Lecture 18 Cobalamin (Vitamin B12) - MC

Question 1

*What was Vitamin B12 originally identified as?
A) The anti-oxidant factor
B) The anti-pernicious anemia factor
C) The anti-inflammatory factor
D) The anti-nutrient factor

Answer 1

B

Question 2

Which forms of Vitamin B12 are active as coenzymes in humans?
A) Cyanocobalamin and Hydroxycobalamin
B) Aquo- or Hydrocobalamin and Cyanocobalamin
C) 5’-deoxyadenosylcobalamin and Methylcobalamin
D) Methylcobalamin and Cyanocobalamin

Answer 2

C

Question 3

How is Vitamin B12 protected from degradation in the stomach?
A) By binding to a glycoprotein known as protein R
B) By forming a complex with hydrochloric acid
C) By encapsulation in lipid layers
D) By attaching to dietary fibers

Answer 3

A

Question 4

What happens to Vitamin B12 in the small intestine?
A) It is degraded by pancreatic proteases.
B) It is hydrolyzed from protein R by pancreatic proteases.
C) It is absorbed directly without modifications.
D) It binds directly to amino acids for absorption.

Answer 4

B

Question 5

Which statement best describes the absorption of Vitamin B12 in individuals lacking intrinsic factor (IF)?
A) They absorb it efficiently and store it in the liver.
B) They have a reduced ability to absorb Vitamin B12, leading to increased fecal excretion.
C) They convert it efficiently into its active coenzyme forms.
D) They synthesize it endogenously from plant sources.

Answer 5

B

Question 6

What is the physiological role of Vitamin B12 in the body?
A) It acts primarily as an antioxidant.
B) It is crucial for the conversion of homocysteine into methionine.
C) It primarily functions in the regulation of blood pressure.
D) It aids in the absorption of vitamin C.

Answer 6

B