ATP Flashcards
What is ATP and why is it important for cells?
ATP (Adenosine Triphosphate) is the primary energy carrier in cells. It stores and transfers energy for various cellular processes such as:
-Mechanical work (e.g., muscle contraction).
-Transport work (e.g., active transport of ions like Na⁺/K⁺).
-Chemical work (e.g., protein synthesis, DNA replication). ATP is essential for maintaining cell function and survival.
What are the three components of an ATP molecule?
An ATP molecule consists of:
Adenine – a nitrogenous base.
Ribose – a 5-carbon sugar.
Three phosphate groups – attached in a chain.
What happens when ATP is hydrolyzed? Write the reaction.
When ATP is hydrolyzed, the terminal phosphate group is removed, releasing energy. The reaction is:
𝐴𝑇𝑃+𝐻2𝑂→𝐴𝐷𝑃+𝑃𝑖+Energy
ADP (Adenosine Diphosphate) is formed.
Inorganic phosphate (P_i) is released.
Energy is released, which is used by the cell for various processes.
What makes the bonds between phosphate groups in ATP “high-energy”?
Electrostatic repulsion: The negatively charged phosphate groups repel each other.
Resonance stabilization: After hydrolysis, the products (ADP and P_i) are more stable due to better distribution of negative charge.
Increased entropy: The breakdown of ATP results in products (ADP and P_i) that are more disordered than the ATP molecule itself.
What is phosphorylation, and what effect does it have on a molecule’s energy?
Phosphorylation is the process of adding a phosphate group (PO₄³⁻) to a molecule. This typically increases the molecule’s potential energy, making it more reactive or ready to participate in further reactions. Phosphorylation often activates enzymes and other proteins, enabling them to perform their specific functions.
Name the three mechanisms by which ATP is synthesized.
Substrate-level phosphorylation: ATP is generated by transferring a phosphate group directly from a high-energy substrate to ADP (occurs in the cytosol and mitochondrial matrix).
Oxidative phosphorylation: ATP is synthesized using energy from electrons passed through the electron transport chain (ETC) and chemiosmosis (occurs in the inner mitochondrial membrane).
Photophosphorylation: ATP is produced using energy from light (occurs in plant cells and certain bacteria).
Where does substrate-level phosphorylation occur in the cell?
Substrate-level phosphorylation occurs in two places:
In the cytosol (during glycolysis).
In the mitochondrial matrix (during the Krebs cycle).
How does oxidative phosphorylation differ from substrate-level phosphorylation?
Oxidative phosphorylation:
Takes place in the inner mitochondrial membrane.
Involves the electron transport chain (ETC) and chemiosmosis.
ATP is generated indirectly via the movement of protons (H⁺) across the membrane and their return via ATP synthase.
Requires oxygen as the final electron acceptor.
Substrate-level phosphorylation:
Occurs in the cytosol (during glycolysis) or in the mitochondrial matrix (during the Krebs cycle).
ATP is generated directly by transferring a phosphate group from a substrate to ADP.
Does not require oxygen.
Explain what happens during oxidative phosphorylation in the mitochondria.
During oxidative phosphorylation:
NADH and FADH₂ (from glycolysis and the Krebs cycle) donate electrons to the electron transport chain (ETC).
The electrons move through a series of protein complexes in the inner mitochondrial membrane.
This releases energy, which pumps protons (H⁺) into the intermembrane space, creating a proton gradient.
Protons flow back into the matrix through ATP synthase, which uses the energy to synthesize ATP from ADP and inorganic phosphate.
Oxygen is the final electron acceptor, forming water (H₂O).
What are catabolic reactions, and why are they considered exergonic? Provide an example.
Question:
What are catabolic reactions, and why are they considered exergonic? Provide an example.
Answer:
Catabolic reactions are those that break down larger molecules into smaller components, releasing energy in the process. They are considered exergonic because they release energy as they move toward a more stable, lower-energy state.
