Transcript Chapter 6 - Capital High School

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 and1or 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 FLAMES
Activation energy
The 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
H
elping substrates get together
Orienting 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
H
igh 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
Cofactors
Atoms or molecules (other than proteins) that are
necessary for enzyme function
Example: Iron atoms in catalase
Coenzymes
Organic cofactors such as vitamins
May become modified during a reaction
White 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
BIOLUMINESCENCE
Bioluminescence
Light 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