CHAPTER 6 METABOLISM AND ENZYMES. LIFE IS FULL OF CHEMICAL REACTIONS Chemical reactions Reactants...
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Transcript of CHAPTER 6 METABOLISM AND ENZYMES. LIFE IS FULL OF CHEMICAL REACTIONS Chemical reactions Reactants...
CHAPTER 6
ME
T AB
OL I S
M A
ND
EN
ZY
ME
S
LIFE IS FULL OF CHEMICAL REACTIONS
Chemical reactions
Reactants – what you start with
Products – what you end with!
Reactants that are acted upon
by an enzyme are called substrates
WHAT IS AN ENZYME?
Enzyme = molecules that make chemical reactions faster than they would be on their own (organic catalyst)
- most are proteins, some are RNA
- most are not used up in a reaction – they can be used again and again
-common ending = -ase
HOW DO ENZYMES WORK
Proteins (polypeptide chains) are folded into a 3D shape and have one or more active site
Active sites = pockets where substrates bind to a protein and the reaction occurs
WHAT FACTORS INFLUENCE THE RATE ENZYMES WORK?
Toothpickase Lab
-Do all trials without the person looking.
-All members must have their own graphs.
-You may choose to complete your questions (complete sentences) as a group or as individuals (turn in 3 graph papers and 1 or 3 question sheets)
ENZYME FUNCTION
In the liver, alcohol dehydrogenase helps break down toxic alcohols, but at the expense of liver function and energy metabolism
REACTIONS REQUIRE OR RELEASE ENERGY
-We can predict whether a reaction requires or releases energy by comparing the bond energies of reactants with those of products
- Endergonic (“energy in”)Reactions that require a net input of energy
- Exergonic (“energy out”)Reactions that end with a net release of energy
WHY THE WORLD DOESN’T GO UP IN FLAMESActivation energyThe minimum amount of energy needed to get a reaction started
Some reactions require a lot of activation energy, others do not
ACTIVATION ENERGY
MECHANISMS OF ENZYME-MEDIATED REACTIONS
Binding at enzyme active sites may bring on the transition state by 4 mechanisms
Helping substrates get togetherOrienting substrates in positions that favor reaction
Inducing a fit between enzyme and substrate (induced-fit model)
Shutting out water molecules
EFFECTS OF TEMPERATURE, PH, AND SALINITY
Raising the temperature boosts reaction rates by increasing a substrate’s energy
High temperatures denature enzymes
Each enzyme has an optimum pH range In humans, most enzymes work at ph 6 to 8
Salt levels affect the hydrogen bonds that hold enzymes in their three-dimensional shape
ENZYMES AND TEMPERATURE
Warm = dark fur
HELP FROM COFACTORS
CofactorsAtoms or molecules (other than proteins) that are necessary for enzyme function
Example: Iron atoms in catalase
CoenzymesOrganic cofactors such as vitaminsMay become modified during a reactionWhite board Cofactor and Coenzyme
CATALASE AND COFACTORS
Catalase is an antioxidant that neutralizes free radicals (atoms or molecules with unpaired electrons that attack biological molecules)
Catalase works by holding a substrate molecule close to one of its iron atoms (cofactors)
Iron pulls on the substrate’s electrons, bringing on the transition state
The enzyme song
ALLOSTERIC SITES
Allosteric sites – a region away from an active site that can bind regulatory molecules
Kahn Allosteric Competition Short Allosteric Regulation
FEEDBACK INHIBITION
Feedback Inhibition = the end product inhibits the first enzyme in a series
BIOLUMINESCENCEBioluminescenceLight emitted from metabolic reactions in living organisms
-Bioluminescent organisms emit light when enzymes (generic = luciferases) convert chemical bond energy in luciferins to light energy
luciferin + ATP → luciferin-ADP + Pi
luciferin-ADP + O2 → oxyluciferin + AMP + CO2 + light
BIOLUMINESCENCE VIDEOS
National Geographic
Waves Explained
BBC - deep sea