free energy required 544 00:36:32,910 --> 00:36:36,090 to manufacture ATP during exercise. 545 00:36:36,090 --> 00:36:39,030 A major point of entry for amino acid skeletons 546 00:36:39,030 --> 00:36:43,140 into the energy pathways, specifically the Krebs cycle, 547 00:36:43,140 --> 00:36:45,330 is acetyl-CoA. 548 00:36:45,330 --> 00:36:48,780 And the maximal contribution of amino acid oxidation 549 00:36:48,780 --> 00:36:51,060 to total ATP production during exercise 550 00:36:51,060 --> 00:36:54,000 is somewhere between five and 10%. 551 00:36:54,000 --> 00:36:58,143 So it's not like the carbs or the fats. 552 00:37:00,720 --> 00:37:04,350 Our exercise science textbook refers to these processes 553 00:37:04,350 --> 00:37:09,350 of metabolizing these nutrients into energy 554 00:37:10,470 --> 00:37:11,730 as the metabolic mill. 555 00:37:11,730 --> 00:37:12,930 And they have a nice video 556 00:37:12,930 --> 00:37:14,670 that I've put on Blackboard that you can see. 557 00:37:14,670 --> 00:37:17,520 It's pretty short, and it's visual, 558 00:37:17,520 --> 00:37:19,350 so it will help cement the ideas in. 559 00:37:19,350 --> 00:37:21,300 So definitely look at the video 560 00:37:21,300 --> 00:37:24,000 and use the textbook as a reference 561 00:37:24,000 --> 00:37:27,660 'cause I've skimmed over many of the the details here. 562 00:37:27,660 --> 00:37:30,720 I'm just trying to capture the important components for you, 563 00:37:30,720 --> 00:37:32,880 the take-home messages. 564 00:37:32,880 --> 00:37:36,840 And just understanding that all three fuels, 565 00:37:36,840 --> 00:37:38,520 carbohydrates, proteins, and fats, 566 00:37:38,520 --> 00:37:40,350 serve integrated roles in contributing 567 00:37:40,350 --> 00:37:42,720 to the production of energy. 568 00:37:42,720 --> 00:37:45,360 Pyruvate is transported into the mitochondria 569 00:37:45,360 --> 00:37:47,730 for conversion to acetyl-CoA 570 00:37:47,730 --> 00:37:50,100 or converted to lactate in the sarcoplasm. 571 00:37:50,100 --> 00:37:52,557 And if you recall, pyruvate is produced 572 00:37:52,557 --> 00:37:56,853 via glycolysis using either glucose or glycogen. 573 00:37:58,230 --> 00:38:00,630 Triglycerides or fats separate 574 00:38:00,630 --> 00:38:04,680 into free fatty acids before entering the mitochondria, 575 00:38:04,680 --> 00:38:07,500 where they're shuttled in via that carnitine shuttle 576 00:38:07,500 --> 00:38:09,450 where they undergo beta-oxidation 577 00:38:09,450 --> 00:38:11,463 for the conversion to acetyl-CoA. 578 00:38:12,630 --> 00:38:15,210 Since free fatty acids enter the metabolic pathway 579 00:38:15,210 --> 00:38:18,510 at this point, they cannot be converted to glucose. 580 00:38:18,510 --> 00:38:20,940 Glycerol is a three-carbon structure, 581 00:38:20,940 --> 00:38:23,580 and it's capable of entering the glycolytic pathway 582 00:38:23,580 --> 00:38:27,270 or can be converted to either glucose or pyruvate. 583 00:38:27,270 --> 00:38:30,093 And we saw this in the glycolysis pathway. 584 00:38:31,140 --> 00:38:33,090 Glucogenic amino acids are those 585 00:38:33,090 --> 00:38:35,760 that enter the pathway before the formation of pyruvate 586 00:38:35,760 --> 00:38:37,980 and can be converted to glucose. 587 00:38:37,980 --> 00:38:42,030 And ketogenic amino acids enter the pathway as acetyl-CoA 588 00:38:42,030 --> 00:38:45,780 or as a citric-acid-cycle intermediate product. 589 00:38:45,780 --> 00:38:48,573 And so they can only be used to produce energy. 590 00:38:54,600 --> 00:38:59,010 Looking at the role of energy pathway in exercise fatigue. 