A-7: Glossary

A

Absorption: Process by which nutrients are transferred from the digestive tract into the bloodstream.

Acetylcholine: Neurotransmitter at the nerve-muscle synapse.

Acid: Molecule that releases hydrogen ions into a solution.

Activase: Trade name for the tissue plasminogen activator (TPA) made by biotechnology and used to dissolve blood clots. See also TPA.

Adenosine triphosphate (ATP): Main chemical form of energy that is made and used in metabolism. Serves to transfer energy from energy-producing reactions to energy-using reactions.

Adipose cell: “Fat cell,” that stores excess calories as body fat.

Aerobic metabolism: Oxygen‑requiring reactions occurring in mitochondria which produce energy from the breakdown of acetyl CoA into carbon dioxide and water.

Aflatoxin: Highly toxic substance(s) formed by the growth of a mold (especially Aspergillus flavus) on peanuts, corn, etc.

AIDS: Acquired Immunodeficiency Syndrome caused by infection with HIV, characterized by infections stemming from a loss of crucial white blood cells necessary for proper function of the immune system.

Albumin: Protein found in the plasma portion of blood which helps transport substances, regulates pH of blood, and regulates the amount of fluid held in blood. A deficiency of albumin can lead to edema.

Alcohol: Fermentation product of carbohydrate that has a high caloric content (7 calories per gram) and is essentially devoid of nutrients.

Ames test: Test that uses specially‑altered bacteria to identify a substance as a mutagen and, thus, a potential carcinogen.

Amino acid: Structural unit (“building block”) of protein; contains an amino (‑NH2 ) and an acid (‑COOH) group.

Amino acid pattern: Relative proportions of the nine diet-essential amino acids in a protein. Anabolic steroid: Synthetic hormone that mimics the growth-promoting effects of male sex hormone testosterone.

Anabolism: Energy‑requiring metabolic reactions in which larger molecules (e.g., protein, cholesterol) are made from smaller ones (e.g., amino acids, acetyl CoA).

Anemia: Lower‑than‑normal amount of red blood cells or hemoglobin. Nutritional deficiencies of iron, and folate, and lack of intrinsic factor for B₁₂ absorption are common causes.

Anaerobic: Doesn’t require oxygen. Anaerobic metabolism: Energy‑producing reactions which break glucose into pyruvate without the need for oxygen. Also known as glycolysis.

Aneurysm: Outpouching of a weakened portion of the arterial wall. Usually caused by a defect in the affected artery and/or high blood pressure.

Anorexia: Loss of appetite.

Anorexia nervosa: Eating disorder characterized by a dramatic reduction of food intake for fear of becoming fat, resulting in extreme weight loss and sometimes death.

Antioxidant: Substance that prevents or retards oxidation. BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene) are common antioxidants used in foods. Vitamins C and E can also function as antioxidants in food and in the body.

Appetite: Learned response which causes the desire for food.

Artery: Thick, muscular, blood vessel that carries blood away from the heart. Blood carried in arteries is oxygenated, except for the pulmonary artery which carries blood from the heart to the lungs to be oxygenated. ‑ase: Suffix used in forming the name of an enzyme, such as lipase, sucrase, and lactase.

Atherosclerosis: Disease caused by an accumulation of fatty material in the lining of the arterial wall, resulting in the thickening, hardening, and loss of elasticity of the arteries.

Atom: Smallest particle that can no longer be subdivided without losing its characteristic properties. Atoms contain protons, neutrons, and electrons.

ATP: see Adenosine triphosphate.

Autoimmune disease: Disease that occurs when a part of the body is mistakenly seen as foreign and is destroyed by the immune system, e.g., insulin-producing cells in the pancreas destroyed by the immune system resulting in type-1 diabetes.

Axon: Extension of a nerve cell that conducts a nerve impulse away from the body of the nerve cell.

B

Basal Metabolic Rate (BMR): Rate at which energy (calories) is used for a person’s involuntary functions. Measured under standard conditions, directly by the heat expended, or indirectly by the amount of oxygen consumed.

