Topic 4, 5 & 6 Biology Ib

Page 1 of 9

Topic 4, 5 & 6 Biology Ib

By | September 2012
Page 1 of 9
3.6 Enzymes
Genes determine the amino acid seq. of proteins. Some proteins contain more than one type of polypeptide. e.g hemoglobin! Contains two types. A different gene is needed to make each polypeptide. One gene one polypeptide hypothesis some exceptions some code for tRNA or mRNA. Some act as regulators of gene expression are not translated. In lymphocytes pieces of DNA used to produce antibodies.

CATALYSTS speed up chem. reactions without being changed themselves. Enzymes biological catalysts. ENZYMES are globular proteins which act as catalysts of chemical reactions. Without enzymes many processes occur at a very slow rate. By making some enzymes and not others cells can control which processes to take place in their cytoplasm. Structure of enzymes quite delicate and can be damaged by various subst. and conditions denaturation: changing the structure of an enzyme or other protein so that it can no longer carry out its function.

Enzyme-substrate specificity: most enzymes are specific they catalyse few diff reactions. Substrates bind to active site (region on surface of enzyme which catalyses chem. reactions) which has a precise shape and distinctive chem. properties. Match shape of substrates others do not fit or are not chemically attracted. Enzymes in action: Temperature, pH, substrate concentration affect rate of catalysis. Usually at 7. Acids and alkalis can denature enzymes

Because of denaturing

Most active sites are occupied.
Random collisions occur more frequently.

Lactose is the sugar that is naturally present in milk. Lactoseglucose +galactose (by enzyme lactase). Biotechnology companies culture yeast and purify it to take lactase in food processing used for: * Lactose intolerant people (need lactose reduced milk)

* Galactose and glucose sweeter than lactose, less sugar needs to be added to sweet foods containing milk. * Lactose tends to crystallize during prod. of ice cream. Glucose and galactose are more...