Transcript Proteins
Proteins …The most diverse molecules in living organisms! Proteins have 2 main roles: 1. Structural building blocks (ex: spider web) 2. Functional molecules (ex: enzymes) Images courtesy of google images Examples of proteins: Functional: • Enzymes: biological catalysts • Immunoglobulins: protect animals from foreign microbes and cancer cells (antobodies) • Hemoglobin: shuttles oxygen Structural: • Keratin: tough structures in hair, fingernails • Fibrin: helps clot blood • Collagen: forms protein component of bones, skin, ligaments and tendons Images courtesy of google images What are they made of? • Amino acids (a.a.) are the subunits: R group = “side chain” Images courtesy of google images A bit about the amino acids… • There are 20 a.a.’s (p42+ 43) • 8-10 are “essential” because our body cannot synthesize them so we need to get them from our diet. The amino acids: Images courtesy of google images No… you don’t have to memorize them… maybe in university though How are proteins made? • DNA directs ribosomes, RNA and enzymes to join a.a.’s together in the correct sequence (this is called protein synthesis) • The aa’s are joined together by peptide bonds (aka amide bond) • Resulting polymer is called a polypeptide Images courtesy of google images Polypeptides are formed by condensation reaction between the amino group of one amino acid and the carboxyl group of the adjacent amino acid Two general categories of proteins 1. Polypeptide: a few aa in length to >1000. Usually linear: strands or sheets AND 2. Globular: are made of 1 or more polypeptide chains in a rounded, spherical shape (ex: enzymes) Images courtesy of google images The final shape (conformation) of a protein is determined by a.a. sequence and can be: • Primary: straight chain of a.a (ex: insulin) • Secondary: The a.a. chain coils and folds making helices and pleated sheets (ex: keratin, spider silk) • Tertiary: A secondary protein undergoes more folding due to environmental forces. This can be done by a chaperone protein. Is now globular. • Quarternary: 2 or more polypeptides come together to make one functional protein (ex: keratin, collagen, hemoglobin). Is also globular. Images courtesy of google images Denaturation • Chemical and physical environmental factors (temperature, pH, ionic concentration) can cause proteins to change shape (denature) and lose their function. • Denaturation can be: – Dangerous: example- prolonged fever above 39 celcius can denature critical enzymes in the brain. – Useful: blanching of fruit, straightening hair, cooking meat to make it easier to chew Images courtesy of google images