Answer:
C
Explanation:
A cell can communicate with nearby cells (paracrine signaling) and with cells far away from them (endocrine signaling). These signalings are dependent on the cell membrane receptors on the cell and their response to ligands that bind to them. An example of close cell communication is that of neurotransmitters in neural synapses. An example of cells communicating with faraway cells is that of the pancreas that produces insulin into the blood. The insulin induces other cells across the body to take up glucose.
The zygote simply is the fertilized ovum or egg cell or female reproductive cell. It is the result of the process of fertilization of the fusion of the male reproductive cell (gamete) and the female reproductive cell ( gamete). In human, the zygote is the resulted cell of fertilization of the sperm and the ovum. It is diploid or 2N which means it contains two sets of chromosomes; one set from the male and the other from the female.
The gamete is the reproductive cell. There are two types of gametes; male gamete and female gamete. In human, the male gamete is called the sperm and the female gamete is called the ovum. The gamete is the last stage of the reproductive cells to be completely formed.
Fertilization is the fusion of the male gamete and the female gamete to form the zygote. Fertilization may be external as in fish or internal as in human.
Answer:
D. Calcium ions.
Explanation:
Here we are talking about the mechanism of muscle contraction. The most accepted theory of muscle contraction is sliding filament theory. It was given by Huxley and Huxley. During the process actin filaments slides over myosin filament by forming cross bridges. The sequence of events are as follows:
a. An action potential propagates through the motor nerve and reach the nerve endings on the muscle fiber at neuro-muscular junction.
b. Neurotransmitter called acetylcholine is released by the nerve endings.
c. Acetylcholine binds to the receptors on muscle fiber and opens the gated channels which causes flow of Na+ ions into the muscle fiber.
d. This influx of sodium ions initiates an action potential in the muscle fiber which reaches the T- tubules or transverse tubules. Here it causes the sarcoplasmic reticulum to release large amounts of calcium ion.
e. Calcium ions are responsible for initiating the attractive forces between actin and myosin filaments. Cross bridges are formed, actin slides over myosin causing the contraction of muscle.
Glycolysis results in the formation of 2 ATP molecules, 2 Pyruvic Acid molecules (Or Pyruvate), and 2 NADH molecules.
