Protein, Amino Acid Metabolism, Minerals, and Vitamins

Comprehensive vocabulary flashcards covering amino acid pools and metabolism, protein structure and requirements, major and trace minerals, water- and fat-soluble vitamins, and dietary phytochemicals.

Amino Acid Pool

A dynamic reservoir of free amino acids (approximately $100\,\text{g}$ in an adult body) that has no anatomical structure but provides readily available building units replenished by protein turnover, dietary intake, and non-essential amino acid synthesis.

Dynamic Equilibrium (Cellular)

The metabolic condition where a cell absorbs as many amino acids as it loses; when loss exceeds uptake, the cell wastes, and when uptake exceeds loss, the cell grows.

Protein Turnover Rate Hierarchy

The relative speed of tissue protein replacement throughout the body, ranked in descending order: intestinal mucosa $>$ kidneys $>$ liver $>$ muscle.

Amino Acid Metabolic Pathway

The biochemical routing of amino acids toward protein synthesis, conversion to keto acids via transamination (producing $\alpha\text{-ketoglutarate}$ and glutamate) for energy, glucose, or fat, and nitrogen synthesis leading to ammonia ($\text{NH}_3$) and urea formation.

Diurnal Amino Acid Fluctuations

The daily biological variation in plasma amino acid concentrations, which reach their lowest level at $4\text{ am}$ and increase by $15\text{--}35\%$ by noon to early afternoon.

Protein Turnover

The net balance between protein remodeling pathways, calculated as: $\text{Protein Turnover} = \text{Protein Synthesis (Anabolic)} - \text{Protein Breakdown (Catabolic)}$.

Minerals

Essential, inorganic chemical elements that provide no caloric energy and are not broken down or degraded by cooking or human digestion.

Major Minerals

Inorganic dietary nutrients required by the body in quantities greater than $100\,\text{mg}$ per day, including sodium, potassium, calcium, phosphorus, magnesium, chloride, and sulfur.

Calcium

The most abundant major mineral in the body; functions in blood clotting, muscle contraction, nerve transmission, and bone formation, with an RDA of $1{,}000\,\text{mg}$ ($19\text{--}50\,\text{years}$) to $1{,}200\,\text{mg}$ ($50+\,\text{females}, 70+\,\text{males}$) and a UL of $2{,}500\,\text{mg}$ ($19\text{--}50\,\text{years}$).

Phosphorus

A major mineral necessary for bone and tooth formation, cell membrane structure, and enzyme activity, having an AI/RDA of $700\,\text{mg}$ and a UL of $4{,}000\,\text{mg}$; toxicity can alter calcium metabolism.

Magnesium

A major mineral involved in bone structure, blood clotting, blood pressure regulation, and enzyme function; features an RDA of $400\text{--}420\,\text{mg}$ for men and $310\text{--}320\,\text{mg}$ for women, with a supplement-specific UL of $350\,\text{mg}$.

Sodium

A major electrolyte operating in fluid balance, nerve transmission, and muscle contraction, with an AI of $1{,}500\,\text{mg}$ and a Chronic Disease Risk Reduction (CDRR) threshold advising reduction of intakes above $2{,}300\,\text{mg}$.

Chloride

A major electrolyte essential for nerve conduction, fluid balance, and digestion as a constituent of gastric hydrochloric acid ($\text{HCl}$), featuring an AI of $2{,}300\,\text{mg}$ and a UL of $3{,}600\,\text{mg}$.

Potassium

A major intracellular electrolyte that facilitates nerve impulse transmission, muscle contraction, and blood pressure regulation, with an AI of $3{,}400\,\text{mg}$ for men and $2{,}600\,\text{mg}$ for women over $19\,\text{years}$.

Iron

A trace mineral essential for oxygen transport and utilization as a component of hemoglobin and myoglobin, with an RDA of $18\,\text{mg}$ for premenopausal women, $8\,\text{mg}$ for men and postmenopausal women ($32\,\text{mg}$ and $14\,\text{mg}$ for vegetarians), and a UL of $45\,\text{mg}$.

Exercise-Induced Iron Depletion

Mechanisms that increase iron deficiency risks in athletes, comprising inadequate dietary intake, sweat loss, training-induced demands for hemoglobin and myoglobin, and mechanical hemolysis.

Zinc

A trace mineral functioning as a cofactor for over $200$ enzymatic reactions, protein synthesis, wound healing, and immune defense; its RDA is $11\,\text{mg}$ for men and $8\,\text{mg}$ for women, with a UL of $40\,\text{mg}$.

