Chemical reactions of life Enzymes can help in: – building molecules synthesis – breaking down molecules digestion ++
Nothing works without enzymes! How important are enzymes? – all chemical reactions in living organisms require enzymes to work building molecules – synthesis enzymes breaking down molecules – digestive enzymes – enzymes speed up reactions “catalysts” ++ enzyme We can ’ t live without enzymes!
Enzymes A protein catalyst Enzymes are important proteins found in living things. An enzyme is a protein that changes the rate of a chemical reaction. They speed metabolic reactions.
Enzymes do not catalyze processes that would not take place on their on. They just make processes take place faster!
Enzymes aren’t used up Enzymes are not permanently changed or used up in reactions. – used only temporarily – re-used again for the same reaction with other molecules – very little enzyme needed to help in many reactions enzyme substrateproduct active site
Enzymes are proteins Each enzyme fits only one specific type of reaction, but can catalyze many of this particular reaction one after another. – each enzyme needs to be the right shape for the job – enzymes are named for the reaction they help sucrase breaks down sucrose proteases breakdown proteins lipases breakdown lipids DNA polymerase builds DNA Oh, I get it! They end in -ase
Substrates Substrate – A molecule that enzymes work on – Substrates undergo chemical changes to form new substances called products. Products – what the enzyme helps produce from the reaction Active site – part of enzyme that substrate molecule fits into
It’s shape that matters! Lock & Key model – shape of protein allows enzyme & substrate to fit – specific enzyme for each specific reaction
Activation Energy The activation energy of a reaction is the minimum amount of energy needed to start a reaction. It is like traveling over a hill because the peak represents the activation energy needed for the reaction.
What affects enzyme action The rate of a reaction depends in part on the shape of the enzyme. If the enzyme is large, its concentration is high, which increases reaction rate. Correct protein structure – correct order of amino acids – why? enzyme has to be right shape Temperature pH (acids & bases) – why? enzyme has to be right shape
37° Temperature temperature reaction rate What’s happening here?! human enzymes
Order of amino acids Wrong order = wrong shape = can’t do its job! DNA chain of amino acids folded protein right shape! wrong shape!
Temperature Effect on rates of enzyme activity – Optimum temperature greatest number of collisions between enzyme & substrate human enzymes – 35°- 40°C (body temp = 37°C) – Raise temperature (boiling) denature protein = unfold = lose shape – Lower temperature T° molecules move slower fewer collisions between enzyme & substrate
pH Effect on rates of enzyme activity – changes in pH changes protein shape~ Denatures – most human enzymes = pH 6-8 depends on where in body pepsin (stomach) = pH 3 trypsin (small intestines) = pH 8
Other important facts about enzymes! Enzymes are a type of protein! Enzymes usually end in the suffix –ase. Examples: – Carbonic anhydrase: removes carbon dioxide from the blood before it becomes toxic. – Lipase: speeds up the digestion of fats – RNA polymerase: speeds up protein production
Enzyme Disorders PKU: phenylketonuria *Cells fail to make an enzyme that is used to break down phenylalanine. *If phenylalanine builds up in the blood, it can cause death.
Tay-Sachs: *It is a genetic disease that affects the human brain. *In this disease, cells do not produce an enzyme that breaks down lipids. *Over time, the buildup of lipids in and around the brain cells causes blindness, seizures, and usually death.