Week 14 / Enzymes 1 Flashcards
Q: What are enzymes?
A: Specialized biological macromolecules that act as specific, efficient, and active catalysts of chemical reactions in aqueous solutions.
Q: What are most enzymes made of?
A: Most enzymes are globular proteins.
Q: Can enzymes be made of RNA?
A: Yes, some enzymes are RNA, such as ribozymes and ribosomal RNA.
Q: What is the main function of enzymes?
A: To speed up chemical reactions as highly specific and efficient catalysts.
Q: How are enzymes typically named?
A: By adding the suffix “-ase” to the name of their substrate or a word/phrase describing their catalytic action.
Q: On what basis are enzymes classified?
A: Based on the type of reaction they catalyze.
Q: What reaction is catalyzed by oxidoreductases?
A: Oxidation-reduction reactions.
Q: What reaction is catalyzed by transferases?
A: Transfer of functional groups.
Q: What reaction is catalyzed by hydrolases?
A: Hydrolysis reactions.
Q: What reaction is catalyzed by lyases?
A: Group elimination to form double bonds.
Q: What reaction is catalyzed by isomerases?
A: Isomerization.
Q: What reaction is catalyzed by ligases?
A: Bond formation coupled with ATP hydrolysis.
Q: What type of macromolecule are most enzymes?
A: Enzymes are proteins.
Q: What determines the specificity of an enzyme for its substrate?
A: The unique shape and chemical environment of the enzyme’s active site.
Q: What is the shape and structure of enzymes?
A: Enzymes have a globular shape and a complex 3D structure.
Q: What are metal ion cofactors?
A: Small inorganic ions that assist with enzyme catalysis.
Q: What is the role of the active site in an enzyme?
A: It determines which substrate(s) will bind and facilitates the catalytic reaction.
Q: What forms can cofactors take?
A: Cofactors may be:
Metal ions (e.g., Zn²⁺, Mg²⁺).
Organic/metallo-organic molecules (e.g., vitamins or coenzymes).
Q: What are cofactors, and why are they important?
A: Cofactors are non-protein “helper” molecules required by some enzymes for proper function.
Q: Can you name some examples of metal ion cofactors?
A: Examples include Mg²⁺, K⁺, Ca²⁺, Zn²⁺, Cu⁺, Co, and Fe.
Q: How can metal ion cofactors exist in relation to enzymes?
A:
Free ions: E.g., Na⁺, K⁺.
Coordination complexes: Held with the enzyme protein, e.g., Zn²⁺, Ca²⁺.
Q: What is the main role of metal ion cofactors in enzymes?
A: They assist in enzyme catalysis.
Q: What are coenzymes?
A: Organic cofactors that are loosely bound to enzymes and easily released.
Q: What are prosthetic groups?
A: Organic cofactors that are tightly bound to enzymes.
Q: What role do coenzymes typically play?
A: Coenzymes act as “co-substrates” or transient carriers of specific functional groups during enzymatic reactions.
Q: Where are most coenzymes derived from?
A: They are derived from vitamins, essential organic nutrients required in small amounts in the diet.
Q: Can you give examples of coenzymes and their vitamin sources?
A:
NAD: Derived from niacin (Vitamin B3).
FAD: Derived from riboflavin (Vitamin B2).
Coenzyme A: Derived from pantothenic acid.
Q: What is a holoenzyme?
A: The complete, catalytically active enzyme together with its bound coenzyme and/or metal ion.
Q: What is the apoenzyme (or apoprotein)?
A: The protein part of an enzyme, without its coenzyme or cofactor.
Q: Why are enzymes essential for life?
A: They catalyze (accelerate) biochemical reactions in the body, enabling the chemical reactions of life to occur quickly enough to sustain life.
Q: How do enzymes affect the pace of biochemical and physiological reactions?
A: They speed up reactions that would otherwise proceed very slowly or not at all.
Q: What would happen to life’s chemical reactions without enzymes?
A: Most reactions would occur so slowly (or not at all) that life could not exist.
Q: What is metabolism?
A: The sum of all chemical reactions that take place in an organism.
Q: What are the two main types of metabolic reactions?
A:
Anabolism (Anabolic reactions): Formation of bonds between molecules, catalyzed by anabolic enzymes.
Catabolism (Catabolic reactions): Breaking of bonds between molecules, catalyzed by catabolic enzymes.
Q: What role do enzymes play in metabolism?
A: Enzymes catalyze cellular metabolic reactions, making them faster and more efficient.
Q: What is anabolism?
A: A biosynthetic process that builds complex molecules from simpler ones.
Q: What type of bonds are involved in anabolic reactions?
A: Formation of bonds between molecules.
Q: Do anabolic reactions consume or release energy?
A: They are energy-utilizing processes, consuming more energy than they produce (endergonic).
