enzymes for hbs
TRANSCRIPT
Enzymes
Enzymes Enzymes are substances that are necessary
for most of the chemical reactions that occur in living cells.
Chemical reactions that occur in the body are done in small steps. In some of these small steps, the enzyme works on the reaction to help it take place, rearranging the molecules involved.
Enzymes Are Biological Catalysts• Enzymes are proteins that carry out most
catalysis in living organisms.– Unique three-dimensional shape enables an
enzyme to react with specific substrates.– Because the enzyme itself is not changed or
consumed in the reaction, only a small amount is needed, and can then be reused.
Enzyme names Usually end in “-ase” like isomerase
Most enzymes are used within the cell, but some are used outside of the cell. Example: Digestive enzymes
Free Energy• Free energy refers to the amount of energy
actually available to break and subsequently form other chemical bonds.– in a cell - amt of energy contained in a molecules
chemical bonds• Energy involved in chemical reactions:
• endergonic - any reaction that absorbs free energy
• exergonic - any reaction that releases free energy
Activation Energy
• Activation energy refers to the extra energy required to destabilize existing chemical bonds and initiate a chemical reaction.
• catalyst - substance that lowers the activation energy
• Enzymes are catalysts.
Activation Energy and Catalysis
How do enzymes work?
• An enzyme reacts only with specific substrates (Another word for reactants)
– Active site- the part of an enzyme that actually
interacts with the reactants
Enzyme Active Site• Amino acid side chains interact, metal ions,• Various types of polar, non-polar, ionic interactions
Enzymes
• Most enzymes are globular proteins with one or more active sites.– Substrates bind to the enzyme at these active
sites, forming an enzyme-substrate complex.
How Does It Fit? 2 Models Old – Lock and Key Model – the active site
only fits certain substrates. Newer – Induced Fit Model – Enzyme
changes shape in reaction to being exposed to the substrate.
• Lock and Key Analogy: lock = enzyme, key = substrate.
Induced Fit Model
Control of enzyme activity:• Concentration of enzyme and substrate molecules
• Temperature
• pH
Enzymes - Activity• Enzyme and substrate concentrations
Enzymes - Activity• Temperature and pH effect enzyme action
Enzymes - Activity• Temperature and pH effect enzyme action