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Describe Glucose Catabolism

Chapter 7: How Cells Release Energy

Chapter 7: How Cells Release Energy

1. Name the process in which most of the energy from glucose is converted to ATP. What roles does oxygen play in this process? What gas is produced as a waste product? Where in a cell do these reactions occur? Through electron transport chain, most of the energy from glucose is converted into ATP. Oxygen is the final acceptors of electrons in ETC and forms water as it combines with hydrogen ions. Carbon dioxide is produced as a waste product. These reactions occur in mitochondria. 2. Why is the electron transport pathway divided into so many small reactions? It is divided into many small reactions, so energy would be released in many small steps instead of one large one. 3. Across what euakryotic membrane is a gradient established during cellular respiration? What is unequally distributed across these membranes and what caused this unequal distribution? A gradient is established across the inner membrane of the mitochondria. Hydrogen ions or protons are unequally distributed. Energy from the electron flow is used to pump hydrogen ions; thus, causing unequal distribution. 4. Describe and name three stages cellular respiration that aerobic organisms use to extract energy from glucose. Glycolysis: One molecule of glucose is broken down into two molecules of pyruvates, and 2 NADH and 2 ATP are formed. Krebs Cycle: As 2 molecules of pyruvates enter the mitochondria, they are converted into 2 molecules of acetyl-CoA, 2 NADH are formed, and 2 molecules of CO2 are released. As 2 acetyl-CoA enter the Krebs cycle one at a time, 4 CO2, 2 ATP, 6 NADH, and 2 FADH2 are formed in two cycles. Electron Transport Chain: As NADH and FADH2 give up their electrons to ETC in the inner membrane of the mitochondria, the energy from the electron flow is used to pump hydrogen ions, creating a pr Continue reading >>

Concepts Of Biology

Concepts Of Biology

CO2 + H2O + energy (ATP = chemical energy, heat) A. So, what can we learn/deduce from this equation: Glucose catabolism is essentially the "reverse" of photosynthesis Glucose catabolism is a redox reaction. Glucose (carbohydrate) is oxidized to carbon dioxide. The acceptor for the electrons is oxygen which is reduced to water. The chemical bond energy of glucose is released as ATP and heat This is the primary source of ATP for all aerobic organisms B. Hill Model Revisited - a diagram of the hill will be provided in class. Some take-home-lessons from the hilltop: Anabolism (synthetic reactions) is analogous to pushing the rock uphill, catabolism (degradative reactions) is analogous to the rock rolling downhill; Photosynthesis (an anabolic process) is analogous to pushing the rock uphill, respiration (a catabolic process) is analogous to the rock rolling downhill; The energy required to push the rock (glucose) uphill comes from light (radiant energy); The release of energy from glucose rolling downhill is coupled to ATP production (ca. 40% of the energy is trapped in ATP but more than half of the energy is lost as heat). II. Rolling metabolic rocks downhill - A look at Glucose Catabolism Glucose catabolism occurs in a series of small, sequential, highly controlled and regulated steps (reactions). The processes involved are glycolysis, which is the first step of glucose breakdown, and it is followed by either fermentation or cellular respiration (depending on the availability of oxygen). Why so many steps? Back to our hill model for an answer. There are two kinds of hills - those with a gradual, step-wise slope and those with a steep precipice or overhang. In each case the rock will roll down the hill and release the same total amount of energy, which is equal to the ener Continue reading >>

