Jake W: Nutrition Quiz #2

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Proteins

The predominant structural and functional material in every cell, containing carbon, hydrogen, oxygen, and nitrogen, and constructed from chains of $20$ amino acids.

Peptide

A chain of fewer than $50$ amino acids, distinguished from longer amino acid chains that fold into specific three-dimensional proteins.

Protein Turnover

The continuous biological process of breaking down and rebuilding body proteins using amino acids from food, recycled body protein, and the amino-acid pool.

Collagen

The body's most abundant protein, responsible for structural support in connective tissues such as tendons, ligaments, and bones.

Protein Denaturation

The unfolding or alteration of a protein's three-dimensional shape caused by heat, acids, bases, salts, or mechanical agitation, which changes its function without altering its primary amino-acid sequence.

Pepsin

A stomach enzyme activated by hydrochloric acid that hydrolyzes and breaks down denatured proteins into shorter polypeptides.

Essential Amino Acids

The nine amino acids that cannot be synthesized by the human body and therefore must be consumed through dietary food sources.

Nonessential Amino Acids

The eleven amino acids that the body can synthesize internally from other amino acids or by adding nitrogen to carbon skeletons.

Conditionally Essential Amino Acids

Amino acids that are normally nonessential, but must be obtained from food during illness, stress, or when precursor molecules and necessary enzymes are lacking.

Nitrogen Balance

The state in which the amount of nitrogen consumed in dietary protein precisely equals the amount of nitrogen excreted, primarily via the urine.

Positive Nitrogen Balance

A physiological state where the body retains more nitrogen than it excretes to synthesize new tissue, occurring in infants, growing children, and during pregnancy.

Negative Nitrogen Balance

A physiological state where nitrogen excretion exceeds intake due to protein breakdown outstripping synthesis, typical during starvation, severe injury, or acute illness.

Complete Proteins

Proteins that contain all nine essential amino acids in adequate amounts; examples include animal proteins, soy, and quinoa.

Incomplete Proteins

Proteins that are low or lacking in one or more essential amino acids, characteristic of many plant foods and gelatin.

Complementary Proteins

Two or more incomplete plant protein sources combined over the course of a day (such as beans and grains) to supply limiting essential amino acids.

PDCAAS (Protein Digestibility Corrected Amino Acid Score)

A protein quality evaluation score expressed as a percentage that combines protein digestibility and amino-acid profile, serving as the basis for %DV on food labels.

Protein RDA

The baseline adult recommendation of $0.8\,\text{g}$ of protein per kilogram of body weight per day to avoid deficiency, calculated by dividing weight in pounds by $2.2$ and multiplying by $0.8$.

Protein-Energy Malnutrition (PEM)

A condition caused by an inadequate intake of dietary calories, protein, or both, commonly seen in young children facing poverty, early weaning, or unsanitary conditions.

Marasmus

A form of severe protein-energy malnutrition caused by severe calorie deficiency, characterized by extreme emaciation, loss of fat stores, and stunted growth.

Kwashiorkor

A severe protein deficiency condition characterized by edema, muscle loss, skin rashes, hair changes, and severe fluid and electrolyte imbalances.

Vitamins

A family of $13$ ‘mostly’ essential, organic micronutrients needed in small amounts for growth, reproduction, and overall physiological health that do not yield calories.

Fat-Soluble Vitamins

Vitamins A, D, E, and K, which require dietary fat for absorption, are incorporated into micelles and chylomicrons, travel via lymph, and accumulate in the liver, fat, and muscle.

Water-Soluble Vitamins

The B-complex vitamins and vitamin C, which are absorbed with water directly into the bloodstream, are generally not stored (except $B_{12}$), and have excess amounts excreted in urine.

Antioxidants

Substances including vitamin C, vitamin E, and beta-carotene that counteract oxidation by donating electrons to neutralize harmful free radicals.

