Chapter 6 – Proteins & Amino Acids

Vocabulary flashcards covering key terms and concepts from the Chapter 6 lecture on proteins and amino acids.

Protein

Molecule made of carbon, hydrogen, oxygen, and nitrogen arranged in strands of amino acids.

Amino Acid (AA)

Protein building block containing a central carbon, an amine group, an acid group, and a unique side chain.

Essential (Indispensable) Amino Acid

Amino acid the body cannot synthesize in adequate amounts and must obtain from food.

Conditionally Essential Amino Acid

Amino acid that becomes essential during certain conditions such as illness or rapid growth (e.g., histidine).

Peptide Bond

Chemical bond linking two amino acids together in a protein chain.

Dipeptide

Compound consisting of two linked amino acids.

Tripeptide

Compound consisting of three linked amino acids.

Polypeptide

Chain of more than three amino acids that forms part or all of a protein.

Protein Denaturation

Uncoiling of a protein’s shape by heat, acid, or other factors, making it easier to digest.

Protein Digestion

Breakdown of proteins starting with HCl and pepsin in the stomach and continuing with pancreatic and brush-border enzymes in the small intestine.

Pepsin

Stomach enzyme that cleaves peptide bonds after proteins are denatured by gastric acid.

Pancreatic Enzymes

Protein-splitting enzymes released into the small intestine that cut polypeptides into di- and tripeptides.

Brush Border Enzymes

Enzymes on intestinal microvilli that split di- and tripeptides into single amino acids for absorption.

Protein Absorption

Uptake of amino acids and small peptides by intestinal cells followed by release into the bloodstream and transport to the liver.

Protein Synthesis

Cellular process in which DNA dictates the specific sequence of amino acids to build a protein.

Sickle Cell Disease

Genetic disorder caused by one incorrect amino acid in hemoglobin, producing misshapen red blood cells.

Working Proteins

Functional proteins such as enzymes, antibodies, hormones, and oxygen carriers.

Structural Proteins

Proteins that provide support in tendons, ligaments, muscles, bones, teeth, hair, and nails.

Gluconeogenesis

Formation of glucose from amino acid carbon skeletons after removal of the amino group.

Lipogenesis

Conversion of amino acid carbon skeletons to fat for fuel or storage after deamination.

Protein Buffer

Protein that helps maintain acid-base balance by accepting or releasing hydrogen ions.

Edema

Swelling caused by fluid accumulation when low blood protein reduces fluid return to the bloodstream.

Complementary Proteins

Two or more plant proteins whose amino acid patterns together supply all essential amino acids.

High-Quality Protein

Protein that is highly digestible and contains ample amounts of all essential amino acids.

Protein Digestibility

Percentage of ingested protein that is absorbed; generally >90 % for animal sources and 70–90 % for plant sources.

PDCAAS

Protein Digestibility-Corrected Amino Acid Score (0–100) that rates protein quality using amino acid content and digestibility.

Nitrogen Balance

Comparison of nitrogen intake with nitrogen excretion to assess protein status.

Positive Nitrogen Balance

State in which nitrogen intake exceeds excretion, typical of growth, pregnancy, or tissue repair.

Negative Nitrogen Balance

State in which nitrogen excretion exceeds intake, seen during illness, injury, or starvation.

Protein Energy Malnutrition (PEM)

Deficiency of protein and/or energy leading to conditions such as marasmus and kwashiorkor.

Marasmus

Chronic severe undernutrition in children under two causing extreme wasting without edema.

Kwashiorkor

Acute protein deficiency in 1–3-year-olds marked by edema, some wasting, and fatty liver.

Amino Acid Wasting

Loss of amino acids for protein building when energy, essential amino acids, or overall protein is inadequate or oversupplied.

Protein Recommendation (DRI)

Adult guideline of 0.8 g protein per kg body weight, or 10–35 % of total energy.

Protein Excess

Intake above 35 % of calories from protein, linked to renal stress, bone mineral loss, and high saturated fat intake.

High-Protein Diet

Weight-loss plan low in carbohydrate that promotes ketosis and increases urea production.

Vegetarian Diet

Eating pattern centered on plant foods with some or all animal products excluded.

Vegan

Vegetarian who consumes only plant-based foods, excluding all animal-derived products.

Lacto-Ovo-Vegetarian

Vegetarian who eats dairy products and eggs but no meat, poultry, or fish.

Lacto-Vegetarian

Vegetarian who consumes dairy products but no eggs, meat, poultry, or fish.

Ovo-Vegetarian

Vegetarian who eats eggs but no dairy, meat, poultry, or fish.

Pescatarian (Pesco-Vegetarian)

Person who eats fish but avoids red meat and poultry.

Fruitarian

Diet consisting mainly of raw or dried fruits, seeds, and nuts.

Macrobiotic Diet

Highly restrictive diet that gradually limits foods to primarily brown rice and herbal tea, risking malnutrition.

Complementary Protein Timing

Practice of consuming complementary proteins within the same day to obtain all essential amino acids.