USMLE Step 1 Lecture: Biochemistry
Vitamins: What You Need to Know for Your Test
Vitamins are incredibly high yield for your test. It is almost certain that you will encounter at least one
vitamin question, if not multiple, on your test. When it comes to vitamins, you need to know what the
deficiency looks like. This is where the highest yield comes from. For example, niacin deficiency is
commonly discussed and is a topic that you should be familiar with.
Knowing the deficiency pathway is the key to answering most vitamin deficiency questions. If someone
is missing niacin, you need to be able to quickly identify the problem and the symptoms that come with
it. To help you with this, there is a large chart of vitamins available in your book on pages 150-151.
Additionally, you can use the josh double lists, which are the symptoms that are always mentioned in a
vitamin deficiency question.
• Diarrhea
• Dementia
• Dermatitis (primarily of sun-exposed areas)
The highest yield topic for vitamins is what it looks like when the vitamin is missing. However, the test
makers will try to trip you up by giving you a patient where you have to realize the problem is likely a
specific vitamin deficiency, such as niacin.
In addition to knowing the symptoms of vitamin deficiencies, you should also be familiar with why we
need specific vitamins. For example, niacin generates nicotinic and nicotinamide, which are used in
energy and oxidant phosphorylation. Niacin is also needed for producing molecules and nadph, which is
needed for synthesis and cholesterol production. In your immune system, nadph is needed for fighting
off certain infectious agents with an oxidative burst. And in your red blood cells, nadph is needed to
reproduce glutathione and protect the cells.
Vitamins are also important for dehydrogenases, which are enzymes that move hydrogen's and
electrons. Niacin is very good at accepting electrons and protons, which is why dehydrogenases use it. If
you are missing niacin, you may experience symptoms such as diarrhea, dementia, and dermatitis.
When it comes to vitamins, it's useful to remember that dehydrogenase enzymes, which move hydrogen
and electrons, require B3 (niacin). There are hundreds of dehydrogenases, so it's more efficient to learn
the exceptions to this rule than memorize every enzyme that requires B3. There are four special
dehydrogenases that don't require B3, but they do need other vitamins, such as thiamine (B1), riboflavin
(B2), and pantothenic acid (B5).
• Thiamine is essential for the structure of three of these enzymes, which are dehydrogenases.
• Pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain alpha-keto
acid dehydrogenase are the three enzymes that require thiamine.
• Vitamin B5 and lipoic acid are also necessary for these special dehydrogenases.
It's important to recognize the symptoms of vitamin deficiencies, such as Wernicke-Korsakoff syndrome
for thiamine deficiency, which can lead to brain damage and memory issues. Beriberi is another
Vitamins: What You Need to Know for Your Test
Vitamins are incredibly high yield for your test. It is almost certain that you will encounter at least one
vitamin question, if not multiple, on your test. When it comes to vitamins, you need to know what the
deficiency looks like. This is where the highest yield comes from. For example, niacin deficiency is
commonly discussed and is a topic that you should be familiar with.
Knowing the deficiency pathway is the key to answering most vitamin deficiency questions. If someone
is missing niacin, you need to be able to quickly identify the problem and the symptoms that come with
it. To help you with this, there is a large chart of vitamins available in your book on pages 150-151.
Additionally, you can use the josh double lists, which are the symptoms that are always mentioned in a
vitamin deficiency question.
• Diarrhea
• Dementia
• Dermatitis (primarily of sun-exposed areas)
The highest yield topic for vitamins is what it looks like when the vitamin is missing. However, the test
makers will try to trip you up by giving you a patient where you have to realize the problem is likely a
specific vitamin deficiency, such as niacin.
In addition to knowing the symptoms of vitamin deficiencies, you should also be familiar with why we
need specific vitamins. For example, niacin generates nicotinic and nicotinamide, which are used in
energy and oxidant phosphorylation. Niacin is also needed for producing molecules and nadph, which is
needed for synthesis and cholesterol production. In your immune system, nadph is needed for fighting
off certain infectious agents with an oxidative burst. And in your red blood cells, nadph is needed to
reproduce glutathione and protect the cells.
Vitamins are also important for dehydrogenases, which are enzymes that move hydrogen's and
electrons. Niacin is very good at accepting electrons and protons, which is why dehydrogenases use it. If
you are missing niacin, you may experience symptoms such as diarrhea, dementia, and dermatitis.
When it comes to vitamins, it's useful to remember that dehydrogenase enzymes, which move hydrogen
and electrons, require B3 (niacin). There are hundreds of dehydrogenases, so it's more efficient to learn
the exceptions to this rule than memorize every enzyme that requires B3. There are four special
dehydrogenases that don't require B3, but they do need other vitamins, such as thiamine (B1), riboflavin
(B2), and pantothenic acid (B5).
• Thiamine is essential for the structure of three of these enzymes, which are dehydrogenases.
• Pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain alpha-keto
acid dehydrogenase are the three enzymes that require thiamine.
• Vitamin B5 and lipoic acid are also necessary for these special dehydrogenases.
It's important to recognize the symptoms of vitamin deficiencies, such as Wernicke-Korsakoff syndrome
for thiamine deficiency, which can lead to brain damage and memory issues. Beriberi is another
