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Unit 1 : Cell Function & Inheritance. Ch. 1 Structure & Variety of proteins. Protein Structure. All contain Carbon, Hydrogen, Oxygen and Nitrogen (some have Sulphur) These join to form amino acids There are about 20 types of amino acid
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Unit 1 : Cell Function & Inheritance Ch. 1 Structure & Variety of proteins
Protein Structure • All contain Carbon, Hydrogen, Oxygen and Nitrogen (some have Sulphur) • These join to form amino acids • There are about 20 types of amino acid • Amino acids are joined together by strong covalent (or peptide) bonds = polypeptides • This joining of amino acids is called the proteins PRIMARY STRUCTURE
Protein Structure • The polypeptide chain folds over • Weak hydrogen bonds form between certain amino acids • Forms a spiral helix - the SECONDARY STRUCTURE • Further cross-connections bridge across several polypeptide chains • This gives the final TERTIARY STRUCTURE (important in determining protein function)
Variety & Role of Proteins • Fibrous Proteins • Several of the same polypeptides linked in parallel (rope-like) • Used for structural roles: • - actin & myosin (muscle contraction) • - collagen (skin, bone, tendons, ligaments) • - keratin (found in hair) • - elastin (found in artery walls)
Variety & Role of Proteins • Globular Proteins (ball of string shape): • Carry out active roles e.g. • - enzymes, hormones, antibodies, transport proteins • Conjugated Proteins: • Globular proteins with non-protein parts • - lipoproteins (contain lipids) • - glycoproteins (contain carbohydrates) • - haemoproteins (contain haem e.g. haemoglobin)
Muscular Contraction • Muscle fibres are made up of myofibrils • Each myofibril is divided into sacromeres • Each myofibril contains 2 slender, thread-like filaments • Thick filaments = myosin • Thin filaments = actin • During muscle contraction the thin filament slide over the thick filaments • Sacromere shortens overall