Lipids 3 - Dietary Digestion

Flashcards on Dietary Digestion of Lipids

Dietary Lipids

Found within foods containing vegetable oils or fats (animal and plant). Some spices and herbs are also good dietary sources.

• inorganic food additives (like salt and sugar) lack this biomolecule

• cooking may alter lipid characteristics but doesn’t eliminate it from food

Essential Fatty Acids

They are precursors to local hormones and essential for neural cell membranes. Deficiencies are rare.

• these molecules are usually constinutents in dietary triacylglycerols in vegatable oils, nuts

Omega-3 Fatty Acids in Nuts/Fish

Plant-based omega-3 is ALA (alpha-linolenic acid). Fish-based omega-3s are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).

Lingual Lipase

Secreted by von Ebner’s glands in the tongue. It digests fats by breaking down triglycerides into diacylglycerols and free fatty acids.

Gastric Lipase

Cleaves triacylglycerols (TAGs) into diacylglycerols (DAGs) in the stomach, contributing to 10-30% of fat degradation.

Bile Salts

They non-enzymatically emulsify fats in the small intestine and destabilize bacterial membranes. They also aid in the absorption of fat-soluble vitamins (A, D, E, and K).

• glycocholic acid is a major bile salt found in humans

Pancreatic Lipase

Sequentially cleaves remaining TAGs and DAGs in the stomach, generating free fatty acids (FAs) and monoacylglycerol (MAG).

• FA and MAG then moved across cells plasma membrane

FABP

Fatty Acid Binding Protein, an embedded transporter that moves free fatty acids and MAG across the cell's plasma membrane.

FATP

Fatty Acid Transport Protein, a cytoplasmic protein that moves free fatty acids and MAG across the cell's plasma membrane.

Chylomicrons

Lipoprotein particles formed in enterocytes (intestinal cells) after TAGs are broken down into FA and MAGs that transport dietary fats to adipose tissue (for storage) or muscles (for energy).

CCK, GLP-1 and GLP-2, insulin

Hormones that support the digestion, absorption, and repackaging of dietary fats into chylomicrons.

Omega-3 Fatty Acid

Alpha linolenic acid (18:3)

Omega-6 Fatty Acid

Linoleic acid (18:2)

Omega 6 in nuts/fish

• Most nuts are much higher in omega-6 than omega-3

• fish generally have much lower omega-6 than omega-3 (making them anit-inflammatory and beneficial for heart/brain health)

• Farmed fish tend to have higher omega-6 than wild-caught due to their grain-based diets

Lingual Lipase activity

Most activity occurs when the enzyme is transported with food to the stomach where it is more active under acidic conditions

• key enzyme in digesting milk fats in newborns

• highly hydrophobic and readily enters fat globules

Hydrolysases

Enzymes that catalyze the hydrolysis of chemical bonds using water

Proteases (peptidases or proteinases)

Hydrolyze peptide bonds in proteins

Lipases

Hydrolyze ester bonds in lipids (triglycerides)

Hydrolase Family of enzymes

Both proteases and lipases belong to this- same catalytic triad

Vitamins A, D, and E

NOT precursors to coenzymes

Vitamin K

Essential for carboxylase activity

95% of FA

Percentage of FA absorbed by the small intestine

• the rest is thought to provide nutrition to intestinal microbiota

TAGs in adipose tissue

Dietary fatty acids are stored here for later use

Metabolsim

Involves the beta-oxidation pathway and cellular respiration

Lipoprotein particles

contain fat-soluble vitamins and cholesterol and deliver dietary fat to adipose tissue (for storage) and other tissues in the body like muscles (for energy)