Base: Molecule that releases hydroxy ions (‑OH) into a solution. (It removes hydrogen ions from the solution by combining hydroxy and hydrogen ions to form water.) Bile: Fluid made by the liver and stored and concentrated in the gallbladder. Released into the upper part of the small intestine (the duodenum) and serves to emulsify fats, aiding fat digestion.

Bile acid: Component of bile made in the liver from cholesterol.

Biotechnology: Use of technology to study or solve problems of living organisms, e.g., production of human proteins (insulin, growth factor, etc.) by cells/bacteria that have had the human gene for that protein inserted into their DNA. Biotechnology often used interchangeably with genetic engineering, recombinant DNA, and biotech.

BMI: see Body Mass Index.

BMR: see Basal Metabolic Rate.

Body Mass Index (BMI): Your weight in kilograms divided by the square of your height in meters. Used to assess whether a person is underweight, normal weight, overweight.

Bomb calorimeter: Apparatus used to determine the energy value of food by measuring the amount of heat produced by complete oxidation (“burning”) of a food sample.

Buffer: Substance that makes a fluid relatively resistant to changes in pH by taking up or releasing hydrogen ions.

Bulimia: Eating disorder characterized by a compulsion to eat large quantities of food in a short period of time, followed by “purging” the food, typically by inducing vomiting or taking laxatives.

C

Caffeine: Stimulant, found in coffee, energy drinks, etc., which makes the nervous system more excitable. Also refers to related substances found in tea and chocolate which act as stimulants.

Calorie: Amount of heat needed to raise the temperature of one liter of water one degree Celsius. In nutrition, a calorie is 1,000 X the calorie of physics/chemistry and is sometimes called a kilocalorie. Cancer: Uncontrolled growth of cells which can lead to death.

Capillary: Small, thin‑walled blood vessel. Reaching every living cell in the body, capillaries provide the means for exchange of substances between the blood and each cell.

Carbohydrate: One of the three classes of nutrients in food that provide energy to the body; an organic compound made up of carbon, hydrogen, and oxygen atoms. Carbohydrates have an energy value of 4 calories per gram.

Carbohydrate loading: Regimen used by endurance athletes to increase muscle glycogen by emptying the muscle of glycogen by exercise, and then, in the days immediately prior to competition, resting and reloading the muscles with glycogen by eating a high carbohydrate diet. This regimen temporarily increases the muscle’s supply of glycogen to higher-than-normal levels.

Carcinogen: Substance that causes cancer.

Catabolism: Energy‑generating metabolic reactions that systematically break down energy-providing nutrients (e.g., fatty acids, glucose) into smaller molecules (e.g., acetyl CoA, carbon dioxide).

Catalyst: Substance which increases the rate of a chemical reaction. (Enzymes are biological catalysts.)

Cell: Basic structural unit of an organism.

Cell membrane: The outside layer of a cell.

Cholesterol: A fat found in all cell membranes. Found in animal tissues, but not in plants.

Chromosome: Structures in the cell nucleus that are made of DNA and protein, and contain the cell’s genetic information.

Clinical trial: Prospective human study that, for example, tests for the effectiveness of a new drug, or tests to see if a change in diet can lower risk of disease. Because of the magnitude and expense of a clinical trial, preliminary studies in the laboratory and in animals must first show ample evidence of effectiveness and safety before it is approved.

Coenzyme: Non‑protein substance which can be required for the activity of an enzyme. Coenzymes often have B‑vitamins as part of their structures.

Cofactor: Non‑protein substance, often a mineral, that can be required for activity of an enzyme.

Collagen: A protein found in bone, cartilage, and connective tissue.

Compound: Two or more different elements that are combined chemically, e.g., NaCl (sodium chloride, “table salt”).

Constipation: Difficult or infrequent passage of stool. Insoluble dietary fiber helps prevent constipation by absorbing water, making stools bulkier and softer.

Covalent bond: Chemical bond in which one or more electrons are shared between two atoms.

CRISPR-Cas: A revolutionary DNA-editing tool that can simply and precisely edit DNA in any organism.

Cytoplasm: The fluid in a cell.

D

Delaney clause: Adopted in 1958; prohibited the Food and Drug Administration (FDA) from approving food additives that had been shown, at any dose, to cause cancer in any animal. Repealed/replaced in 1996.

