Nutrition: Concepts and Controversies - Chapter 6: The Proteins and Amino Acids

Vocabulary practice flashcards covering protein structure, essential amino acids, digestion, absorption, functions, nitrogen balance, dietary requirements, and plant-based nutrition based on Chapter 6 of Nutrition Concepts & Controversies.

Amino Acid Structure

The structural unit of proteins composed of a central carbon backbone, an amine group containing nitrogen, an acid group, and a distinctive side chain that dictates size, shape, and electrical charge.

Essential Amino Acids

Amino acids that cannot be synthesized by the human body in sufficient quantities to meet physiological needs and therefore must be supplied directly through the diet.

Nonessential Amino Acids

Amino acids that the body is capable of manufacturing for itself from other dietary components and fragments.

Conditionally Essential Amino Acids

Amino acids that are normally nonessential but must be supplied by the diet when specific physiological conditions or illnesses impair the body's ability to synthesize them.

Peptide Bond

A covalent chemical bond formed between the amine group of one amino acid and the acid group of another, linking them together into protein chains.

Polypeptide

A strand consisting of multiple amino acids joined together by peptide bonds, which twists and folds into a functional protein.

Denaturation

The irreversible alteration and unfolding of a protein's three-dimensional structure caused by agents such as heat, acid, alcohol, bases, radiation, or heavy metal salts, resulting in the loss of biological activity.

Hydrochloric Acid (Stomach)

Gastric acid that uncoils and denatures tangled dietary protein strands during digestion and activates the inactive enzyme pepsinogen into active pepsin.

Protein Turnover

The continuous, dynamic bodily process involving the breakdown, amino acid recovery, and resynthesis of cellular proteins.

Buffers

Molecules, such as proteins, that assist in maintaining the acid-base balance of body fluids by taking up or releasing hydrogen ions to prevent significant shifts in pH.

Urea

The principal nitrogenous waste product produced by the liver to eliminate excess, unused nitrogen derived from amino acid deamination, requiring water for excretion through the kidneys.

DRI for Protein

The recommended dietary intake for healthy adults, set at $0.8\,\text{g}$ of protein per kilogram ($0.8\,\text{g/kg}$) of body weight per day ($1.2$ to $1.7\,\text{g/kg/day}$ for athletes).

AMDR for Protein

The Acceptable Macronutrient Distribution Range specifying that $10\%$ to $35\%$ of daily total caloric intake should come from protein.

Nitrogen Balance States

The comparison between nitrogen intake and excretion: positive balance occurs during growth, equilibrium occurs in healthy maintenance, and negative balance occurs during muscle wasting or trauma.

Positive Nitrogen Balance

A nutritional state where nitrogen intake exceeds daily nitrogen excretion, observed in growing children, pregnant women, and individuals gaining muscle mass.

Negative Nitrogen Balance

A state where nitrogen excretion exceeds nitrogen intake, signifying net body protein breakdown, commonly occurring in astronauts and surgery patients.

Nitrogen Equilibrium

The baseline state where daily dietary nitrogen intake precisely equals daily nitrogen output, typical of healthy college students and healthy retirees.

Limiting Amino Acid

An essential amino acid that is present in a dietary protein in an insufficient amount relative to the body's need, thereby limiting protein synthesis.

Complementary Proteins

Two or more dietary protein sources (such as legumes and grains) whose incomplete amino acid patterns balance each other so that the limiting amino acids of one are supplied by the other.

Gluten

A specific structural protein found in grains such as wheat, barley, rye, and triticale that triggers immune responses in individuals with celiac disease.

Plant-Based Diet

An eating pattern composed primarily of vegetables, grains, legumes, fruits, and nuts, which may or may not include limited amounts of animal products such as meat, dairy, fish, or poultry.