Free Radicals

Unstable, highly reactive oxygen-containing molecules generated during metabolism or from environmental exposures that can damage cellular components.

Bioavailability

The degree to which a ingested nutrient is absorbed from food and made available for metabolic use in the body.

Folate

The naturally occurring form of vitamin $B_9$ in food, essential for DNA synthesis, cell division, and healthy red blood cell production; deficiency causes macrocytic anemia.

Folic Acid

The synthetic form of vitamin $B_9$ used in supplements and fortified foods, absorbed about $1.7$ times more efficiently than natural food folate.

Neural Tube Defects

Severe birth defects such as spina bifida and anencephaly resulting from maternal folate deficiency during early embryonic development.

Intrinsic Factor

A gastric secretion required for the proper binding and absorption of vitamin $B_{12}$ in the lower small intestine, the absence of which leads to pernicious anemia.

Major Minerals

Essential inorganic elements required in dietary quantities greater than $100\,\text{mg/day}$, including calcium, sodium, potassium, and magnesium.

Trace Minerals

Essential inorganic elements required in small amounts of less than $20\,\text{mg/day}$, including iron, zinc, iodine, and fluoride.

Fluorosis

A cosmetic condition resulting in the mottling or staining of tooth enamel caused by excessive fluoride consumption during infancy and early childhood tooth formation.

Heme Iron

The more readily absorbed form of iron derived from hemoglobin and myoglobin in animal flesh (meat, fish, poultry).

Nonheme Iron

The form of iron found in plant foods and enriched grain products, which has a lower absorption rate that is enhanced by the presence of vitamin C.

Hemochromatosis

A genetic disorder causing excessive intestinal iron absorption and systemic overload, leading to potential damage in the heart, liver, and kidneys.

Hyperkalemia

An elevated potassium concentration in the blood that can disrupt normal cardiac rhythm and cause fatal arrhythmias.

Hypokalemia

A dangerously low level of blood potassium, often induced by vomiting, diarrhea, or eating disorders, causing muscle weakness, cramps, and paralysis.

Body Mass Index (BMI)

A screening metric calculated from weight and height that categorizes adults as underweight ($< 18.5$); desirable ($18.5\text{--}24.9$); overweight ($\ge 25$); or obese ($\ge 30$).

Basal Metabolic Rate (BMR)

The minimum energy required to sustain basic involuntary life-supporting processes, representing roughly $60\%$ of total daily energy expenditure and chiefly determined by lean body mass.

Thermic Effect of Food (TEF)

The energy expended by the body to digest, absorb, transport, and metabolize ingested food, accounting for approximately $10\%$ of consumed calories.

NEAT (Non-Exercise Activity Thermogenesis)

The energy expended for all spontaneous physical activity outside of planned exercise, including standing, pacing, and fidgeting.

Ghrelin

A stomach-derived hormone that acts on the brain to stimulate appetite and trigger the sensation of hunger.

Leptin

A hormone produced by adipose tissue that communicates energy sufficiency to the brain, promoting satiety and fullness.

Volumetrics

A dietary approach emphasizing foods with low energy density and high water and fiber content, allowing individuals to consume satisfying volumes with reduced calories.

Anorexia Nervosa

An eating disorder characterized by self-starvation, severe calorie restriction, an intense fear of gaining weight, and significantly low body weight.

Bulimia Nervosa

An eating disorder characterized by recurring cycles of binge eating followed by compensatory purging behaviors such as self-induced vomiting.

VO x Max

A physiological measure of cardiorespiratory fitness representing the maximum volume of oxygen the muscles can extract and utilize during maximal exertion.

FITT Principle

A foundational fitness prescription framework defining Frequency (how often), Intensity (how hard), Time (duration), and Type (activity mode).

Carbohydrate Loading

A nutrition strategy used prior to prolonged endurance competition to maximize muscle glycogen reserves and postpone fatigue or 'hitting the wall'.