Denaturation: Permanent change in the 3- dimensional shape of a protein molecule, thereby changing its biological activity.

Dendrite: One of the many extensions of a neuron’s cell body that receives nerve impulses from other neurons.

Dental plaque: Soft patches, containing bacteria and food debris, that cling to teeth. Involved in tooth decay and gum disease.

Deoxyribonucleic acid: see DNA.

Dextrose: see Glucose.

Diabetes: Disease characterized by high blood sugar resulting from insulin deficiency, or cell resistance to insulin action.

Diarrhea: Rapid movement of fecal matter through the colon, producing watery stool.

Digestion: Breakdown of foods by digestive enzymes into smaller units that can be absorbed by the body.

Digestive tract: Series of organs responsible for the digestion and absorption of nutrients. Also called the gastrointestinal (GI) tract.

Direct calorimetry: Method for determining the amount of calories expended by an organism by measuring the amount of heat produced.

Disaccharide: see Double sugar

Diverticulosis: Outpouching of the colon wall. Fiber is thought to lower risk by providing bulk to contents of the colon.

DNA (Deoxyribonucleic acid): Nucleic acid found in the cell nucleus, that holds genetic information in the form of genes.

DNA fingerprinting: In an early method, DNA enzymatically broken into pieces of different lengths, depending on its sequence of bases. Pieces are separated by length, giving a “fingerprint” that looks like a bar code.

Double‑blind study: Study in which neither the subjects nor the investigators actively involved know whether a particular subject is in the experimental group or the control group.

Duodenum: Uppermost region (about the first 12 inches) of the small intestine. Site where pancreatic and liver secretions enter the small intestine through the bile duct to neutralize the acidity of the partially digested food coming from the stomach

E

Edema: Swelling caused by excess fluids in body tissues. Seen in severe protein deficiency and some other medical conditions.

Electron: Negatively charged particle that orbits the nucleus of an atom. Element: Substance containing only one kind of atom.

Emulsifier: Substance which finely divides and suspends fat in a water-based solution.

Energy: Ability to do work. The energy value of foods and the energy needs of the body are expressed as calories.

Enrichment: Addition of specific nutrients (thiamin, riboflavin, niacin, folic acid, iron) to refined grains and cereals such as white rice and white flour.

Enzyme: Biological catalyst, usually a protein, that speeds biochemical reactions.

Estrogen: Female sex hormone.

Esophagus: Muscular tube, serving as a passageway for food, that extends from the throat to the stomach.

F

Fast‑twitch muscle fiber: see White muscle fiber. Fat: One of the three classes of nutrients in food that provide energy (9 Calories per gram) to the body. Fats dissolve in organic solvents but not in water.

Fat‑soluble vitamins: Vitamins that dissolve in fat: vitamins A, D, E, and K.

Fatty acid: Chain of carbon (and hydrogen) atoms with an acid group (‑COOH) on one end; the main component of triglycerides.

Fermentation: Anaerobic production of alcohol by the enzyme-catalyzed breakdown of carbohydrates. Fermentation can involve other substances as well.

Fiber: Indigestible substances found in plants. Insoluble fibers might help prevent diverticulosis, constipation, and possibly colon cancer. Soluble fibers may help lower cholesterol levels in the blood.

Fortification: Improvement of nutritional quality by the addition of one or more nutrients not normally found in the food (e.g., vitamin D in milk, vitamin A in margarine, calcium in orange juice).

Fructose: Single‑sugar found in such foods as honey and fruit. Makes up half of the double sugar sucrose and regular high-fructose corn syrup (the other half is glucose).

G

Galactose: Single‑sugar that’s a part of the double-sugar lactose.

Gastric juice: Acidic (about pH 2) secretion from the stomach lining responsible for such things as killing bacteria ingested along with food, denaturing proteins, and aiding mineral absorption.

Genetic engineering: see Biotechnology. Genetically Modified Organism: see GMO.

Ghrelin: A hormone made mainly by the cells lining the stomach that stimulates appetite.

Glial cell: One of the two basic types of nervous system cells. Functions to nurture and protect the less numerous neurons.

