Cellular Energy and Respiration PDF

8/27/24, 8:24 PM Platform | Study Fetch Cellular Energy and Respiration (00:00 - 00:14) Overview of Cellular Respiration (00:14 - 00:26) Cellular respiration is a series of metabolic reactions that convert chemical energy...

8/27/24, 8:24 PM Platform | Study Fetch Cellular Energy and Respiration (00:00 - 00:14) Overview of Cellular Respiration (00:14 - 00:26) Cellular respiration is a series of metabolic reactions that convert chemical energy into ATP energy for the cell. Lesson Overview (00:26 - 00:36) We will discuss: Catabolism and an overview of cellular respiration Glycolysis and the citric acid cycle Anaerobic respiration and fermentation Catabolism (00:36 - 00:53) Catabolism is the process of breaking down complex molecules into simpler ones: Proteins into amino acids Polysaccharides into monosaccharides Fats into fatty acids These breakdown products will feed into the citric acid cycle to generate ATP. Cellular Respiration Equation (00:53 - 01:06) The overall equation for cellular respiration is: Glucose + 6 Oxygen → 6 Carbon Dioxide + 6 Water + Energy (ATP) Overview of Cellular Respiration Steps (01:06 - 01:28) Cellular respiration involves several steps: 1. Digestion of food into simpler molecules (amino acids, monosaccharides, fatty acids) 2. Glycolysis to break down glucose into pyruvate 3. Citric acid cycle and oxidative phosphorylation in the mitochondria to generate ATP Digestion (Stage 1) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6be48ab287f54e41f2af/document?go=note 1/7 8/27/24, 8:24 PM Platform | Study Fetch (01:28 - 01:51) Digestion breaks down complex molecules into simpler ones: Starches and polysaccharides into simple sugars Fats into fatty acids and glycerol Proteins into amino acids This occurs primarily in the gut lumen (stomach and small intestine) The simpler molecules are then absorbed into the bloodstream. Glycolysis (Stage 2) (01:51 - 02:23) Glycolysis means "splitting of sugar" It is the process of breaking down a glucose molecule into pyruvate This is the first step in harnessing the energy from the food we eat. Citric Acid Cycle and Oxidative Phosphorylation (Stage 3) (02:23 - 03:31) The citric acid cycle and oxidative phosphorylation generate more energy from the pyruvate: The citric acid cycle further breaks down the pyruvate Oxidative phosphorylation uses the products to generate a proton gradient that drives ATP synthesis Oxidative phosphorylation uses the NADH and FADH2 produced earlier to pump hydrogen ions across the inner mitochondrial membrane This proton gradient then flows back through ATP synthase to catalyze the formation of ATP from ADP and inorganic phosphate. Substrate-Level Phosphorylation (03:31 - 04:08) Substrate-level phosphorylation is when a phosphate group is directly transferred to ADP to form ATP, without the need for the proton gradient and ATP synthase. This occurs earlier in the process, such as during glycolysis. Phosphate Transfer and ATP Synthesis (00:04:08 - 00:04:30) When a phosphate group is directly transferred to something, it would be a diphosphate. Why are there many steps in ATP synthesis? If glucose was oxidized to CO2 and H2O in a single step, it would release a large amount of energy that cannot be fully captured by any carrier molecule. The step-wise process of ATP synthesis allows for the maximal harnessing of energy from the glucose molecule. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6be48ab287f54e41f2af/document?go=note 2/7 8/27/24, 8:24 PM Platform | Study Fetch (00:04:30 - 00:04:54) The many steps in ATP synthesis happen rapidly in the cell, but are necessary to sequentially store the energy from glucose in ATP. Cellular Respiration Overview (00:04:54 - 00:05:17) Cellular respiration includes glycolysis and the citric acid cycle. Glycolysis is the breakdown of glucose, resulting in: 2 pyruvate 2 ATP 2 NADH (00:05:17 - 00:05:31) Glycolysis is thought to be the initial mechanism by which organisms first harnessed energy. Early organisms may have simply gotten rid of the pyruvate or converted it to lactate. (00:05:31 - 00:05:42) Glycolysis is now the first step in the breakdown of sugar in the cell. Steps of Glycolysis (00:05:42 - 00:06:09) Glycolysis is a series of reactions: 1. Energy investment step: ATP is added by hexokinase/glucokinase to trap glucose in the cell as glucose-6- phosphate. 2. The 6-carbon glucose is cleaved into two 3-carbon pyruvate. 