1.16. Cell respiration 2 Flashcards
aerobic CR yields ___ ___ energy per glucose molecule than anaerobic
19 x, more
1st step of CR for both aerobic and anaerobic pathway (how does it go)
glycolysis:
glucose -> 2 pyruvate + 2 ATP
(glucose has 6 carbon atoms, pyruvate has 3)
2nd step of CR for anaerobic pathway
humans: pyruvate -> lactate
yeast: pyruvate -> ethanol + CO2
- no further yield of ATP
- very inefficient but quick
- in cytoplasm
2nd step of CR for aerobic pathway
pyruvate -> CO2 + H2O + 36 ATP
- in mitochondrion
- total yield is 38 ATP (36+2 from 1st)
4 stages of cell respiration
1|glycolysis
2|link reaction
3|Krebs cycle
4|electron transport chain and oxidative phosphorylation
1|glycolysis (equation)
substrates: glucose, 2 NAD^+, O2 (in aerobic), 2 ADP
products: 2 pyruvate molecules, 2 ATP, 2 NADH+H^+
- occurs in cell cytoplasm
- partial breakdown of glucose which is oxidized into pyruvate (pyruvate contains less but still significant amount of potential E chem because it is chemically simpler than glucose)
glucose -> pyruvate + energy
-> ATP
->NAD^+ -> NADH + H^+
C-C-C-C-C-C -> 2 C-C-C - split in two
(substeps are phosphorylation, lysis, and oxidation/ATP formation)
2|link reaction
products: 2 acetyl groups, 2 CO2 (each 1 per pyruvate), NADH+H^+
C-C-C -> C-C
- links aerobic and anaerobic parts of CR
3|Krebs cycle
substrates: 2 acetyl groups
products: 4 NADH+H^+, 4 CO2 (each 2 per acetyl)
- function: to exhaust the last drop of energy left from the food molecule - does this by oxidizing the acetyl group
where do the hydrogen atoms in NADH+H^+ come from?
from the food molecule - glucose-pyruvate-acetyl group
how is glucose destabilized so that it can interact?
- by phosphorylation
phosphate groups donated by 2 ATP molecules are added to its ends - this energizes the molecule, making it less stable and more likely to interact with other molecules:
C-C-C-C-C-C + 2 ATP -> P-C-C-C-C-C-C-P + 2 ADP
this molecule is called 1-6 hexose biphosphate
lysis (splitting)
1-6 hexose biphosphate -> 2 triose phosphate
P-C-C-C-C-C-C-P -> 2 C-C-C-P
oxidation/ATP formation
2 C-C-C-P + ADP + NAD^+ -> 2 C-C-C + ATP + NADH + H^+
pyruvate formation
how does phosphorylation make a molecule more reactive?
P groups allow for stronger interaction between a hexose and enzyme that catalysis the 2nd stage of glycolysis (lysis) - also makes it less stable by energizing it
(it can activate any molecule inside of the cell)
3rd stage: oxidation/ATP formation
- main oxidative stage of glycolysis - formation of ATP and NADH+H^+
- P group and 2 H+ ions removed from triose phosphate to produce pyruvate
- P group used to create 2 ATPs from 2 ADPs
- H ions used to create NADH+H^+ from NAD^+
how many ATPs are produced in oxidation/ATP formation?
4 - 2 per each triose phosphate
- additional P group comes from H2PO4