Biology, Answering The Big Questions Of Life/metabolism/metabolism3

Biology, Answering The Big Questions Of Life/metabolism/metabolism3

Biology, Answering the Big Questions of Life/Metabolism/Metabolism3 How many ATPs are generated by Aerobic respiration? Edit To begin glycolysis requires the input of two ATP from the cytoplasm. This is the activation energy needed to start this reaction. ATPs made by glycolysis. Note the Net Yield for glycolysis would be 2ATPs (4 ATP-2ATP). These molecules are created by glycolysis, but they can only be converted into ATP in the mitochondrial electron transport chain. This requires them to enter the mitochondria. A step that is free in some organisms, and costs 2ATP in others. This is what causes the differences in the Net yield of aerobic respiration. From the complete breakdown of one glucose molecule to carbon dioxide and oxidation of all the high energy molecules. What is the purpose of anaerobic and aerobic respiration? Edit The sugar glucose is the major food molecule in the cell, but it is too energetic to use directly in most chemical reactions. To be useful, glucose is broken down into an energy storing molecule (ATP) that can be used throughout the cell. Why do cells need to ferment if they already get 2 ATP from glycolysis? Edit Glycolysis yields 2 net ATPs and 2NADHs. NADH is another high energy molecule. (NAD has low energy, NADH has higher energy). NADH has many fewer uses in the cell than ATP. It is normally converted into ATP in the mitochondrial electron transport chain if oxygen is present. If no oxygen is present, then NADH builds up and the cell can run completely out of NAD. Without NAD glycolysis stops. NAD becomes a "limiting reagent" The chemical whose concentration determines whether the reaction will happen or not. In the absence of Oxygen, the cell runs out of NAD and glycolysis is stopped until it can be regenerated. To regenerate NAD the c Continue reading >>

A General Overview Of The Major Metabolic Pathways

A General Overview Of The Major Metabolic Pathways

A general overview of the major metabolic pathways Assistant Professor, Universidade FernandoPessoa Metabolism is the set of chemical rections that occur in a cell, which enable it to keep living, growing and dividing.Metabolic processes are usually classified as: catabolism - obtaining energy and reducing power from nutrients. anabolism - production of new cell components, usually through processes that require energy and reducing power obtained from nutrient catabolism. There is a very large number of metabolic pathways. In humans, the most important metabolic pathways are: glycolysis - glucose oxidation in order to obtain ATP citric acid cycle (Krebs' cycle) - acetyl-CoA oxidation in order to obtain GTP and valuable intermediates. oxidative phosphorylation - disposal of the electrons released by glycolysis and citric acid cycle. Much of the energy released in this process can be stored as ATP. pentose phosphate pathway - synthesis of pentoses and release of the reducing power needed for anabolic reactions. urea cycle - disposal of NH4+ in less toxic forms fatty acid -oxidation - fatty acids breakdown into acetyl-CoA, to be used by the Krebs' cycle. gluconeogenesis - glucose synthesis from smaller percursors, to be used by the brain. Click on the picture to get information on each pathway Metabolic pathways interact in a complex way in order to allow an adequate regulation. This interaction includes the enzymatic control of each pathway, each organ's metabolic profile and hormone control . Flow is regulated in the gluconeogenesis-specific reactions. Pyruvate carboxilase is activated by acetyl-CoA, which signals the abundance of citric acid cycle intermediates, i.e., a decreased need of glucose. The citric acid cycle is regulated mostly by substrate availability, prod Continue reading >>

Cellular Respiration Summary

Cellular Respiration Summary

It is expected that you have studied this topic in High School Biology. This subject may not be covered in the lectures, but you are responsible for all of the information in these notes because it is important background for topics in this course, suchas muscle cell physiology (Chapter 7). Please be familiar with this material before we reach those topics in lecture. Pay special attention to bold and underlined terms. is the enzymatic breakdown of glucose (C6H12O6) in the presence of oxygen (O2) to produce cellular energy (ATP): a ten-step process that occurs in the cytoplasm converts each molecule of glucose to two molecules of pyruvic acid (a 3-carbon molecule) - proceeds whether or not O2 is present ; O2 is not required net yield of 2 NADH per glucose (NADH is nicotine adenine dinucleotide, a co-enzyme that serves as a carrier for H+ ions liberated as glucose is oxidized.) The pyruvic acid diffuses into the inner compartment of the mitochondrion where a transition reaction (Fig. 18-3) occurs that serves to prepare pyruvic acid for entry into the next stage of respiration: (a) pyruvic acid acetic acid + CO2 (a waste product of cell metabolism) + NADH+ (b) acetic acid + co-enzyme A acetyl CoA the acetyl group detaches from the co-enzyme A and enters the reaction cycle an aerobic process; will proceed only in the presence of O2 net yield of 2 ATP per glucose molecule (per 2 acetyl CoA) net yield of 6 NADH and 2 FADH2 (FAD serves the same purpose as NAD) in this stage of cellular respiration, the oxidation of glucose to CO2 is completed consists of a series of enzymes on the inner mitochondrial membrane electrons are released from NADH and from FADH2 and as they are passed along the series of enzymes, they give up energy which is used to fuel a process called chemiosmo Continue reading >>

