Download Endergonic vs. exergonic reactions

Chapter 8: Metabolism & Enzymes
Flow of energy through life
Life is built on ___________________________
transforming __________ from one form to another
Examples
 dehydration synthesis (synthesis)
+
enzyme
Metabolism
Chemical reactions of life
HO
o forming
between molecules
 hydrolysis (digestion)
 _____________________ synthesis
 synthesis
+
enzyme

reactions
o Breaking
between molecules
HO
AP Biology
 _________________________
 digestion

reactions
Chemical reactions & energy
o Some chemical reactions release energy
Examples
 ________________________
 dehydration synthesis (synthesis)
 digesting ____________________
 hydrolysis = _________________
enzyme
o Some chemical reactions require
input of_____________________
 _________________________
 hydrolysis (digestion)
 ___________________ polymers
 dehydration synthesis =
enzyme
________________
Energy & life
AP Biology
o Organisms require energy to live
 where does that energy come from?
coupling
reactions (___________________ energy)
with ____________________ reactions (___________________ energy)
What drives reactions?
o If reactions are “__________________”,
why don’t they just happen spontaneously?
Endergonic vs. exergonic reactions
 because covalent bonds are
exergonic
endergonic
____________________ bonds
- energy released
- energy invested
Activation energy
- digestion
- synthesis
o Breaking down large molecules requires an
initial ___________________ of energy
 _________________________
+ G
 large biomolecules are _________
 must absorb energy to break
- G
bonds
Too much activation energy for _____________
o Activation energy
AP Biology
G = change in free energy = ability to do work
 amount of energy needed to
_____________________________ the bonds of a molecule
 moves the reaction over an “___________________________”
2
2
Reducing Activation energy
o _____________________
 reducing the amount of
energy to
start a reaction
_______________________
o So what’s a cell got to do to
__________ activation energy?
 get help!…chemical
help…Enzymes
__________________
o Biological catalysts
 proteins (& RNA)
 facilitate chemical reactions
increase rate of reaction without being __________________
reduce activation energy
don’t change free energy
(____) released or required
 required for most biological
reactions
 highly___________________
_________________ of
different enzymes in cells
 control reactions of __________
o Enzymes vocabulary
 _________________________
reactant which binds to enzyme
enzyme-substrate complex: temporary association
 _________________________
end result of reaction
 _________________________
enzyme’s catalytic site; substrate fits into active site
o Properties of enzymes
 Reaction specific
each enzyme works with a
specific __________________
chemical fit between
___________ site & substrate
H bonds & ionic bonds
 Not
in reaction
single enzyme molecule can
________________ thousands
or more reactions per second
enzymes _________________
by the reaction
 Affected by
conditions
any condition that affects
protein structure
________________________
o
o
o
Naming conventions
 Enzymes named for reaction they catalyze
_________________________ breaks down sucrose
break down proteins
break down lipids
DNA
builds DNA and adds nucleotides to DNA strand
breaks down proteins (polypeptides)
____________________________________ model
 Simplistic model of _____________________ action
substrate fits into 3-D structure of enzyme’ active site
o ____________ bonds between substrate & enzyme
like “key fits into lock”
_____________________________________ model
 More accurate model of _____________________ action
3-D structure of enzyme fits substrate
substrate binding cause enzyme to change
leading to a tighter fit
o “
change”
o bring chemical groups in position to catalyze reaction
 How does it work?
Variety of mechanisms to lower activation energy & speed up reaction
o Synthesis - active site orients
in correct
position for reaction
 enzyme brings substrate _____________________ together
o ___________________________ - active site binds substrate &
puts stress on bonds that must be
, making
it easier to separate molecules
Factors that Affect Enzymes
Factors Affecting Enzyme Function
o ____________________________ concentration
o Substrate ______________________
o Temperature
o ____________
o Salinity
o _______________________
o Inhibitors
Enzyme concentration
o Factors affecting enzyme function
 Enzyme concentration
as ________ enzyme = ________ reaction rate
o more enzymes = more frequently ________________ with substrate
___________________________ rate levels off
o substrate becomes _______________________________
o not all enzyme ___________________________ can find substrate
Substrate concentration
o Factors affecting enzyme function
 Substrate concentration
as ______ substrate = ______ reaction rate
o more substrate = more frequently ________________ with enzyme
reaction rate levels off
o all enzymes have active site _____________________
o enzyme is ________________________
o maximum _____________________ of reaction
reaction rate
reaction rate
Temperature
o Factors affecting enzyme function
