1. Explain the difference between fast and slow block to polyspermy? 2. Explain
ID: 77954 • Letter: 1
Question
1. Explain the difference between fast and slow block to polyspermy?
2. Explain how the amount of yolk in an egg affects cleavage and early development.
3. Hormones play a significant role in the digestion and processing of nutrients. Explain where each of the following comes from and how each functions in nutritional processes: secretin, insulin, glucagon.
4. Compare and contrast the following mechanisms for hormone transport: endocrine signaling, paracrine signaling, autocrine signaling, synaptic signaling, neuroendocrine signaling, and pheromone signaling.
5. Explain the general effects of an endocrine disruptor. Why is much of what we know about endocrine disruption from model organisms?
6. Imagine a hummingbird species has detected the odor of nectar. Explain how the signal is received and then transmitted from one neuron to the next. In your explanation diagram the6 stages of an action potential and indicate what initiates the action potential.
Explanation / Answer
1 Ans. Polyspermy means fertilization by more than one sperm. This results in duplications of genetic material. block to polyspermy comes from two mechanisms: the fast block and the slow block.
The fast block is an electrical block to polyspermy which is due to the change in electrical charge of the egg's membrane. By default, the egg membrane is negatively charged -70mv However upon entrance of the first sperm, this condition changes and the egg possesses a positive charge (Partially due to internal release of Ca2+ ions). The positively charged fertilized egg will now repel other sperms, because sperms are positively charged by default.
The slow block is through a biochemical mechanism triggered by a wave of calcium increase. It occurs after fast block. During this phase a Zona Pellucida is pushed away from the inner membrane of egg, creating a physical space prevents the sperms from penetrating the egg.
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