Presentation on theme: "Mr. Safford’s Biological Sciences. All enzymes are globular proteins thus spherical in shape Control biochemical reactions in cells They have the."— Presentation transcript:
All enzymes are globular proteins thus spherical in shape Control biochemical reactions in cells They have the suffix "-ase"
Intracellular enzymes are found inside the cell Extracellular enzymes act outside the cell (e.g. digestive enzymes) Enzymes are catalysts → speed up chemical reactions Reduce activation energy required to start a reaction between molecules Substrate molecules (reactants) are converted into products Reaction may not take place in absence of enzymes (each enzyme has a specific catalytic action) Enzymes catalyze a reaction at max. rate at an optimum state
Lock and key theory Only one substrate (key) can fit into the enzyme's active site (lock) Both structures have a unique shape Enzyme is not used (reusable) up in the reaction (unlike substrates)
Let’s See it in Action! Let’s See it in Action!
1. Changes in pH Affect attraction between substrate and enzyme Ionic bonds can break and change shape → enzyme is denatured Charges on amino acids can change → Enzyme Substrate complex cannot form Optimum pH (enzymes work best) pH 7 for intracellular enzymes Acidic range (pH 1-6) in the stomach for digestive enzymes (pepsin) Alkaline range (pH 8-14) in oral cavity (amylase)
2. Temperature Increased Temperature Increases speed of molecular movement → increased chances of molecular collisions → more ES complexes Enzymes have optimum temp. for their action (usually 37°C in humans) Just above ≈42°C, enzyme is denatured due to the breaking Hydrogen bonds and higher temps. break covalent bonds Denaturation -the loss of appropriate structure rendering the enzyme inactive. Shape is changed → active site can't be used, ever again
Decreased Temperature Enzymes become less and less active, due to reductions in speed of molecular movement Below freezing point Inactivated, not denatured Regain their function when returning to normal temperature
A typical graph of rate against temperature might look like this:
4. The presence of inhibitors Enzyme inhibitors are substances which alter the catalytic action of the enzyme and consequently slow down, or in some cases, stop catalysis. three common types of enzyme inhibition – Competitive-compete for active site Non-competitive- bind to enzyme somewhere other than the active site and change the active site