Water-Soluble Vitamins Overview Quiz

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15 Questions

Which of the following is a characteristic of water-soluble vitamins?

They are essential for normal health and growth

Which vitamin is a provitamin that can be converted into Vitamin A inside the body?

Vitamin D

Which vitamins are classified as fat soluble?

Vitamin D and E

What is the main characteristic of fat-soluble vitamins?

They can be stored in the body

What are precursors of vitamins that can be converted into vitamins inside the body called?

Provitamins

What is the main cause of the formation of ketone bodies (KB) in the fasting state?

Increased acetylCoA accumulation

Which enzyme is considered the key enzyme of ketogenesis?

HMG-CoA lyase

What is the main fate of ketone bodies in extrahepatic tissues?

Utilization as fuel

Which condition leads to the increased formation of ketone bodies?

Hypoglycemia

During ketolysis, what is the main fate of acetoacetate picked up from the blood in the mitochondria?

Activation to form acetyl CoA

Which enzyme is responsible for the oxidation of 3-hydroxybutyrate to acetoacetate in extrahepatic tissues?

Thiophorase enzyme

Which tissue lacks the enzyme necessary for metabolizing ketone bodies?

Liver

What is the fate of acetone, a minor side product of ketone bodies?

It is lost in expired air at lungs and in urine

In which condition do patients with type 1 insulin-dependent diabetes mellitus (DM) develop ketoacidosis?

When fatty acid release from adipose tissue exceeds ketone synthesis in the liver

Why are patients with type II non–insulin-dependent diabetes mellitus (NIDDM) much less likely to show ketoacidosis?

Insulin resistance in the periphery is not complete

Study Notes

Vitamins

  • Water-soluble vitamins are characterized by being easily excreted in urine, non-toxic, and not stored in the body.
  • Vitamin A is a provitamin that can be converted into Vitamin A inside the body.
  • Vitamins A, D, E, and K are classified as fat-soluble vitamins.
  • The main characteristic of fat-soluble vitamins is that they are stored in the body and can be toxic in high doses.

Ketogenesis

  • The main cause of the formation of ketone bodies (KB) in the fasting state is the breakdown of fatty acids in the liver.
  • The enzyme HMG-CoA synthase is considered the key enzyme of ketogenesis.
  • In extrahepatic tissues, ketone bodies are primarily used as an energy source.

Ketolysis

  • During ketolysis, acetoacetate is converted into acetyl-CoA, which is then used in the citric acid cycle.
  • The enzyme 3-hydroxybutyrate dehydrogenase is responsible for the oxidation of 3-hydroxybutyrate to acetoacetate in extrahepatic tissues.
  • The brain is the tissue that lacks the enzyme necessary for metabolizing ketone bodies.

Ketoacidosis

  • Acetone, a minor side product of ketone bodies, is exhaled through the lungs.
  • Patients with type 1 insulin-dependent diabetes mellitus (DM) develop ketoacidosis when they have low insulin levels and high glucagon levels, leading to increased glucose production and ketone body formation.
  • Patients with type II non–insulin-dependent diabetes mellitus (NIDDM) are much less likely to show ketoacidosis due to their insulin resistance, which leads to higher insulin levels and lower glucagon levels.

Test your knowledge on water-soluble vitamins and coenzymes with this quiz. Explore the classifications, functions, and associated pathologies of water-soluble vitamins.

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