Medicine & USMLE


  1. Vitamin B1 (Thiamine) Biochemistry
  2. Vitamin B1 (Thiamine) Deficiency
  3. Vitamin B2 (Riboflavin)
  4. Vitamin B3 (Niacin) Biochemistry
  5. Vitamin B3 (Niacin) Deficiency and Excess
  6. Hartnup Disease
  7. Vitamin B5 (Pantothenic Acid)
  8. Vitamin B6 (Pyridoxine)
  9. Vitamin B7 (Biotin)
  10. Vitamin B9 (Folate)
  11. Vitamin B12 (Cobalamin) Biochemistry
  12. Vitamins B9 and B12 Deficiencies
  13. Vitamin A (Retinol) Biochemistry
  14. Vitamin A (Retinol) Deficiency and Excess
  15. Vitamin C (Ascorbic Acid) Biochemistry
  16. Vitamin C (Ascorbic Acid) Deficiency and Excess
  17. Vitamin D Biochemistry
  18. Vitamin D Deficiency and Excess
  19. Vitamin E (Tocopherol/Tocotrienol)
  20. Vitamin K Biochemistry
  21. Vitamin K Deficiency
  22. Zinc
  23. Kwashiorkor and Marasmus


Zinc is an essential trace element that is required for the function of a wide variety of enzymes and transcription factors. One such enzyme requiring zinc is collagenase III, an enzyme involved in wound healing. Notably, a coordinated zinc icon is also required for zinc fingers, which are important DNA-binding structural motifs.

Since zinc plays such an important biological role, zinc deficiency leads to a number of characteristic signs and symptoms. Related to its role in collagenase III, zinc deficiency classically presents with delayed wound healing. Furthermore, zinc deficiency is characterized by decreased adult hair, notably in the axillary, facial, and pubic regions. It also leads to a number of sensory problems, such as anosmia (loss of smell) and dysgeusia (loss of taste). Zinc deficiency can also lead to liver problems, as it predisposes patients to alcoholic cirrhosis. Another notable characteristic is hypogonadism.

An important disease to note is acrodermatitis enteropathica, a metabolic disorder that affects zinc uptake through the bowel mucous membrane. It is characterized by a perioral, perianal, and perianal rash.

Key Points

  • Zinc (Zn)
    • Essential trace mineral needed for function of many enzymes
      • Classic role is in formation of zinc fingers
        • DNA-binding motif found in transcription factors
  • Zinc Deficiency
    • Symptoms
      • Delayed wound healing
        • Collagenase III requires zinc as a cofactor
      • Hypogonadism and azoospermia
      • Hair loss (axillary, facial, and pubic)
      • Impaired taste (dysgeusia), impaired smell (anosmia), night blindness also seen
      • May predispose to alcoholic cirrhosis
        • many liver enzymes are zinc-dependent
    • Acrodermatitis enteropathica
      • autosomal recessive metabolic disorder affecting zinc uptake at GI tract
      • characterized by vesicular and pustular rash around body orifices
        • as well as symptoms of zinc deficiency above

Find Zinc among our Vitamins playlist in Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.