591 00:38:59,010 --> 00:39:00,360 When we're working out, 592 00:39:00,360 --> 00:39:02,430 muscle contraction depends on the ability 593 00:39:02,430 --> 00:39:05,470 of the metabolic pathways to contribute 594 00:39:07,230 --> 00:39:09,360 to the production of ATP. 595 00:39:09,360 --> 00:39:12,150 Mitochondrial respiration is a primary supplier 596 00:39:12,150 --> 00:39:15,210 of ATP using fat, carbohydrates, 597 00:39:15,210 --> 00:39:18,453 and proteins made available for mitochondrial aspiration, 598 00:39:19,350 --> 00:39:22,140 so the beta-oxidation cycle. 599 00:39:22,140 --> 00:39:26,520 The availability of muscle glycogen limits glycolysis 600 00:39:26,520 --> 00:39:30,390 and maintenance of maximal rate of ATP production. 601 00:39:30,390 --> 00:39:31,650 Research has reported 602 00:39:31,650 --> 00:39:34,020 that muscle glycogen stores become depleted 603 00:39:34,020 --> 00:39:37,050 after approximately two hours of exercise 604 00:39:37,050 --> 00:39:41,433 under high-intensity exercise or maximal usage. 605 00:39:44,460 --> 00:39:47,880 The relative contribution of each energy system is dictated 606 00:39:47,880 --> 00:39:50,610 by the required energy demands. 607 00:39:50,610 --> 00:39:53,340 So there's not really a fine line of when one starts 608 00:39:53,340 --> 00:39:56,520 and the other stops. 609 00:39:56,520 --> 00:40:00,540 There's a definite contribution in overlap. 610 00:40:00,540 --> 00:40:02,550 Each system contributes from the beginning 611 00:40:02,550 --> 00:40:05,130 of an exercise balance to steady state exercise. 612 00:40:05,130 --> 00:40:07,290 And steady state is often referred to 613 00:40:07,290 --> 00:40:09,510 as when you get your second wind during exercise. 614 00:40:09,510 --> 00:40:12,120 So if you're running, and you start running, 615 00:40:12,120 --> 00:40:14,640 and the first couple minutes you feel like you're gonna die, 616 00:40:14,640 --> 00:40:16,230 and you can't catch your breath, 617 00:40:16,230 --> 00:40:17,613 but then all of a sudden, 618 00:40:18,510 --> 00:40:21,120 you kind of shift into a different gear. 619 00:40:21,120 --> 00:40:24,090 And that's when you get in your second wind, 620 00:40:24,090 --> 00:40:25,500 and you're in the steady state. 621 00:40:25,500 --> 00:40:29,160 This says generally takes between 45 to 90 seconds 622 00:40:29,160 --> 00:40:31,143 or up to four hours to achieve. 623 00:40:34,830 --> 00:40:36,300 These are some nice slides 624 00:40:36,300 --> 00:40:39,990 showing the different energy systems in the overlap. 625 00:40:39,990 --> 00:40:42,570 Looking here at the very start of exercise, 626 00:40:42,570 --> 00:40:44,400 100% of the energy is 627 00:40:44,400 --> 00:40:48,330 through the creatine phosphate hydrolysis. 628 00:40:48,330 --> 00:40:51,360 But that drops off really, really quickly. 629 00:40:51,360 --> 00:40:55,050 And then we will go into our glycolysis 630 00:40:55,050 --> 00:40:58,560 for the first minute up to four minutes 631 00:40:58,560 --> 00:41:02,130 and where our mitochondrial respiration is also starting. 632 00:41:02,130 --> 00:41:04,110 So they're all overlapping. 633 00:41:04,110 --> 00:41:06,180 But as glycolysis drops off, 634 00:41:06,180 --> 00:41:09,450 and we're depleting those glycogen stores, 635 00:41:09,450 --> 00:41:13,380 we're going into that mitochondrial respiration 636 00:41:13,380 --> 00:41:15,333 and hitting our steady state. 637 00:41:19,620 --> 00:41:24,620 Another table looking at the different energy systems. 638 00:41:24,960 --> 00:41:27,360 For a quick burst of energy, maximal effort, 639 00:41:27,360 --> 00:41:28,830 zero to five seconds, 640 00:41:28,830 --> 00:41:32,820 we're primarily utilizing the phosphagen system. 641 00:41:32,820 --> 00:41:36,120 Six to 30 seconds of very intense exercise, 642 00:41:36,120 --> 00:41:38,280 again, we're using that phosphagen system, 643 00:41:38,280 --> 00:41:42,540 which becomes depleted after about 10 seconds. 644 00:41:42,540 --> 00:41:45,660 From 30 to 120 seconds of intense exercise, 645 00:41:45,660 --> 00:41:49,230 we're using our fast glycolytic system. 