C1.1 enzymes and metabolism Flashcards
Enzymes
Catalysts that facilitate reactions by interacting with substrates and other molecules.
Adenosine triphosphate (ATP)
Primary energy carrier in cells. Stores and releases energy during cellular activities.
Catalysts in cells
Enzymes are organic catalysts that accelerate cellular reactions, ensuring vital life functions proceed efficiently.
Define metabolism.
Metabolism encompasses all chemical reactions in an organism. These reactions can be independent or interconnected, controlled by specific enzymes. Reactants are substances involved, and products are what’s formed.
Define anabolic reactions.
Anabolic reactions build complex molecules from simpler ones, needing energy and releasing water. Examples: photosynthesis, protein synthesis.
Define catabolic reactions.
Catabolic reactions break down complex molecules into simpler ones, releasing energy via hydrolysis. Examples: digestion, respiration’s substrate oxidation.
Kinetic energy
Energy of motion, including movement of molecules within objects.
Potential energy
Stored energy not being used at a point in time.
Chemical energy
Potential energy available for release during a chemical reaction.
Thermal energy
Kinetic energy stored within objects, transferable as heat.
Adenosine diphosphate (ADP)
Similar to ATP but lacks one phosphate group. Results from ATP losing a phosphate.
ATP in macromolecule synthesis
Supplies energy required to synthesize macromolecules.
ATP in mechanical work
Supplies energy for muscle action, chromosome movement, and cilia/flagellum motion.
ATP in membrane transport
Provides energy for moving substances across the cell membrane (e.g., sodium-potassium pump).
Enzyme Structure
- Enzymes are complex globular proteins.
- They possess specific three-dimensional shapes.
- Active site: a region matching the substrate’s shape.
- Active site comprises a few crucial amino acids.
Denaturation
- Denaturation changes an enzyme’s structure.
- Factors causing denaturation: altered chemical bonds among amino acids.
- Denatured enzymes lose their catalytic abilities.
Lock-and-Key Model
- Emil Fischer’s 1890s proposal for enzyme-substrate interaction.
- Represents enzymes (lock) and substrates (key) with specific shapes.
- Suggested specificity in enzyme-substrate binding.
Induced-Fit Model
- Modification of Fischer’s lock-and-key model.
- Enzymes undergo shape changes upon substrate binding.
- Analogy: Hand (substrate) and glove (enzyme) interaction.
- Induced fit leads to destabilization of substrate bonds, facilitating reactions.
Activation Energy
- Energy needed to destabilize existing bonds in a substrate for a reaction to occur.
- Determines the speed of a reaction; larger activation energies lead to slower reactions.
- Enzymes lower the activation energy required for reactions.
Enzymes and Activation Energy
- Enzymes don’t provide energy for reactions; they lower the required activation energy.
- Enzymes function as catalysts and are not consumed in the reaction.
- Catalysts facilitate reactions by decreasing the energy barrier for the reaction to start.
Factors Affecting Reaction Rates
- Increasing energy of reacting molecules boosts collision rates.
- Lowering activation energy facilitates breaking specific chemical bonds.
Enzymes and Reaction Rates
- Enzymes lower activation energy, accelerating reactions.
- Most chemical reactions in organisms are hastened by enzymes.
Enzymes and Reaction Facilitation
- Enzymes don’t force reactions; they lower the energy needed for reactions to occur.
- They make reactions more likely but don’t cause reactions that wouldn’t happen otherwise.
Equilibrium in Reactions
- Reactions reach equilibrium between reactants and products.
- Enzymes, by lowering activation energy, don’t change this equilibrium state.
Reversible Reactions and Enzymes
- Some reversible reactions need different enzymes to lower activation energy in the reverse direction.
- Enzymes act independently in either direction of reversible reactions.
Active sites and movement are crucial for enzyme action. What must align for proper substrate-enzyme binding?
Active site and substrate based on shape
What is essential for substrates to react in enzyme action?
Movement and collisions with adequate energy
How does immobilization in membranes affect enzyme-substrate interaction?
Enhances efficient joining of substrate and active site
Name two biological processes utilizing membrane-embedded enzymes.
Cellular respiration and photosynthesis
How has life’s evolution been influenced by chemical reactions?
Life’s progression due to the development of more efficient chemical reactions
What are the stages of enzyme action?
Substrate contacts active site -> Shapes align -> Enzyme-substrate complex forms -> Activation energy lowered -> Product released -> Enzyme free for new substrates
How can enzyme action be represented as an equation?
E + S → ES → E + P (E: enzyme, S: substrate, ES: enzyme-substrate complex, P: product)
Why is the structure of an enzyme crucial?
Essential for specific active site formation and enzyme-substrate complex; any changes affect enzyme function rate
What are the fundamental causes of chemical reactions?
Molecules colliding at sufficient speed and capability to react can initiate a reaction.
