C1 Flashcards
Catalyst
Substance that increases rate of chemical reactions without being used up
Metabolism
Set of interacting and independent chemical reactions that happen in the body
Active site
Region of an enzyme where substrate molecules bind. Formed by tertiary folds of proteins to create unique shape with exposed R groups that are chemically compatible with substrate
Substrate
Reactant in the enzyme-catalysed reaction/initial chemical that binds to the active site and is transformed into a product
Induced-fit model
Idea that shape of an active site/enzyme can be adjusted to fit bonding. They need to be chemically compatible but not an exact fit
Activation energy
Energy needed to get reactants into a transition state by breaking existing bonds
Enzyme-substrate complex
Temporary molecule formed when a substrate bunds to an enzyme’s active site. Complex must form for bonds in a substrate to be broken and a reaction in progress.
Enzyme-substrate specificity
Each enzyme acting on one or a group of specific substrates that are chemically compatible with the active site of that enzyme may
What makes enzymes unique to other catalysts?
Made up of protein and within a living organism
How does the shape of a globular protein make them ideal for acting as enzymes
Folded complex spherical shape allows for folding to create specific grooves that have R groups exposed that are chemically attracted to the substrate
How do enzymes affect activation energy?
Lower activation energy by breaking bonds which means less energy is required to progress. This means reactions can occur more quickly and spontaneously (ie increasing rate of reaction)
Exergonic reaction
Released energy stored in reactants
Endergonic resctions
Consume energy to produce higher energy products
Anabolic reactions / anabolism
Two or more substrates to create one product
Catabolism / catabolic reaction
One substrate -> two or more products
Examples of anabolic enzymes
DNA and RNA polymerase
ATP synthase
What does the induced fit model allow that the lock and key model doesn’t?
Allows the substrate to be a group and allows for regulation by inhibitors
Example of catabolic reaction
Enzyme = sucrase. Breaks the bonds of sucrose, making the substrate reactive and increasing the reaction race. Produces fructose and glucose
Example of endergonic reaction
Photosynthesis
Role of enzyme
Lower activation energy
Example of exergonic reaction
Respiration
Collision theory
Substrate and enzyme must collide and in the correct orientation for substrate to be chemically aligned to bond to active site
Denaturation
Temporary shape change of proteins due to extreme environments that break weak bonds
What role does molecular motion play in enzyme activity?
Motion provides an opportunity for substrate to collide into an enzyme
How can enzymes and substrates be immobilised to increase activity?
Can work well to have one stationary well-placed active site and a moving substrate (or vice versa)
How does temperature impact the effectiveness of enzymes?
Increased temperature = increased kinetic energy = more successful collisions = increased reaction rate. At very high temperatures, weaker bonds in the tertiary structure of an enzyme can break and denaturation occurs
How can rate of a reaction be measured?
Disappearance of a reactant or appearance/accumulation of product
What is the optimum temperature for organism?
Different for each organism
What is the optimum temperature
Temperature with highest rate of reaction
What is the effect of pH on enzymes?
Below optimum pH = excess H+ ions can disrupt ionic bonds of an enzyme, so the active site changes shape and the substrate can no longer bond. Above optimum temperature and the same thing happens with OH- ions above pH.
Optimum pH of enzymes
Usually ~7 but exceptions
Optimum pH of pepsin
2
Effect of substrate concentration on enzymes
Increases rate of reaction until saturation point, where the maximum rate of reaction is reached as all active sites are occupied and cannot act at a faster rate
Assuming that the concentration of enzymes is fixed
Equation to measure rate of enzyme reactions
Change in product / change in time
Multi enzyme complexes
Multiple enzymes located close to one another to work on one metabolic pathway
Inhibitor
Molecule that temporarily binds to an enzyme, halting activity while the inhibitor is bound
Allosteric site
2nd key site on an enzyme that can be used for regulation or to (in)activate an enzyme
Feedback inhibition
Inhibitors as products to prevent them working when not needed
Difference between an intracellular and extra cellular enzyme-catalysed reactikn
Intra = inside cells
Extra = secreted outside cells
Why is heat loss from metabolic reactions useful for endotherms?
Heat loss stays in the body therefore can be used to maintain constant internal temperature
Difference between a linear and cyclical metabolic pathway
Linear = no recycling of reactants
Cyclical = some reactants are recycled during reactions
How do statins act as an inhibitor
Medication to reduce high cholesterol by acting as a competitive inhibitor, binding to active site of the enzyme that synthesis cholesterol
Example of a linear pathway
Glycolysis
Competitive inhibition
Inhibitor blocks active site by occupying it. Therefore, the substrate cannot enter. Temporary
Examples of cyclical pathway
Krebs Cycle
What happens to competitor inhibitors when substrate concentration is increased
Less inhibition as competing
Non competitive inhibition
Inhibition binds to allosteric site which changes the shape of the active site, so the substrate cannot hind.
Temporary
Effect of substrate concentration on non-competitive inhibition
None
Example of non-competitive inhibition
Cyanide poisoning, binds to last step enzymes in cellular respiration
What is end product inhibition
When the end product of a reaction acts as an inhibitor for the first enzyme
General type of end product inhibition
Non-competitive
Threonine to isoleucine pathway
Threonine -> intermediate -> intermediate -> intermediate->
intermediate
-> isoleucine
How does end product inhibition work for the threonine-isoleucine pathway?
Excess isoleucine (from pathway build up or diet) binds to the allosteric site of the first enzyme, which stops the pathway. When isoleucine levels are low, it is removed from the allosteric site and the pathway starts again
Benefits of end product inhibition with threonine- isoleucine pathway
Natural regulation of levels
Binds to first enzyme so unnecessary intermediates are not used
