B Vitamin Overview and Definition
📌 Vitamins are essential micronutrients needed in small doses that cannot be produced by the body cells themselves.
💧 Water-soluble vitamins include all B vitamins and Vitamin C, which are readily excreted in urine, making overdosing difficult.
💊 Fat-soluble vitamins (A, D, E, K) can be stored in body fat, increasing the risk of toxicity if consumed in excess.
🔬 The B vitamins discussed are B₁, B₂, B₃, B₅, B₆, B₇, B₉, and B₁₂; the others were removed as the body can synthesize them.

Active Forms of B Vitamins
🔗 B vitamins must be converted into active coenzyme forms to function in metabolic processes.
* B₁ (Thiamine) works as Thiamine Pyrophosphate (TPP).
* B₂ (Riboflavin) produces Flavin Adenine Dinucleotide (FAD) and Flavin Mononucleotide (FMN).
* B₃ (Niacin) produces Nicotinamide Adenine Dinucleotide ($\text{NAD}^{+}$), which is functional in its oxidized form.
* B₅ (Pantothenic Acid) acts as Coenzyme A ($\text{CoA}$).
* B₆ (Pyridoxine) works as Pyridoxal Phosphate ($\text{PLP}$).
* B₇ (Biotin) functions as Biotin.
* B₉ (Folate) acts as Tetrahydrofolate ($\text{THF}$).
* B₁₂ (Cobalamin) functions as Cobalamin.

B Vitamins in Energy Metabolism (Glycolysis, Krebs Cycle, ETC)
⚙️ B vitamins are crucial coenzymes involved in breaking down carbohydrates, proteins, and fats to produce ATP.
* B₁ ($\text{TPP}$) is essential for converting Pyruvate to Acetyl $\text{CoA}$ and for reactions converting $\alpha$-ketoglutarate to succinyl $\text{CoA}$.
* B₂ ($\text{FAD}$) is required for the conversion of succinate to fumarate in the Krebs cycle, producing $\text{FADH}_2$.
* B₃ ($\text{NAD}^{+}$) plays multiple roles in dehydrogenation steps, converting $\text{NAD}^{+}$ to $\text{NADH}$ in pathways like pyruvate conversion and the Krebs cycle.
* $\text{NADH}$ and $\text{FADH}_2$ (products facilitated by $\text{B}_2$ and $\text{B}_3$) transfer electrons to the Electron Transport Chain, ultimately generating 32 to 36 ATP molecules per glucose molecule via the hydrogen gradient.
* B₅ ($\text{CoA}$) is necessary whenever a molecule is converted into a $\text{CoA}$ derivative, such as Pyruvate to Acetyl $\text{CoA}$.

B Vitamins in Amino Acid and Nucleotide Metabolism
🔗 B vitamins facilitate the transfer of functional groups necessary for building blocks.
* B₆ ($\text{PLP}$) acts as an amino transferase, transferring amine groups; deficiency can impair conversion of glutamate to $\text{GABA}$ (an inhibitory neurotransmitter), potentially causing seizures.
* B₇ (Biotin) is vital for transferring carbon dioxide groups, specifically in the conversion from propionyl $\text{CoA}$ to methylmalonyl $\text{CoA}$; deficiency leads to propionic acidemia (accumulation of organic acids).
* B₁ ($\text{TPP}$) is needed in the Pentos Phosphate Pathway for converting glucose 6-phosphate to ribose 5-phosphate, which synthesizes nucleotides for DNA/RNA.

B₉ (Folate) and B₁₂ (Cobalamin) in DNA Synthesis
🧬 $\text{B}_9$ ($\text{THF}$) and $\text{B}_{12}$ are critical for DNA and RNA synthesis because they facilitate the transfer of single-carbon units (like methyl groups).
* $\text{B}_9$ ($\text{THF}$) gets methylated (becoming methyl-$\text{THF}$) and stops functioning until $\text{B}_{12}$ removes the methyl group.
* $\text{B}_{12}$ uses the methyl group to convert homocysteine to methionine, freeing up $\text{THF}$ to continue nucleotide synthesis.
* Cells undergoing rapid division, such as those involved in erythropoiesis (red blood cell production), are highly dependent on adequate $\text{B}_9$ and $\text{B}_{12}$.
* Dietary $\text{B}_{12}$ absorption requires Intrinsic Factor produced in the stomach; lack of this factor causes $\text{B}_{12}$ deficiency anemia known as pernicious anemia.

Key Points & Insights
➡️ The primary function of B vitamins in metabolism is as active coenzymes (e.g., $\text{FAD}$, $\text{NAD}^{+}$, $\text{TPP}$).
➡️ $\text{B}_1$, $\text{B}_2$, and $\text{B}_3$ are fundamental for generating the high-energy molecules ($\text{NADH}$ and $\text{FADH}_2$) that drive ATP production in the electron transport chain.
➡️ Investigate the specific coenzyme form (e.g., Googling $\text{TPP}$ instead of just $\text{B}_1$) to understand detailed metabolic roles.
➡️ $\text{B}_6$ deficiency can severely impact the nervous system by inhibiting the synthesis of the inhibitory neurotransmitter $\text{GABA}$.

📸 Video summarized with SummaryTube.com on Nov 13, 2025, 11:12 UTC