Micro - Exam 3

Question 1

B12 absorption

Answer 1

Gastric acid removes B12 from food protein&raquo_space; gets bound to R-binder to protect from acid&raquo_space; in duodenum, B12 gets bound to intrinsic factor which allows it to be transported into enterocyte

Question 2

Manifestations of B12 deficiency

Answer 2

B12:
methylmalonyl CoA -> succinyl CoA

No B12:
methylmalonyl CoA -> methylmalonyl acid

• High MMA
• High homocysteine
• RBC macrocytosis
• Neurological problems

Question 3

B12 functions (two)

Answer 3

1. Coenzyme to convert homocysteine to methionine (and SAM) – methylation
2. involved in degradation of FA and amino acids for energy – necessary for enzyme methylmalonyl-Coa mutase

Question 4

Cons of folic acid fortification

Answer 4

May increase risk of cancer (cancer cells need folate for nucleic acid synthesis/proliferation)

High maternal folate may lead to allergy/respiratory problems

Mask B12 deficiency, exacerbate problems
Folate enters folate cycle after the blocked step of B12 deficiency, so nucleic acids can still be produced and macrocytosis does not occur

Question 5

Dietary sources of folate vs folic acid

Answer 5

Folate: widespread, naturally

Folic acid: fortified foods, cereals, supplements

Question 6

Effects of Thiamine deficiency (two names of diseases)

Answer 6

Cellular energy failure
Not making ATP
Reduced neurotransmitter synthesis

Beriberi – impaired sensory, motor functions; tachycardia, heart failure
Wernicke-Korsakoff syndrome

Question 7

Folate deficiency (biochemical and physical manifestations)

Answer 7

Decrease in methylation, DNA repair, nucleic acid synthesis

Neural tube defect

Question 8

Manifestations of B12 deficiency (three)

Answer 8

Low biomolecule methylation

Low RBC proliferation

Low catabolism of FA and AA

Question 9

Folate MTHFR 677C->R polymorphism

Answer 9

Polymorphism impairs folate metabolism –> high homocysteine concentration –> lowers SAM concentration –> 50% reduction in DNA methylation –> increased risk for CHD

Question 10

Pros of folic acid fortification

Answer 10

Increased concentration of plasma folate, lower rates of neural tube defects.

Question 11

Riboflavin function (three main)

Answer 11

Precursor for FAD

Used in TCA cycle: succinate -> fumerate

Used in Beta-oxidation of FA

Used in ETC (complex II)

Question 12

Thiamine deficiency risk factors

Answer 12

Inadequate intake
Alcohol abuse (reduced THTR-1 and -2 expression; liver damage impairs storage)
Bariatric surgery
Mutation in THTR-1

Question 13

Thiamine function

Answer 13

Enzyme cofactor for NADPH biosynthesis, AA catabolism

Question 14

Niacin function

Answer 14

Precursor to NAD

Non-consumptive: energy metabolism in TCA and ETC
Consumptive: DNA repair, gene expression

Question 15

Folate and cancer

Answer 15

Too much or too little disrupts homeostatic methylation pathways

Also may exacerbate cancer by allowing nucleic acid synthesis

Question 16

Folate functions

Answer 16

Folate coenzyme is required for synthesis of methionine from homocysteine

Involved in nucleic acid synthesis, methylation

Question 17

Biomarker of folate

Answer 17

Plasma, serum, urine folate levels

Homocysteine accumulates with low folate status

Question 18

Niacin salvage pathway

Answer 18

Allows for constant supply of NAD from NA, NAM, and NR

Allows body to contain regenerating NAD even when niacin intake decreases for a while

Question 19

Pantothenic acid

Answer 19

Component of Coenzyme A

Participates in a number of metabolic reactions

CHO, Protein, and FA metabolism
Acetylation

Question 20

Biotin

Answer 20

Lysine binding
Biotinylation of carboxylases
Gene expression

Question 21

Vitamin B6 function and connection with inflammation

Answer 21

Coenzyme of over 100 enzymes
Protein metabolism, hemoglobin synthesis
Inflammation may impair status