Chromium

A trace mineral that enhances insulin function and decreases cellular insulin resistance, featuring an AI of $35\,\mu\text{g}$ for men and $25\,\mu\text{g}$ for women.

Fluoride

A trace mineral that strengthens bones, ligaments, and tendons while protecting teeth against dental caries, having an AI of $4\,\text{mg}$ for men and $3\,\text{mg}$ for women, with a UL of $10\,\text{mg}$.

Copper

A trace mineral serving as an enzyme cofactor in iron metabolism, tissue growth, and antioxidant protection; deficiency can produce Menkes syndrome, while toxicity complications include Wilson's disease (RDA $900\,\mu\text{g}$, UL $10{,}000\,\mu\text{g}$).

Manganese

A trace mineral acting as an enzyme cofactor for metabolic systems, tissue growth, and antioxidant mechanisms, having an AI of $2.3\,\text{mg}$ for men and $1.8\,\text{mg}$ for women, with a UL of $11\,\text{mg}$.

Iodine

A trace mineral required for the synthesis of thyroid hormones; deficiencies or toxicities manifest as goiter (RDA $150\,\mu\text{g}$, UL $1{,}100\,\mu\text{g}$).

Molybdenum

A trace mineral enzyme cofactor involved in antioxidant activity and the catabolism of sulfur-containing amino acids, with an RDA of $45\,\mu\text{g}$ and a UL of $2{,}000\,\mu\text{g}$.

Selenium

A trace mineral incorporated into diverse body proteins and acting as a cofactor for thyroid, immune, and antioxidant systems; deficiency can result in cardiomyopathy, whereas toxicity results in brittle hair and nails (RDA $55\,\mu\text{g}$, UL $400\,\mu\text{g}$).

Other Trace Minerals

Ultratrace elements including arsenic, boron, nickel, silicon, and vanadium that have no established biological function in humans and no justification for dietary supplementation in athletes.

Peptide Bond Formation

The chemical linkage formed between two amino acids when the carboxylic acid group ($-\text{COOH}$) of one binds to the amino group ($-\text{NH}_2$) of another, releasing a molecule of water ($\text{H}_2\text{O}$).

Conditionally Essential Amino Acids

Non-essential amino acids that become indispensable under specific physiological or metabolic circumstances; identified examples include tyrosine and cysteine.

High-Quality Protein

A complete protein source—predominantly derived from animal foods—that exhibits high digestibility and supplies all essential amino acids plus extra amino acids for protein synthesis.

Low-Quality Protein

An incomplete protein source—typically originating from plant foods—that lacks sufficient quantities of one or more limiting essential amino acids.

Complementary Protein Pairing

The dietary practice of combining two incomplete plant proteins—such as grains with legumes, or legumes with nuts/seeds—to provide a full complement of all $9$ essential amino acids.

Nitrogen Balance

A clinical assessment of protein status and nutritional adequacy calculated using the difference formula: $\text{Nitrogen Balance} = (\text{Nitrogen in}) - (\text{Nitrogen out})$.

Daily Protein Recommendations

Established protein intake guidelines: $0.8\,\text{g/kg}$ ($10\text{--}20\%$ of calories) for sedentary individuals, $1.2\text{--}2.0\,\text{g/kg}$ ($15\text{--}35\%$) for athletes, and $\ge 2.0\,\text{g/kg}$ ($25\text{--}35\%$) for special circumstances such as injury or intense training.

Kwashiorkor

A severe form of protein deficiency characterized by edema (swelling), severe muscle wasting, and growth retardation despite adequate total energy consumption.

Marasmus

A severe form of protein-energy malnutrition characterized by extensive wasting of both muscle mass and subcutaneous fat stores along with stunted growth.

Sarcopenia

The progressive, age-related loss of skeletal muscle mass and strength observed in older adult populations.

Branched-Chain Amino Acid (BCAA) Metabolism

The unique metabolic sequence whereby leucine, isoleucine, and valine undergo deamination within skeletal muscle rather than the liver, forming acetyl-CoA and succinyl-CoA for energy production in the citric acid cycle.

Post-Exercise Protein Timing

The recovery protocol recommending the intake of $15\text{--}25\,\text{g}$ of high-quality protein (or $0.25\text{--}0.30\,\text{g/kg}$) rich in essential amino acids (such as whey, casein, or soy) within $2\text{--}3\,\text{hours}$ following athletic activity.

