Human Nutrition: Proteins

Proteins

Essential for body regulation and maintenance.

Calories per gram

Proteins provide 4 calories of energy.

Lean body tissue

Proteins constitute 17% of lean body mass.

Amino acids

Building blocks of proteins, consist of four atoms.

Essential amino acids

9 amino acids not synthesized by the body.

Nonessential amino acids

11 amino acids synthesized by the body.

Conditionally essential amino acids

Amino acids needed during illness or malnutrition.

Phenylketonuria (PKU)

Genetic disorder affecting phenylalanine metabolism.

Dipeptide

Protein made of 2 amino acids.

Tripeptide

Protein made of 3 amino acids.

Oligopeptide

Protein made of 4 to 9 amino acids.

Polypeptide

Protein made of more than 10 amino acids.

Peptide bond

Chemical bond linking amino acids in proteins.

Denaturation

Change in protein shape reducing its activity.

Heat-based denaturation

Cooking alters protein structure for digestion.

Acid-based denaturation

Cooking with acids enhances flavor and tenderness.

Incomplete proteins

Do not provide all essential amino acids.

Complete proteins

Contain all essential amino acids in sufficient amounts.

Complementary proteins

Two incomplete proteins combined to form complete protein.

Protein digestion

Begins with cooking and continues in stomach.

Pepsin

Gastric enzyme breaking down proteins in stomach.

Trypsin

Pancreatic enzyme further digesting proteins in small intestine.

RDA for protein

0.8 - 1 g protein per kg body weight.

Protein consumption recommendations

10 - 15% of total calories from protein.

Protein malnutrition

Insufficient protein intake affecting health.

Protein functions

Includes building body components and immune function.