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What is the primary reason tumour cells convert a large amount of glucose to lactate, even with sufficient oxygen?
What is the primary reason tumour cells convert a large amount of glucose to lactate, even with sufficient oxygen?
What pharmacological strategy is being considered for obesity treatment concerning brown adipose tissue?
What pharmacological strategy is being considered for obesity treatment concerning brown adipose tissue?
Which metabolic pathway do tumour cells primarily use to produce energy?
Which metabolic pathway do tumour cells primarily use to produce energy?
When comparing glycolysis and oxidative phosphorylation, which statement is true about ATP production?
When comparing glycolysis and oxidative phosphorylation, which statement is true about ATP production?
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Which of the following accurately describes the fate of pyruvate in tumour cells under aerobic conditions?
Which of the following accurately describes the fate of pyruvate in tumour cells under aerobic conditions?
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What is the primary purpose of cellular respiration?
What is the primary purpose of cellular respiration?
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Which metabolic pathway is used by cells to directly produce ATP?
Which metabolic pathway is used by cells to directly produce ATP?
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What strategy might inhibit the growth of tumors in cancer cells?
What strategy might inhibit the growth of tumors in cancer cells?
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What does ATP primarily provide for cellular processes?
What does ATP primarily provide for cellular processes?
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What is released when ATP is hydrolyzed?
What is released when ATP is hydrolyzed?
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What role does thermogenesis play in energy metabolism?
What role does thermogenesis play in energy metabolism?
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What type of bond does ATP utilize to store energy?
What type of bond does ATP utilize to store energy?
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What is a consequence of shifting cellular metabolism to glycolysis during ischemic injury?
What is a consequence of shifting cellular metabolism to glycolysis during ischemic injury?
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What does DHAP convert to during glycolysis?
What does DHAP convert to during glycolysis?
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What is the end product of glyceraldehyde-3-phosphate in the energy-releasing phase of glycolysis?
What is the end product of glyceraldehyde-3-phosphate in the energy-releasing phase of glycolysis?
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How many ATP molecules are generated from one molecule of glyceraldehyde-3-phosphate?
How many ATP molecules are generated from one molecule of glyceraldehyde-3-phosphate?
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During which phase of glycolysis is ADP phosphorylated?
During which phase of glycolysis is ADP phosphorylated?
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What is released during the decarboxylation of pyruvate?
What is released during the decarboxylation of pyruvate?
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What happens to NAD+ during the conversion of glyceraldehyde-3-phosphate?
What happens to NAD+ during the conversion of glyceraldehyde-3-phosphate?
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What type of reaction primarily describes the conversion of glyceraldehyde-3-phosphate in glycolysis?
What type of reaction primarily describes the conversion of glyceraldehyde-3-phosphate in glycolysis?
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What is formed when pyruvate is oxidized after decarboxylation?
What is formed when pyruvate is oxidized after decarboxylation?
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What is the primary function of energy released in an exergonic reaction?
What is the primary function of energy released in an exergonic reaction?
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What is substrate level phosphorylation?
What is substrate level phosphorylation?
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Which type of work can ATP power after transferring its phosphate group?
Which type of work can ATP power after transferring its phosphate group?
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What is the relationship between oxidation and reduction reactions?
What is the relationship between oxidation and reduction reactions?
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In which forms does NAD exist related to its role in cellular respiration?
In which forms does NAD exist related to its role in cellular respiration?
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What happens to energy when NAD+ is reduced to NADH?
What happens to energy when NAD+ is reduced to NADH?
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Which of the following statements about oxidative phosphorylation is accurate?
Which of the following statements about oxidative phosphorylation is accurate?
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Why do oxygen and carbon tend to 'hog' electrons in biochemical reactions?
Why do oxygen and carbon tend to 'hog' electrons in biochemical reactions?
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What is the role of NAD+ in metabolic reactions?
What is the role of NAD+ in metabolic reactions?
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During the process of glycolysis, what are the end products formed from one glucose molecule?
During the process of glycolysis, what are the end products formed from one glucose molecule?
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What occurs to the hydrogen ions during the oxidation of a molecule?
What occurs to the hydrogen ions during the oxidation of a molecule?
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What type of phase does glycolysis include?
What type of phase does glycolysis include?
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What is the first step of the energy-requiring phase of glycolysis?
What is the first step of the energy-requiring phase of glycolysis?
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What does fructose-1,6-bisphosphate split into during glycolysis?
What does fructose-1,6-bisphosphate split into during glycolysis?
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What is generated during the energy-releasing phase of glycolysis?
What is generated during the energy-releasing phase of glycolysis?
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What describes the isomers formed during glycolysis?
What describes the isomers formed during glycolysis?
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Which process is significantly faster in generating ATP from glucose?
Which process is significantly faster in generating ATP from glucose?
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What is the ATP yield from complete oxidative phosphorylation of glucose?
What is the ATP yield from complete oxidative phosphorylation of glucose?
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Which metabolite produced from glucose is essential for nucleotide and protein biosynthesis?
Which metabolite produced from glucose is essential for nucleotide and protein biosynthesis?
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What strategy do tumour cells employ concerning glucose metabolism?
What strategy do tumour cells employ concerning glucose metabolism?
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How does high glucose consumption in tumour cells affect surrounding cells?
How does high glucose consumption in tumour cells affect surrounding cells?
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What is the relationship between glucose metabolism and protein translation in tumour cells?
What is the relationship between glucose metabolism and protein translation in tumour cells?
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Why might tumour cells prefer aerobic glycolysis over complete oxidation of glucose?
Why might tumour cells prefer aerobic glycolysis over complete oxidation of glucose?
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What is a potential consequence of the metabolic preferences of tumour cells?
What is a potential consequence of the metabolic preferences of tumour cells?
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Study Notes
Cellular Respiration
- Cellular respiration is a metabolic pathway where cells release energy from glucose, producing ATP.
- Cells can switch between glycolysis and oxidative phosphorylation, depending on energy needs.
- This flexibility in metabolism is crucial for cells and impacts therapeutic strategies.
ATP: The Energy Currency of the Cell
- ATP (adenosine triphosphate) is a nucleotide with a nitrogenous base (nucleobase), a five-carbon sugar (pentose), and one to three phosphates.
- ATP stores energy in high-energy phosphoanhydride bonds.
- Hydrolysis of ATP (breaking a bond) releases energy, converting ATP to ADP and a phosphate group (Pi).
- Cells constantly use ATP, so it must be replenished. This uses energy from exergonic reactions to rebuild the ATP from ADP.
Mechanisms for Generating ATP
-
Substrate-level phosphorylation: Phosphate is directly transferred from a substrate to ADP, forming ATP.
- This occurs in glycolysis and the citric acid cycle.
-
Oxidative phosphorylation: This process produces a significant amount of ATP.
- Electrons are transferred through a series of protein complexes in the inner mitochondrial membrane (electron transport chain). This movement releases energy.
- This energy is used to pump H+ ions (protons) across the inner membrane, creating a concentration gradient
- The flow of hydrogen ions back through a protein called ATP synthase, provides the energy to add a phosphate group to ADP, and create ATP
Oxidation and Reduction
- Oxidation and reduction reactions are always coupled.
- Oxidation is the removal of electrons (and sometimes hydrogen ions).
- Reduction is the gain of electrons (and sometimes hydrogen ions).
- The transfer of electrons between molecules is a vital part of energy production.
NAD+/NADH
- NAD+ (nicotinamide adenine dinucleotide) is a coenzyme crucial for cellular respiration.
- NAD+ can exist in oxidized (NAD+) and reduced (NADH) forms.
- Energy is stored when NAD+ is reduced to NADH.
- Energy is released when NADH is re-oxidized to NAD+.
Glycolysis
- Occurs in the cytosol.
- Begins with glucose and produces two molecules of pyruvate.
- Consists of both energy-requiring and energy-releasing phases.
- Net gain of 2 ATP and 2 NADH molecules.
Pyruvate Oxidation
- Pyruvate is transported into the mitochondria.
- A carboxyl group is removed from pyruvate, releasing carbon dioxide (CO2).
- The remaining two-carbon molecule is oxidized to form an acetyl group.
- NAD+ is reduced to NADH, and the acetyl group is attached to coenzyme A (CoA), forming acetyl CoA.
- This prepares the acetyl CoA for entry into the citric acid cycle.
Citric Acid Cycle
- Also known as the Krebs cycle.
- Occurs in the mitochondrial matrix.
- A series of oxidation-reduction and decarboxylation reactions. A product of the cycle is CO2.
- NAD+ and FAD are reduced to NADH and FADH2, respectively
- 1 ATP is produced per cycle.
- An important role for this process is that it provides starting materials for later reactions in cellular respiration
Oxidative Phosphorylation
- Occurs in the inner mitochondrial membrane.
- Uses an electron transport chain to generate ATP.
- Electron carriers (like NADH and FADH2) release energy as they transfer electrons.
- This energy is used to pump protons (H+) across the inner mitochondrial membrane, generating a proton gradient.
- ATP synthase uses the flow of protons back across the membrane to generate ATP.
What if Oxygen is Limited?
- In the absence of oxygen, cells can use fermentation to produce ATP.
- Lactic acid fermentation is one example in humans. In this case, pyruvate is reduced to lactate.
Glucose metabolism in Tumor Cells
- Cancer cells often utilize a higher rate of glycolysis (the Warburg effect).
- This is fast enough to produce ATP, even in the presence of adequate oxygen, compared to using the more complete oxidative phosphorylation pathway.
- Increased glycolysis creates a rapid supply of glucose-derived molecules, needed building blocks for proteins, lipids and nucleic acids.
- This increased glucose uptake allows for increased growth and proliferation of tumor cells.
Other Relevant Points
- Brown adipocytes use uncoupling protein 1 (UCP1).
- Instead of going through the ATP synthase process to produce ATP, these cells use UCP1 to dissipate the proton gradient by a different mechanism. This releases energy as heat.
- This is important for maintaining body temperature.
- Pharmacological activation of thermogenesis in brown adipose tissue using UCP1 might be useful in therapeutic strategies for obesity.
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Description
Test your understanding of cellular respiration, focusing on ATP generation, metabolic pathways, and mechanisms like substrate-level phosphorylation. Explore how cells utilize glucose to produce energy efficiently and the significance of ATP as the energy currency in various cellular processes.