Q: What type of chemical reaction is typical of anabolism?
A: Dehydration synthesis reactions, which release water (e.g., carbohydrate and protein synthesis).
Q: What is catabolism?
A: A degradative process that breaks down complex molecules into simpler ones.
Q: Can you give an example of an anabolic process?
A: Synthesis of proteins from amino acids or carbohydrates from monosaccharides.
Q: What type of bonds are involved in catabolic reactions?
A: Breaking of bonds between molecules.
Q: Do catabolic reactions consume or release energy?
A: They are energy-releasing processes, producing more energy than they consume (exergonic).
Q: What type of chemical reaction is typical of catabolism?
A: Hydrolytic reactions, which use water to break chemical bonds (e.g., digestion of carbohydrates).
Q: Can you give an example of a catabolic process?
A: Digestion of carbohydrates into simple sugars like glucose.
Q: What is activation energy (E)?
A: The initial energy required for a chemical or metabolic reaction to proceed.
Q: Why is activation energy needed in chemical/metabolic reactions?
A:
To increase collisions between reactant molecules.
To shift reactant molecules into a ‘transition state’, where bonds can be broken and new ones formed.
Q: Why can’t most metabolic reactions proceed at ambient temperature without enzymes?
A: Activation energy is usually too high for the reactions to occur significantly at normal body temperature.
Q: How do enzymes help in metabolic reactions?
A: Enzymes lower the activation energy, allowing metabolic reactions to proceed at a faster rate.
Q: How do enzymes function in biochemical reactions?
A: Enzymes act as catalysts, speeding up reactions without being consumed or chemically altered.
Q: What do enzymes provide to lower activation energy?
A: Enzymes provide an alternative pathway or mechanism for the reaction.
Q: How do enzymes interact with reactants (substrates)?
A: Enzymes bind to substrates and form an intermediate, which is released when the product is formed.
Q: How do enzymes bind to their substrates?
A: Enzymes bind their substrates with high specificity, determined by the 3D arrangement of atoms in the enzyme’s active site.
Q: How do enzymes affect the equilibrium of a reaction?
A: Enzymes accelerate the rate of the reaction without shifting or changing the equilibrium. The equilibrium is simply reached faster with the enzyme.
Q: What is the ES complex?
A: The enzyme-substrate (ES) complex is formed when the enzyme binds to the substrate at its active site.
Q: What is the ‘Lock and Key’ model of enzyme action?
A: The ‘Lock and Key’ model is a simplistic model where the substrate fits perfectly into the enzyme’s active site, forming weak chemical bonds, like a key fitting into a lock.
Q: How does the substrate interact with the enzyme in the ‘Lock and Key’ model?
A: The substrate fits precisely into the 3D structure of the enzyme’s active site, and weak chemical bonds are formed between the substrate and the enzyme.
Q: What is the ‘Induced Fit’ model of enzyme action?
A: The ‘Induced Fit’ model is a more accurate model where the binding of the substrate causes the enzyme to undergo a conformational change, leading to a tighter fit.
Q: How does the enzyme change in the ‘Induced Fit’ model?
A: The enzyme changes shape when the substrate binds, bringing chemical groups into position to catalyze the reaction more effectively.
Q: What factors affect enzyme function?
A:
Enzyme concentration
Substrate concentration
Temperature
pH
Salinity
Q: How does enzyme concentration initially affect reaction rate?
A: As enzyme concentration increases, the reaction rate increases because more enzyme molecules lead to more frequent collisions with the substrate.
Q: What happens to the reaction rate when enzyme concentration continues to increase?
A: Eventually, the reaction rate levels off because substrate concentration becomes the limiting factor, and not all enzyme molecules can find a substrate to bind to.
Q: How does substrate concentration initially affect reaction rate?
A: As substrate concentration increases, the reaction rate increases because more substrate leads to more frequent collisions with the enzyme.
Q: What happens to the reaction rate as substrate concentration continues to increase?
A: The reaction rate levels off when all enzyme active sites become engaged (saturated), and the maximum rate of reaction is reached.
Q: How does temperature initially affect enzyme reaction rate?
A: As temperature increases, the reaction rate increases because molecules move faster, leading to more frequent collisions between the enzyme and substrate.
Q: What happens to the reaction rate as temperature continues to increase?
A: At high temperatures beyond the optimum, the reaction rate decreases because the enzyme may denature, disrupting the bonds in the enzyme and between the enzyme and substrate.
Q: What is the optimum temperature for enzyme-catalyzed reactions?
A: The optimum temperature is the temperature at which the reaction rate is highest, due to the greatest number of molecular collisions between the enzyme and substrate.
Q: What happens when the temperature exceeds the optimum?
A: The enzyme may denature, losing its 3D shape (tertiary structure), which reduces its ability to bind to the substrate.
