Inhibitors

Free online life science study material. Hi Some inhibitors with their role. Azide - it inhibits electron transport chain in mitochondria. Atractyloside - It inhibits ATP ADP translocation. Rotenone - It inhibits electron transport chain in mitochondria. Antimycin A - inhibits electron transport chain in mitochondria. Dinitrophenol - uncoupling of electron transport and oxidative phosphorylation. Carbon Monoxide- Inhibits electrons transport chain in mitochondria. Oligomycin - It inhibits ATP Synthesis. FCCP - makes membrane permeable to proton. Malonate - Prevents oxidation of succinate. Cyanide- inhibit cytochrome oxidase.

Inhibitors of transcription: Alpha amanitin -inhibition of RNA plymerase II of eukaryotes.(Polymerase III require high concentration for inhibition and Polymerase I is not affected) Acridine and actinomycin D -intercalate between successive Guanine and Cytosine in RNA as well as DNA. Rifampicin - bind to beta subunit of bacterial RNA polymerase prevent promoter clearance step.

Inhibitors of translation: Ricin - Inactivates 60S subunit of eucaryotic ribosome. Streptomycin- Binds with 30S subunit of ribosome of bacteria and cause misreading of mRNA. Puromycin- Binds to A site of Ribosome. Erythromycin- binds to 50S of ribosome to inhibit peptide chain elongation.

Inhibitor of replication Cyclophosphamide is a cyclic phosphamide with a bis-(2-chloroethyl) group that can be metabolized by cells into phosphoramide mustard which alkylates macromolecules, including DNA,and cross-links the two DNA strands. Cisplatin (CDDP)is an inorganic complex of platinum that cross-links DNA.

Tryptophan Operon

Free online life science study material. Tryptophan Operon It is a repressible operon. Tryptophan synthesising genes are off when tryptophan is present in the medium. When trp is high it binds to aporepressor and binds to operator and hence blocks transcription(RNAP binding is blocked). Trp is corepressor. When trp is low in concentration, the operon should be activated for trp synthesis, hence the aporepressor binds to another aporepressor molecule (dimerise) and its confirmation gets changed due to which it can not bind to Operator of operon. Therefore, operon gets activated. Trp operon is weak operon, fully repressed level is not achieved with this repression hence, another control is required which is called attenuation. Attenuation is rho dependent. There is a trp R gene, then trp Promoter and Operator are present, trp O is overlapping trp P. Then five genes for trp synthesis are present trpE,trpD,trpC, trpB and trpA. Two loci, trp leader sequence and trp attenuator lie between Operator and trpE. Attenuator contains transcription stop signal, an inverted repeat followed by string of A's. In leader sequence two trp codons are present.There are four elements present 1,2,3 and 4. During trp starvation, 2 pairs with 3 and the transcription for trp continues. Hairpin termination does not form and it is called antitermination. when trp is present termination is required and is achieved by pairing of 1 with 2 and 3 with 4.3-4 pairing forms antitermination loop with G-C rich region followed by string of U. Due to pairing of 1 and 2 the ribosome falls off and transcription is halted. (Consult diagram for better understanding).

Some facts

Free online life science study material. Some important facts 1. Schwann cell are responsible for myelin synthesis. 2. Perineurium surrounds fascicles of axons in PNS. 3. Autonomic nervous system controls smooth muscle, cardiac muscle and gland activity. 4. The action potential of neuron is terminated by efflux of K+ ions. 5. The parasympathetic nervous stimulation of heart is increased activity of AV node. 6. Taste receptor of fishes are most sensitive chemoreceptor of of vertebrates. 7. The fovea of the eye is the region of highest visual activity. 8. Aqueous humor fills the anterior of eye and vitrous humor fills the posterior chamber. 9. CO2 is transported mostly as dissolved bicarbonate in blood. 10. Vasopressin and oxytocin are produced by posterior lobe of pituitary gland. 11. Testosterone does not act by secondry messanger system. 12. All hormones of adrenal cortex are synthesised from cholesterol. 13. Ecdysone is moulting hormone of insects. 14. Epinephrine and norepinephrine are hormones as well as neurotransmitters. 15. Epinephrine is modified amino acid. 16. Thyroxine is important for normal metabolic rate. 17. Hemoglobin is most abundant protein in human body. 18. Cholecystokinin and secretin are produced in small intestine. 19. A graffian follicle is a mature follicle ready to ovulate. 20. Absence of parietal cell could lead to pernicious anemia.

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.