<span>The ovaries produce estrogen and progesterone in women. Both play an important role in the menstrual cycle: estrogen stops FSH production and stimulates LH release by the pituitary gland. Progesterone maintains the uterus’ lining. Men also produce estrogen, though at lower levels, and this is done through changing testosterone into estrogen with an enzyme.</span>
Answer:
Step 1: Pollination
In general, male gametes are contained in pollen, which is carried by wind, water, or wildlife (both insects and animals) to reach female gametes. The pollen is deposited on a plant's stigma, which is part of the pistil (the elongated part of a flower extending from the ovary). This process is called pollination.
Step 2: Germination
Within a few minutes, pollen tubes begin growing, or germinating, toward the egg cell. These tubes will provide a path for the sperm carried in the pollen to reach the egg.
Step 3: Penetration of the Ovule
The pollen tubes penetrate the ovule, which contains the female gametes.
Step 4: Fertilization
Sperm travel down the pollen tubes and fertilize an egg. Most angiosperms undergo double fertilization, where both an egg and the polar nuclei in the embryonic sac are fertilized.
Explanation:
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<h2>Membrane potential </h2>
Explanation:
- Membrane potential represents charge difference across the membrane, all biological cells are negative inside (cytoplasm) and positive outside (due to difference in ionic distribution)
- In a typical neuron cell membrane potential of cytoplasm is negative at rest (when no stimulus is applied) hence called resting membrane potential
- Resting membrane potential of excitable cells is established by Na+ and K+pump
- Repolarization starts with the efflux of K+ by the opening of voltage gated K+ channels
- Voltage gated K+ channels starts to open when voltage gated Na+ channels becomes inactive
- Hyperpolarization occurs due to excessive efflux of K+ by voltage gated K+ channels
- Additional efflux of K+ occurs due to slow inactivation of voltage gated K+ channels
Diffusion , the movement of gas molecules .
