1.  Definition of metabolism  Definition of a substrate  Characteristics of metabolic pathways  Why we need metabolic pathways

2. Ms Caldarola

3.  Substances are changed into other forms ◦ Ex) Carbohydrates broken down to CO 2 and H 2 O Generally:A + B ---------  C + D  A and B are the reactants or substrates  C and D are the products

4.  A term to collectively describe all of the chemical reactions happening in a cell that maintain homeostasis

5.  Occurs in cells, it is a set of chemical reactions Characteristics  Starts with specific reactants and produces a specific end product  One reaction leads to the next  Highly structured  Requires enzymes ◦ Each enzyme is specific to only one step

6. Why do these pathways exist? 1. Most reactions are complex! ◦ Cannot produce such complex molecules in one step ◦ Many steps needed 2. One pathway can lead to many others ◦ Intermediate products can serve as substrates for other reactions 3. More than one step means greater control

9.  Proteins that speed up chemical reactions  Provide sites for the reaction to take place  Not used up or changed permanently  Specific E + S  ES  E + P  ES = enzyme substrate complex  Active site – where the substrates bind on the enzyme

10.  Two models  Lock and Key Theory ◦ Enzyme and substrate fit together perfectly ◦ Enzyme is rigid

11.  Induced Fit Theory ◦ Enzyme changes shape slightly when substrate binds ◦ Substrate better fits into the active site ◦ Enzyme resumes original shape after

13.  Molecules react because they collide together in the right orientation ◦ This requires energy  Activation Energy ◦ The energy required to cause molecules to react with each other  Enzymes lower activation energy ◦ Provide a spot for the reaction to happen

15.  Similar to proteins! ◦ Particular shape needed to fit substrate into active site ◦ Anything that changes protein shape interrupts enzymes  Temperature  pH  Concentration of Substrate  Concentration of Enzyme  Inhibitors  Cofactors

16.  Decrease temperature = slow rate of reaction ◦ Low temperature doesn’t denature proteins  Slightly higher temperature = increase rate of reaction ◦ Enzyme has a specific operating range  Very high temperature = denature enzyme (no reaction rate)

17.  Enzymes have an optimal pH  Too low or too high = enzyme denatures  Cannot bind substrate

18.  Low substrate concentration = low product formation  High substrate concentration = more product ◦ Higher reaction rate  Enzymes eventually become saturated – no more substrate can bind ◦ Rate levels off!

19.  Limits the overall rate of reaction  If you have enough substrate ◦ More enzyme = higher reaction rate ◦ Less enzyme = less reaction rate  Usually you don’t run out of substrate  Enzyme may need to be activated to work ◦ Add ATP

20.  Inhibitor ◦ Binds to enzyme to prevent or reduce substrate binding  Competitive Inhibition ◦ Inhibitor looks like the substrate and binds to the active site ◦ Competition for active site slows down reaction rate ◦ Reversible or irreversible

21.  Non-Competitive Inhibition ◦ Inhibitor binds to another site on the enzyme ◦ Not the active site – still open ◦ Inhibitor changes the active site so the substrate can’t bind ◦ Also known as allosteric inhibition ◦ Reversible or irreversible

23.  Cofactors ◦ Molecules that help enzymes function ◦ Examples: Copper, zinc, vitamins ◦ May accept or donate atoms to the reaction

24.  Definition of an enzyme, substrate, and activation energy, and cofactor  Two models of enzymes  Factors that affect enzyme function ◦ How do they do it and what is the result?  Different types of inhibition