# Vitamin C (Ascorbic Acid) Biochemistry

**Summary**

Vitamin C (Ascorbic Acid) is a water-soluble vitamin important as a cofactor for hydroxylase enzymes. It is a cofactor for dopamine beta-hydroxylase, facilitating the conversion of dopamine to norepinephrine. Vitamin C is also involved in collagen synthesis, as a cofactor for hydroxylation of proline and lysine residues. As an antioxidant, Vitamin C also plays an important role in the reduction of iron (III) to iron (II), which is required for enteric absorption of iron. This property also makes vitamin C useful as an ancillary treatment for methemoglobinemia.

**Key Points**

- **Ascorbic Acid (Vitamin C)**  
  - Water-soluble **antioxidant** found in **fruits and vegetables**  
  - **Reduces iron**: Fe3+ to Fe2+  
    - Facilitates iron absorption at GI tract  
    - Mechanism of treatment for **methemoglobinemia**  
  - Key roles in **hydroxylase enzymes**  
    - **Hydroxylation** of proline and lysine residues (in [**Collagen Synthesis**](/content/view/4840/index.html))  
      - prolyl and lysyl hydroxylases  
    - **dopamine** **_B_** **–hydroxylase**, converts dopamine to norepinephrine (in [**Catecholamine Synthesis**](/content/view/4681/index.html))

Find Vitamin C Biochemistry and other [Vitamins](/content/browse#playlist-2700/index.html) among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.