Biochemistry: Proteins and Amino Acids

Food Proteins

• Essential macronutrients, composed of amino acids
• Vital for bodily functions

Protein Degradation

• Natural process breaking proteins into amino acids
• Ensures cellular quality control and homeostasis
• Ubiquitin-proteasome pathway and autophagy-lysosome pathway are primary mechanisms

Emulsions

• Mixtures of two or more immiscible liquids
• Stabilized by emulsifiers, preventing separation

Amino Acids

• Essential amino acids cannot be produced by the body and must be obtained from the diet
• Non-essential amino acids can be produced by the body
• Amino acids have an amino group (-NH2), a carboxyl group (-COOH), and a side chain (R group)

Protein Structure

• Primary: Linear sequence of amino acids in a polypeptide chain
• Secondary: Local folding patterns (alpha-helices and beta-sheets) stabilized by hydrogen bonds
• Tertiary: Three-dimensional shape of a single polypeptide chain, determined by side chain interactions
• Quaternary: Arrangement of multiple polypeptide chains to form a functional protein complex

Protein Classification

• Globular: Spherical, often soluble in water (enzymes, hormones, antibodies)
• Fibrous: Long, fibrous, often insoluble in water (collagen, keratin, elastin)
• Simple: Composed only of amino acids
• Conjugated: Contain a non-protein component (metal ion, lipid, carbohydrate)

Lipid Degradation (Rancidity)

• Undesirable changes over time, leading to quality deterioration
• Primarily driven by hydrolysis and oxidation, altering lipid structure and properties

Types of Lipid Degradation

• Hydrolysis: Lipid breakdown by water, releasing free fatty acids and glycerol
• Oxidation: Lipid reaction with oxygen, forming free radicals and oxidation products
• Polymerization: Lipid molecules reacting to form polymers, affecting viscosity and texture
• Isomerization: Rearranging double bonds in unsaturated fatty acids, changing melting point and reactivity
• Photolysis: Lipid breakdown by light, forming free radicals and degradation products

Lipid Technology: Refinement and Modification

• Degumming: Removing non-lipid impurities
• Neutralization: Removing free fatty acids
• Bleaching: Removing pigments
• Deodorization: Removing off-flavors
• Hydrogenation: Converting unsaturated to saturated fatty acids (increasing melting point and stability)
• Interesterification: Rearranging fatty acids within triglycerides (altering melting point and texture)
• Fractionation: Separating lipids into fractions by controlled crystallization
• Enzymatic Modification: Using enzymes to selectively modify lipids

Lipids in Food

• Flavor and texture: Dissolving flavor molecules, creating smooth/creamy textures
• Satiety: Contributing to feelings of fullness
• Cooking and Baking: Heat transfer medium, influencing food texture

Lipid Structure

• Fatty acids: Saturated or unsaturated, depending on presence of double bonds
• Phospholipids: Glycerol backbone with two fatty acids and a phosphate group
• Glycolipids: Glycerol backbone with one or two fatty acids and a carbohydrate group
• Sterols: Four-ring structure and a hydroxyl group
• Waxes: Esters of long-chain fatty acids and long-chain alcohols

Carbohydrates

• Glucose is the most abundant carbohydrate, with 6 carbon atoms.
• Classified into fast-releasing and slow-releasing types.
• Monosaccharides include glucose, fructose, and galactose
• Dissacharides include lactose, maltose, and sucrose

Carbohydrate Structure

• Open chain: Long straight-chain form
• Hemi-acetal: Cyclized structure
• Haworth: Ring structure of carbohydrates

Carbohydrate Physical Properties

• Stereoisomers: Compounds with the same chemical formula but different spatial arrangement
• Optical activity: Rotation of plane-polarized light, forming (+) and (-) glucose
• Diastereoisomers: Configurational changes concerning C2, C3, or C4 on glucose
• Annomerism: Spatial configuration concerning the first carbon atom on aldoses and the second carbon on ketoses

Carbohydrate Chemical Properties

• Osazone formation: Reaction with phenylhydrazine to produce osazones
• Oxidation: Monosaccharides acting as reducing sugars, converting carbonyl groups to carboxylic acids

Functional Protein Properties in Food

• Water absorption and retention
• Solubility
• Color (Maillard reaction)
• Gelation
• Viscosity and texture
• Emulsification
• Foam formation
• Flavor binding
• Curdling
• Enzymatic Browning: non-enzymatic browning caused by the action of an enzyme (polyphenol oxidase) which oxidizes phenol compounds in food in the presence of oxygen leading to a brown product called melanin.

Denaturation

• Proteins losing their quaternary, tertiary, and secondary structure under certain conditions: strong acids/bases, high temperature, organic solvents, radiation etc

Explore the essential macronutrients known as food proteins and their roles in bodily functions. This quiz delves into protein structure, degradation processes, and the characteristics of amino acids. Test your knowledge on emulsions and the significance of protein quality control.