Unit 1 Cell Function Inheritance Ch 1 Structure

Unit 1 : Cell Function & Inheritance Ch. 1 Structure & Variety of proteins

Protein Structure • All contain Carbon, • • • Hydrogen, Oxygen and Nitrogen These join to form amino acids There about 20 types of amino acid Amino acids are joined together by strong covalent (or peptide) bonds - to form 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 • • 1) 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)

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 actin slides over the myosin Sacromere shortens overall

Variety & Role of Proteins • 2) Globular Proteins (ball of string • • shape): Carry out active roles e. g. - enzymes, hormones, antibodies, transport proteins (transferrin) Conjugated Proteins: Globular proteins with non-protein parts - lipoproteins (contain lipids) - glycoproteins (contain carbohydrates) - haemoproteins (contain haem e. g. haemoglobin)