 Optimum T°
Enzymes and temperature
greatest number of
 Different enzymes function in different
molecular ________
organisms in different environments
human enzymes =
hot spring
____°- ____°C
human enzyme
bacteria enzyme
o body temp =
_____°C
 Heat:
beyond
optimum T°
increased ________
level of molecules
disrupts bonds in
37°C
70°C
temperature
AP Biology
enzyme & between
(158°F)
enzyme & substrate
o H, ionic = ____
bonds
pH
_________ = lose 3D
What’s
shape (3° structure)
happening here?!
 Cold:
T°
molecules move _____
pepsin
trypsin
decrease collisions
between __________
& substrate
pepsin
o Enzymes and __________________
 Different enzymes function in
trypsin
different organisms in
different environments
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
pH
pH
AP Biology
o Factors affecting enzyme function
 changes in pH
adds or removes _________
____________________ bonds, disrupts _______ shape
o disrupts attractions between charged ________________________
o affect ___° & ___° structure
o ____________________ protein
 optimal pH?
most human enzymes = pH 6-8
o depends on localized conditions
o pepsin (stomach) = pH 2-3
o trypsin (small intestines) = pH 8
Salinity
o Factors affecting enzyme function
 Salt concentration
changes in ____________________
o adds or removes _____________ (+) & _____________ (–)
o disrupts _______________, disrupts 3D shape
 disrupts attractions between _______________ amino acids
 affect ___° & ___° structure
 _________________________ protein
enzymes _______________________ of extreme salinity
o _________________________ is called dead for a reason!
Compounds which help enzymes
o Activators
 __________________________
non-protein, small ________________________ compounds & ions
o Mg, K, Ca, Zn, Fe, Cu
o bound __________________ enzyme molecule
 __________________________
non-protein, _________________ molecules
o bind temporarily or permanently to enzyme near ________________
many _____________________
o NAD (___________________; B3)
o FAD (____________________; B2)
o _______________________ A
Compounds which regulate enzymes
o ___________________________
 molecules that reduce enzyme activity
 _______________________ inhibition
 _______________________ inhibition
 _______________________ inhibition
 _______________________ inhibition
o ____________________________ Inhibitor
 Inhibitor & substrate “_________________________” for active site
______________________ blocks enzyme bacteria use to build cell walls
disulfiram (________________________) treats chronic alcoholism
o blocks enzyme that breaks down ______________________
o severe hangover & _______________ 5-10 minutes after drinking
 Overcome by _________________________ substrate concentration
saturate solution with substrate so it ______________________________
inhibitor for active site on enzyme
o Non-Competitive Inhibitor
 Inhibitor binds to site other than active site
_________inhibitor binds to allosteric site
causes enzyme to change ______________
o conformational change
o active site is no longer functional
__________________ site
 keeps enzyme __________
some
drugs inhibit
enzymes involved in DNA synthesis
o stop _________ production
o stop division of more cancer _____
irreversible inhibitor of Cytochrome C,
an enzyme in cellular respiration
o stops production of __________
o Irreversible inhibition
 Inhibitor ______________________ binds to enzyme
competitor
o permanently binds to _______________________
_______________________
o permanently binds to allosteric site
o permanently changes __________________ of enzyme
o nerve gas, sarin, many insecticides (malathion, parathion…)
 ___________________________ inhibitors
doesn’t breakdown the neurotransmitter, __________
o Allosteric regulation
 Conformational changes by
________________ molecules
_____________- keeps
enzyme in inactive form
____________ - keeps
enzyme in active form
______________________ pathways
o Chemical reactions of life are organized
in ___________________
 divide chemical reaction into
many _____________ steps
artifact of _________________________
___ efficiency
o intermediate branching points
threonine
___ control = ___________________
Efficiency
Example
o _______________________
groups of enzymes
 enzymes are embedded
in membrane of
andamino
arranged
 synthesis
_______________________
acid, isoleucine from
o Link ________________________ & exergonic reactions
amino acid, threonine
Feedback Inhibition
 isoleucine becomes
o _______________________
& coordination of production
the
allosteric in pathway
 product is used by next
_____________
inhibitor
of the
firststep
 ______________ product is inhibitor
of earlier
stepofin
the____________
pathway
allosteric inhibitor
earlier
_____________________
inhibition
 as product
 no unnecessary ____________________
accumulates itof product
collides with enzyme
o Example
more often than
 synthesis of amino acid, ______________________
substrate does
isoleucin
from amino acid, __________________________
AP Biology
e
 isoleucine becomes the
inhibitor
of the first step in the pathway
as product _________________________ it collides with enzyme more
often than substrate does
Feedback inhibition
