Unit 2 Flashcards
what does work do
work creates order. it lowers the entropy of the system
energy is always
converted when work is done. energy is degraded as heat in any reaction when work is done so it lowers the work potential
second law of thermodynamics
entropy is continuously increasing and energy transformations proceed spontaneously to convert matter from more/less stable to more/less stable forms.
positive Gibbs free energy
products have more free energy than reactants. this is endergonic
negative Gibbs free energy
products have lower free energy than reactants. this is spontaneous and exergonic
endergonic
this is anabolic (stores energy) and may not occur even when enzyme is present because the activation energy is so high
exergonic
is catabolic (releases energy) and may occur spontaneously. the negative delta g can be used to do work
metabolism
sum of catabolic and anabolic reactions
coupling
to accomplish anabolic reactions, you can pair them with an exergonic reaction such that the net delta g is negative
combustion vs aerobic respiration
different as the bonds are not broken by heat in combustion. it also is a generalized reaction, there are mayn intermediate steps.
why can’t you break down glucose all at once
beause then all the energy would release at once and when that happens, a lot of heat is released
oxidation
looses electrons and energy. can also transfer protins (H+)
reduction
gains electrons and energy
glycolysis takes place in
the cytoplasm
cleavage why
it becomes an acid here (before it was a sugar). it was also really unstable so it splits
substrate level phosphorylation
occurs in glycolysis times 2. yields 4 atp.
substrate level phosphorylation process
ATP is formed by transferring a phosphate group directly to ADP from an intermediate. during glycolysis, chemical bonds are shifted around to provide energy required to form ATP.
reduction of NAD+
(endergonic maybe) carries electrons around to donate hydrogen to other molecules
net yield of glycolysis
2 ATP, 2 NADH + H+, 2 pyruvate
glycolysis is limited by
glucose supply and availability of oxidized NAD+ carriers
What is NAD+
enzymes use NAD+ as a cofactor for oxidation reactions.
energy stored in NADH vs ATP
ATP: you can release it suddenly. it can’t be stored
NADH: this can store potential energy for longer periods of time than ATP
how does ATP drive an endergonic reaction?
enzymes that catalyze reactions have two binding sites: one for reactant and one for ATP. the ATP site splits the ATP molecule which releases energy allowing the endergonic reaction to occur.
ATP synthesis is a ___ reaction
endergonic reaction which requires energy from cellular exergonic reactions
oxidative phosphorylation
ATP is synthesized by ATP synthase using energy from a proton gradient. this gradient is formed by high-energy electrons from the oxidation of glucose passing down an electron transport chain. These electrons, with their energy depleted, are then donated to oxygen, hence the term oxidative phosphorylation
why don’t cells just link the oxidation of glucose directly to cellular functions that require the energy
would be inefficient
recycling NAD+
as long as there are food molecules, cell can churn out ATP but it accumulates NADH and depletes the pool of NAD+. A cell does not contain a lot of NAD+so it must recycle it
1) aerobic respiration
2) fermentation
pyruvate after glycolysis
aerobic conditions: pyruvate is further oxidized to yield ATP
anaerobic: pyruvate is converted to lactic acid
from cytoplasm to the mitochondrial matrix
the 2NADH+H+ gets oxidized by a protein. the electrons get transferred to FAD (turns to 2FADH2). pyruvate also crosses the membrane. this process requires two ATP which is why there are usually 38 ATP in prokaryotic cells since they don’t have membranes to cross
glycolysis reactions summary
1) priming reactions use up two ATP to reduce activation energy
2) cleavage occurs and there are 2 G3P (3 carbon phosphates)
3) oxidation and ATP formation NAD+ gets reduced (x2) to add in another phoshate. ATP is formed using substrate level phosphorylation (x2x2) as phosphates are removed
Krebs cycle takes place in
the mitochondrial matrix
how many electrons does it take to reduce NAD+?
two electrons
pyruvate oxidation
link reaction that results in pyruvate being oxidatively dehydrogenated by an enzyme.
1) oxidation of pyruvate produces reduced NAD+ to NADH + H+
2) decarboxylation which produces CO2
3) addition of remaining Acetyl group to coenzyme A through condensation synthesis.
after pyruvate oxidation, what happens
pyruvate + NAD+ + coA turns to Acetyl-coA and NADH+H+ + CO2
krebs cycle steps
1) condensation: addition of acetyl group through coenzyme A. adds to 4 carbon group and becomes a 6 carbon.
2) first oxidation: oxidation and decarboxylation of the 6 carbon then produces reduced NADH + H+ and carbon dioxide which turning it into a 5 carbon
3) second oxidation: 5 carbon becomes 4 carbon through this process again
4) substrate-level phosphorylation: adding in another coA is a high energy bond. bond is cleaved and the energy is used to produce ATP. still a 4 carbon
5) third oxidation: FAD gets reduced here to FADH2 since the bonds are lower in NADHenergy between this 4 carbon molecule. still stays as 4 carbon
6) regeneration of oxaloacetate: NAD+ gets reduced and 4 carbon original returns
Krebs cycle totals
2 pyruvate turns to: 8NADH + H+ + 2FADH2 + 2ATP
2 NADH + H+: 2FADH2
Electron Transport chain
1) NADH Dehydrogenase: 8NADH+H+ oxidizes to 8NAD+ and drops of 16 electrons which is used to pump an H+
2) 4FADH2 drops off 8 electrons and becomes 4FAD through oxidation
3) electrons move to bc1 complex (through cytochrome c) and it pumps out another H+
4) cytochrome oxidase complex: uses 24 protons (16 and 8) to reduce oxygen into water.
5) the H+s are stored inside the christae of the intermembrane space, they are looking for a way out since the cytoplasm doesn’t have a equilibrium
5) ATP synthase: can be located anywhere in the membrane. due to the above steps, a chemical gradient is created. the outside of the inner mitochondrial membrane is positive due to the H+ ions and the inside is -ve due to the loss of the protons. protons are pushed through the ATP synthase protein which causes the rotor to spin and make ATP by binding together ADP and P.
ETC Totals
8NAD+ + 4FAD + 12 H2O +26-32 ATP from oxidative phosphorylation
why is it 26-32 ATP
the proton gradient is sometimes not always the same and the process can also be ineffiecient sometimes. Each person’s body is different
why regulate cellular respiration?
ATP can’t be stored for long periods of time
metabolic pathway
every step is catabolized by enzymes in a chain reaction
enzymes that are regulated
phosphofructokinase and pyruvate dehydrogenase
phosphofructokinase
(Noncompetitive- binds to allosteric site)
ACTIVATE: ADP allows more efficient binding of substrate therefore more glucose production
INHIBIT: ATP binds to the allosteric site using energy which means less breakdown and less ATP produced
- high levels of citrate can also inhibit this enzyme
pyruvate dehydrogenase
main commitment step in krebs cycle is converting pyruvate to acetyl-coA using dehydrogenase
INHIBIT: high levels of NADH from Krebs cycle competitively binds to this enzyme which stops the exchange of electrons of pyruvate to Acetyl coA. also Acetyl-Coa and ATP
ACTIVATE: NAD+, ADP, Pyruvate