5: cellular respiration Flashcards
Catabolism and bonds
Breakdown of organic molecules to harvest energy in C-H bonds
Glycolysis inputs and outputs
Inputs: Glucose and 2 ATP
Outputs: Pyruvate, 4 ATP, and water
Glycolysis steps
1) Priming [preparing to cleave glucose]: 2 ATP become 2 ADP (release phosphates), which attach to both ends of glucose molecule (P - 6C - P).
2) Cleavage: The glucose molecule is split into 2 PGAL/G3P molecules (P - 3C and 3C - P).
3) Phosphorylation: NAD+ takes electrons from PGAL, allowing a free phosphate to bond to PGAL (becomes P - 3C - P). One phosphate breaks off, releasing ATP, and the molecules are rearranged by intermediates, releasing water. After the rearrangement is done, the last phosphate breaks off the former PGAL, and another ATP is released, the product being pyruvate. This happened twice per glucose, yielding 4 ATP.
Pyruvate oxidation steps & location
Location: matrix
1) Pyruvate loses carbon dioxide (3C to 2C). This is also called oxidation (losing electrons that were orbiting the carbon).
2) NAD+ (empty) picks up protons/electrons from the 2-C molecule, becoming NADH (full).
3) The 2-C molecule is known as acetyl.
4) Coenzyme A (CoA) picks up acetyl and takes it to the Krebs cycle.
Krebs cycle steps & location
Location: matrix
1) Acetyl CoA (2-carbon) joins with oxaloacetate (4-C) from previous Krebs cycle, forming citric acid (6-C).
2) A carbon is removed (6C -> 5C) and expelled as CO2. NAD+ (empty) picks up protons/electrons, becoming NADH (full).
3) Another carbon is removed (5C -> 4C). Same process as #2.
4) GDP gains a phosphate, becoming GTP.
5) ADP takes a phosphate from GTP. ADP becomes ATP, and GTP goes back to GDP. (only ATP produced in Krebs - 2ATP total b/c Krebs happens twice.)
6) FAD (empty) gains 2 protons and 2 electrons, from the 4-C molecule, becoming FADH2 (full) and going to ETC.
6) Water is added to rearrange the molecule.
7) The 4-C molecule becomes oxaloacetate again.
Pyruvate oxidation inputs and outputs
Inputs: pyruvate, NAD+, CoA
Outputs: Co2 (waste), NADH, acetyl CoA
Krebs inputs and outputs
Inputs: Oxaloacetate, Acetyl CoA, NAD+, FAD
Outputs: Oxaloacetate, NADH, FADH2, 1 ATP, Co2
ETC steps/location
Location: matrix
1) NADH and FADH2 (full) drop off electrons at beginning of ETC and protons into the matrix.
2) Electrons travel down a series of enzymes, going from high energy to low energy. This powers proton pumps.
3) Proton pumps pump protons against the gradient (to outside the matrix).
4) Protons flow back into the matrix through ATP synthase (like a water wheel / wind turbine), generating ATP.
5) ATP is transported out of the mitochondria (wherever it’s needed).
6) 2 protons and an oxygen combine to form H2O, which is expelled as water vapor.
ETC inputs and outputs
Inputs: electrons, protons, NADH, FADH2, O2
Outputs: 30-32 ATP, NAD+, FAD, H2O
Chemiosmosis
Diffusion of ions down a gradient across a membrane (in this case, protons flowing through ATP synthase, generating ATP)
Lactic acid fermentation steps
1) Glycolysis produces pyruvate.
2) NAD+ takes electrons and protons and donates them to pyruvate.
3) Pyruvate becomes lactic acid.
4) Lactic acid is turned back into glucose (in the liver for humans).
5) Cycle restarts
Ethyl alcohol fermentation steps
1) Glycolysis produces pyruvate.
2) Co2 is removed from pyruvate, allowing it to become acetaldehyde.
3) Acetaldehyde accepts protons and electrons from NADH (full), allowing NADH to turn back into NAD+.
4) Acetaldehyde becomes ethyl alcohol because it accepted these protons/electrons.
5) Energy remains in acetaldehyde.
Redox reaction
A reaction where electrons are transferred
Reducing / oxidizing agent
Reducing agent - Donates electrons (that allows another substance to BECOME reduced by donating electrons)
Oxidizing agent - Accepts electrons (allowing another substance to BECOME oxidized)
Substrate-level phosphorylation
A phosphate group is directly transferred from a phosphorylated intermediate to ADP, producing ATP.
