MB unit 21: Microbial transformation and bioconversions.

10 flashcards · Other · by Yaiza Anido

1. Describe what a microbial transformation is

   Microbial transformations are point or few-step reactions within a biosynthetic or degradative pathway performed by living micro-organisms by cell extracts or by enzymes of the micro-organisms. It is never a complete synthesis or degradation process it is only a few steps. These micro-organisms or extracts of micro-organisms are immobilised, so the processes are cost-effective. We use 1 or several enzymes from micro-organisms to perform a conversion.

2. Why do we use microorganisms for these type of conversions?

   We use microorganisms because: Microorganism enzymes have substrate specificity and exhibit stereospecificity. They perform point site transformations of complex molecules: they have regiospecificity.

3. Mention the process conditions for microbial transformations

   These microbial transformations work at room temperature and at atmospheric pressure. (on the contrary to many chemical reactions which have to be heated to 200 degrees in a nitrogen atmosphere etc)

4. Classifications of steranes

   sterols bile acids sexual hormones cardiac glucosides saponins

5. What are sterols? Explain the structure of sterols

   Sterols are a group of compounds of hihg molecular weight that present as a chemical function a secondary alcohol group and insaturation sin the sterol group The structure contains one or more OH groups in the steroid ring. There is an R chain which represents a lateral aliphatic chain.

6. What is cholesterol?

   Cholesterol is the principal sterol synthesized by all animals. Cholesterol is a lipid molecule that is biosynthesized by all animal cells, because it is an essential structural component of all animal cell membranes; essential to maintain both membrane structural integrity and fluidity. Cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid and vitamin D.

7. In which m.o is cholesterol absent and which one is the exception?

   It is absent in prokaryotes (bacteria and archaea), although there are some exceptions, such as Mycoplasma, which require cholesterol to growth.

8. Explain the relationship between cholesterol, pregnenolone , progesterone and adrenocorticoids.

   Cholesterol is the biosynthetic precursor of steroid hormones. By enzymatic degradation of the side chain, it can produce pregnenolone, which can be transformed into progesterone, a female hormone that is a precursor of sexual hormones and adrenocorticoids.

9. By what are bile acids produced and where are they accumulated? What bile acid is the most abundant? What are the physiological function sof bile acids?

   Bile acids are accumulated in the bile gut and are produced by the liver. Colic acid is the most abundant. Physiological function: Their main function is to emulsify fats in the intestine. Bile salts are usually present as sodic salts.

10. Which are the female sexual hormones? Where are they syntehsized? What is their function?

    The female sex hormones are oestrone, oestriol and oestradiol. T hey are synthesised in the ovary and have functions such as determining the body development characteristic of the female sex, stimulating the growth of the uterine musculature, the development of the milk ducts and controlling the first phase of the menstrual cycle. Both hormones have an aromatic ring in their structure.