Nutrition and Energy Metabolism Vocabulary Review

Comprehensive vocabulary flashcards covering carbohydrates, lipids, proteins, energy metabolism pathways, and clinical conditions across Chapters 5, 6, 7, and 8.

Carbohydrates

A class of nutrients that is a major source of energy for the body, classified as simple or complex and derived primarily from plants.

Monosaccharide

A simple sugar that serves as the basic molecular unit of carbohydrates, possessing the chemical formula $C_6H_{12}O_6$.

Glucose

A monosaccharide that serves as the primary fuel for muscles, red blood cells, and the nervous system; commonly known as "blood sugar".

Fructose

A monosaccharide found naturally in fruits, honey, and certain vegetables; commonly known as "fruit sugar".

Galactose

A monosaccharide that is an essential component of lactose, the sugar found in cow's milk.

Disaccharide

A simple sugar composed of two monosaccharide molecules bonded together.

Maltose

A disaccharide composed of two glucose molecules; commonly referred to as "malt sugar".

Sucrose

A disaccharide composed of one glucose molecule and one fructose molecule; commonly known as "table sugar".

Lactose

A disaccharide composed of one glucose molecule and one galactose molecule; commonly referred to as "milk sugar".

Condensation Reaction

A chemical reaction in which two molecules bond to form a larger molecule, releasing a water molecule in the process.

Nutritive Sweeteners

Substances that sweeten foods and contribute digestible energy, supplying $4\,kcal/g$ for mono- and disaccharides.

Sugar Alcohols

Alternative sweeteners such as sorbitol, xylitol, and mannitol that supply $2\,kcal/g$, are not fully absorbed in the intestinal tract, and do not promote dental decay.

Nonnutritive Sweeteners

A group of synthetic or natural high-intensity compounds that taste intensely sweet compared to sugar while supplying little to no kilocalories per serving.

Aspartame

A nonnutritive sweetener $200\text{ times}$ sweeter than sugar that contains phenylalanine and aspartic acid, requiring avoidance by individuals with PKU.

Oligosaccharide

A complex carbohydrate comprised of $3\text{ to }10$ monosaccharides bonded together, such as raffinose and stachyose.

Polysaccharide

A complex carbohydrate comprised of $10\text{ or more}$ monosaccharides bonded together.

Starch

A storage polysaccharide in plants composed of amylose (linear polymer) and amylopectin (branched polymer), providing $4\,kcal/g$.

Glycogen

A highly branched storage polysaccharide in animals stored mainly in liver and muscle tissue.

Dietary Fiber

Nondigestible plant material composed mostly of polysaccharides whose monosaccharide bonds cannot be broken by human digestive enzymes.

Soluble Fiber

Forms of dietary fiber (such as pectins, gums, and mucilages) that dissolve or swell in water, delaying stomach emptying, slowing glucose absorption, and lowering blood cholesterol.

Insoluble Fiber

Forms of dietary fiber (such as cellulose, hemicelluloses, and lignin) that generally do not dissolve in water, increasing fecal bulk and speeding transit through the GI tract.

Pancreatic Amylase

An enzyme secreted by the pancreas into the small intestine that breaks down starch into maltose molecules.

Insulin

An anabolic hormone secreted by pancreatic beta cells that lowers blood glucose levels by enabling cellular glucose entry and promoting storage pathways.

Glucagon

A catabolic hormone secreted by pancreatic alpha cells that elevates blood glucose levels by stimulating glycogenolysis, gluconeogenesis, and lipolysis.

Ketone Bodies

Molecules (acetoacetate, beta-hydroxybutyrate, and acetone) synthesized in the liver from acetyl CoA when blood glucose levels are low.

Ketosis

An adaptive metabolic state in which the body primarily uses fat-derived ketone bodies for energy.

Ketoacidosis

A dangerous, potentially life-threatening condition in which excessive ketone bodies accumulate in the bloodstream, severely acidifying blood pH.

Hyperglycemia

An abnormally elevated level of glucose in the bloodstream, defined as a fasting level of $\ge 126\,mg/dL$ for diabetes diagnosis.

Type 1 Diabetes

An autoimmune disease characterized by the immune destruction of pancreatic beta cells, requiring exogenous insulin administration.

Type 2 Diabetes

The most common form of diabetes, characterized by insulin resistance in target cells despite ongoing pancreatic insulin production.

Glycemic Index (GI)

A standard tool that measures the body's relative blood insulin and glucose response to a specific carbohydrate-containing food.

Glycemic Load (GL)

A measurement of the body's insulin response to a food that accounts for both its Glycemic Index and the total carbohydrate content in a typical serving size.

Metabolic Syndrome

A clinical condition diagnosed by having at least three risk markers (large waist circumference, elevated blood pressure, high triglycerides, low HDL, elevated fasting glucose) that increase CVD and type 2 diabetes risk.

Lactose Intolerance

The inability to digest lactose properly due to an insufficiency of the intestinal brush-border enzyme lactase.

