1.5.4.j. Other Vitamin-Like Factors

An amino acid-like compound that occurs freely rather than in peptide linkage

What type of compound is taurine?

Regulation of brain and nerve functions

What nervous-system role has been associated with taurine?

To provide taurine concentrations more similar to those found in human milk

Why is taurine commonly added to infant formulas?

It is a component of bile acids.

What is taurine's role in bile metabolism?

Regulation of heartbeat

What cardiovascular function is associated with taurine?

It helps maintain membrane stabilization and normal electrophysiologic activity.

What is taurine's role in cell membranes?

It has a depressor or inhibitory effect on neurons.

What effect does taurine have on brain neurons?

It helps protect cells against free-radical formation and membrane peroxidation.

What antioxidant-related function is associated with taurine?

Retina

What sensory organ requires taurine for optimal development and function?

Fish and meats

What are the major dietary sources of taurine?

No. The text notes that it is generally absent from strict vegetarian diets.

Is taurine naturally abundant in strict vegetarian diets?

A sulfur-containing fatty acid

What type of compound is lipoic acid?

The body can synthesize adequate amounts of it.

Why is lipoic acid not considered a true vitamin?

It functions as a coenzyme in energy metabolism.

What is the major metabolic role of lipoic acid?

Thiamine pyrophosphate (TPP)

Lipoic acid works with which vitamin-derived coenzyme during pyruvate metabolism?

Acetyl-CoA

Lipoic acid participates in the conversion of pyruvate into what compound?

Oxidative decarboxylation of pyruvate to acetyl-CoA

Which metabolic reaction particularly requires lipoic acid?

No established requirement is given because the body can synthesize it.

Is there an established dietary requirement for lipoic acid?

Yeast and liver

What concentrated food sources of lipoic acid are listed in the text?

Coenzyme Q

What is another name for ubiquinone?

Vitamin K

Ubiquinone is a lipid structurally related to which vitamin?

It acts as a coenzyme in cellular respiration and energy metabolism.

What is the major metabolic function of coenzyme Q?

Electron transfer

What is coenzyme Q's key role in cellular energy production?

The electron transport chain

In which major pathway is coenzyme Q involved through electron transfer?

A large group of phenolic compounds widely distributed in plants

What type of compounds are bioflavonoids?

Vitamin P

What older vitamin-like name is sometimes given to bioflavonoids?

Flavonoid pigments

What gives many fruits and vegetables their yellow to red-blue colors?

Aldose reductase

Which enzyme associated with diabetic cataract formation may be inhibited by bioflavonoids?

Capillary fragility

Bioflavonoids have been associated with reducing bleeding caused by what vascular abnormality?

L-carnitine

Which form of carnitine is produced naturally by the human body?

Liver and kidneys

In which organs is L-carnitine primarily synthesized?

Skeletal muscle, heart, brain, and sperm

Where is carnitine stored or concentrated in the body according to the text?

Transport of long-chain fatty acids into mitochondria

What is the major metabolic function of carnitine?

For fat breakdown and energy production

Why must long-chain fatty acids enter the mitochondria?

β-Oxidation of long-chain fatty acids

Carnitine is especially important for which pathway of fatty-acid metabolism?

Acetyl-L-carnitine (ALC)

What acetyl derivative of carnitine is found throughout the central nervous system?

Red meat and dairy products

What are the primary dietary sources of carnitine?

Lamb

Which red meat is specifically identified as particularly rich in carnitine?

Fish, poultry, tempeh, wheat, asparagus, avocados, and peanut butter

What other foods listed in the text contain carnitine?