ATP Enzymes Why do we need energy Energy

ATP & Enzymes

Why do we need energy?

Energy for a cell � ATP= Adenosine Tri. Phosphate � Adenine, ribose, and inorganic phosphate (Pi)= AMP � ADP? � ATP? � What type of reaction when adding a phosphate group?

How does ATP transfer energy? O– –O P O ATP ADP O– O– –O–P O O– O– –O P O O– + O § ATP ADP u releases energy § ∆G = -7. 3 kcal/mole § Fuel other reactions § Phosphorylation u released Pi can transfer to other molecules § destabilizing the other molecules AP Biology u enzyme that phosphorylates = “kinase” 7. 3 energy

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Enzymes!

Too much activation energy for life § Activation energy amount of energy needed to destabilize the bonds of a molecule u moves the reaction over an “energy hill” u glucose AP Biology Not a match! That’s too much energy to expose living cells to!

Reducing Activation energy § Catalysts AP Biology

Enzymes � Biological catalysts �Reduce activation energy without changing G! �Increase rate without being consumed!

Enzymes vocabulary substrate § reactant which binds to enzyme § enzyme-substrate complex: temporary association product § end result of reaction active site § enzyme’s catalytic site; substrate fits into active site substrate AP Biology enzyme active site products

Properties of enzymes § Reaction specific u each enzyme works with a specific substrate § Not consumed in reaction u single enzyme can catalyze thousands of reactions per second and not be consumed § Affected by cellular conditions u any condition that affects protein structure § temperature, p. H, salinity AP Biology

Lock and Key model § Simplistic model § H bonds between substrate & enzyme u AP Biology “key fits into lock”

Compounds which help enzymes Cofactors Fe in hemoglobin § Non-protein, small inorganic compounds & ions w. Help give active site proper shape § Many vitamins Mg in chlorophyll AP Biology

Competitive Inhibition § Substrate is blocked from reaching active site by a different molecule. AP Biology

Noncompetitive Inhibition § Molecule binds to site other than the active site (allosteric site) and changes shape of active site. AP Biology

Feedback Inhibition § Regulation & coordination of production u u product is used by next step in pathway final product is inhibitor of earlier step § allosteric inhibitor of earlier enzyme § feedback inhibition u no unnecessary accumulation of product A B C D E F G 1 2 3 4 5 6 X enzyme enzyme AP Biology allosteric inhibitor of enzyme 1