Carbohydrate Catabolism

Carbohydrate Catabolism

Digestion is the breakdown of carbohydrates to yield an energy rich compound called ATP . The production of ATP is achieved through the oxidation of glucose molecules. In oxidation, the electrons are stripped from a glucose molecule to reduce NAD+ and FAD . NAD+ and FAD possess a high energy potential to drive the production of ATP in the electron transport chain . ATP production occurs in the mitochondria of the cell. There are two methods of producing ATP: aerobic and anaerobic . In aerobic respiration, oxygen is required. Oxygen plays a key role as it increases ATP production from 4 ATP molecules to about 30 ATP molecules. In anaerobic respiration, oxygen is not required. When oxygen is absent, the generation of ATP continues through fermentation.There are two types of fermentation: alcohol fermentation and lactic acid fermentation . There are several different types of carbohydrates : polysaccharides (e.g., starch , amylopectin , glycogen , cellulose ), monosaccharides (e.g., glucose , galactose , fructose , ribose ) and the disaccharides (e.g., sucrose , maltose , lactose ). Glucose reacts with oxygen in the following redox reaction, C6H12O6 + 6O2 6CO2 + 6H2O, Carbon dioxide and water are waste products, and the overall reaction is exothermic . The breakdown of glucose into energy in the form of molecules of ATP is therefore one of the most important biochemical pathways found in living organisms. Glycolysis , which means sugar splitting, is the initial process in the cellular respiration pathway. Glycolysis can be either an aerobic or anaerobic process. When oxygen is present, glycolysis continues along the aerobic respiration pathway. If oxygen is not present, then ATP production is restricted to anaerobic respiration . The location where glycolysis, aerobic or Continue reading >>

Bc - Ch 15 - Glucose Catabolism

Bc - Ch 15 - Glucose Catabolism

Mechanisms of enzyme conversion and intermediates Mechanisms controlling the flux of metabolites through the pathway Pyruvalte while generagting two molecules Animals use. Pyruvate converted to CO2 and H2O via citric acid cycle and oxidative phosphorylation In fungi and bacteria. Alcoholic fermentation in yeast Once glucose is phosphorylated within cel.. It cannot scape cell and has to go through glycolysis Glucose Catabolism Pathway Overview (3 steps) 1. Add phosphoryl groups to activate glucose. 2. Convert the phosphorylated intermediates into high energy phosphate compounds 3. Couple the transfer of the phosphate to ADP to form ATP. First Stage of coupling the transfer of phosphate to ADP to form ATP Stage I. A preparatory stage in which glucose is phosphorylated and cleaved to yield two molecules of glyceraldehyde-3-phosphate - uses two ATPs Second Stage of coupling the transfer of phosphate to ADP to form ATP Stage II. glyceraldehyde-3-phosphate is converted to pyruvate with the concomitant generation of four ATPs-net profit is Oxidizing Power of NAD+ must be recycled in Glucose Catabolism. NADH produced must be converted back to NAD+ Under anaerobic conditions in muscle, NADH's role reduces pyruvate to lactate (homolactic fermentation) Under anaerobic conditions in yeast, NADH's role pyruvate is decarboxylated to yeild COabd acetaldehyde and the latter is reduced by NADH to ethanol whereby NAD+ is regenerated. The mitorchondrial oxidation of each NADH to NAD+ yields 3 ATP Stage I: Energy investment (rxns. 1-5), glucose phosphorylated and cleaved to yield 2 GAP and consumes 2 ATP State II: Energy recovery (rxns. 6-10), GAP converted to pyruvate with generation of 4 ATP **Glucose + 2NAD+ + 2ADP + 2Pi 2NADH + 2pyruvate + 2ATP + Isozymes: Enzymes that catalyze the sa Continue reading >>

The Proinflammatory Mediator Macrophage Migration Inhibitory Factor Induces Glucose Catabolism In Muscle.