Energy Metabolism

The sum total of all chemical pathways in the body that break down molecules to release energy and utilize energy to synthesize new compounds.

Catabolism

Metabolic pathways that break down larger complex molecules into smaller ones, releasing energy.

Anabolism

Metabolic pathways that construct larger molecules from smaller precursors, requiring energy input.

Coenzymes

Organic compounds, often derived from B vitamins, that assist enzymes in carrying out biochemical reactions.

Adenosine Triphosphate (ATP)

A high-energy molecule comprised of adenosine attached to three inorganic phosphate groups that acts as the universal cellular energy currency.

Phosphorylation

An anabolic chemical reaction that attaches an inorganic phosphate group to ADP, storing energy to reform ATP.

Mitochondria

Double-membraned cell organelles responsible for synthesizing the majority of cellular ATP via aerobic metabolic pathways.

Aerobic Metabolism

Oxygen-requiring metabolic pathways in mitochondria that completely oxidize fuels to yield ATP, $CO_2$, and $H_2O$.

Anaerobic Metabolism

Metabolic pathways for ATP production that function in the absence of oxygen, yielding significantly less ATP per substrate molecule.

Glycolysis

An anaerobic cytoplasmic pathway that oxidizes one $6\text{-carbon}$ glucose molecule into two $3\text{-carbon}$ pyruvate molecules, generating a net $2\text{ ATP}$ and $2\text{ NADH}$.

Cori Cycle

The metabolic pathway in which muscle-derived lactate enters the bloodstream, is taken up by the liver, converted back into glucose via gluconeogenesis, and returned to circulation.

Citric Acid Cycle

A mitochondrial pathway that oxidizes acetyl CoA to $CO_2$, releasing high-energy electrons to $NAD^+$ and FAD coenzymes.

Oxaloacetate

A four-carbon intermediate of the citric acid cycle that combines with two-carbon acetyl CoA in the initial reaction step to form citrate.

Electron Transport Chain

A series of mitochondrial inner-membrane complexes that transfer electrons from NADH and $FADH_2$ to oxygen, driving ATP synthesis via oxidative phosphorylation.

Glycogenolysis

The catabolic process of breaking down stored glycogen into glucose molecules, requiring the coenzyme PLP (Vitamin B-6).

Gluconeogenesis

The anabolic synthesis of glucose from noncarbohydrate precursors such as glycerol, lactate, pyruvate, and glucogenic amino acids.

Hormone-Sensitive Lipase (HSL)

An enzyme inside adipocytes that cleaves fatty acids from triglycerides during times of low blood glucose and suppressed insulin levels.

Carnitine

A carrier molecule required to transport activated fatty acids from the cytoplasm across mitochondrial membranes into the matrix for beta-oxidation.

Beta-Oxidation

The catabolic mitochondrial pathway that sequentially cleaves two-carbon segments from fatty acid chains to produce acetyl CoA, NADH, and $FADH_2$.

Ketogenesis

The hepatic synthesis of ketone bodies from excess acetyl CoA when carbohydrate availability is severely restricted.

Glucogenic Amino Acids

Amino acids whose carbon skeletons can be catabolized into pyruvate or citric acid cycle intermediates to synthesize glucose.

Ketogenic Amino Acids

Amino acids that enter energy pathways directly as acetyl CoA and can be converted into ketone bodies or fatty acids.

Adaptive Thermogenesis

The physiological process of dissipating energy as heat in mitochondria in response to cold temperatures, dietary intake, or hormonal cues.

Nonexercise Activity Thermogenesis (NEAT)

Energy expended during involuntary or spontaneous physical actions such as fidgeting, posture adjustment, and muscle maintenance.

Cortisol

A catabolic adrenal steroid hormone released during stress that promotes protein breakdown and hepatic gluconeogenesis.

Epinephrine

An adrenal hormone secreted during emergency or physical exertion that rapidly accelerates glycogenolysis and lipolysis.

Nonalcoholic Fatty Liver Disease (NAFLD)

An abnormal buildup of triglycerides in liver cells independent of heavy alcohol consumption, strongly linked to insulin resistance and excessive fructose intake.

Ethanol

A simple two-carbon alcohol molecule ($CH_3-CH_2-OH$) found in alcoholic beverages that provides $7\,kcal/g$ upon metabolism.

Blood Alcohol Concentration (BAC)

The percentage measurement reflecting the concentration of alcohol circulating in the bloodstream, with $0.08\%$ defining legal intoxication for drivers $\ge 21\text{ years}$ in the US.

Alcohol Dehydrogenase Pathway

The primary hepatic pathway for alcohol breakdown, converting ethanol first to toxic acetaldehyde via alcohol dehydrogenase, and then to acetate via aldehyde dehydrogenase.

Microsomal Ethanol-Oxidizing System (MEOS)

A secondary liver enzyme system that metabolizes excessive quantities of alcohol, generating heat and increasing hypothermia risk.