Glucose: Most common single‑sugar, also known as dextrose. Found in various foods, is the sugar found in the blood, and is a part of the double sugars sucrose, maltose, and lactose.

Glycogen: Complex carbohydrate (a storage form of glucose) found in animal tissue, and stored in muscle and liver.

Glycogen loading: see Carbohydrate loading.

Glycolysis: Production of ATP energy from the anaerobic breakdown (metabolism) of glucose in the cytoplasm of the cell.

GMO: (Genetically Modified Organism). An organism that has had its DNA modified by genetic engineering.

Goiter: Enlarged thyroid gland. Called simple goiter when caused by a deficiency of dietary iodine.

Goitrogens: Substances found in foods and some drugs which, when eaten in large amounts over a long time, can cause goiter.

H

HDL (high‑density lipoprotein) cholesterol: Cholesterol in a plasma lipoprotein that’s transporting cholesterol away from cells. Dubbed “good cholesterol” (H for healthy). Low HDL linked to increased risk of cardiovascular disease.

Heme iron: Iron found mainly in the oxygen‑carrying molecules hemoglobin and myoglobin; found only in animal tissue.

Hemoglobin: Iron‑containing protein in red blood cells that carries oxygen.

HIV (Human Inimunodeficiency Virus): The virus that causes AIDS.

Hormone: Chemical messenger, typically secreted by a gland, carried in the bloodstream, and having a specific effect on certain cells.

Hydrogenation: Addition of hydrogen to unsaturated fatty acids to make it more saturated. Double bonds are changed to single bonds, resulting in a more solid fat.

Hyperthyroidism: Condition in which an excessive amount of thyroid hormone is produced.

Hypoglycemia: Abnormally low blood‑glucose.

I

Indirect calorimetry: Measuring oxygen‑use to determine the calories expended by the organism.

Insulin: Hormone made in the pancreas that allows glucose to enter cells.

Integrated Pest Management (IPM): A customized ecological approach to minimize pesticide use by strategies based on pest biology, local soil conditions, etc.

Intrinsic factor: Protein, secreted by the stomach, that’s essential for the absorption of vitamin B₁₂. An insufficient secretion of intrinsic factor results in pernicious anemia, a B12 deficiency.

Ion: Electrically charged atom or molecule. Ionic bond: Chemical bond resulting from the attraction of oppositely charged ions.

K

Ketone: Chemical formed when acetyl CoA accumulates in metabolism, as can happen in starvation and untreated diabetes.

Kilocalorie: see Calorie (Kilocalorie is the technically correct term, but, in nutrition, “calorie” is commonly used.)

L

Lactase: Digestive enzyme that breaks down lactose to galactose and glucose.

Lactic acid: Acid formed by glycolysis when oxygen is limited (e.g., in sustained, strenuous physical activity).

Lactose: Double‑sugar (galactose linked to glucose) found in milk.

Lactose intolerance: Reduced ability (insufficient lactase enzyme in small intestine) to digest the milk-sugar, lactose, that can result in symptoms such as diarrhea and gas.

LDL (Low‑density lipoprotein)‑cholesterol: Cholesterol carried in the plasma lipoprotein that transports cholesterol to cells. Dubbed “bad cholesterol” (L for lousy) because high levels increase risk of cardiovascular disease.

LDL‑receptor: Protein in the membrane of cells that serves as an attachment site for LDL, allowing cholesterol to enter the cell.

Lecithin: Phospholipid (a type of fat) found in food and body tissues; used as an emulsifier in food preparation; contains choline; makes up our cell membranes.

Leptin: A hormone made by fatty tissue that plays a key role in regulating energy intake and energy expenditure, including the regulation (decrease) of appetite and (increase) of metabolism.

Lipoprotein: Spherical particle made of fat and protein; used to transport fat in the plasma portion of blood.

M

Malnutrition: Condition in which the body gets too much or too little of a nutrient, resulting in poor health.

Maltase: Digestive enzyme that breaks down double-sugar maltose into two molecules of glucose.

Maltose: Double‑sugar made of two glucoses linked together.

Menopause: Period in the life cycle of women when menstruation ceases permanently.

