What causes ATP to form during oxidation-reduction reactions?
When molecules are oxidized (lose electrons), energy is released — this energy drives phosphorylation of ADP → forming ATP.
Why do redox reactions matter in metabolism?
They transfer energy from nutrients to high-energy carriers (like NADH and FADH₂), which later drive ATP synthesis
What causes aerobic respiration to produce more ATP than anaerobic respiration?
Oxygen allows electrons to flow through the electron transport chain, maximizing ATP output through oxidative phosphorylation.
Glycolysis is the breakdown of
glucose into pyruvate
Glycogenolysis is the breakdown of
glycogen into glucose
Why does the body rely on cellular respiration instead of only glycolysis?
Glycolysis alone yields only 2 ATP, but linking it with the Krebs cycle and ETC yields up to ~32 ATP per glucose molecule.
Where does Glycolysis main occur?
in the cytosol of the cell
What triggers glycolysis to begin?
The presence of glucose in the cytosol — it’s broken down into 2 pyruvate molecules to extract energy quickly.
Why is phosphofructokinase (PFK) the key control enzyme?
It’s the “commitment step” — once active, glucose is locked into the energy pathway, ensuring ATP is produced.
-It is the last of the steps that uses energy
What causes glycolysis to speed up?
High AMP levels signal low energy → PFK activates → glycolysis accelerates to make ATP.
What causes glycolysis to slow down or stop?
High ATP or citrate levels signal sufficient energy → inhibit PFK → prevents wasteful ATP production.
Why can red blood cells only use glycolysis for ATP?
They lack mitochondria → can’t perform aerobic respiration → depend solely on anaerobic glycolysis for energy.
Are red blood cells capable of aerobic respiration?
No, red blood cells don’t contain a mitochondria
What causes pyruvate to enter the TCA cycle?
Oxygen presence allows pyruvate to enter mitochondria → converted to acetyl-CoA → fuels the TCA cycle.
Citric acid cycle (Kreb’s cycle) takes place in the
matrix of mitochondria
Why does the TCA cycle produce CO₂?
Carbon atoms from acetyl-CoA are oxidized → electrons transferred to NAD⁺ and FAD → CO₂ released as waste.
Why is the TCA cycle considered a “hub” of metabolism?
It connects carbohydrate, fat, and protein metabolism — all can enter as acetyl-CoA or other intermediates.
What’s the main effect of the TCA cycle?
It generates high-energy electron carriers (NADH, FADH₂) → which power ATP synthesis in the electron transport chain.
What is the total Yield of the Kreb Cycle?
1 glucose = 2 pyruvate = 2
Acetyl CoA
Therefore, yield from 1
glucose broken down
through TCA cycle is:
* 2 ATP
* 8 NADH
* 2 FADH2
* CO2 produced
Why does the ETC produce the most ATP?
It uses the energy from electron transfers to pump protons → proton gradient drives ATP synthase → massive ATP yield.
What happens if oxygen isn’t present?
Electrons can’t pass through the chain → proton gradient collapses → ATP production stops → metabolism shifts to fermentation.
Why does NADH produce more ATP than FADH₂?
NADH donates electrons earlier in the ETC → powers more proton pumps → yields ~3 ATP vs. ~2 ATP from FADH₂.
What causes variation in total ATP yield (30–32 ATP instead of 38)?
Some NADH can’t enter mitochondria efficiently, and intermediates are often used for other biosynthetic reactions.
How many redox reaction does the ETC functions as a series of?
four redox reactions
