Principles of Nutrition: Macronutrients, Digestion, Micronutrients, and Food Science

Comprehensive practice flashcards defining foundational terms, chemical structures, metabolic pathways, and regulatory concepts across carbohydrates, lipids, proteins, enzymes, vitamins, and minerals.

Nutrient

Any substance found in food that the human body utilizes to obtain energy, synthesize tissues, or regulate physiological functions.

Macronutrients

Nutrients that the human body requires in large daily quantities, specifically carbohydrates, proteins, and lipids (fats).

Micronutrients

Essential dietary nutrients required by the body only in small quantities, comprising vitamins and minerals.

Kilocalorie (kcal)

The quantity of heat energy required to raise the temperature of one kilogram of water by $1^\bot\circ\text{C}$, equivalent to $1{,}000\text{ calories}$ or $1\text{ food calorie}$.

Bomb Calorimeter

A laboratory instrument used to determine the gross energy content of foods by igniting samples and measuring the heat released.

Basal Metabolic Rate (BMR)

The baseline amount of energy expended by the body to sustain involuntary, life-supporting physiological processes while resting.

Dietary Induced Thermogenesis (DIT)

The energy expended by the body specifically to digest, absorb, transport, and metabolize nutrients from consumed foods.

Peristalsis

Rhythmic, coordinated muscular contractions of circular and longitudinal muscles that mix and propel food through the gastrointestinal tract.

Villi

Fingerlike projections carpeting the folded inner lining of the small intestine that increase surface area for nutrient absorption.

Microvilli

Microscopic, hair-like projections—numbering roughly $1{,}000$ per cell—lining mucosal cells of the intestinal villi to conduct nutrient absorption.

Monosaccharide

A single, simple sugar unit with the chemical formula $\text{C}_6\text{H}_{12}\text{O}_6$, including hexose sugars (glucose and galactose) and the pentose sugar (fructose).

Disaccharide

A carbohydrate composed of two joined monosaccharide units, including sucrose ($\text{glucose} + \text{fructose}$), lactose ($\text{glucose} + \text{galactose}$), and maltose ($\text{glucose} + \text{glucose}$).

Amylose

A digestible form of dietary starch composed of unbranched, straight chains of glucose molecules yielding $4\,\text{cal/g}$.

Amylopectin

A digestible form of plant starch structured as branched chains of glucose molecules yielding $4\,\text{cal/g}$.

Dietary Fiber

Indigestible plant polysaccharides (including cellulose, pectins, and gums) that provide zero net calories to the human diet because human enzymes cannot cleave their chemical bonds.

Cellulose

An insoluble dietary fiber composed of glucose monomers joined by $\beta\text{-1,4}$ glycosidic bonds that resist human enzymatic cleavage.

Soluble Fiber

Dietary fibers (such as pectin and gums) that dissolve in water to form viscous solutions, functioning in the body to lower cholesterol and moderate blood glucose levels.

Insoluble Fiber

Dietary fibers (such as cellulose and wheat bran) that do not dissolve in water, functioning to add bulk, alleviate constipation, and reduce diverticulosis risk.

Whole Grain

An intact cereal grain kernel that retains all three anatomical components: the fiber-rich bran, the starchy endosperm, and the nutrient-dense germ.

Sugar Alcohols (Polyols)

Nutritive bulk sweeteners (such as sorbitol, mannitol, and xylitol) modified with hydroxyl groups ($-\text{OH}$) that provide sweetness with a cooling sensation, promote dental health by being anticariogenic, and can exert a laxative effect in excess.

Aspartame

A synthetic non-heat-stable dipeptide sweetener made from aspartic acid and phenylalanine that is $200\text{ times}$ sweeter than sucrose and requires a warning label for individuals with phenylketonuria (PKU).

Sucralose

A zero-calorie synthetic sweetener sold as Splenda, produced by replacing three hydroxyl groups on sucrose with chlorine atoms, possessing a sweetness $600\text{ times}$ that of table sugar.

Saccharin

A heat-stable artificial sweetener $300\text{ times}$ sweeter than sucrose that provides zero calories but often leaves an unpleasant bitter or metallic aftertaste.

High Fructose Corn Syrup (HFCS)

A liquid sweetener produced from corn starch via sequential enzymatic treatment (amylase, maltase, and glucose isomerase) yielding approximately equal proportions of glucose and fructose.

Triglyceride

The predominant dietary lipid and primary storage form of fat in the body, consisting of one glycerol molecule chemically bonded to three fatty acids.

Monounsaturated Fatty Acid (MUFA)

A fatty acid hydrocarbon chain containing exactly one double bond between carbon atoms.

Polyunsaturated Fatty Acid (PUFA)

A fatty acid hydrocarbon chain containing two or more carbon-carbon double bonds, which markedly lowers its melting point.

Trans Fatty Acid

An unsaturated fatty acid isomer produced during partial hydrogenation where hydrogen atoms attach on opposite sides of the double bond, packing tightly and elevating LDL cholesterol.

