Question

why does citric acid cycle stop when oxygen is removed? Explain!

2) A patient takes an antibiotic that is identified to have toxic effects on some mechanorecsptors. Later, this patient begins to experience hearing loss. Explain the connection!

3) explain why, if someone shines a bright light in your eyes at night, it takes several minutes after the light goes away for you to regain your night vision.

Answer 1

1. In citric acid cycle, the oxidation of the acetyl group occurs ,followed by the acetyl CoA entry.This requires the transfer of electron to the electron carriers .The electron carriers are FADH and NAD+ ,produces NADH nad FADH2 .NADH and FADH2 get oxidized in the electron transport chain cycle .Oxygen moleculs play a role in accepting the electrons at the completion of electron transport chain and combines with the two hydorgen ion and forms the water for the citric acid cycle to continue. In the absence of the oxygen molecule ,the citric acid produces the NADH and FADH2 will not be oxidized for the use in electron transport chain due to lack of electron acceptor. Thus NAD+ and FADH will not be available to oxidize the substrates of citric acid cycle ,would cause stop of the citric acid cycle.

2. The toxic chemical causes ototoxicity that damages the mechanoreceotor present in inner ear.The mechanoreceptor are the hair cells present in the cochlea of inner ear.The sound wave propels through the external ear to inner ear causes activation of mechanoreceptors ,stimulates the auditory nerve for hearing signal output.The mechanoreceptors damage causes loss of signalling of sound wave and balance causing hearing loss.

3 .The human eye contains two types of photoreceptors -cones and rod cells. Cones cells are responsible for the vision in the day light or bright light where as rod cells are responsible for the vision in dim light.However rod and cone both are involved in the dark adaptation. Cones adapt faster but rods take little longer time to respond after the cone mediated adaptation period (which occurs in bright light). Thus, in bright light cone cells are more active and once light goes off ,the cones cells function switches to the rod cells function which takes some time ,thus this adaptation process creates lag in vision.