must proceed at low temperatures

Transcription

1 Bio 20 Enzymes! In Nature, high temperatures cause chemicals to become highly reactive. BUT, high temperatures in cells cause PROBLEMS Ie.//a high fever causes the body to shut down or an egg in boiling water becomes. Chemical reactions in cells must proceed at low temperatures otherwise the cell may become damaged.

2 I Enzymes: Chemical proteins that permit reactions to occur at low temperature Enzymes are also known as CATALYSTS that speed up chemical reactions Activation Energy No Enzyme! Enzyme Present!

3 Enzymes High temperatures lower ACTIVATION ENERGY needed to make a reaction proceed! Enzyme catalysts lower ACTIVATION ENERGY necessary to make a reaction GO! Thus, the reaction can proceed at a LOWER TEMPERATURE in the presence of an enzyme! In Biology an enzyme often ends with the SUFFIX ase or -sin A single enzyme can CATALYZE between 100 to 30 Million reactions/minute!

4 II Factors That Affect Enzyme 1) Temperature: Reactions! - as temp. increases the molecules begin to move faster (particle theory) - as the substrate molecules move faster they collide with the enzymes more frequently - the enzymes are able to form more products quicker

5 Temperature As the temp. goes up, so does the rxn rate At 37 o C a peak in rxn. Rate occurs! Enzymes DENATURE & FAIL beyond 38 o C Rxn. Rate drops since the enzymes are destroyed! Reaction Rate! H L Temperature ( o C)

6 2) Substrate Concentration: Enzymes work on substrates As the substrate concentration increases, the reaction rate also increases (up to an optimal level) As the substrate concentration decreases, the reaction rate also decreases (can decrease to ZERO if no substrate)

7 Substrate Concentration H Reaction Rate! ALL the enzymes are busy causing a PLATEAU! Optimal level is reached! L Substrate Concentration

8 3) ph Range: ph is considered an important COFACTOR, as it is a condition to aid or hinder enzyme function. Certain enzymes work well in a HIGH ph (in your small intestine the ph is 9-11) Other enzymes work well in a LOW ph (in your stomach the ph is 1-2) Changes in ph can alter the SHAPE of enzyme proteins A change in the enzyme shape alters the ACTIVE SITE and renders the enzyme useless (like smashing a key with a hammer no longer works well)

9 4) Competitive Inhibitors: Enzymes compete to fit onto substrates Competitive Inhibitors prevent enzymes from joining with the correct substrates because they are IMPOSTERS Competitive Inhibitors look like Substrates Once an Enzyme joins a Competitive Inhibitor it never lets go!! Examples include poisons like Cyanide or medicines like Penicillin What happens to the reaction rate NOW?

10 Competitive Inhibitors E = S = P = C.I. = Legend:

11 5) Enzyme Concentration: Since enzymes work on substrates If we add more enzymes what can we predict would happen to the reaction rate? It should increase because there are more enzymes to help decompose the substrate quicker! Give me an example of this in our human life

12 Enzyme Concentration Reaction Rate Why does this happen? Enzyme Concentration

13 III Regulating Enzyme Reactions 1) Feedback Inhibition: the final product of the enzyme/substrate reaction is used to stop the function of the enzyme the reaction rate slows due to the shut-down of the enzyme See Whiteboard for drawing!

14 Feedback Inhibition This process is called ALLOSTERIC EFFECT: - the final product binds to the enzyme - this causes the enzyme to change shape - when the shape changes the enzyme no longer fits into the substrate What happens to the reaction rate?

15 2) Cofactors & Coenzymes: For any biochemical reaction to occur often helper chemicals are required A) cofactors are inorganic molecules (minerals) necessary in our diet to help enzymes fit onto substrates: examples include: iron, zinc, potassium & copper B) coenzymes are organic molecules originating from vitamins which do the same job as a cofactor

16 Coenzymes Notice the enzyme & substrate do not match! The coenzyme acts as a bridge between the 2 so that new products can be made. See Whiteboard for drawing!

17 Now What! Toothpickase Investigation Enzyme Drama (Role play!)