PHIDG 1501 Integrated Sequence 1 Quiz

Integrated Sequence 1 - Nutrients

• Course: PHIDG 1501
• Topic: Nutrients (3 lecture hours)
• Recommended Reading: Mahan, L.K., and Escott-Stump, S., Krause's Food and Nutrition Therapy, 12th ed., W.B. Saunders, 2008
• Complementary Material: Meisenberg, G., and Simmons, W.H., Principles of Medical Biochemistry, 2nd ed., Mosby Elsevier, 2006

Outline

• Macronutrients: Carbohydrates, Fats, Protein
• Micronutrients: Vitamins, Minerals

Monosaccharides

• Glucose: Also known as "dextrose" or "blood sugar," it's the primary energy source for the central nervous system (CNS). Daily requirement is 120 g.
• Galactose: Derived from lactose ("milk sugar").
• Fructose: Known as "fruit sugar" or "levulose," it is the sweetest monosaccharide. Invert sugar ratio: Glucose/Fructose = 1:1. Found in fruits, vegetables (3% dry weight), and honey (40%.)

Disaccharides

• Sucrose (Saccharose): Table sugar, cane sugar, beet sugar, and grape sugar. Hydrolysis yields a mixture of glucose and fructose, known as invert sugar. Present in honey.
• Lactose: "Milk sugar," predominantly found in mammalian milk (7.5% human milk, 4.5% cow milk).
• Maltose: Malt sugar, formed from the hydrolysis of starch. Glycosidic bond between Glu C1 and Glu C4.
• Sucrase: Hydrolyses sucrose (a glycosidic bond Glu C1-Fru C2.)
• Lactase: Hydrolyses lactose (β glycosidic bond Gal C1- Glu C4.)
• Maltase: Hydrolyses maltose (a glycosidic bond Glu C1- Glu C4.)
• Isomaltase: Hydrolyses isomaltose (Glu C1-Glu C6)
• All other glycosidic bonds: Undigestible dietary fibers.

Polysaccharides

• Starch: A complex carbohydrate consisting of amylose and amylopectin. "Waxy starch" is primarily amylopectin (corn and rice).
• Amylose: Linear, water-soluble carbohydrate.
• Amylopectin: Branched carbohydrate, also water soluble
• Dextrins: Partially digested amylose, long linear chains, soluble in water; "limit dextrins" are undigested amylopectin with 1,6 branching points.

Fibers

• Dietary Fibers (Intact Plant Components):
  • Less Soluble Fiber: Cellulose, Hemicellulose, Lignin
  • More Soluble Fiber: Gums, Pectins
• Functional Fibers (Isolated from Plants): Chitin, Fructans, Beta-glucans, Algal polysaccharides, Polydextrose, Polyols, Psyllium
• Fiber Functions: Increase water-holding capacity; decrease gut transit times; fermentation produces short-chain fatty acids (decreased risk of tumor formation); cause gel formation, slow digestion, gut transit time, and glucose absorption; bind minerals, lipids, bile, and reduce serum cholesterol.

Fats and Lipids

• Lipid Classification: Simple lipids (Fatty acids, Neutral fats, Waxes, Sterolester, Nonsterolester), Compound lipids (Phospholipids, Glycolipids, Lipoproteins), Miscellaneous lipids (Sterols, Vitamins A, E, K)
• Fatty acids as Energy Source: Highly concentrated energy source (9.3 kcal/g). 15 kg of fat in a normal adult provides 140,000 kcal (covers 15 weeks' energy demand). Fat stores without bound water (unlike glycogen, which needs a higher water content.)
• Unsaturated Fatty Acids: Omega-3 and Omega-6 fatty acids are essential fats (the body cannot produce these). Unsaturated double bonds decrease melting point and create a kink in the hydrocarbon chains, leading to “loose” fit, rather than “tight fit” of saturated fats, creating a fluid structure. Trans fats arise from partial hydrogenation and are not naturally occurring; they are known to increase risk of coronary heart disease.
• Synthetic Lipids (MCTs, medium-chain triglycerides): Coconut oil, palm kernel oil (by-product of margarine); Advantages over long-chain triglycerides: Water soluble, require less bile salt; no re-esterification in enterocytes; quick metabolism to acetic acid; not stored in adipose tissue.

Fat Replacers

• Non-Lipids: Largely derived from carbohydrates and proteins (gums, cellulose, dextrins, starches). Imitate fat texture, but offer low caloric value. These fat replacers are considered safe and effective for diets.

Protein

• Protein Daily Requirements: To maintain daily protein turnover, about 25 g/day must be replaced.
• Protein Nitrogen Balance: compares amount of nitrogen entering the body to the amount exiting the body. Positive nitrogen balance (uptake > excretion) occurs during growth, pregnancy and bodybuilding. Negative nitrogen balance (uptake < excretion) occurs during starvation and disease.

Amino Acids

• Essential Amino Acids: 9 amino acids cannot be synthesized by the body and must be obtained from diet.
• Non-Essential Amino Acids: The body can synthesize these; pathways rely on transamination of metabolites.
• Amino Acid Requirements: Specific amounts based on age and gender are provided.
• Example: The Biological Value of Dietary Protein evaluates how well dietary protein's amino acid composition aligns with the body's protein needs and can be assessed by comparing the nutritional value of proteins like Zein and egg-derived proteins.

Protein Digestibility

• PDCAAS (Protein Digestibility Corrected Amino Acid Score): A measure of protein quality. Soy proteins score 1, indicating they meet human protein needs. Others, like milk and egg proteins, score higher than less valuable ones like corn.

Dietary Guidelines

• USDA/HHS: Carbohydrate (45%-65%), Fat (20%-35%), Protein (10%-35%) recommendations for daily calories. Example: A 2,000 calorie diet should contain 225-325 g carbohydrate, 44-77 g fat, and 50-175 g protein.

Water-Soluble Vitamins

• Definitions: Recommended Dietary Allowances (RDAs), Estimated Average Requirements (EARs), Adequate Intakes (Als), Tolerable Upper Intake Levels (ULs), Estimated Safe and Adequate Daily Dietary Intakes (ESADDIs.)

Specific Micronutrients / Various Vitamins

• General vitamin specifics: RDA values, and various metabolic functions and consequences of deficiency. Example: Riboflavin (B-2) function is a precursor for FMN and FAD, coenzymes for "H" transfer. Niacin (B3) as a component of NAD and NADP, and its function in glucose metabolism and ATP production. Deficiency signs (Pellagra). Vitamin B6 (Pyridoxine), and its function as a coenzyme for amino acid metabolism, phosphorylase, and synthesis of GABA. Biotin and its function as a carrier of carboxy groups, with deficiency signs indicated. Thiamine (B1), as a precursor to TPP (Thymine Pyrophosphate), the coenzyme for oxidative decarboxylation pathways in glucose metabolism.