Presentation on theme: "Today is Thursday, October 3 rd, 2013 Pre-Class In your notebook, write down your definition of what energy is. What does energy do? Better yet, where."— Presentation transcript:
Today is Thursday, October 3 rd, 2013 Pre-Class In your notebook, write down your definition of what energy is. What does energy do? Better yet, where is the energy in this picture? P.S. There’s homework, but it’s short. In This Lesson: Enzymes and Reactions (Lesson 9 of 9)
Pre-Class #2 What is your ideal temperature for the thermostat? – I might ask all of you.
Today’s Agenda Review Energy Outline chemical reactions. Define enzymes. Have an enzyme contest! Where is this in my book? – P. 49 and following…
Quia Today you’ll be trying two activities individually. These are called: – Organic Molecule Matching – Organic Molecule Fill-In This one is particularly good for test prep and studying. You’ll also be doing one as pairs (so put away one computer when you get here). – Organic Molecule Challenge Board
Okay, so about energy… What do we think of energy? What is it? What’d you write for the pre-class? According to science, energy is the capacity to do work. – For our biology class, it might be easier to think of energy as a force. – Example: The force (energy) a cell needs to keep making protein.
Conservation of Energy According to the Law of Conservation of Energy, energy cannot be created or destroyed. – In other words, energy can only change form. For example, a ball at the top of a hill has a lot of potential energy. When it rolls to the bottom, it’s moving nice and fast, and it has a lot of kinetic energy.
Reaction Example Thermite video In this reaction, chemical energy from bonds is changed into thermal energy, which is released as new bonds form.
Putting it together… The reactant(s) are shown on the left of the reaction equation. The product(s) are shown on the right of the reaction equation. The reaction itself is indicated by an arrow ( - say “yields”). Example: Reactant(s) Product(s) Fe 2 O 3 + 2Al 2Fe + Al 2 O 3
Just checking… 2H 2 + O 2 2H 2 O Which is/are the product(s)? –H2O–H2O 2NaCl 2Na + Cl 2 Which is/are the product(s)? – Na + Cl
Enzyme Review! Whiteboards! What do you know about catalase or enzymes? – What kind of organic molecule? – What do they do? – How do they do that?
Some examples… Catalase – Hydrogen peroxide molecules broken into H 2 O and O 2. DNA Helicase – DNA spiral helix shape opened or “unzipped” (breaks Hydrogen bonds). DNA Polymerase – Polymerizes nucleotides into DNA (forms bonds). RNA Polymerase – Polymerizes nucleotides into RNA forms bonds).
What’s in a name? Enzymes typically end in –ase and the first part of the name usually describes what it does. DNA Polymerase – -ase tells you it’s an enzyme. – Polymer- talks about its action – polymerization!
Enzymes Most enzymes are proteins. Enzymes speed up reactions that would otherwise be too slow for life to be efficient. – They don’t directly speed it up. – They lower activation energy of a reaction. Wait, what’s energy again? – Energy is “the capacity to perform work.” – We can think of it as a force. – Activation energy is the force needed to start the reaction.
Activation Energy Example Imagine you earn an allowance of $1 per week. You want to buy a video game system that costs $349. – How many weeks do you need? 349. Enjoy that. If the game system goes on sale for $50, how many weeks would you need? – 50. So you can get the system sooner, but are you earning money at a faster rate? – No. – This is how enzymes work – they lower the “threshold.”
Threshold? In this case, the “threshold” is activation energy. Another way to think of activation energy is by an example from our chemistry textbook: – If you roll clay into a thin rope, then shake it vigorously, eventually the clay will break. – Similarly, a certain amount of energy is required to get molecules to “reorganize” themselves and form bonds. This is activation energy.
Activation Energy Enzymes are catalysts because they catalyze reactions. – In other words, they “kick-start” ‘em. Without Enzyme With Enzyme Sketch me!
Some other enzyme details… Enzymes are typically not used up in a reaction. Enzymes tend to be specific to certain substrates (reactants). – What are substrates again? 2H 2 O > 2H 2 O + O 2 SubstrateProducts Enzyme working…
Putting it all together… Enzymes affect substrates at the enzyme’s active site:
In note form… Recyclable – They don’t get used up in reactions. Substrate-specific – Each enzyme only works on specific reactants. Non-Reversible – Enzymes can either put stuff together or break stuff apart (but not both). – In other words, they break or form bonds. Active Site – Where the bonding and “unbonding” happens.