Menstruation: Monthly flow of blood and cell debris from the uterus during a woman’s reproductive years (puberty to menopause).

Messenger RNA (mRNA): Copy of a gene used to make a particular protein.

Metabolism: Sum total of the chemical changes or reactions occurring in the body.

Microvilli: Ruffled portion of the membrane of cells lining of the small intestine; contains digestive enzymes; nutrients are absorbed through the microvilli.

Minerals: Inorganic compounds. Calcium, phosphorous, potassium, and iron are examples of minerals that are important for proper bodily function.

Mitochondria: Structures found in the cell cytoplasm in which all oxygen‑requiring reactions occur.

Molecule: Two or more atoms linked together. Monosaccharide: see Single‑sugar.

Monounsaturated fatty acid: Fatty acid containing one double bond in its carbon chain. Olive oil is a rich source of monounsaturated fatty acids.

Muscle fiber: Muscle cell, described as a fiber because of its shape. Groups of these cells are held together by connective tissue to form muscle tissue.

Mutagen: Any agent that can change the sequence of bases in DNA.

Mutation: Change in the sequence of bases in DNA.

Myelin: White fatty substance that forms the [myelin] sheath that covers the axon of a nerve cell.

Myoglobin: Iron‑containing protein found in muscle; stores oxygen for use during muscle contraction.

N

Natural food: As defined by the Federal Trade Commission, any food that is minimally processed and contains no artificial ingredients.

Neurotransmitter: Chemical substance involved in transferring a nerve impulse from one nerve cell to another, or from a nerve cell to a muscle cell.

Neuron: Nerve cell, consisting of the cell body and its extensions: dendrites and axons.

Neutron: Electrically neutral particle in the nucleus of an atom.

Nitrosamine: Carcinogen formed by the combination of nitrites and amines.

Non‑heme iron: Iron not associated with oxygen‑­carrying molecules. All plant iron is non-heme iron.

Nucleus, atomic: Center of an atom, where protons and neutrons are located.

Nucleus, cell: Structure within a cell that contains the cell’s genetic information.

Nutrient: Dietary substance essential for the growth, maintenance, function, or reproduction of a cell.

O

Obesity: Excess accumulation of body fat. Generally defined as a Body Mass Index (BMI) of 30 and above.

Obestatin: A hormone made by the cells lining the stomach that affects appetite.

Oil: Generally speaking, a fat (triglyceride) that’s liquid at room temperature, e.g., corn oil, fish oil. (Exceptions include palm oil.)

Organic compounds: All compounds containing carbon (with a few exceptions, e.g., carbonates, cyanides). Fats, protein, carbohydrate, and vitamins are all organic compounds.

Organic foods: In popular terminology, foods grown without use of chemical pesticides or fertilizers; only fertilizers derived from animals or plants are permitted.

Organism: Any living plant or animal.

‑ose: Suffix that is used in forming the name of a carbohydrate, such as cellulose, maltose, and lactose.

Osteomalacia: Vitamin D deficiency in adults, resulting in bone demineralization and easily fractured bones.

Osteoporosis: Loss of bone‑calcium in which bones have lost so much density that they are easily fractured. Occurs most frequently in postmenopausal women.

Oxidation: Addition of oxygen atoms to (or the removal of hydrogen atoms from) a substance.

P

Pacemaker cells: Group of cells in the heart that rhythmically stimulate the contraction of the heart muscle, causing it to beat.

PCR (the Polymerase Chain Reaction): Method by which sections of DNA are replicated to amounts large enough for analysis.

Pectin: A dietary fiber which can help lower blood‑cholesterol levels. Also used to “gel” jams and jellies.

Peptide: Two or more amino acids linked together. Peptide is also used to describe the linkage (peptide bond) in which the amino group of one combines with the acid group of the other.

Periodontal tissue: Gums, periodontal ligament, and other tissue surrounding the teeth.

Peristalsis: Wave-like contractions of the digestive tract muscles that move the digestive material downward.

pH: Number denoting the hydrogen ion concentration in a solution. A pH value of 7 is neutral; less than 7 is acidic; and greater than 7 is basic. Physiological pH is between 7.35 and 7.45. pH literally means hydrogen power from the French pouvoir hydrogene.

