Energy and Enzymes Flashcards
metabolism
sum of all chemical reactions in one organism
extract energy from nutrients
synthesize or breakdown molecules
catabolism
reactions that release energy by breaking down molecules (exergonic)
anabolism
reactions that require energy to build molecules *endergonic
energy
capacity to do work
chemical work
making and breaking chemical bonds, building and breaking molecules
kinetic work
move ion, molecules, large stuff in and out of the cell, move a cell through a tissue of the body
kinetic energy
energy of motion
ex: moving Na+ across the membrane down its concentration gradient
rolling a ball down a hill
potential energy
stored energy aka energy that’s about to happen
ex: ball poised at the top of the hill
disequilibrium of Na+ ready to move down its concentration gradient
thermal energy
heat
chemical energy
potential energy in food or storage molecules
energy transformations
constant changes of energy from one form to another
potential energy–>kinetic energy
chemical energy –>thermal energy
thermodynamics
study of energy transformations
1st law
energy can be neither created nor destroyed just converted from one form to another
2nd law
every energy transfer or transformation increases entropy
entropy
energy lost when trying to convert from one form to another
results in unusable energy
intermediates
molecules involved in reactions that have many steps
A+B–>C–>D–>E
exergonic reaction
when you break a bond, energy is released
endergonic reaction
when you make a new bond, energy is required
where do we get energy for endergonic reactions?
o we can couple an endergonic and exergonic reaction at the same place/time. Use energy from one to fuel the other
o we can store energy as potential energy in electrons carried on nucleotides (NADH, FADH2)
o These energy transfer molecules carry the energy until it can be used in the ADP-ATP conversion
o Side note: ATP forms the bridge between endergonic and exergonic reactions
Cellular reactions
• Often reversible
o Often different enzymes are required for each direction-another level of control!
o Either catabolic or anabolic
o A+b←→C +D
activation energy
energy needed to start a reaction
energy required to bring two molecules close together
enzymes
proteins that catalyze or speed up reactions
substrate
ligand
molecule that the enzyme acts on
co-factor
another binding partner that may control the enzyme
enzymes get too powerful so in order to maintain homeostasis so we need a co-factor to control enzyme activity
keep enzyme inactive, activate when needed
active site
grooves or pockets in the 3-D protein where enzymes bind their substrates
made up of amino acids
enzyme-substrate complex
a temporary molecule including the enzyme and substrates
steps to catalyze a reaction
o Enzyme binds substrate forms enzyme-substrate complex
• A temporary molecule including the enzyme and substrates
o Chemical reaction occurs—enzyme is not bound to product
o Enzyme releases product
• E+S→ES→EP→E+P
• Lactase and lactose form a lactose-lactase complex, then forms an enzyme product complex, then it will release them back into their monomers
o While enzyme is bound, it cannot produce more substrate
enzyme function
- Each enzyme molecule has a single active site
- Once a substrate molecule is bound, the active site is “taken” temporarily
- At the end of the reaction, the products are released and the enzyme is ready to bind to a new substrate
turnover number
number of molecules of substrate that the enzyme can process per second
all enzymes have it
turnover number is determined by its
affinity
affinity
strength that a protein has towards its ligand
enzyme has towards its substrate
more molecules will be passed if your affinity is
LOWER
binding
occurs when a set of noncovalent interactions tie the proteins together
affinity proteins
hemoglobin
can bind CO2, H+, and CO
has a stronger affinity for CO than O2
if affinity is stronger
turnover rate decreases
an active site will demonstrate more specificity and a higher affinity for its ligand when
the site of interaction is more complex
inhibitor
if an inhibitor has a higher affinity for the enzyme than the substrate, there will be a powerful inhibition
affinity of the enzyme for its substrate determines
turnover number
saturation
what happens when an enzyme is operating at its turnover number
reached when each molecule is bound to a substrate and you cannot increase the rate of reaction
competitive inhibitor
something that binds to a substrate’s active site
both molecules are competing for that active site
allosteric inhibitor
binds to a separate site enzyme, which changes the shape of the substrate active site so substrate can no longer bind
low affinity
competitive inhibition
both the inhibitor and the substrate bind to the same active site
due to turnover number, this reduces enzyme activity
if binding of inhibitor has higher affinity than substrate, this can eliminate enzyme activity
beta blockers
- Binds to the epinephrine receptor and blocks it
- Has a higher affinity than epinephrine
- Reduces the rate at which our cells can bind to epinephrine
- Effects: lowers heart rate
- Nervous effects don’t happen
- Tamoxifen
feedback inhibition
product of the pathway acts as an inhibitor to the first steps of the pathway
ex: • Highlevel of testosterone, it inhibits the first enzyme, leads to fewer testosterone molecules being produced
• When we fall short with testosterone, it unhibits and then the regular amount of testosterone will continue to be produced
phosphorylation
addition of a phosphate group
kinases
enzymes that add phosphate groups
phosphatases
enzymes that remove phosphate groups
lysozyme
o Cuts polysaccharide chains on bacterial cell walls by hydrolysis
o These chains are relatively stable until lysozyme binds and bends the substrate, altering the molecular shape and making it vulnerable to water