Can enzymes alter the basic principles behind chemical reactions?
No, enzymes cannot modify the fundamental causes of reactions involving molecular collision.
How does temperature impact enzyme and substrate motion in a fluid environment?
Higher temperatures lead to faster molecular motion, increasing collisions and collision energy.
What happens to enzyme-catalyzed reactions as temperature increases?
Reactions accelerate due to increased molecular motion, but enzyme function has an upper limit due to potential denaturation.
How does pH affect enzyme function related to active sites?
pH changes can affect charge matching between substrate and enzyme, reducing efficiency and potentially causing denaturation.
What happens when a solution becomes acidic or basic concerning enzyme efficiency?
Acidic conditions increase hydrogen ions and basic conditions increase hydroxide ions, both interfering with charge matching, reducing enzyme efficiency.
How does increasing substrate concentration impact enzyme reaction rate?
Initially, increasing substrate concentration increases the reaction rate due to more collisions. Eventually, a plateau is reached as all active sites are occupied.
Explain the relationship between substrate concentration and enzyme activity.
As substrate concentration rises, so does the rate of reaction until all enzyme active sites are saturated.
Define intracellular enzymes.
Enzymes occurring within a cell.
Give examples of reactions catalyzed by intracellular enzymes.
Glycolysis in the cytoplasm and the Krebs cycle in the mitochondria.
Explain extracellular enzymes.
Enzymes found outside a cell.
Provide an example of reactions catalyzed by extracellular enzymes.
Chemical digestion within the gut/digestive system.
What percentage of energy available to an organism is used for cellular activities?
Roughly 35%.
Explain the fate of the remaining energy after ATP provides usable energy to the cell.
Transferred as heat.
What is the significance of heat release in endotherms?
Essential for maintaining constant internal body temperature.
Provide examples of true endotherms.
Birds and mammals.
What are metabolic or biochemical pathways?
Specific sequences of reactions catalyzed by enzymes.
types of metabolic pathways.
- a chain or linear metabolic pathway.
- a cyclical or cyclic metabolic pathway.
What does regulation at each step in a metabolic pathway allow?
Fine control of the overall process and prevents large amounts of energy release at once.
Provide examples of metabolic pathways in cellular processes.
Glycolysis (linear) and the Krebs cycle (cyclical) in cellular respiration.
The Calvin cycle (cyclical) in photosynthesis.
What is non-competitive inhibition in enzyme action?
When an inhibitor binds to an enzyme at a site other than the active site, altering its shape and decreasing its activity.
What is another term for non-competitive inhibition?
Allosteric inhibition
Explain the effect of non-competitive inhibition on the enzyme’s active site.
The inhibitor binding to an allosteric site induces a change in the active site’s shape, rendering it non-functional
Provide an example of a non-competitive inhibitor and its action.
Metallic ions like mercury bind to enzyme sulfur groups, inducing shape changes that inhibit the enzyme.
Are the effects of non-competitive inhibitors reversible?
Yes, typically the effects are reversible, and the enzyme is not permanently damaged.
Competitive Inhibition
Occurs when a molecule (competitive inhibitor) competes with the substrate for the enzyme’s active site, reducing the rate of the chemical reaction.
Detail of Competitive inhibitor’s structure
Competitive inhibitor’s structure must resemble the substrate to bind to the active site and hinder substrate binding.
Competitive Inhibition: Substrate Influence
Competitive inhibition is affected by substrate concentration. Increasing the substrate concentration can overcome this inhibition by allowing more substrates to bind to available active sites.
How do statins function in controlling cholesterol levels in the body?
Statins act as competitive inhibitors by binding to the active site of an essential enzyme in liver cholesterol biosynthesis. This competition reduces cholesterol production, lowering the risk of cardiovascular disease.
What is end product inhibition in metabolic pathways?
End product inhibition, or feedback inhibition, occurs when a sufficient quantity of the end product of a metabolic pathway inhibits the first enzyme by binding to its allosteric site, shutting down the pathway to prevent excess production.
End product inhibition
Prevents waste by stopping metabolic pathways when end products are sufficient. Allosteric enzymes get inhibited by the end product’s high concentration.
Isoleucine in humans
Critical for growth, metabolism, and immunity. Humans can’t synthesize it; rely on diet. Feedback inhibition controls its production in plants and bacteria
Penicillin Discovery
Discovered by Alexander Fleming in 1928; effectively treated bacterial infections after mass production in 1944. Dorothy Hodgkin’s X-ray studies provided its structure
Penicillin Mechanism
Inhibits bacterial cell wall formation by binding irreversibly to transpeptidase. Defective cell walls cause bacterial cell death; no effect on human cells lacking cell walls
Penicillin Resistance
Resistance due to penicillinase production, breaking down penicillin. Mutated transpeptidases prevent penicillin binding; research aims to modify penicillin for restored efficacy