The Proinflammatory Mediator Macrophage Migration Inhibitory Factor Induces Glucose Catabolism In Muscle.

The proinflammatory mediator macrophage migration inhibitory factor induces glucose catabolism in muscle. The Picower Institute for Medical Research, Manhasset, New York 10030, USA. Severe infection or tissue invasion can provoke a catabolic response, leading to severe metabolic derangement, cachexia, and even death. Macrophage migration inhibitory factor (MIF) is an important regulator of the host response to infection. Released by various immune cells and by the anterior pituitary gland, MIF plays a critical role in the systemic inflammatory response by counterregulating the inhibitory effect of glucocorticoids on immune-cell activation and proinflammatory cytokine production. We describe herein an unexpected role for MIF in the regulation of glycolysis. The addition of MIF to differentiated L6 rat myotubes increased synthesis of fructose 2,6-bisphosphate (F2,6BP), a positive allosteric regulator of glycolysis. Increased expression of the enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) enhanced F2,6BP production and, consequently, cellular lactate production. The catabolic effect of TNF-alpha on myotubes was mediated by MIF, which served as an autocrine stimulus for F2, 6BP production. TNF-alpha administered to mice decreased serum glucose levels and increased muscle F2,6BP levels; pretreatment with a neutralizing anti-MIF mAb completely inhibited these effects. Anti-MIF also prevented hypoglycemia and increased muscle F2,6BP levels in TNF-alpha-knockout mice that were administered LPS, supporting the intrinsic contribution of MIF to these inflammation-induced metabolic changes. Taken together with the recent finding that MIF is a positive, autocrine stimulator of insulin release, these data suggest an important role for MIF in the control of host Continue reading >>

26.7: The Catabolism Of Carbohydrates

26.7: The Catabolism Of Carbohydrates

Describe the function of glycolysis and identify its major products. Describe how the presence or absence of oxygen determines what happens to the pyruvate and the NADH that are produced in glycolysis. Determine the amount of ATP produced by the oxidation of glucose in the presence and absence of oxygen. In stage II of catabolism, the metabolic pathway known as glycolysis converts glucose into two molecules of pyruvate (a three-carbon compound with three carbon atoms) with the corresponding production of adenosine triphosphate (ATP). The individual reactions in glycolysis were determined during the first part of the 20th century. It was the first metabolic pathway to be elucidated, in part because the participating enzymes are found in soluble form in the cell and are readily isolated and purified. The pathway is structured so that the product of one enzyme-catalyzed reaction becomes the substrate of the next. The transfer of intermediates from one enzyme to the next occurs by diffusion. The 10 reactions of glycolysis, summarized in Figures \(\PageIndex{1}\) and \(\PageIndex{2}\), can be divided into two phases. In the first 5 reactionsphase Iglucose is broken down into two molecules of glyceraldehyde 3-phosphate. In the last five reactionsphase IIeach glyceraldehyde 3-phosphate is converted into pyruvate, and ATP is generated. Notice that all the intermediates in glycolysis are phosphorylated and contain either six or three carbon atoms. Figure \(\PageIndex{1}\):Phase 1 of Glycolysis When glucose enters a cell, it is immediately phosphorylated to form glucose 6-phosphate, in the first reaction of phase I. The phosphate donor in this reaction is ATP, and the enzymewhich requires magnesium ions for its activityis hexokinase. In this reaction, ATP is being used rather th Continue reading >>

What Are The Four Phases Of Complete Glucose Breakdown?

What Are The Four Phases Of Complete Glucose Breakdown?