Example:
Cellular respiration: Glucose is broken down into CO₂ and H₂O, releasing energy used to form ATP.
What are anabolic reactions, and why are they considered endergonic? Provide an example.
Anabolic reactions build larger molecules from smaller ones, requiring an input of energy. They are considered endergonic because they consume energy to form bonds between molecules.
Example:
Protein synthesis: Amino acids are linked together to form polypeptides, requiring energy input from ATP.
How do catabolism and anabolism interact via ATP? Why is ATP the “energy link”?
Catabolic reactions break down molecules and release energy, which is used to produce ATP.
Anabolic reactions require ATP to build larger molecules. Thus, ATP is the “energy link” that connects energy-releasing catabolic processes with energy-consuming anabolic processes. ATP stores energy from catabolism and provides it to power anabolism.
Describe the role of the electron transport chain (ETC) in ATP production.
Answer:
The electron transport chain (ETC) is a series of protein complexes located in the inner mitochondrial membrane. Its role in ATP production is:
NADH and FADH₂ donate electrons to the ETC.
The electrons pass through protein complexes, releasing energy.
This energy pumps protons (H⁺) across the membrane, creating a proton gradient.
The protons flow back into the matrix via ATP synthase, which uses the energy to produce ATP.
Oxygen is the final electron acceptor, forming water.
What is chemiosmosis, and how does it drive ATP synthesis?
Chemiosmosis is the movement of protons (H⁺) across a membrane through ATP synthase due to a proton gradient. This gradient is created by the electron transport chain (ETC). As protons flow through ATP synthase, it uses the energy to synthesize ATP from ADP and inorganic phosphate.
Chemiosmosis is the primary mechanism by which ATP is generated in oxidative phosphorylation.
Why is ATP considered a short-term energy carrier rather than a long-term energy store?
ATP is considered a short-term energy carrier because it is used almost immediately after being produced. It has a limited storage capacity. Cells use other molecules, like glycogen or fat, for long-term energy storage. ATP is quickly consumed in processes like muscle contraction, protein synthesis, and active transport, making it suitable for immediate energy needs but not for long-term storage.
Explain why energy is released when the terminal phosphate group of ATP is split off
Energy is released when the terminal phosphate group is split off from ATP due to the high-energy bonds between the phosphate groups. The terminal phosphate group is unstable because of electrostatic repulsion between the negatively charged phosphates. Breaking this bond results in the production of ADP and inorganic phosphate (P_i), which are more stable and lower in energy. The energy released from this hydrolysis reaction is used by the cell for work.
How does ATP power active transport in cells (e.g., the sodium-potassium pump)?
ATP powers active transport by providing energy to pump ions against their concentration gradients. For example, the sodium-potassium pump uses ATP to transport:
3 sodium ions (Na⁺) out of the cell.
2 potassium ions (K⁺) into the cell.
This process requires ATP because it is moving ions from areas of low concentration to high concentration, which is energetically unfavorable and must be driven by ATP hydrolysis.
What are two key metabolic processes that occur in the mitochondria besides ATP production?
Besides ATP production, two key metabolic processes that occur in the mitochondria are:
The Krebs Cycle (Citric Acid Cycle): Acetyl-CoA is oxidized to produce high-energy molecules (NADH, FADH₂) and CO₂.
Beta-oxidation of fatty acids: Fatty acids are broken down into acetyl-CoA, which enters the Krebs cycle for further energy extraction
What is the difference between oxidative phosphorylation and photophosphorylation?
Oxidative phosphorylation occurs in mitochondria and involves the electron transport chain (ETC) and chemiosmosis, using electrons from organic molecules like NADH and FADH₂ to produce ATP.
Photophosphorylation occurs in chloroplasts (or certain bacteria) and involves light energy to excite electrons, which are passed through a chain of proteins to produce ATP, using water as an electron donor. It’s part of the light reactions in photosynthesis.
