Enzymes and metabolism Flashcards
Why do most chemical reactions in cells require catalysts?
Most chemical reactions either do not occur spontaneously or occur very slowly. Enzymes act as biological catalysts to speed up these reactions under the conditions found in living organisms.
What are some factors that can speed up chemical reactions in laboratory or industrial settings?
High temperatures, high pressures, extreme pH levels, and high concentrations of reactants can increase reaction rates.
Why can’t cells use high temperatures, pressures, or extreme pH levels to speed up reactions?
Cells are very sensitive to extreme conditions, so using high temperatures, pressures, or pH extremes would damage them. Instead, they rely on enzymes to catalyze reactions.
What are enzymes, and what role do they play in cells?
Enzymes are proteins that act as biological catalysts, allowing chemical reactions to occur at a suitable rate in living organisms.
How do enzymes speed up reactions?
Enzymes ensure that substrate molecules are correctly oriented and close enough for a reaction to occur, increasing the chances of successful collisions.
Why are only a small number of enzymes needed in a cell?
Enzymes are reusable and remain unchanged by the reactions they catalyze, so only a small number is needed to catalyze many reactions.
What would happen if enzymes were not present in cells?
Without enzymes, the rate of chemical reactions would be too slow to support life.
What is metabolism?
Metabolism refers to all the chemical reactions that take place within cells and organisms.
What are metabolites?
Metabolites are the molecules involved in metabolic reactions.
What is a metabolic pathway?
A metabolic pathway is a series of interlinked metabolic reactions, each catalyzed by a separate enzyme.
Why are thousands of different enzymes needed in an organism?
Because enzymes are specific to certain reactions, thousands of different enzymes are required to catalyze all the chemical reactions in an organism.
What is enzyme-substrate specificity?
Enzyme-substrate specificity means that enzymes are specific to certain substrates because their shapes and chemical properties are complementary, like puzzle pieces fitting together.
What are anabolic reactions?
Anabolic reactions build large molecules from smaller ones and require an input of energy (endergonic).
Give three examples of anabolic reactions.
Photosynthesis (building sugars from CO₂ and water)
Protein synthesis (linking amino acids into proteins)
Formation of glycogen (storing glucose molecules)
What type of reaction is commonly involved in anabolism?
Condensation reactions, which link molecules together, are commonly involved in anabolic reactions.
What are catabolic reactions?
Catabolic reactions break down large molecules into smaller ones, releasing energy (exergonic).
Give three examples of catabolic reactions.
Respiration (breaking down sugars to release energy)
Deamination (breaking down proteins to release urea)
Digestion (breaking macromolecules into monomers)
What type of reaction is commonly involved in catabolism?
Hydrolysis reactions, which break bonds using water, are commonly involved in catabolic reactions.
How do anabolic and catabolic reactions differ in terms of energy?
Anabolic reactions require an input of energy (endergonic).
Catabolic reactions release energy (exergonic).
What is the role of ATP in anabolic and catabolic reactions?
Both anabolism and catabolism are coupled to ATP, which acts as the principal energy carrier in cells.
How does enzyme catalysis involve molecular motion and substrate-active site collisions?
Enzyme catalysis relies on random collisions between substrates and the enzyme’s active site.
These collisions must occur at the correct orientation and speed for a reaction to take place.
Unsuccessful collisions happen when molecules are misaligned, causing them to “bounce” off without reacting.
What is the enzyme-substrate complex, and how does it form?
The enzyme-substrate complex is a temporary structure formed when a substrate binds to an enzyme’s active site.
The active site has a specific shape and chemical properties that complement the substrate.
After the reaction, products are released, and the enzyme remains unchanged and reusable.
How does enzyme specificity work?
Enzyme specificity results from the complementary fit between an enzyme’s active site and its substrate.
This is determined by the enzyme’s unique 3D protein structure.
Only specific substrates can bind, ensuring precise biochemical reactions.
What is the difference between the lock-and-key model and the induced-fit hypothesis?
The lock-and-key model suggests that the active site is a perfect fit for the substrate.
The induced-fit hypothesis states that the active site undergoes slight conformational changes to better accommodate the substrate.
These changes enhance enzyme efficiency and stability during catalysis.
How does molecular motion affect enzyme activity?
Enzyme and substrate molecules move due to their kinetic energy.
Higher kinetic energy increases the frequency of successful collisions, leading to more enzyme-substrate complexes and a faster reaction rate.
What are immobilised enzymes, and how are they used?
Immobilised enzymes are enzymes fixed onto surfaces or trapped in gels/membranes.
They are widely used in industries like food processing, pharmaceuticals, and environmental management.
Immobilisation allows for enzyme reuse, reduces contamination, and increases stability under different conditions.
What are the advantages of using immobilised enzymes?
No enzyme contamination in the final product.
Enzymes can be reused multiple times, making them cost-effective.
Greater tolerance to temperature and pH changes.
Higher enzyme concentrations can be used, increasing reaction efficiency.
How do enzymes become denatured?
Enzymes denature at high temperatures or extreme pH levels.
The bonds maintaining the enzyme’s 3D shape break, altering the active site.
A denatured enzyme can no longer bind to its substrate, stopping the reaction.
What happens when an enzyme is exposed to high temperatures?
Increased heat causes vibrations that break the bonds in the enzyme’s structure.
This permanently alters the active site, preventing substrate binding.
Most human enzymes denature above 40–50°C, as body temperature is around 37°C.
