Topic 12 Energy and Respiration. Flashcards
Describe the structure and components of ATP.
Adenosine triphosphate (ATP) is a nucleotide derivative composed of three main components: ribose, adenine, and three phosphate groups.
The ribose is a five-carbon sugar, while adenine is a nitrogenous base. The three phosphate groups are linked by high-energy bonds, and when ATP is hydrolyzed, energy is released, converting it into adenosine diphosphate (ADP) and an inorganic phosphate. This structure is crucial for energy transfer in biological systems.
Explain the process of ATP hydrolysis and its significance.
ATP hydrolysis is the process by which ATP is broken down into ADP and an inorganic phosphate, releasing energy.
This reaction is catalyzed by the enzyme ATP hydrolase. The energy released during hydrolysis is vital for various cellular processes, including muscle contraction, active transport, and biosynthesis.
Additionally, the inorganic phosphate released can be used to phosphorylate other molecules, enhancing their reactivity and facilitating metabolic reactions.
How is ATP synthesized during respiration?
ATP is synthesized through two primary mechanisms: chemiosmosis and substrate-level phosphorylation.
In chemiosmosis, protons move across a membrane, creating a concentration gradient that drives ATP synthesis via ATP synthase.
In substrate-level phosphorylation, ATP is produced directly from ADP and a phosphate group transferred from a reactive intermediate, such as during glycolysis and the Krebs cycle.
Both processes are essential for energy production in cells.
Differentiate between aerobic and anaerobic respiration.
Aerobic respiration occurs in the presence of oxygen and is characterized by the complete breakdown of glucose, resulting in the production of a large amount of ATP, typically around 36-38 ATP molecules per glucose molecule.
In contrast, anaerobic respiration takes place in the absence of oxygen, leading to the partial breakdown of glucose and producing significantly less ATP, usually around 2 ATP molecules per glucose. Anaerobic respiration is less efficient and results in byproducts like lactic acid or ethanol.
Define chemiosmosis and its role in ATP synthesis.
Chemiosmosis is the process by which ATP is synthesized as protons (H+) move across a selectively permeable membrane, typically in mitochondria.
This movement occurs down a concentration gradient, releasing energy that is harnessed by ATP synthase to attach ADP to an inorganic phosphate, forming ATP. This mechanism is crucial in cellular respiration, as it allows for efficient energy conversion and storage.
What is substrate-level phosphorylation and where does it occur?
Substrate-level phosphorylation is a method of ATP production that occurs when a phosphate group is directly transferred from a high-energy substrate to ADP, forming ATP.
This process takes place during glycolysis, where triose bisphosphate molecules donate phosphate groups to ADP, resulting in the formation of ATP. It also occurs in the Krebs cycle, where similar transfers happen. This method is distinct from oxidative phosphorylation, which relies on the electron transport chain.
Describe the process of glycolysis in respiration.
Glycolysis is the initial stage of both aerobic and anaerobic respiration, occurring in the cytoplasm of cells.
It begins with the phosphorylation of glucose to form fructose 1,6 bisphosphate, which then splits into 2 triose phosphate molecules.
Each triose phosphate is oxidized to produce pyruvate, yielding 2 ATP and 1 NADH per molecule.
Overall, one glucose molecule results in 2 pyruvate, 2 ATP, and 2 NADH.
How do anaerobic conditions affect respiration in yeast and plants and mammals?
Under anaerobic conditions, yeast and plants undergo fermentation, resulting in the production of ethanol and carbon dioxide as end-products. This process allows them to generate energy without oxygen, albeit less efficiently than aerobic respiration.
In contrast, mammalian muscle tissue produces lactate when oxygen is scarce, which can lead to fatigue.
Define the link reaction in aerobic respiration.
The link reaction is a crucial step in aerobic respiration that occurs in the mitochondrial matrix.
It begins when pyruvate, produced from glycolysis, enters the matrix via active transport.
Pyruvate undergoes oxidative decarboxylation, resulting in the formation of an acetyl group and NADH.
The acetyl group then binds to coenzyme A, forming acetyl coenzyme A, which is essential for th Krebs cycle.
This reaction produces 2 carbon dioxide, 2 NADH, and 2 acetyl CoA from 1 glucose molecule.
Explain the role of the Krebs cycle in cellular respiration.
The Krebs cycle, also known as the citric acid cycle, takes place in the mitochondrial matrix and is a key component of aerobic respiration.
It begins when acetyl coenzyme A, derived from the link reaction, enters the cycle.
Through a series of enzymatic reactions, the cycle generates energy-rich molecules, including ATP, NADH, and FADH2, while releasing carbon dioxide as a waste product.
This cycle is vital for the complete oxidation of glucose.
How does lactate production occur in mammalian muscle tissue?
Lactate production in mammalian muscle tissue occurs during anaerobic respiration when oxygen levels are low, such as during intense exercise.
In this scenario, pyruvate, the end product of glycolysis, is converted into lactate with the help of NADH.
This process allows for the regeneration of NAD+, which is necessary for glycolysis to continue producing ATP.
However, the accumulation of lactate can lead to muscle fatigue, highlighting the trade-off between energy production and metabolic by- products.
Describe the role of the 2C acetyl group in the Krebs cycle.
The 2C acetyl group plays a crucial role in the Krebs cycle by combining with the 4C oxaloacetate to form a 6C citrate.
The formation of citrate marks the beginning of a series of transformations that ultimately lead to the regeneration of oxaloacetate, allowing the cycle to continue and produce energy-rich molecules.
How does the Krebs cycle contribute to energy production in cells?
The Krebs cycle contributes to energy production by systematically breaking down acetyl-CoA derived from carbohydrates, fats, and proteins.
Through a series of decarboxylation and dehydrogenation reactions, it generates energy-rich molecules such as ATP, reduced NAD, and reduced FAD.
These molecules are vital for the electron transport chain, where they facilitate the production of additional ATP.
Define the process of decarboxylation in the context of the Krebs cycle.
Decarboxylation in the Krebs cycle refers to the enzymatic removal of carbon dioxide from organic compounds.
This process occurs multiple times as the cycle progresses, specifically during the conversion of 6C citrate to 5C compounds and further down to 4C oxaloacetate.
Each decarboxylation step not only reduces the carbon skeleton of the molecule but also releases CO2 as a byproduct, contributing to the overall carbon balance in cellular respiration.
Explain the significance of NAD and FAD reduction during the Krebs cycle.
The reduction of NAD and FAD during the Krebs cycle is significant because these coenzymes act as electron carriers.
As the cycle progresses, they accept electrons during dehydrogenation reactions, becoming NADH and FADH2.
These reduced forms are crucial for the electron transport chain, where they donate electrons to generate a proton gradient, ultimately leading to the synthesis of ATP.