Vitamins

Essential organic micronutrients required for human survival that exist in water-soluble and fat-soluble classifications without contributing direct caloric energy.

Fat-Soluble Vitamins

Vitamins A, D, E, and K, which do not dissolve in water, require dietary lipids for intestinal absorption and blood transport, store in adipose tissue, and pose an increased risk of toxicity.

Thiamin (Vitamin B1)

A water-soluble B vitamin essential for nervous system health and energy production, with an RDA of $1.2\,\text{mg}$ for men, $1.1\,\text{mg}$ for women (or $0.5\,\text{mg}/1{,}000\,\text{kcal}$ expended); extreme deficiency results in beriberi.

Riboflavin (Vitamin B2)

A water-soluble B vitamin functioning in electron transport during aerobic energy metabolism, with an RDA of $1.3\,\text{mg}$ for men and $1.1\,\text{mg}$ for women; deficiency causes cracked lips, sore throat, and an inflamed tongue.

Niacin (Vitamin B3)

A water-soluble B vitamin involved in electron transport across both aerobic and anaerobic pathways (RDA $16\,\text{mg}$ men, $14\,\text{mg}$ women); deficiency causes pellagra, while toxicity over the $35\,\text{mg}$ UL produces flushing and liver complications.

Vitamin B6 (Pyridoxine)

A water-soluble B vitamin facilitating transamination, glycogenolysis, and neural pathways (RDA $1.3\,\text{mg}$); megadoses above the $100\,\text{mg}$ UL cause irreversible peripheral nerve damage and impaired gait.

Vitamin B12 (Cobalamin)

A water-soluble vitamin found naturally only in animal-source foods that supports neural tissue, cardiovascular health, and erythropoiesis (RDA $2.4\,\mu\text{g}$); deficiency causes elevated homocysteine and pernicious anemia.

Folate (Folic Acid)

A water-soluble vitamin required for DNA synthesis, cell division, and red blood cell maturation (RDA $400\,\mu\text{g}$, UL $1{,}000\,\mu\text{g}$); maternal deficiency during gestation causes neural tube defects.

Choline

A water-soluble nutrient functioning in muscle activation and membrane structural integrity, with an AI of $550\,\text{mg}$ for men and $425\,\text{mg}$ for women, and a UL of $3{,}500\,\text{mg}$ (toxicity produces fishy odor and hypotension).

Vitamin C (Ascorbic Acid)

A water-soluble antioxidant vitamin required for collagen synthesis and immune function (RDA $90\,\text{mg}$ men, $75\,\text{mg}$ women; additional $+35\,\text{mg}$ for smokers; UL $2{,}000\,\text{mg}$); severe deficiency produces scurvy.

Vitamin A (Retinoids)

A fat-soluble vitamin necessary for vision, cell differentiation, and immune function (RDA $900\,\mu\text{g}\,\text{RAE}$ men, $700\,\mu\text{g}\,\text{RAE}$ women; UL $3{,}000\,\mu\text{g}\,\text{RAE}$); deficiency causes night blindness and hyperkeratosis.

Vitamin D (Calcitriol)

A fat-soluble vitamin synthesized through skin UV exposure and activated by the liver and kidneys to maintain blood calcium and bone density (RDA $600\,\text{IU}$ up to age $70$, $800\,\text{IU}$ for $70+$; UL $50\,\mu\text{g}$); deficiency causes rickets and osteoporosis.

Vitamin E (Alpha-Tocopherol)

A fat-soluble antioxidant vitamin that protects membrane polyunsaturated fatty acids from free-radical oxidation (RDA $15\,\text{mg}$, UL $1{,}000\,\text{mg}$); deficiency produces hemolytic anemia and ataxia.

Vitamin K (Quinones)

A fat-soluble vitamin family vital for hepatic blood clotting factor synthesis and bone mineralization, having an AI of $120\,\mu\text{g}$ for men and $90\,\mu\text{g}$ for women.

Phytochemicals

Non-nutritive bioactive chemical substances found in plant foods (roughly $50$ consumed in standard diets) that reduce risks for cardiovascular disease and various cancers.

Phenolic Compounds

A broad class of plant phytochemicals—notably flavonoids and phenolic acids found in grapes, wine, and tea—that exhibit antioxidant properties protective against cardiovascular disease.

Organosulfides

Anticancer phytochemical compounds including indoles, isothiocyanates, and glucosinolates present in cruciferous (brassica) vegetables, onions, and garlic.

