narrated notes_enzymes 2.25

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Narrated notes on enzymes

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M 2/25/13: Enzymes:

M 2/25/13: Enzymes Today’s objectives: Describe the structure of an enzyme. Describe how enzymes and substrates interact. Explain how enzymes help biological reactions. Warm up: Enzymes are proteins. Name three other things that proteins can do. What happens if a protein falls apart?

What happens to our food after we eat it?:

What happens to our food after we eat it? What does food give us? Energy! Where is that energy stored? In the chemical bonds of our food How do we get that energy? By breaking the chemical bonds! Breaking bonds = release energy = energy for us

Chemical reactions:

Chemical reactions Chemical reactions involve breaking molecular bonds and forming new bonds. Chemical reactions release or absorb energy. Example (photosynthesis): 6 CO 2 + 12 H 2 O + light  C 6 H 12 O 6 + 6 O 2 Carbon dioxide + water + light  glucose + oxygen

Activation energy:

Activation energy Sometimes, the reactions have to hit a certain point before they will happen. This prevents reactions from happening all the time, non-stop. Activation energy – energy needed to get a reaction started

Activation energy:

Activation energy

Enzymes:

Enzymes Some of the chemical reactions we need are too slow – they would never happen, and you would not be alive! Enzymes – biological catalysts Catalyst – a substance that speeds up a reaction Catalysts are not changed in the reaction. They are just a tool! Lowers the activation energy needed

PowerPoint Presentation:

http://www.biologyinmotion.com/minilec/wrench.html

How enzymes work:

How enzymes work Enzymes provide a place for reactions to take place. Substrates – the reactants (the things getting changed) Active site – part of the enzyme where the substrate sits

An example enzyme-substrate reaction:

An example enzyme-substrate reaction

Active sites:

Active sites Enzymes are very specific – only one substrate will fit into their active site. Lock and key model – enzymes and substrates are like a lock and a key

Enzyme specifics:

Enzyme specifics Enzymes have specific conditions where they can work the best pH levels Stomach enzymes – work best at pH 2 Small intestine enzymes – work best at pH 6 Temperatures All of your enzymes work best at regular body temperature (37 C, 98 F) Denature – when proteins (including enzymes) are put in unfavorable environments, they will fall apart and be destroyed

Enzyme specifics (cont.):

Enzyme specifics (cont.) Cofactors – inorganic, non-protein enzyme helpers AKA minerals! Coenzymes – organic, non-protein enzyme helpers AKA vitamins! Enzyme inhibitors – stop an enzyme from working May block the active site May change the shape of the enzyme so that it can’t work (Many toxins and poisons are enzyme inhibitors.)

Wrap up 2/22:

Wrap up 2/22 All proteins are created from DNA. What would happen if there was an error in the DNA that coded for an enzyme? Pepsin is an enzyme that works in your stomach to digest proteins. Could pepsin be used to digest other molecules? Would pepsin work in your small intestine?

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