2.1.4 Enzymes
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- Created on: 27-05-17 16:50
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- 2.1.4 Enzymes
- What are enzymes?
- globular proteins with a specific tertiary structure, which catalyse metabolic reactions in living organisms
- Role of enzymes
- chemical reactions for growth: ANABOLIC: catalysed by enzymes.
- DIGESTION reactions: catalysed by enzymes
- Intracellular
- Enzymes that work within a cell
- hydrogen peroxide is a toxic product of many metabolic pathways.
- Enzyme CATALASE ensures hydrogen peroxide is broken down into oxygen and water, preventing accumulation
- hydrogen peroxide is a toxic product of many metabolic pathways.
- Enzymes that work within a cell
- Extracellular
- enzymes that work outside the cell that made them
- Enzymes released from cells, break down large nutrient molecules into smaller molecules in process of digestion
- Many multicellular organisms eat food to gain nutrients. Nutrients taken into digestive system, absorbed in bloodstream, transported around body- used as SUBSTRATES
- AMYLASE and TRYPSIN involved in digestion of humans.
- Many multicellular organisms eat food to gain nutrients. Nutrients taken into digestive system, absorbed in bloodstream, transported around body- used as SUBSTRATES
- Enzymes released from cells, break down large nutrient molecules into smaller molecules in process of digestion
- enzymes that work outside the cell that made them
- Mechanism of enzyme action
- Specificity
- active site specific shape depending on reaction
- Active site
- area of enzyme with shape complementary to specific substrate, allowing to bind with specificity
- Lock-and-key mechanism
- specific substrate will bind to active site. (specificity)
- Induced-fit hypothesis
- active site changes shape slightly as the substrate enters
- Enzyme-substrate complex
- when the substrate is bound to the active site
- Enzyme-product complex
- substrate(s) react and product(s) form. Product(s) released, leaving enzyme unchanged.
- Activation energy
- complexes formed, temporary bonds form or weakened. Lowering activation energy
- Specificity
- Effects of (...) on enzyme activity
- pH
- Hydrogen bond and ionic bonds between amino acid R-group hold proteins.
- Change in pH refers to change in hydrogen ion concentration
- LOW pH = MORE hydrogen ions
- HIGH pH = LESS hydrogen ions
- Temperature
- Increasing temp. increases KINETIC ENERGY of particles. Move faster, more successful collisions
- INCREASE temp. = MORE frequent successful collisions between SUBSTRATE and ENZYME
- Enzyme concentration
- enzyme conc. INCREASES = rate INCREASES. MORE ACTIVE SITES AVAILABLE
- Substrate concentration
- Substrate conc. INCREASES = rate INCREASE. MORE SUBSTRATE MOLECULES TO REACT
- HIGHER CONC. = all active sites become FILLED, rate STAYS THE SAME
- Substrate conc. INCREASES = rate INCREASE. MORE SUBSTRATE MOLECULES TO REACT
- Increasing temp. increases KINETIC ENERGY of particles. Move faster, more successful collisions
- pH
- Need for...
- Cofactors
- obtained via diet, MINERALS
- enzyme AMYLASE, catalyses breakdown of STARCH, contains CHLORIDE ION- necessary for formation of correctly shaped active site
- Coenzymes
- Derived from VITAMINS, class of organic molecule found in diet
- B5, makes coenzyme A. Essential in breakdown of FATTY ACIDS and CARBOHYDRATES in respiration
- Prosthetic groups
- (COFACTORS)tightly bound and form PERMANENT FEATURE of protein
- ZINC IONS form important part of structure of CARBONIC ANHYDROUS,enzyme necessary for metabolism of CARBON DIOXIDE
- (COFACTORS)tightly bound and form PERMANENT FEATURE of protein
- Derived from VITAMINS, class of organic molecule found in diet
- obtained via diet, MINERALS
- Cofactors
- Enzyme inhibitors
- Competitive inhibition
- Binds to active site
- blocks substrate from entering active site. Preventing enzyme catalysing reaction
- Reduces no. substrate molecules binding to active site. SLOWS RATE OF REACTION.
- Doesn't change Vmax
- Reduces no. substrate molecules binding to active site. SLOWS RATE OF REACTION.
- blocks substrate from entering active site. Preventing enzyme catalysing reaction
- Non-competetitive inhibition
- Binds to enzymes other than active site. ALLOSTERIC SITE
- Binding = tertiary structure changes, active site changes.
- Active site no longer complementary shape to substrate. SLOWS RATE OF REACTION
- Binding = tertiary structure changes, active site changes.
- Binds to enzymes other than active site. ALLOSTERIC SITE
- Binds to active site
- Competitive inhibition
- What are enzymes?
- Q10, temperature coefficient of a reaction is a measure of how much the rate of reaction increases with a 10 degrees rise.
- V max = maximum initial velocity or rate of an enzyme catalysed reaction
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