Chapter 6: Protein and Amino Acids Vocabulary Flashcards

Vocabulary flashcards covering basic chemical structures, digestion, body utilization, protein quality, and recommended intake from Chapter 6.

Amino acid

The building block of protein, consisting of a central carbon attached to an amino group ($-NH_2$), a carboxyl/acid group ($-COOH$), a hydrogen, and a unique R group (side chain).

Essential amino acids

The $9$ amino acids that the body cannot make enough of, which must be obtained from food.

Nonessential amino acids

Amino acids that the body can normally synthesize on its own.

Conditionally essential amino acids

Amino acids that the body can usually make, but become required from the diet during periods of rapid growth, illness, or injury.

Peptide bond

The chemical bond that joins amino acids together to form peptides and polypeptides.

Denaturation

A change in a protein's normal functional shape caused by heat, acids, or other conditions, without changing the basic amino-acid sequence.

Hydrochloric acid (HCl)

Acid produced in the stomach that creates an acidic environment and denatures proteins, unfolding them for enzyme access.

Pepsin

A protein-digesting stomach enzyme that begins breaking peptide bonds to form smaller polypeptides and peptides.

Amino acid pool

The body's available supply of amino acids derived from dietary protein and tissue breakdown, used to synthesize proteins and other nitrogen compounds.

Deamination

The removal of the nitrogen-containing amino group from an amino acid before its carbon skeleton is used for energy, glucose production, or fat synthesis.

Urea

A nitrogen-containing waste product produced mainly by the liver from removed amino groups and excreted by the kidneys in urine.

Complete protein

A high-quality protein source, such as animal foods or soy, that provides all $9$ essential amino acids in adequate amounts.

Incomplete protein

A lower-quality protein source, typically from plants, that provides relatively low amounts of one or more essential amino acids.

Limiting amino acid

The essential amino acid present in the shortest supply in a food relative to the body's requirement.

Complementary proteins

Two or more protein sources whose amino-acid patterns complement each other to supply all essential amino acids when combined (e.g., beans and rice).

Protein turnover

The continuous process of breaking down and rebuilding proteins in the body.

Protein RDA

The general adult Recommended Dietary Allowance for protein, which is $0.8$ grams of protein per kilogram of body weight per day ($0.8\,g/kg/day$).

Protein AMDR

The Acceptable Macronutrient Distribution Range for protein in adults, defined as $10-35\%$ of total daily calories.

Positive nitrogen balance

A state in which nitrogen intake exceeds nitrogen loss, indicating that the body is building protein (e.g., during growth, pregnancy, or muscle building).

Negative nitrogen balance

A state in which nitrogen loss exceeds nitrogen intake, indicating that the body is losing protein (e.g., during severe illness, injury, or starvation).