Classifying Proteins

Classifying Proteins

Introduction:

• Proteins can be classified into two main categories: fibrous and globular. This classification is determined by the molecular shape of the protein, which is influenced by hydrogen bonding within the protein molecule.
• Proteins are composed of amino acid molecules linked together through amide (peptide) bonds. These amide links are regularly spaced along the protein chain, allowing for hydrogen bonding between them.

Fibrous Proteins

• Description: Fibrous proteins have long, spiral chains that can easily form sheets and coils, giving them a three-dimensional shape.
• Solubility: Fibrous proteins are generally insoluble in water because their polar groups are located inside the structure, making it difficult to form hydrogen bonds with water molecules.
• Examples: Fibrous proteins serve as the major structural components in animals and are found in tissues like hair, skin, tendons, and muscle.

Globular Proteins

• Description: Globular proteins have a portion of their polar amide links exposed on the outside of their structure, allowing them to form hydrogen bonds with water.
• Solubility: Globular proteins are generally soluble in water and play essential roles in maintaining and regulating various life processes.
• Examples: Globular proteins include haemoglobin, enzymes, and hormones like insulin.

Impact of Temperature on Proteins

• When cooking or preparing meats, different temperatures must be used depending on the protein content in the tissue.
• Tender, Lean Meats: Lean meats like fillet steak should be cooked at lower temperatures to retain their texture. This is because the protein molecules in the meat undergo chemical changes when exposed to heat.

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Classifying Proteins

Protein Structure During Cooking

• Regardless of whether proteins are fibrous or globular, they are held in specific shapes by intermolecular bonding between the side chains of the amino acids involved.
• During cooking, as proteins are heated, the molecules become agitated and move around, leading to the breaking of intermolecular bonds between molecules.
• This process allows the proteins to denature, causing a change in shape and consequently, altering the texture of foods. This explains the structural difference between a raw egg and a fried egg.

Conclusion: