Ch 08 Lecture Presentation Video
Reggie Cobb・2 minutes read
Cellular respiration is a multi-phase process that breaks down glucose to produce ATP while consuming oxygen and releasing carbon dioxide, with key stages including glycolysis, the citric acid cycle, and the electron transport chain. Glycolysis results in the net gain of 2 ATP and 2 NADH from one glucose molecule, which is further processed in subsequent stages to yield a total of 36 to 38 ATP, highlighting its essential role in energy metabolism.
Insights
- Cellular respiration is a vital process that occurs in four stages: glycolysis, the preparatory reaction, the citric acid cycle, and the electron transport chain, with the primary goal of converting glucose into ATP while releasing carbon dioxide as a waste product. Glycolysis takes place in the cytoplasm, while the other stages occur in the mitochondria, highlighting the importance of cellular structures in energy production.
- Glycolysis initiates the breakdown of glucose by converting it into two pyruvate molecules, requiring an investment of 2 ATP but yielding a net gain of 2 ATP and 2 NADH. This process is crucial as it sets the stage for further energy extraction in the mitochondria, where pyruvate is transformed into acetyl-CoA for entry into the citric acid cycle.
- The electron transport chain generates the majority of ATP during cellular respiration, producing approximately 28-34 ATP from one glucose molecule by utilizing energy from NADH and FADH2. This stage emphasizes the critical role of oxygen, which is necessary for recycling NADH back to NAD+ and for forming water, thus underscoring the interconnectedness of respiration and energy efficiency in living organisms.
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Recent questions
What is cellular respiration?
Cellular respiration is a metabolic process that occurs in cells to convert the energy stored in glucose into adenosine triphosphate (ATP), which is the primary energy currency of the cell. This process involves a series of biochemical reactions that break down glucose molecules, utilizing oxygen and producing carbon dioxide as a byproduct. The overall goal of cellular respiration is to generate ATP, which powers various cellular activities. It is essential for maintaining the energy balance in living organisms and supports vital functions such as growth, repair, and maintenance of cellular structures.
How does glycolysis work?
Glycolysis is the first stage of cellular respiration and occurs in the cytoplasm of the cell. It involves the breakdown of one molecule of glucose (C6H12O6) into two molecules of pyruvate (C3H4O3). The process consists of ten enzymatic reactions and is divided into two phases: the energy investment phase and the energy harvesting phase. Initially, two ATP molecules are consumed to activate glucose, but the process ultimately yields a net gain of two ATP and two NADH molecules. Glycolysis is crucial as it prepares glucose for further oxidation in the mitochondria, leading to more ATP production in subsequent stages of cellular respiration.
What happens in the citric acid cycle?
The citric acid cycle, also known as the Krebs cycle, takes place in the mitochondrial matrix and is a key component of cellular respiration. It begins with the conversion of acetyl-CoA, derived from pyruvate, into citric acid. Throughout the cycle, citric acid undergoes a series of transformations, resulting in the production of energy carriers: two ATP, six NADH, and two FADH2 molecules per glucose molecule. Additionally, carbon dioxide is released as a waste product during this cycle. The citric acid cycle is vital for extracting high-energy electrons from acetyl-CoA, which are later used in the electron transport chain to generate a significant amount of ATP.
What is the electron transport chain?
The electron transport chain (ETC) is the final stage of cellular respiration and occurs along the inner mitochondrial membrane, specifically in the cristae. It utilizes the high-energy electrons carried by NADH and FADH2, produced in earlier stages, to create a proton gradient across the membrane. As electrons are transferred through a series of protein complexes, hydrogen ions (H+) are pumped into the intermembrane space, creating a concentration gradient. This gradient drives ATP synthesis as protons flow back into the mitochondrial matrix through ATP synthase. The ETC is responsible for producing the majority of ATP during cellular respiration, generating approximately 28-34 ATP from one glucose molecule, and requires oxygen to function, as it combines with electrons and protons to form water.
What is fermentation?
Fermentation is an anaerobic metabolic process that occurs when oxygen is not available for cellular respiration. It allows cells to generate energy by converting glucose into simpler compounds, such as lactic acid in animals or ethanol and carbon dioxide in yeast and plants. During fermentation, glycolysis still takes place, producing a net gain of two ATP molecules per glucose molecule, but the pyruvate produced is then converted into lactic acid or ethanol instead of entering the mitochondria for aerobic respiration. While fermentation is less efficient than aerobic respiration, yielding only two ATP compared to the 36-38 ATP produced through complete oxidation of glucose, it is crucial for organisms in low-oxygen environments and plays a significant role in various industrial applications, such as brewing and baking.
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