Denaturation So what’s your ideal temperature (from the pre- class)? It turns out that enzymes (and other proteins) have an ideal set of conditions too. If the environment (the body or elsewhere) gets too hot or too cold, they will break or not function efficiently. Basically, they change shape, and not in a good way. If the environment gets too acidic or basic, the same thing occurs.
Denaturation This process of changing shape, breaking down, or not functioning efficiently is called denaturation. – Typically due to pH or temperature swings. In a sentence: – The small child had such a high fever that some of his enzymes actually began to denature. In an example: – Protein denaturation is why raw eggs are liquidy and cooked eggs are solidy.
Enzyme Contest I need 3 volunteers and 3 official judges. Each volunteer will simulate an enzyme. We’ll call this enzyme “Splint Splittase.” When I say go, you will have 60 seconds to break in half (and half again) as many wooden splints as you can. – Judges will count the total.
Enzyme Contest Splint Splittase 1 – You are operating normally. Go! Splint Splittase 2 – pH in the body has gotten too acidic. As a result, your structure has changed. Cross your fingers on both hands before beginning. Splint Splittase 3 – Temperature has gone down. Stick your hands in ice-water for 60 seconds before beginning.
Enzyme Contest Okay, so what was the active site? – The enzymes’ “hands.” What was the substrate? – Splints. And what did you notice about the results? Denaturation is a serious problem if it happens in a living thing. – The body’s necessary chemical reactions may halt. – This is why if you get a really high fever you need to go to the doctor immediately.
One more thing… Here’s an off-topic example: – Let’s say you’re sick and you take a dose of medicine. You start to feel a little better. – If you were to have taken half a dose, you might not have felt as good. – However, taking two doses wouldn’t make you feel EVEN better than one dose, right? So, medicine only helps up to a certain point. Similarly, your car can only go so fast.
One more thing… You also may have noticed that it didn’t really matter how many splints I gave the enzymes. As long as I gave them enough that they couldn’t possibly run out, they’d keep working. Therefore, in reality, enzymes can only work up to a certain speed, no matter how much substrate you give them. – A small amount of substrate and they may slow down. – A medium amount of substrate and they’ll work well. – Lots of substrate? They won’t work any faster.
Enzyme Activity as a Function of Substrate Availability Amount of Substrate Enzyme Activity
Poisons and Enzymes Many poisons and drugs (both illegal and pharmaceutical) work by bonding to enzymes and staying there. Because the active site is taken up, the enzyme can’t do its normal job.
Enzyme Competition Sometimes enzymes are shut off by competition with enzyme inhibitors. – Can be a good thing or a bad thing…
Real Enzymes Some real enzymes to note: – Amylase: Found in saliva – breaks down carbohydrates. – Protease: Found in stomach – breaks down proteins. – Lipase: Made by pancreas – breaks down fats.
Enzyme Closure For today’s closure: 1.Write the definition of “denaturation” in your own words in your notebook. 2.Write the word “denaturation” with your fingers crossed (on your writing hand).
One More Thing… We can’t forget to talk about how monomers are linked together and polymers are broken apart (digested). Two basic chemical reactions are typically the way living things do this. – Dehydration synthesis – Hydrolysis Which reaction does what, do you suppose?
Dehydration Synthesis Enzyme(s) required. Water removed (de-hydration) to put monomers together (synthesis). – Results in two linked monomers + 1 extra H 2 O. Dehydration synthesis is sometimes known as a condensation reaction because water is a by-product.
Dehydration Synthesis Forming a glycosidic bond:
Dehydration Synthesis Forming a peptide bond:
Hydrolysis Enzyme(s) required. Water added (hydro-) to break polymers apart (lyse). – Results in a monomer or two, minus 1 H 2 O. How to remember? – Hydrolysis: “Hydro-slices”
Closure Work on the half-worksheet called “Enzyme Reactions.”
Closure BBC – Bitesize Enzymes
Homework Watch/read this animation: – ons/content/proteinstructure.html – Also available by Googling protein structure egg. First result… – Also available as a link from my website: Eggs and Protein Structure.