3. A small amount of energy is generated from each pyruvate. (00:06:09 - 00:06:25) Step 1: Hexokinase/glucokinase adds a phosphate to glucose to make glucose-6-phosphate. This is an irreversible step in glycolysis. (00:06:25 - 00:06:39) Hexokinase is used in the pancreas and liver, while glucokinase is used in other tissues. (00:06:39 - 00:06:51) Glycolysis has 3 irreversible steps, and trapping glucose as glucose-6-phosphate is one of them. (00:06:51 - 00:07:14) Step 2: Isomerization of glucose-6-phosphate into fructose-6-phosphate. Step 3: Phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate by phosphofructokinase. This is another irreversible step in glycolysis. (00:07:14 - 00:07:47) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6be48ab287f54e41f2af/document?go=note 3/7 8/27/24, 8:24 PM Platform | Study Fetch The next steps of glycolysis will continue the breakdown of the 6-carbon fructose-1,6-bisphosphate into two 3- carbon pyruvate molecules. Glycolysis and the Citric Acid Cycle Glycolysis (00:07:47 - 00:08:05) Glycolysis involves the conversion of glucose to fructose-6-phosphate and then to fructose-1,6-bisphosphate There is an additional step that generates fructose-2,6-bisphosphate, which helps modulate the rate of glycolysis (00:08:05 - 00:08:20) The 6-carbon sugar is cleaved into two 3-carbon molecules (glyceraldehyde-3-phosphate) The products of the previous step are isomerized into glyceraldehyde-3-phosphate (00:08:20 - 00:08:37) Glyceraldehyde-3-phosphate is oxidized The transfer of high-energy phosphate groups from the previous step creates ATP (00:08:37 - 00:08:48) This energy generation step produces 1,3-bisphosphoglycerate, which is then converted to 3-phosphoglycerate This is the first instance where ATP is produced from the sugar molecule (00:08:48 - 00:08:58) The final irreversible step of glycolysis is the creation of pyruvate by pyruvate kinase (00:08:58 - 00:09:16) Gluconeogenesis is the process of creating glucose from other energy sources, typically in the liver The irreversible steps of glycolysis require specialized enzymes to bypass them in the reverse direction (00:09:16 - 00:09:30) The liver can take products of metabolism or other energy sources and convert them back into glucose for release into the bloodstream (00:09:30 - 00:09:43) The irreversible enzymes in glycolysis require additional "sister" enzymes to go in the reverse direction, unlike the other enzymes that can go both ways based on concentration gradients (00:09:43 - 00:09:56) Summary of glycolysis: Breaks down 1 glucose molecule into 2 pyruvate, 2 NADH, and 2 ATP Involves an initial energy investment of 2 ATP The end product, pyruvate, feeds into the next step, the citric acid cycle The Citric Acid Cycle https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6be48ab287f54e41f2af/document?go=note 4/7 8/27/24, 8:24 PM Platform | Study Fetch (00:10:21 - 00:10:36) The citric acid cycle, also known as the Krebs cycle, is the next step after glycolysis It involves many steps and produces NADH, FADH2, and CO2 per pyruvate molecule (00:10:36 - 00:10:55) The products of the citric acid cycle include 3 NADH, 1 FADH2, and 1 CO2 per pyruvate molecule These high-energy electrons from NADH and FADH2 then feed into the electron transport chain (00:10:55 - 00:11:22) The electron transport chain is a series of enzymes embedded in the inner mitochondrial membrane As electrons hop from one enzyme to the next, energy is released, which is used to pump hydrogen ions into the intermembrane space This creates a proton gradient that drives the production of ATP through the enzyme ATP synthase Electron Transport Chain and ATP Synthesis (00:11:22 - 00:11:33) Chromium (Cr) is a non-protein component that is important for living organisms. Some of these components have roles in cell death, apoptosis, and modulating different processes. (00:11:33 - 00:11:46) The establishment of a proton (H+) gradient is very important. Energy is released at specific sites in the electron transport chain. (00:11:46 - 00:12:00) The energy from NADH and FADH2 is used to pump H+ protons across the inner mitochondrial membrane into the intermembrane space. This movement generates a proton gradient that serves as a source of energy. (00:12:00 - 00:12:21) The proton gradient can be thought of like a battery or a dam. The energy from NADH and FADH2 is used to "push water up" the dam, and then the water can be "uncorked" to release energy. This is similar