Animal physiology

Hi Here is something in brief about animal physiology. The topic covered here is hormones. Adrenal hormone is secreted by adrenal gland present on top of each kidney.This gland is pyramidal in shape and is divided into two sections the outer cortex and inner medulla. So, outer cortex secretes three types of hormones viz. glucocorticoid, mineralocortecoid and adrenocorticoid.Hence, these are called adrenal cortical hormones. Glucocortecoid includes cortisol, corticosterone, cortisone. Mineralocortecoid includes aldosterone. Adrenocorticoid includes progestrone, estrogen, androgen. Cholestrol is backbone of all these hormone or we can say it is their precursor. Cholestrol is 26 C atom molecule(Consult any book for diagram). Cholestrol attached with LDL is carried into blood. For formation of mineralocorticoid and glucocorticoid the side chain is removed from cholestrol.The antenna of cholestrol ( C22-C27)is removed in mitochondria. Desmolase enzyme act on cholestrol which converts it into pregnanalone. (ACTH gives positive feedback to this enzyme.) 3Beta Steroid dehydrogenase enzyme acts on pregnanalone (At 3 Carbon OH group is present from which H is removed to increase the mobility of molecule)and convert it into progestrone. Later progestrone is acted by number of enzyme to get converted into aldostrerone, glucocorticoid and androgen. 17 hydroxylase enzyme synthesise testosterone from progestrone. It adds OH group on C17 and enzyme 17-20 lyase detach 18-20C from the progestrone molecule. For synthesis of aldosterone 17 hydroxylase enz. is also required.Also enzyme 21 beta hydroxylase and 11 beta hydroxylase enz. are also required. Another set of enz. called aldosterone synthase (18 beta hydroxylase + 18 dehydrogenase)are required for final step of formation of aldosterone. Testosterone later converts into estrogen.In this pathway progestrone convert into DHEA, and DHEA modification converts into androstenedione. Both are weak androgen. These both are present in both male and female also are responsible for secondary sexual characterstics. Both DHEA and androstenedione contain ketogroup at 17C. 19C molecule is testosterone, when aromatase enz. act on it, it converts into estrogen (18C) and when enz. 5alpha reductase acts on it it get converted into dihydrotestosterone (in males). Free online life science study material.