646 00:41:49,230 --> 00:41:52,080 Two to three minutes with moderate activity, 647 00:41:52,080 --> 00:41:55,680 our fast glycolytic, but that becomes depleted. 648 00:41:55,680 --> 00:42:00,510 And then we're crossing over into our aerobic system. 649 00:42:00,510 --> 00:42:02,340 And greater than three minutes, 650 00:42:02,340 --> 00:42:06,033 we're using our oxidative system almost exclusively. 651 00:42:08,310 --> 00:42:11,520 The differences in our energy systems, 652 00:42:11,520 --> 00:42:15,630 there are some gender or actually sex differences. 653 00:42:15,630 --> 00:42:18,630 Men have a greater proportion of type-two muscle fibers, 654 00:42:18,630 --> 00:42:20,460 which means they have a greater potential 655 00:42:20,460 --> 00:42:22,320 for the phosphagen system. 656 00:42:22,320 --> 00:42:25,650 They have greater creatine kinase activity, 657 00:42:25,650 --> 00:42:29,073 and this accompanies increased creatine phosphate levels. 658 00:42:30,420 --> 00:42:35,370 So the interpretation is that the ATP contribution 659 00:42:35,370 --> 00:42:36,600 from the phosphagen system 660 00:42:36,600 --> 00:42:40,500 will support greater anaerobic performance in men. 661 00:42:40,500 --> 00:42:43,170 The key enzymes involved in glycolysis, 662 00:42:43,170 --> 00:42:47,820 including phosphorylase and phosphofructokinase, or PFK, 663 00:42:47,820 --> 00:42:52,500 have also been found in higher concentrations in men. 664 00:42:52,500 --> 00:42:55,380 And there's no difference 665 00:42:55,380 --> 00:42:57,000 that has been reported between genders 666 00:42:57,000 --> 00:43:01,650 in the key enzymes involved in mitochondrial respiration, 667 00:43:01,650 --> 00:43:03,780 the Krebs cycle and electronic transport chain 668 00:43:03,780 --> 00:43:06,333 and beta-oxidation. 669 00:43:12,330 --> 00:43:14,790 It's difficult to separate changes 670 00:43:14,790 --> 00:43:17,670 in physiologic function that occur from age alone 671 00:43:17,670 --> 00:43:19,680 versus the effects of aging combined 672 00:43:19,680 --> 00:43:21,630 with physical inactivity. 673 00:43:21,630 --> 00:43:24,060 So this is a issue here. 674 00:43:24,060 --> 00:43:29,060 Many older adults lose muscle mass, lose VO2 capacity, 675 00:43:31,200 --> 00:43:34,710 not solely from the effects of aging, 676 00:43:34,710 --> 00:43:36,780 but more from the effects of being sedentary. 677 00:43:36,780 --> 00:43:39,060 So in many of the studies, 678 00:43:39,060 --> 00:43:40,350 if you just take a population 679 00:43:40,350 --> 00:43:42,960 of older adults that are heterogeneous, 680 00:43:42,960 --> 00:43:46,113 you can't really sift out the changes. 681 00:43:47,340 --> 00:43:51,600 A better study is to look at active older adults to do that. 682 00:43:51,600 --> 00:43:55,050 So at this point, it's hard to separate out the changes. 683 00:43:55,050 --> 00:43:57,120 Aging does contribute to an overall decline 684 00:43:57,120 --> 00:43:58,560 in skeletal muscle fibers. 685 00:43:58,560 --> 00:44:00,933 We do get sarcopenia as we age. 686 00:44:03,090 --> 00:44:05,190 Differences in the energy systems, 687 00:44:05,190 --> 00:44:08,040 the capacity of energy pathways and the effects of training, 688 00:44:08,040 --> 00:44:09,663 so looking at training. 689 00:44:10,500 --> 00:44:12,240 For short-term high-intensity training, 690 00:44:12,240 --> 00:44:14,970 there's a significant increase in resting concentrations 691 00:44:14,970 --> 00:44:17,670 of creatine phosphate stores in the skeletal muscle. 692 00:44:17,670 --> 00:44:21,570 So even though I talked about those biologic sex differences 693 00:44:21,570 --> 00:44:24,870 in men or the male sex 694 00:44:24,870 --> 00:44:27,990 having more creatine phosphate stores, 695 00:44:27,990 --> 00:44:30,663 with training, you can increase those stores. 