Lycopene

A carotenoid phytochemical abundant in tomatoes and tomato products that possesses potent antioxidant and anticancer properties.

Amino Acid Pool

A dynamic reservoir of free amino acids (approximately $100\text{ g}$ in the adult body) derived from body protein breakdown, dietary intake, and non-essential amino acid synthesis, having no distinct anatomical structure.

Dynamic Equilibrium (Protein Metabolism)

The metabolic state in which a cell assimilates as many amino acids as it loses; net loss results in cellular wasting, whereas net gain results in cellular growth.

Order of Tissue Protein Turnover

The relative rate at which body tissues turn over protein, ordered from fastest to slowest: intestinal mucosa > kidneys > liver > muscle.

Protein Turnover

The net dynamic balance of protein metabolism calculated as Protein Synthesis (anabolic) minus Protein Breakdown (catabolic).

Diurnal Plasma Amino Acid Fluctuation

The $24\text{-hour}$ biological variation where plasma amino acid levels hit their lowest concentration at $4\text{ am}$ and rise by $15\text{--}35\%$ by noon to early afternoon.

Positive Nitrogen Balance

A metabolic state in which protein synthesis exceeds protein degradation, required for tissue accretion and muscle growth.

Amino Acid Oxidation

The metabolic degradation of amino acids for energy, typically contributing $10\text{--}15\%$ of total body energy requirements and increasing during prolonged, high-intensity exercise or glycogen depletion.

Minerals

Inorganic elements essential for human survival that provide no caloric value and are not destroyed or degraded by cooking or digestion.

Major Minerals

Essential minerals required by the human body in dietary quantities greater than $100\text{ mg}$ per day, including calcium, phosphorus, magnesium, sodium, potassium, and chloride.

Calcium

The most abundant mineral in the body; functions in blood clotting, muscle contraction, nerve impulse transmission, and bone formation, with an RDA of $1{,}000\text{ mg}$ for ages 19–50 and a UL of $2{,}500\text{ mg}$.

Hypocalcemia

A rare deficiency state of calcium characterized clinically by muscle spasms, convulsions, and decreased bone mineral density.

Phosphorus

A major mineral that aids bone and tooth formation, cell membrane structure, and enzyme activity, having an AI of $700\text{ mg}$ and a UL of $4{,}000\text{ mg}$.

Magnesium

A major mineral involved in bone structure, blood clotting, blood pressure regulation, and enzyme catalysis, with an RDA of $400\text{--}420\text{ mg}$ for adult males, $310\text{--}320\text{ mg}$ for adult females, and a supplement UL of $350\text{ mg}$.

Sodium

A major extracellular electrolyte responsible for nerve impulse transmission, muscle contraction, and blood pressure maintenance, with an AI of $1{,}500\text{ mg}$ and a CDRR reduction target for intakes exceeding $2{,}300\text{ mg}$.

Hyponatremia

A clinical deficiency of sodium characterized by low serum sodium concentrations that can manifest as nausea, vomiting, seizures, and coma.

Chloride

A major electrolyte with an AI of $2{,}300\text{ mg}$ and a UL of $3{,}600\text{ mg}$ that maintains fluid balance, facilitates nerve impulse transmission, and aids gastric digestion as hydrochloric acid ($\text{HCl}$).

Potassium

A major intracellular electrolyte that regulates nerve impulses, muscle contraction, and blood pressure, with an AI of $3{,}400\text{ mg}$ for adult males and $2{,}600\text{ mg}$ for adult females.

Iron

A trace mineral essential for oxygen transport and utilization as a central component of hemoglobin and myoglobin, with an RDA of $18\text{ mg}$ for premenopausal women and $8\text{ mg}$ for adult men.

Hemochromatosis

A clinical toxicity condition involving excessive iron accumulation in tissues; iron has a Tolerable Upper Intake Level (UL) of $45\text{ mg}$.

Mechanical Hemolysis

Physical destruction of red blood cells during repetitive impact activity (such as running), identified as a primary contributor to athlete iron depletion alongside sweat loss and inadequate dietary intake.

Zinc

A trace mineral acting as a cofactor in over 200 enzymatic systems, protein synthesis, wound repair, and immune function, with an RDA of $11\text{ mg}$ for men, $8\text{ mg}$ for women, and a UL of $40\text{ mg}$.

Chromium

A trace mineral that enhances the physiological action of insulin and decreases cellular insulin resistance, with an AI of $35\,\mu\text{g}$ for men and $25\,\mu\text{g}$ for women.

