🧪 The Krebs cycle and cellular respiration: how B-complex, iron and CoQ10 produce ATP
How cells turn food into energy and which nutrients are needed for this
All the energy we get from food is ultimately converted into the ATP molecule — the "energy currency" of the cell. This process takes place in the mitochondria and includes the Krebs cycle and the respiratory chain. Without B vitamins, iron, magnesium and coenzyme Q10, this machine works poorly.
Understanding exactly how ATP is produced explains why vitamin deficiency causes fatigue, weakness and "brain fog". Below is the biochemistry of energy metabolism in simple terms and the role of key nutrients.
What is the Krebs cycle and why it matters
The Krebs cycle (citric acid cycle) is a series of chemical reactions in the mitochondria where the breakdown products of glucose, fats and proteins are converted into energy carriers — NADH and FADH2. These molecules then feed the respiratory chain.
Acetyl-CoA
A common product of the breakdown of carbohydrates, fats and partly proteins. The cycle starts from it.
NADH and FADH2
Electron carriers that transfer energy to the respiratory chain for ATP synthesis.
The respiratory chain and ATP synthesis
In the respiratory chain (oxidative phosphorylation), electrons from NADH and FADH2 pass through a chain of protein complexes, creating a proton gradient. This gradient spins ATP synthase, which produces ATP.
Electron transfer
Electrons from NADH/FADH2 pass through complexes I–IV of the respiratory chain.
CoQ10 — the "shuttle"
Coenzyme Q10 transfers electrons between complexes I/II and III — a critical link.
Proton gradient
The energy of electrons pumps protons across the membrane, creating a potential.
ATP synthesis
ATP synthase uses the gradient to convert ADP into ATP. Iron in the complexes is a required cofactor.
The role of B vitamins
B vitamins are required cofactors of energy metabolism at different stages.
| B vitamin | Role in energy metabolism |
|---|---|
| B1 (thiamine) | Cofactor of glucose breakdown, entry into the Krebs cycle |
| B2 (riboflavin) | Part of FADH2, electron carrier |
| B3 (niacin) | Part of NADH, key electron carrier |
| B5 (pantothenic acid) | Part of coenzyme A (acetyl-CoA) |
| B6 (pyridoxine) | Amino acid metabolism and gluconeogenesis |
| B7 (biotin) | Carboxylation, fat metabolism |
| B12 | Metabolism, nervous system function, blood formation |
Iron, magnesium and CoQ10
Heme cofactors
Iron is part of the cytochromes of the respiratory chain (complexes I–IV). With anemia, energy also drops.
ATP stabilization
Magnesium binds ATP molecules and participates in hundreds of energy metabolism reactions.
Electron transport
Transfers electrons between respiratory chain complexes, critical for ATP synthesis.
The NAD cycle
With age, NAD+ levels decline, which is linked to reduced energy and aging.
Norms and deficiency symptoms
| Nutrient | Daily norm (adults) | Deficiency symptoms |
|---|---|---|
| B1 | ~1.2 mg | Fatigue, weakness, nervous system disorders |
| B2 | ~1.3 mg | Apathy, cracks at the corners of the mouth |
| B3 | ~16 mg | Fatigability, pellagra (in severe cases) |
| Iron | 8–18 mg | Anemia, weakness, pallor |
| Magnesium | 310–420 mg | Cramps, fatigue, anxiety |
Which food supports energy metabolism
| Food | What it gives for ATP |
|---|---|
| Whole grains, buckwheat | B1, B2, magnesium — fuel and cofactors |
| Meat, organ meats (liver) | Iron, B12, B-complex, CoQ10 |
| Fatty fish (mackerel, sardines) | CoQ10, omega-3, B-complex |
| Nuts and seeds | Magnesium, B1, energy |
| Legumes | B1, B6, magnesium, iron |
| Eggs | B12, biotin, choline |
What is the Krebs cycle?
A series of reactions in the mitochondria where the breakdown products of food are converted into NADH and FADH2 — energy carriers for the respiratory chain.
Who discovered the Krebs cycle?
Hans Krebs in 1937. For the discovery he received the Nobel Prize in Physiology or Medicine in 1953.
Why is CoQ10 needed in energy metabolism?
CoQ10 transfers electrons between respiratory chain complexes. Without it, ATP synthesis stops.
Why is the B-complex important for energy?
B vitamins are part of NADH (B3), FADH2 (B2), coenzyme A (B5) and other energy metabolism cofactors.
Does iron affect energy?
Yes. Iron is part of the cytochromes of the respiratory chain. With anemia, ATP production drops and weakness appears.
What is ATP?
Adenosine triphosphate — the main energy molecule of the cell, the "energy currency" produced in the mitochondria.
Why do you get tired with vitamin deficiency?
Because B vitamins, iron, magnesium and CoQ10 are cofactors of energy metabolism. Their lack reduces ATP production.
How to increase energy naturally?
Proper nutrition with whole foods, enough B-complex, magnesium and iron, physical activity and sleep.
What is NAD+?
NAD (from vitamin B3) is an electron carrier. Its active form NAD+ participates in hundreds of reactions, including energy metabolism.
Is magnesium needed for ATP?
Yes. Magnesium binds ATP molecules (the active form is Mg-ATP) and participates in hundreds of enzymatic reactions.