Cirrhosis

An irreversible liver condition characterized by extensive scar tissue formation and cell destruction resulting from chronic injury such as alcoholism or hepatitis.

Proteins

Large, complex organic molecules composed of amino acids linked by peptide bonds, containing carbon, hydrogen, oxygen, and nitrogen.

Amino Acid

The structural building block of proteins, featuring a central carbon anchored to a hydrogen, an amino group, a carboxylic acid group, and a variable side chain (R group).

Nonessential Amino Acids

The group of $11\text{ amino acids}$ that the human body can synthesize internally in sufficient quantities.

Essential Amino Acids

The group of $9\text{ amino acids}$ that cannot be synthesized by the human body and must be supplied by the diet.

Conditionally Essential Amino Acid

An amino acid that is normally nonessential but must be supplied by the diet under specific physiological conditions or disease states.

Peptide Bond

The chemical covalent bond linking the carboxylic acid group of one amino acid to the amino group of an adjacent amino acid.

Polypeptide

A long chain polymer consisting of $50\text{ or more}$ amino acids linked together by peptide bonds.

Primary Structure

The linear sequential order of specific amino acids linked by peptide bonds within a polypeptide chain.

Secondary Structure

The localized folding or coiling pattern (such as alpha-helices or beta-pleated sheets) of a polypeptide chain.

Tertiary Structure

The complete three-dimensional, folded, and twisted spatial arrangement of an entire polypeptide chain.

Quaternary Structure

The complex protein structure formed by the interaction and assembly of two or more independent polypeptide chains (e.g., hemoglobin).

Denaturation

The process of altering a protein's natural 3D shape and biological function by exposing it to heat, acids, bases, or mechanical agitation.

Sickle Cell Anemia

An inherited blood disorder caused by a genetic mutation altering a single amino acid in hemoglobin chains, creating misshapen, sickled red blood cells.

Complete Protein

A high-quality protein food source containing adequate proportions of all nine essential amino acids with high human digestibility.

Incomplete Protein

A low-quality protein food source that lacks sufficient amounts of one or more of the nine essential amino acids.

Limiting Amino Acid

The specific essential amino acid present in the smallest concentration relative to human requirements in an incomplete protein food.

Pepsin

An active gastric enzyme activated by hydrochloric acid that initiates protein digestion by cleaving denatured polypeptides into smaller peptide fragments.

Protein Turnover

The continuous physiological cellular process of degrading body proteins and recycling their constituent amino acids.

Deamination

The enzymatic removal of the nitrogen-containing amino group ($NH_2$) from an amino acid, yielding a carbon skeleton and ammonia.

Transamination

The reversible enzymatic transfer of an amino group from an unneeded amino acid to a carbon skeleton to synthesize a new amino acid.

Blood Urea Nitrogen (BUN)

A clinical blood assay measuring urea concentration used to evaluate renal function and protein intake balance, with a normal range of $6\text{ to }20\,mg/dL$.

Positive Nitrogen Balance

A physiological state in which total daily nitrogen intake exceeds total nitrogen losses, occurring during growth, pregnancy, and tissue repair.

Negative Nitrogen Balance

A physiological state in which total daily nitrogen losses exceed nitrogen intake, seen during starvation, severe illness, burns, or physical trauma.

Complementary Combinations

The dietary practice of combining different plant foods whose limiting amino acids mutualize to yield all nine essential amino acids.

Marasmus

A severe form of protein-energy malnutrition resulting from starvation, leading to severe body wasting, emaciation, and loss of subcutaneous fat.

Kwashiorkor

A form of protein-energy malnutrition caused by inadequate high-quality protein consumption despite sufficient calories, leading to peripheral edema and swollen abdomen.

Anaphylaxis

A severe, systemic, life-threatening allergic reaction resulting in airway constriction and a dangerous drop in blood pressure.

Celiac Disease

An autoimmune disorder triggered by dietary gluten, resulting in immune destruction of small intestinal villi and severe nutrient malabsorption.

Non-Celiac Gluten Sensitivity (NCGS)

A clinical dietary intolerance to wheat products presenting IBS-like gastrointestinal and systemic symptoms without autoimmune villous atrophy.

Phenylketonuria (PKU)

An inherited metabolic disorder caused by a lack of active phenylalanine hydroxylase, preventing conversion of phenylalanine to tyrosine and causing toxic neural accumulation.

Nutrigenomics

The scientific discipline studying how specific dietary nutrients and food components directly influence gene expression and genome activity.

Nutrigenetics

The scientific discipline studying how inherited genetic variations alter an individual's metabolic response to specific nutrients and diets.

Lipids

A major class of organic macronutrients that do not dissolve in water, encompassing triglycerides, phospholipids, and sterols.

Fatty Acid

A hydrocarbon chain found in lipids with a methyl (omega) group at one end and a carboxylic acid group at the opposite end.