696 00:44:31,740 --> 00:44:35,190 Creating kinase, which is the enzyme 697 00:44:35,190 --> 00:44:36,990 that stimulates the phosphagen system, 698 00:44:36,990 --> 00:44:39,450 also is up-regulated with training. 699 00:44:39,450 --> 00:44:41,670 With training, there's increased glucose delivery 700 00:44:41,670 --> 00:44:42,960 to the working muscles. 701 00:44:42,960 --> 00:44:46,170 There's increased resting concentrations of muscle glycogen, 702 00:44:46,170 --> 00:44:48,903 so it's there ready for you to start working. 703 00:44:49,980 --> 00:44:51,000 There's an elevation 704 00:44:51,000 --> 00:44:53,589 of the primary rate-limiting enzymes of glycolysis, 705 00:44:53,589 --> 00:44:56,100 so the phosphorylase and phosphofructokinase. 706 00:44:56,100 --> 00:44:59,280 So those enzymes are there ready to get things going. 707 00:44:59,280 --> 00:45:00,570 There's an enhanced capacity 708 00:45:00,570 --> 00:45:03,540 for tolerating proton accumulation and clearance, 709 00:45:03,540 --> 00:45:05,280 so we can better tolerate 710 00:45:05,280 --> 00:45:08,130 when that lactate is in our system. 711 00:45:08,130 --> 00:45:09,780 We also have an increased activity 712 00:45:09,780 --> 00:45:12,450 of the enzyme lactate dehydrogenase, 713 00:45:12,450 --> 00:45:15,030 the enzyme that permits rapid conversion 714 00:45:15,030 --> 00:45:16,833 of the pyruvate to lactate. 715 00:45:18,300 --> 00:45:22,590 Two, if you recall, cleave that hydrogen off of the NADH 716 00:45:22,590 --> 00:45:25,353 to allow that glycolysis to continue. 717 00:45:29,700 --> 00:45:33,180 With prolonged sub-max endurance training, 718 00:45:33,180 --> 00:45:38,180 this is primarily reliant on our mitochondrial respiration. 719 00:45:38,190 --> 00:45:39,600 We will see an increase 720 00:45:39,600 --> 00:45:41,610 in our mitochondria mass and numbers, 721 00:45:41,610 --> 00:45:44,550 which will allow us to become more efficient 722 00:45:44,550 --> 00:45:46,800 and utilize more oxygen. 723 00:45:46,800 --> 00:45:48,900 This will also increase, 724 00:45:48,900 --> 00:45:52,230 We see increases in glucose and free fatty acid delivery 725 00:45:52,230 --> 00:45:55,680 and resting concentrations of muscle glycogen. 726 00:45:55,680 --> 00:45:59,610 We have increases in the muscle glycogen content, 727 00:45:59,610 --> 00:46:01,860 which is what I said in the other line above. 728 00:46:03,060 --> 00:46:06,210 There's a greater capacity for pyruvate uptake 729 00:46:06,210 --> 00:46:09,150 and oxidation through mitochondrial respiration, 730 00:46:09,150 --> 00:46:11,670 resulting in increased ATP production 731 00:46:11,670 --> 00:46:14,190 and the potential to sustain higher intensities 732 00:46:14,190 --> 00:46:16,560 of steady state exercise. 733 00:46:16,560 --> 00:46:19,560 We become conditioned to be able to work longer 734 00:46:19,560 --> 00:46:21,180 at a higher rate. 735 00:46:21,180 --> 00:46:23,970 There are really good multiple adaptations 736 00:46:23,970 --> 00:46:26,010 to our cardiovascular system. 737 00:46:26,010 --> 00:46:28,440 There's expanded blood volume. 738 00:46:28,440 --> 00:46:31,170 There's expanded left ventricular chamber size, 739 00:46:31,170 --> 00:46:34,650 capillary density, and our pulmonary system. 740 00:46:34,650 --> 00:46:37,080 There's more conditioned respiratory muscles. 741 00:46:37,080 --> 00:46:39,180 We have a bigger air volume, 742 00:46:39,180 --> 00:46:41,970 and so these cellular adaptions 743 00:46:41,970 --> 00:46:45,063 help improve our overall metabolic efficiency. 744 00:46:49,680 --> 00:46:51,570 This is gonna be our activity for labs, 745 00:46:51,570 --> 00:46:53,973 so I am not going to talk about this right now. 746 00:46:56,430 --> 00:46:59,583 And I think this is complete.