Hydrogenation

A chemical process wherein hydrogen atoms are added across double bonds of liquid plant oils over a metal catalyst to yield solid or semi-solid fats.

Phospholipid

A lipid composed of a glycerol backbone, two fatty acids, and a phosphate group, naturally functioning in membranes and commercially used as an emulsifier (such as lecithin).

Cholesterol

A multi-ring sterol synthesized primarily by the liver that acts as a structural component of cell membranes and serves as a biological precursor to vitamin D, bile salts, and steroid hormones.

High-Density Lipoproteins (HDL)

Blood transport particles containing approximately $50\%$ protein and $20\%$ cholesterol, commonly known as 'good cholesterol.'

Low-Density Lipoproteins (LDL)

Blood transport particles containing approximately $25\%$ protein and $55\%$ cholesterol, labeled 'bad cholesterol' due to their association with arterial plaque buildup.

Olestra

A synthetic, non-digestible sucrose polyester fat replacer yielding $0\,\text{cal/g}$ that can induce abdominal cramps, loose stools, and bind fat-soluble vitamins (A, D, E, K), hindering their absorption.

Amino Acid

The organic monomer of proteins, characterized by a central carbon bonded to a hydrogen atom, an amino group ($-\text{NH}_2$), a carboxylic acid group ($-\text{COOH}$), and an idiosyncratic side chain (R-group).

Essential Amino Acids

The nine amino acids that cannot be synthesized endogenously in sufficient quantities and must be obtained from food: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Peptide Bond

A covalent chemical bond formed between the carboxylic acid group of one amino acid and the amino group of an adjacent amino acid with the elimination of a water molecule.

Primary Protein Structure

The fundamental linear sequence of amino acids linked together in a polypeptide chain.

Complementary Proteins

Two or more incomplete protein sources (such as grains low in lysine paired with legumes low in methionine) that together supply all nine essential amino acids in adequate amounts.

Protein Denaturation

The unfolding and loss of secondary and tertiary protein structure brought about by heat, acid, or chemical agents, while leaving the primary amino acid sequence intact.

Kwashiorkor

A severe form of protein-energy malnutrition caused by an acute dietary deficiency of protein despite receiving adequate caloric energy.

Marasmus

A severe form of protein-energy malnutrition caused by chronic starvation and insufficient intake of both dietary protein and total calories.

Maillard Browning

A non-enzymatic browning reaction taking place under high heat between the amino group of a protein and a reducing sugar, producing brown pigments and distinct flavors in crusts, chocolate, and coffee.

Enzyme

A biological protein catalyst that increases the rate of specific biochemical reactions by lowering activation energy without undergoing permanent chemical alteration.

Lock and Key Model

A structural model describing enzyme specificity, wherein the enzyme's geometric active site precisely matches its complementary substrate molecule to catalyze product formation.

Fortification

The intentional addition of nutrients to a food product that were not originally present prior to manufacturing (e.g., adding calcium to orange juice).

Enrichment

The restoration or elevation of levels of nutrients originally present in a food during processing to satisfy specified FDA standards (e.g., adding B-vitamins and iron to refined flour).

Vitamin A (Retinol)

A fat-soluble vitamin essential for visual phototransduction and tissue maintenance, whose deficiency causes blindness; obtained preformed in animal fats or as provitamin $\beta$-carotene from plants.

Vitamin D

A fat-soluble vitamin facilitating calcium absorption to maintain skeletal integrity, whose deficiency leads to rickets in children and osteoporosis in adults.

Vitamin E (Alpha-tocopherol)

A fat-soluble antioxidant vitamin that shields cell membranes from oxidative stress, found abundantly in wheat germ, nuts, seeds, and vegetable oils.

Vitamin K

A fat-soluble vitamin critical for synthesizing blood-clotting factors, supplied via dietary greens and synthesized endogenously ($10\text{--}15\%$) by normal intestinal microflora.

Folate (Folic Acid)

A water-soluble B-vitamin coenzyme necessary for DNA synthesis, cellular proliferation, and red blood cell maturation, recommended during early gestation to prevent neural tube defects like spina bifida.

Vitamin B12

A water-soluble vitamin required for DNA synthesis, red blood cell generation, and amino acid metabolism, naturally present exclusively in animal foods and requiring supplementation in strict vegans.

Vitamin C (Ascorbic Acid)

A water-soluble antioxidant vitamin vital for wound healing, tissue integrity, and enhanced plant iron absorption, whose absence results in scurvy.

Goiter

An enlargement of the thyroid gland resulting from a chronic deficiency of the trace mineral iodine, widely controlled in the United States through salt iodization.

Dietary Supplement Health and Education Act (DSHEA) of 1994

United States legislation classifying oral supplements as dietary ingredients exempt from premarket FDA efficacy and safety testing, permitting structure/function claims with a standard disclaimer.