Phenylalanine: One of the 9 amino acids required in the diet.

Phospholipid: Phosphorus‑containing fat (lipid) made of glycerol, two fatty acids, and one phosphorus-containing compound. Phospholipids are the basic unit in cell membranes and are used as emulsifiers in foods. Lecithin is a common phospholipid.

Photosynthesis: Process whereby plants use light, carbon dioxide, and water to create carbohydrates and oxygen.

Placebo: Inert substance which seems identical to the test substance in studies.

Placebo effect: Effect that results from, but is not caused by, the test-substance or procedure. A psychological effect that occurs because it is expected (e.g., feeling better simply because you expect to).

Plaque: see Dental plaque.

Plasma: Fluid portion of blood in which red blood cells, white blood cells, and platelets are suspended.

Platelets: Small blood cells which cluster at the site of injury to a blood vessel, acting immediately to stop the bleeding until a clot of plasma proteins can form.

Polarization: Physical separation of positive and negative charges.

Polymerase Chain Reaction: see PCR

Polysaccharide: Carbohydrate of three or more single‑sugars linked together. Subdivided into digestible (e.g., starch) and indigestible (e.g., fiber). Digestible polysaccharides are commonly called complex carbohydrates.

Polyunsaturated fatty acid: Fatty acid with two or more double bonds in its carbon chain.

Prospective study: Study that follows the development of, for example, a disease in healthy people who have been grouped according to the presence or absence of the characteristic believed to be involved in the disease (e.g., follows healthy smokers and nonsmokers for the development of lung cancer).

Protein: One of the three classes of nutrients in food that provide energy to the body; an organic compound composed of amino acids linked together by peptide bonds. Protein has a caloric value of 4 calories per gram.

Protein‑calorie malnutrition: Severe protein deficiency caused most often by the combination of both calorie and protein deficiencies in the diet.

Protein complementation: Combination of one plant protein low in one or more amino acids with another protein that provides more of the limiting amino acid(s), thus providing a better mixture of amino acids to satisfy the body’s amino acid requirements.

Proton: Positively charged particle found in the nucleus of an atom.

Pyruvate: End‑product of anaerobic metabolism (glycolysis) that can be made into lactic acid or acetyl CoA.

R

Rancid: Having the disagreeable taste and/or smell of decomposed oils or fats, caused by oxidation of double bonds in unsaturated fats.

Recombinant DNA: see Biotechnology.

Red muscle fiber: Muscle cell with a high capacity for aerobic energy production. Important for sustained muscle activity.

Relative Risk: Statistical measure of the risk of developing a disease. Defines the risk of a group with a certain characteristic as compared to the risk of the general population.

Restoration: Addition of nutrients that were originally present in the food but were either lost or destroyed in processing (e.g., vitamin C to instant mashed potatoes).

Retrospective study: Study in which people are grouped according to the presence or absence of a disease or condition. By examining the physical characteristics and earlier habits of each group, scientists try to determine the reason(s) for the disease or condition.

Reverse transcription: Process in which a virus causes a cell to make a DNA copy of the viral RNA. This strand of foreign DNA may then become a part of the cell’s own DNA. This occurs with the AIDS virus.

Ribonucleic acid (RNA): see RNA.

Ribosome: Structure located in the cytoplasm of a cell that is the site of protein synthesis.

Rickets: Bone deformities due to deficiency of vitamin D and/or calcium in childhood.

Risk factor: Anything that increases one’s risk of an adverse effect, e.g., smoking is a risk factor for lung cancer; high LDL‑cholesterol is a risk factor for cardiovascular disease.

RNA (Ribonucleic acid): A nucleic acid important in protein synthesis. Messenger RNA carries the directions to make a protein from DNA to ribosomes (“ribosomal RNA”) where protein is made. Transfer RNA carries the amino acids needed for protein synthesis. see Messenger RNA, Transfer RNA.

S

Satiety: Feeling of fullness or of being satisfied. Fat provides a longer satiety than carbohydrate or protein.

Saturated fatty acid: Fatty acid that doesn’t have any double bonds in its carbon chain because it’s saturated with hydrogen atoms.

