Human Nutrition Flashcards

Vocabulary flashcards for key terms in human nutrition, based on lecture notes.

Fiber Intake

Generic recommendation of 25 g to 40 g daily for adults, met by ingesting whole-grain products, vegetables, fruits, and legumes.

Lipids

Main types are fatty acids, TG, phospholipids, and sterols, participating in energy production, storage, insulation, cell signaling, structural support, inflammatory responses, and hormonal production.

Fatty acids

Simplest of the lipids, containing methyl (non-polar) and carboxyl (polar) ends that do not cyclize; classified by chain size and saturation.

Delta (A) System

Counting carbons from the carboxyl end to identify the location of double bonds in fatty acids.

Omega (w) System

Counting carbons from the methyl end and identifies only the position of the first carbon where the initial double bond is located.

Essential fatty acids

Fatty acids that cannot be synthesized by the body and must be obtained through diet; linoleic and a-linolenic acids.

Cis-fatty acids

Most unsaturated fatty acids in nature have hydrogens located next to the double bond on the same side of the carbon chain

Trans-Fatty acids

Fatty acids that have hydrogens next to the double bonds on the opposite side of the carbon chain.

Triglycerides (TG)

Composed of three fatty acids esterified to one glycerol molecule; found in salad dressing, butter, margarine, cooking oil, nuts, dairy products, bacon, beef, and skin of chicken.

Catabolism of TGs and fatty acids

Yields glycerol and three fatty acids; fatty acids are activated by the attachment of coenzyme A to form acyl-CoA.

Phospholipids

Composed of glycerol, two fatty acids, and a phosphate group (PO4); amphiphilic molecules that are ideal structural components for cellular membranes and lipoprotein shells.

Sterols

Lipids characterized by a four-ring core structure (cyclopentanoperhydrophenanthrene) or steroid nucleus; cholesterol is the most common sterol in animals.

Endogenous cholesterol synthesis

Cholesterol synthesis pathway: 1) conversion of Acetyl-CoA into mevalonate, 2) mevalonate into squalene, and 3) squalene into cholesterol.

Statins

Drug used to inhibit HMG-CoA reductase activity and lower endogenous cholesterol production.

Enterohepatic circulation

Process by which bile salts are reabsorbed in the gut.

Diet-heart hypothesis

States that dietary saturated fat elevates circulating cholesterol levels leading to the development of CAD.

Transport and fate of lipids in the blood

Due to their hydrophobic nature, lipids are transported in the bloodstream as constituents of lipoproteins.

Chylomicrons

Lipoproteins that contain ApoB-48 that originates from the intestine.

VLDL and LDL

Lipoproteins that contain ApoB-100 that originates in the liver.

Lipoprotein lipase (LPL)

Enzyme that hydrolyzes TG molecules present in lipoproteins passing through the capillary bed of tissues such as adipose, skeletal muscles, and heart.

HDL

Particle that removes unesterified cholesterol from cells and other lipoproteins and transports them to the liver (reverse cholesterol transport) to be excreted in the bile.

Cholesterol ester transfer protein (CETP)

Protein that transfers cholesterol esters from HDL to VLDL and Chylomicrons in exchange for phospholipids (PL).

Proprotein convertase subtilisin/kexin 9 (PCSK9)

Mutations were identified as the third genetic cause of autosomal dominant familial hypercholesterolemia (FH).

Lp(a)

Lipoprotein that consists of a unique protein homologous to plasminogen named apolipoprotein (a), which is covalently bound to the apoB-100 moiety of an LDL particle.

Proteins

Essential nutrients because they are critical components of all cells and tissues; contribute to cell growth, repair and maintenance.

Peptide bonds

Proteins are made up of amino acids that are linked to each other.

High-quality Proteins

Foods that contain all 9 essential amino acids.

Pepsin

Proteolytic enzyme secreted in the stomach in an inactive form (pepsinogen).

Secretin and CCK

Hormones secreted as chyme enters the duodenum that stimulate the release of alkaline pancreatic juice, bicarbonate, electrolytes, water, and zymogens.

Enteropeptidase

Enzyme that converts trypsinogen into trypsin, secreted by enterocytes.

Trypsin

Cleaves peptide bonds at the carboxy end of basic amino acids (lysine and arginine).

Chymotrypsin

Specific for peptide bonds at the carboxy end of aromatic amino acids (phenylalanine, tyrosine, and tryptophan) and for peptide bonds adjacent to methionine, asparagine, and histidine.

Carboxipeptidases

Hydrolyzes peptides with C-terminal aromatic or aliphatic (non-polar) neutral amino acids, whereas Carboxypeptidase B cleaves basic amino acids from the C-terminal end.

Aminopeptidases

Responsible for cleaving amino acids from the amino (N)-terminal end of oligopeptides.

Amino acid transport systems

Transporters that allow amino acids to cross the brush border and basolateral membranes (apical and serosa, respectively) on the lumen of the small intestine.

Transport of peptides

Movement of peptides across the brush border membrane of enterocytes along with protons (H+).

Ribosomes

Structures in the cytoplasm of cells that translate mRNA into protein.