The cytochrome P450 constitute a superfamily of heme-containing enzymes that occur in nearly all living organisms, from bacteria to mammals, These monooxygenases, which in animals are embedded in the endoplasmic reticulum membrane, catalyze reactions of the sort

                  RH + O₂ + 2 H⁺ + 2e⁻ → ROH + H₂O 

The electrons (e−) are supplied by NADPH, which passes them to cytochrome P450’s heme prosthetic group via the intermediacy of the enzyme NADPH P450 reductase. Here RH represents a wide variety of usually lipophilic compounds for which the different cytochromes P450 are specific. They include

a. polycyclic aromatic hydrocarbons 

b. polycyclic biphenyls

c. frequently carcinogenic compounds that are present in tobacco smoke, broiled meats, and other pyrolysis products

d. which were widely used in electrical insulators and as plasticizers and are also carcinogenic.

TLS Online TPP Program

#Question id: 12202

#Unit 6. System Physiology – Plant

Auxin-responsive genes typically have

TLS Online TPP Program

#Question id: 12203

#Unit 6. System Physiology – Plant

Which factor function as auxin co-receptors, with auxin acting as a “molecular glue”?

TLS Online TPP Program

#Question id: 12204

#Unit 6. System Physiology – Plant

Feedback regulation represents another key mechanism employed to attenuate a response such as

a) AUX/IAA proteins can bind to the promoters of their own genes and repress their own expression

b) auxin signaling triggers the degradation of AUX/IAA repressors, the ensuing transcription of auxin response genes leads to the replacement of AUX/IAA proteins and thus to response attenuation or termination

c) AUX/IAA genes, which encode the AUX/IAA auxin repressor proteins, have auxin response element binding sites located in their promoter regions

During the feedback regulation mechanism of auxin several responses are trigger, find out the correct sequences of these responses.

TLS Online TPP Program

#Question id: 12205

#Unit 7. System Physiology – Animal

Before the preovulatory surge in luteinizing hormone, granulosa cells of the follicle secrete which of the following?

TLS Online TPP Program

#Question id: 12206

#Unit 7. System Physiology – Animal

Neonates that are kept in 100% oxygen incubators for several days become blind when they are removed from the incubator, a condition referred to as retrolental fibroplasia. What is the explanation for the loss of sight?

TLS Online TPP Program

#Question id: 12207

#Unit 7. System Physiology – Animal

Which of the following hormones activate enzyme-linked receptors?