to how the proton gradient is used to generate ATP. (00:12:21 - 00:12:41) The electron transport chain consists of different complexes, including NADH dehydrogenase, Coenzyme Q, Cytochrome c reductase, and Cytochrome c oxidase. As the electrons are passed through these complexes, H+ protons are pumped into the intermembrane space. (00:12:41 - 00:12:53) The total ATP generated from one glucose molecule is 36 ATP. This includes 2 ATP from glycolysis and the rest from the electron transport chain and ATP synthase. (00:12:53 - 00:13:21) The exact number of ATP generated can vary from 32 to 36 ATP, depending on the shuttles used and the tissue type. The variation is due to factors like the aspartate or malate shuttle. (00:13:21 - 00:13:31) The mitochondrial structure includes an outer membrane, intermembrane space, inner membrane, and matrix. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6be48ab287f54e41f2af/document?go=note 5/7 8/27/24, 8:24 PM Platform | Study Fetch The electron transport chain and ATP synthase are located in the inner membrane. (00:13:31 - 00:13:51) The intermembrane space is where the H+ protons accumulate, creating the proton gradient. The matrix is where the citric acid cycle and the conversion of pyruvate to acetyl-CoA occur. (00:13:51 - 00:14:02) Glycolysis occurs in the cytoplasm, while the citric acid cycle and oxidative phosphorylation happen within the mitochondria. This is why the mitochondria are often referred to as the "powerhouse of the cell." (00:14:02 - 00:14:14) Chemiosmosis is the mechanism of ATP generation that uses the proton gradient to drive ATP synthase and produce ATP. (00:14:14 - 00:14:26) Chemiosmosis is the process where the energy stored in the proton gradient is used by ATP synthase to generate ATP. (00:14:26 - 00:14:42) Anaerobic respiration and fermentation occur in the absence of oxygen. There are two main types: lactic acid fermentation and alcoholic fermentation. Fermentation: Regenerating NAD+ for Glycolysis (00:14:42 - 00:15:06) NAD+ made by glycolysis remains in the cytosol, and the pyruvate is converted into products that are excreted from the cell Lactic fermentation produces lactate, which is secreted from muscle cells Alcohol fermentation produces ethanol (C2) Fermentation is important to regenerate NAD+ from NADH, allowing glycolysis to continue (00:15:06 - 00:15:23) If you constantly generate NADH, you'll eventually run out of NAD+ and can no longer proceed through glycolysis Fermentation is the process that regenerates NAD+ in order to keep glycolysis going (00:15:23 - 00:15:36) Without an electron receptor like NAD+, you couldn't continue glycolysis Regenerating NAD+ is crucial to keep glycolysis going (00:15:36 - 00:15:47) In mammals, pyruvate is converted to lactate, which regenerates NAD+ from NADH The lactate is then excreted from the cell (00:15:47 - 00:15:59) If all cells were just producing lactate/lactic acid, it would make the body very acidic This can happen in cases of infection, where high lactate levels make the body more acidic https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6be48ab287f54e41f2af/document?go=note 6/7 8/27/24, 8:24 PM Platform | Study Fetch (00:15:59 - 00:16:13) High lactate levels and acidity are not good for muscle cells When muscles are working anaerobically (without enough oxygen), they produce lactate and lactic acid, causing the "burning" sensation (00:16:13 - 00:16:25) Yeast, in contrast to mammals, generate ethanol instead of lactate to regenerate NAD+ (00:16:25 - 00:16:41) Evolutionarily, mammals have adapted to generate lactate rather than ethanol for NAD+ regeneration (00:16:41 - 00:16:53) Fermentation occurs in plants, yeast, and bacteria to regenerate NAD+ from NADH (00:16:53 - 00:17:10) For each 2 pyruvate converted, 1 CO2 and 1 acetaldehyde are produced Acetaldehyde is then converted to ethanol, regenerating NAD+ (00:17:10 - 00:17:29) In lactic acid fermentation, pyruvate is converted to lactate, regenerating NAD+ This allows glycolysis to continue, producing ATP (00:17:29 - 00:17:53) The ethanol produced in fermentation is the source of alcohol in beverages like beer and wine Lactic acid fermentation in mammals regenerates NAD+ from NADH (00:17:53 - 00:18:09) Fermentation is a complex but important process that allows cells to regenerate NAD+ and continue glycolysis to produce ATP https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6be48ab287f54e41f2af/document?go=note 7/7