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Chapter 7A: Respiration Energetics - Coggle Diagram
Chapter 7A: Respiration Energetics
How is ATP generated?
Endergonic reactions can be driven by
Directly coupled exergonic reactions
coupled by occurring in same active site at the same time ("immediate exchange"
OR the controlled dissipation of electrochemical differentials across a membrane ("revolving door"
Life requires a constant input of energy
Entire process is spontaneous (negative deltaG)
If reaches equilibrium (deltaG=0) = DEATH
Important source of free energy for cells: 6-carbon sugars
cellular respiration BOTH converts sugar into usable forms of energy AND serves as basis for synthesis
Cellular respiration can be divided into four phases
GLYCOLYSIS: glucose is partially broken down to produce pyruvate, and energy is transferred to ATP and reduced electron carriers
PYRUVATE OXIDATION: pyruvate is oxidized to acetyl-CoA, producing reduced electron carriers and releasing carbon dioxide
CITRIC ACID CYCLE: acetyl group is fully oxidized to CO2 and energy is transferred to ATP and reduced electron carriers
OXIDATIVE PHOSPHORYLATION: the reduced electron carriers donate electrons to the electron transport chain and a large amount of ATP is produced
Glucose catabolism captures much of the free energy release in new chemical bond formation
yield = ca. 32 ATP
34% of the energy released is recovered into usable energy
In glycolysis and respiration, a major outcome is ATP SYNTHESIS (ENDERGONIC reaction)
The cell captures much of the free energy released from this reaction in new chemical bond formation by using linked reactions
Generating ATP inside an enzyme ("substrate level phosphorylation")
In glycolysis: produces net 2 ATP/glucose (generate 4 ATP, requires 2 ATP)
In citric acid cycle: produces net 2ATP equivalents/glucose
An organic molecule transfers a phosphate group directly to ADP --> ATP
enzyme carries out two coupled reactions
hydrolysis of an organic molecule to yield a phosphate group (exergonic)
addition of that phosphate group to ADP (endergonic)
hydrolysis reaction releases enough free energy to drive ATP synthesis
What links the two reactions so one doesn't happen without the other
The active site of an enzyme is the "chain" that links these reactions
Energy stored in the new phosphate bond can be recovered at a different time and place in the cell because ATP is a freely diffusable molecule, can move around the cell, stable (doesn't break down spontaneously)
Generating ATP "cashing in" on a proton differential across a membrane
Glycolysis and ATP synthesis - make glucose unstable so it can break down
2 kinases add 2 phosphates onto glucose (uses 2 ATP)
Put molecule on a lot of torsional stress on carbon bond
Break into 2 3C pieces (each has a phosphate on it)
SUBSTRATE LEVEL PHOSPHORYLATION spring loads them (transfer electron out and add another phosphate for transfer of phosphate to ADP
generates net 2 ATP
Oxidative phosphorylation: generating ATP "cashing in" on a proton differential across a membrane
protons move down gradient and at the same time, force movement of mitochondria that drives process
protons bump mitochondrial subunits that forces a conformational change, drives pushing together of P + ADP = ATP
electron carriers are acceptors and donors of electrons
NAD+/FAD: electron ACCEPTOR
NADH/FADH2: electron DONOR
NAD+ can transfer 2 electrons and 1 proton (H+) to make NADH
NADH holds potential energy of "extra" electron
During glycolysis, pyruvate oxidation, citric acid cycle
C-C and C-H bonds are broken, C-O and H-O bonds are formed