Fluoride

A trace mineral functioning in bone and tooth mineralization and ligament strength, with an AI of $4\text{ mg}$ for men, $3\text{ mg}$ for women, and a UL of $10\text{ mg}$ to avoid fluorosis and joint stiffness.

Copper

A trace mineral with an RDA of $900\,\mu\text{g}$ involved in iron metabolism, tissue growth, and antioxidant enzyme systems; deficiency manifests as Menkes syndrome, and toxicity manifests as Wilson's disease.

Manganese

A trace mineral cofactor in metabolism, tissue growth, and antioxidant protection, with an AI of $2.3\text{ mg}$ for men, $1.8\text{ mg}$ for women, and a UL of $11\text{ mg}$.

Iodine

A trace mineral with an RDA of $150\,\mu\text{g}$ and a UL of $1{,}100\,\mu\text{g}$ that is required to synthesize thyroid hormones; both deficiency and toxicity can result in goiter.

Molybdenum

A trace mineral with an RDA of $45\,\mu\text{g}$ and a UL of $2{,}000\,\mu\text{g}$ that functions as an antioxidant cofactor and facilitates the metabolism of sulfur-containing amino acids.

Selenium

A trace mineral component of antioxidant and thyroid enzyme systems, with an RDA of $55\,\mu\text{g}$ and a UL of $400\,\mu\text{g}$; deficiency is linked to cardiomyopathy.

Generic Amino Acid Structure

The fundamental molecular structure consisting of a central alpha-carbon bonded to a hydrogen atom, an amino group ($-\text{NH}_2$), a carboxylic acid group ($-\text{COOH}$), and a distinct side group ($\text{R}$).

Peptide Bond

A covalent chemical linkage formed between the carboxylic acid group ($-\text{COOH}$) of one amino acid and the amino group ($-\text{NH}_2$) of another amino acid, releasing water.

Essential Amino Acids

The nine amino acids that cannot be manufactured endogenously by human physiological processes and must be obtained entirely through dietary sources.

Conditionally Essential Amino Acids

Non-essential amino acids that become indispensable during specific conditions of physiological stress, disease, or prematurity, such as tyrosine and cysteine.

High-Quality (Complete) Protein

A protein that contains all nine essential amino acids in adequate proportions with high bioavailability and digestibility, usually derived from animal foods or soy.

Low-Quality (Incomplete) Protein

A protein source that lacks or has inadequate amounts of one or more essential amino acids (limiting amino acids), characteristic of plant-derived protein sources.

Complementing Proteins

Two or more incomplete protein sources that, when consumed together, mutually supply the limiting amino acids of the other to deliver all essential amino acids (e.g., grains plus legumes).

Nitrogen Balance

A clinical index of nitrogen status and dietary protein adequacy expressed as: $\text{Nitrogen Balance} = (\text{Nitrogen in}) - (\text{Nitrogen out})$.

Daily Protein Recommendation for Sedentary Individuals

The baseline dietary protein requirement of $0.8\text{ g/kg}$ body weight per day, supplying $10\text{--}20\%$ of total daily calories.

Daily Protein Recommendation for Athletes

The daily dietary protein target of $1.2\text{--}2.0\text{ g/kg}$ body weight per day, supplying $15\text{--}35\%$ of total daily calories.

Kwashiorkor

A severe protein deficiency disease characterized by peripheral edema, muscle wasting, and growth retardation.

Marasmus

A severe protein-energy deficiency state characterized by generalized wasting of both somatic muscle and subcutaneous fat alongside growth failure.

Sarcopenia

Age-related involuntary loss of skeletal muscle mass and strength, which can be resisted by higher dietary protein consumption.

Branched-Chain Amino Acids (BCAAs)

Leucine, isoleucine, and valine; amino acids that are unique in their ability to be deaminated and oxidized directly within skeletal muscle tissue rather than requiring hepatic metabolism first.

Post-Exercise Protein Timing

The practice of consuming $15\text{--}25\text{ g}$ of high-quality protein (or $0.25\text{--}0.30\text{ g/kg}$) as soon as possible or within $2\text{--}3\text{ hours}$ after training to stimulate muscle protein synthesis.

Vitamins

Essential organic compounds required in small amounts for physiological maintenance and metabolic functions that do not provide direct energy.

Water-Soluble Vitamins

Vitamins (the B-complex group, choline, and vitamin C) that dissolve in water, circulate easily in blood, are readily excreted in urine when in excess, and carry a low potential for toxicity.