Energy and Enzymes Flashcards
redox
- electrons are energized–> so also transferring energy
Electron carrier
- Intermediate step- holds onto/carries electrons to move somewhere else
NAD + electron carrier ((Nicotinamide adenine dinucleotide)
- Enzyme cofactor that acts to carry electron
- 2 nucleotides: NMP(+) with AMP
- electrons go on + charge N–> to make neutral, also take H+
- -> creates NADH
endergonic
- when delta G is positive
- product takes more energy to make than reactants has
- Unfavorable reactions never go w/o supply of energy from another source. Product higher energy than reactant
exergonic
- when deltaG is negative
- Favorable, spontaneous, some energy given off reactant higher energy state than the product
ATP hydrolysis
- Take ATP, hydrolyzed to ADP, put Phosphate onto OH to create an intermediate product with a high energy phosphate that can fall off
- Products of ATP hydrolysis
- CONDENSATION STEP: connection of “A” back onto the “B”stand
Glu + NH3 > Gln would have a positive Delta G - Glu + NH3 + ATP»_space;> ADP + Pi + Gln has an overall negative DeltaG
- Sum up the Delta G’s and calculate that it is overall a spontaneous reaction
catabolic reactions
- reactions of breakdown are mostly spontaneous reactions
anabolic reactions
- Reactions of synthesis
- steroids, anabolic steroids
- Mostly unfavorable so require energy
Effect of enzyme on the activation energy
- destabilizes chemical bonds to lower activation energy
- More likely to convert to products by lowering the activation energy. Therefore more rapid progression
Action of enzyme
- Polypeptide folded up in 3d shape and has active site
- catalysis happens at active site on the enzyme - the place where the substrate binds (substance acted upon by enzyme)
- induced fit- enzyme tightens up on substrate to destabilize bonds
enzyme-substrate complex
- substrate binds to enzyme and form enzyme-substrate complex
- enzyme places stress on bond bond (substrate)–> breaks bonds and products are released
enzyme pathway
- enzymes have evolved to form chains where the product is the substrate of the adjacent enzyme
- Substrate > enzyme 1 > enzyme 2 > …. > enzyme x > product
- in membrane or cytoplasm
feedback inhibition
- when final product give feedback and inhibits enzyme at the start of the process
- final product able to interact with the beginning of the pathway and turn it down activity
Competitive inhibition
- some other substance fits in this active site and interferes–> substrate cannot bind to enzyme
- Vmax is the same, Km is higher, affinity for substrate is lowered
Noncompetitive inhibition (allosteric inhibition)
- Allosteric site, different shape that binds to different active site–> this changes the shape of enzyme so that the original substrate can no longer bind to the enzyme’s active site
- Vmax is lowered, Km is the same
PH optimum
- Enzymes work best at particular pHs- 7 is normal
- ex. Trypsin- lives in lower digestive tract, can see change in folding shape, 6.8 is optimal
- ex. Pepsin works in the stomach (protein digestion) but has an acid pH and works best at low levels
temperature optimum
- Optimum temp for human enzyme is 40 degrees C, our bodies are 38 degrees C
Michaelis-Menten Plot
- Vmax = (Km)/2Km
- Competitive inhibition- Vmax same, but Km will be larger because the competitor slows down ability of substrate to bind to active site
- noncompetitive- Lower Vmax, Km same because competitor binds to different spot on enzyme
competitive inhibition
inhibitors competing with substrate for binding to active site; competitors slow down ability of substrate to bind with active site. Get to point where there are so many substrate molecules that they out-compete competitive inhibitor.
noncompetitive inhibition
competitor binds to different spot on enzyme (not active site), which inactivates enzyme by changing its shape – knocks out some proportion of enzyme that is not bound by competitor
sucrase enzyme cycle
- enzyme takes sucrose and breaks into glucose and fructose
- enzyme substrate complex- where linkage is destabilized and activation E lowered
- binding site places strain on bond–> products released