Scientific Method: Collective term for the steps and procedures scientists follow to acquire scientific knowledge. It involves formulation of a hypothesis, experimentation, evaluation, discussion of experimental results, and the discussion of conclusions, all subject to peer review.

Serotonin: Neurotransmitter made from the amino acid tryptophan, has a calming effect.

Single‑sugar: Carbohydrate consisting of a single sugar molecule (e.g., glucose, fructose). Also called monosaccharide.

Skinfold thickness: A method for determining the amount of body-fat stored under the skin by measuring the thickness of a fold of skin.

Slow‑twitch muscle fiber: see Red muscle fiber.

SNP (Single Nucleotide Polymorphism): A single base (nucleotide) variation at a precise point along DNA (pronounced “snip”).

Steroid: Synthetic or naturally occurring hormone with a cholesterol-like structure.

Sterol: Type of fat (lipid) which contains a basic four-ring structure (e.g., cholesterol).

Stimulant: As related to the nervous system, a substance that causes a nerve cell to be more easily excited.

Sucrase: Digestive enzyme that breaks down sucrose (a double-sugar) to fructose and glucose (single-sugars).

Sucrose: Double‑sugar made of fructose and glucose (single-sugars) linked together. Commonly known as “table sugar.”

Sugar: Common name for single sugars (e.g., glucose, fructose, and galactose) and double-sugars (e.g., sucrose, lactose, maltose). “Table sugar” is sucrose.

Synapse: Place where a nerve impulse is transferred between nerve cells or between nerve cell and muscle cell.

T

Thyroxine: Iodine‑containing hormone made by the thyroid gland; important in maintaining normal rates of metabolism.

TPA (Tissue plasminogen activator): Substance in blood that triggers the breakdown of clots. Known as Activase when made by biotechnology.

Trans fatty acid: Unsaturated fatty acid that has unusual configuration around the double bond. Most commonly found in partially hydrogenated fat. Like saturated fat, it can raise LDL‑cholesterol.

Transcription: Process in which messenger RNA (mRNA) is made by copying (“transcribing”) the section of bases in DNA that makes up a gene. (A gene has the instructions to make a protein.)

Transfer RNA (tRNA): Transports amino acids to the ribosome for use in protein synthesis. Each of the 20 amino acids needed to make protein has its own special tRNA.

Translation: Process by which information in messenger RNA (mRNA) is translated and implemented to form protein.

Triglyceride: Fat made up of three fatty acids attached to glycerol; makes up most of the fat in food; the body’s storage form of fat.

Tryptophan: One of the nine amino acids required in our diet.

Tumor: Abnormal mass of tissue that results from uncontrolled cell growth; a tumor may be benign or malignant.

U

Umami: One of the 5 basic tastes sensed by the taste buds. It describes the flavor common to savory foods like meat and cheese.

Unsaturated fatty acid: Fatty acid which has one or more double bonds in its carbon chain.

Urea: Waste product of amino acid breakdown that’s excreted in urine.

V

Vegan: Person who eats plant foods only.

Vegetarianism: Consuming a diet entirely of plant foods and plant products. There are modifications of vegetarianism, e.g., a lacto-ovo-vegetarian diet also includes milk and eggs.

Vein: Blood vessel that transports blood to the heart. Veins have valves that direct the blood back to the heart and help prevent pooling of the blood in the veins.

Villus: Small, finger‑like projection in the inner lining of the small intestine. Functions in digestion and absorption. (Plural, villi.)

Virus: Infectious agent containing DNA or RNA that can cause disease in both plants and animals. They’re smaller than bacteria and, unlike bacteria, can’t reproduce unless they infect a cell.

Vitamin: Essential molecule required in the diet. The 13 vitamins are classified into two groups: fat‑soluble and water‑soluble.

W

Warfarin: Anticoagulant drug that lessens blood clotting by interfering with Vitamin K activity. Also used as a rat poison.

Water‑soluble vitamins: Vitamins that dissolve in water: vitamin C and the eight B‑vitamins.

White muscle fiber: Muscle cell with a high capacity for anaerobic energy production. Important for bursts of muscle activity.