What Are the Four Phases of Complete Glucose Breakdown? By Frederick S. Blackmon; Updated April 24, 2017 Glucose is a simple carbohydrate that acts as a primary source of energy for many physiological functions. Through a four phase process called cellular respiration, the body can metabolize and use the energy found in glucose. Glucose is broken down in the parenchymal cells and tissues of the liver. Cellular respiration releases energy in the body but first requires the splitting of glucose into water and carbon dioxide. Glycolysis is the first phase of breakdown in which glucose is broken into two molecules of pyruvate in the cytoplasm. The second phase of glucose breakdown is the transition reaction. During this phase, carbon dioxide is removed and the pyruvate molecules are broken into a 2-carbon aceytl. The citric acid cycle,also called the Krebb's cycle, is the third phase and occurs inside the mitochondria, the cell's powerhouse. A series of oxidation reactions produce NADH, FADH, and ADP. The fourth phase of glucose breakdown is the electron transport system. For every two electrons that enter the system, three ATP are produced. The Medical Biochemistry Page: Glycolysis Frederick S. Blackmon's love for fiction and theater eventually led to a career writing screenplays for the film and television industry. While living in Florida, Blackmon began exploring issues on global warming, health and environmental science. He spent two years as a Parkour and free-running instructor as well. Now he writes everything from how-to blogs to horror films. Continue reading >>

Catabolism

Catabolism

Types of Catabolism Catabolism is the set of metabolic processes that break down large molecules. Learning Objectives Summarize various types of catabolism included in metabolism (catabolism of carbohydrates, proteins and fats) Key Takeaways Key Points The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions. Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their guts. Fats are catabolised by hydrolysis to free fatty acids and glycerol. Amino acids are either used to synthesize proteins and other biomolecules, or oxidized to urea and carbon dioxide as a source of energy. Carbohydrates are usually taken into cells once they have been digested into monosaccharides and then processed inside the cell via glycolysis. Key Terms polymer: A long or larger molecule consisting of a chain or network of many repeating units, formed by chemically bonding together many identical or similar small molecules called monomers. A polymer is formed by polymerization, the joining of many monomer molecules. acetyl CoA: Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production. catabolism: Destructive metabolism, usually includes the release of energy and breakdown of materials. Overview of Catabolism Catabolism is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of catabolic reactions is to provide the energy and components needed by anabolic reactions. The exact nature of these ca Continue reading >>

Chapter 14 : Glycolysis And The Catabolism Of Hexoses

Chapter 14 : Glycolysis And The Catabolism Of Hexoses

Having examined the organizing principles of cell metabolism and bioenergetics, we are ready to see how the chemical energy stored in glucose and other fuel molecules is released to perform biological work. -Glucose is the major fuel of most organisms and occupies a central position in metabolism. It is relatively rich in potential energy; its complete oxidation to carbon dioxide and water proceeds with a standard free-energy change of -2,840 kJ/mol. By storing glucose as a high molecular weight polymer, a cell can stockpile large quantities of hexose units while maintaining a relatively low cytosolic osmolarity. When the cell's energy demands suddenly increase, glucose can be released quickly from these intracellular storage polymers. Glucose is not only an excellent fuel, it is also a remarkably versatile precursor, capable of supplying a huge array of metabolic intermediates, the necessary starting materials for biosynthetic reactions. E. coli can obtain from glucose the carbon skeletons for every one of the amino acids, nucleotides, coenzymes, fatty acids, and other metabolic intermediates needed for growth. A study of the numerous metabolic fates of glucose would encompass hundreds or thousands of transformations. In the higher plants and animals glucose has three major fates: it may be stored (as a polysaccharide or as sucrose), oxidized to a three-carbon compound (pyruvate) via glycolysis, or oxidized to pentoses via the pentose phosphate (phosphogluconate) pathway (Fig. 14-1). This chapter begins with a description of the individual reactions that constitute the glycolytic pathway and of the enzymes that catalyze them. We then consider fermentation, the operation of the glycolytic pathway under anaerobic conditions. The sources of glucose units for glycolysis a Continue reading >>

Metabolism Of Molecules Other Than Glucose

Metabolism Of Molecules Other Than Glucose

You have learned about the catabolism of glucose, which provides energy to living cells. But living things consume more than just glucose for food. How does a turkey sandwich, which contains various carbohydrates, lipids, and protein, provide energy to your cells? Basically, all of these molecules from food are converted into molecules that can enter the cellular respiration pathway somewhere. Some molecules enter at glycolysis, while others enter at the citric acid cycle. This means that all of the catabolic pathways for carbohydrates, proteins, and lipids eventually connect into glycolysis and the citric acid cycle pathways. Metabolic pathways should be thought of as porous—that is, substances enter from other pathways, and other substances leave for other pathways. These pathways are not closed systems. Many of the products in a particular pathway are reactants in other pathways. Carbohydrates So far, we have discussed the carbohydrate from which organisms derive the majority of their energy: glucose. Many carbohydrate molecules can be broken down into glucose or otherwise processed into glucose by the body. Glycogen, a polymer of glucose, is a short-term energy storage molecule in animals (Figure 1). When there is plenty of ATP present, the extra glucose is converted into glycogen for storage. Glycogen is made and stored in the liver and muscle. Glycogen will be taken out of storage if blood sugar levels drop. The presence of glycogen in muscle cells as a source of glucose allows ATP to be produced for a longer time during exercise. Figure 1 Glycogen is made of many molecules of glucose attached together into branching chains. Each of the balls in the bottom diagram represents one molecule of glucose. (Credit: Glycogen by BorisTM. This work has been released into Continue reading >>

Cellular Respiration

Cellular Respiration

Identify the reactants and products of cellular respiration and where these reactions occur in a cell Now that weve learned how autotrophs like plants convert sunlight to sugars, lets take a look at how all eukaryoteswhich includes humans!make use of those sugars. In the process of photosynthesis, plants and other photosynthetic producers createglucose, which stores energy in its chemical bonds. Then, both plantsand consumers, such as animals, undergo a series of metabolic pathwayscollectively called cellular respiration. Cellular respirationextracts the energy from the bonds in glucose and converts it into a form that all living things can use. Describe the process of glycolysis and identify its reactants and products Describe the process of pyruvate oxidation and identify its reactants and products Describe the process of the citric acid cycle (Krebs cycle) and identify its reactants and products Describe the respiratory chain (electron transport chain) and its role in cellular respiration Cellular respiration is a process that all living things use to convert glucose into energy. Autotrophs (like plants)produce glucose during photosynthesis. Heterotrophs (like humans) ingest other living things to obtain glucose. While the process can seem complex, this page takes you through the key elements of each part of cellular respiration. Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Nearly all living organisms carry out glycolysis as part of their metabolism. The process does not use oxygen and is therefore anaerobic (processes that use oxygen are called aerobic). Glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells. Glucose enters heterotrophic cells in two ways. Through secondary active tran Continue reading >>

24.2 Carbohydrate Metabolism Anatomy And Physiology

24.2 Carbohydrate Metabolism Anatomy And Physiology

By the end of this section, you will be able to: Describe the pathway of a pyruvate molecule through the Krebs cycle Explain the transport of electrons through the electron transport chain Describe the process of ATP production through oxidative phosphorylation Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen atoms. The family of carbohydrates includes both simple and complex sugars. Glucose and fructose are examples of simple sugars, and starch, glycogen, and cellulose are all examples of complex sugars. The complex sugars are also called polysaccharides and are made of multiple monosaccharide molecules. Polysaccharides serve as energy storage (e.g., starch and glycogen) and as structural components (e.g., chitin in insects and cellulose in plants). During digestion, carbohydrates are broken down into simple, soluble sugars that can be transported across the intestinal wall into the circulatory system to be transported throughout the body. Carbohydrate digestion begins in the mouth with the action of salivary amylase on starches and ends with monosaccharides being absorbed across the epithelium of the small intestine. Once the absorbed monosaccharides are transported to the tissues, the process of cellular respiration begins ( Figure 1 ). This section will focus first on glycolysis, a process where the monosaccharide glucose is oxidized, releasing the energy stored in its bonds to produce ATP. Figure 1. Cellular Respiration. Cellular respiration oxidizes glucose molecules through glycolysis, the Krebs cycle, and oxidative phosphorylation to produce ATP. Glucose is the bodys most readily available source of energy. After digestive processes break polysaccharides down into monosaccharides, including glucose, the monosaccharides are transporte Continue reading >>

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