In skeletal muscle, the sarcoplasmic reticulum stores a very high concentration of ca++. when ca++ is released into the cytosol of muscle to facilitate contraction, it needs to be removed and pumped back into the sarcoplasmic reticulum so that skeletal muscle can return to its relaxed state. the ca++ is moved from cytosol and pumped back into the sarcoplasmic reticulum where its concentration is much higher. what type of membrane transport does this represent?

Primary active transport.

Explanation:

Active transport may be defined as the movement of particles against the concentration gradient. This is the energy driven process that requires ATP to transport the molecules.

Two main types of active transport are primary active transport and secondary active transport. The calcium has been moved towards its region of higher concentration ( sarcoplamsic reticulum) from its region of lower concentration (cytosol), this transport is against the concentration gradient. The ATP is used by direct hydrolysis. Hence, it is the primary active transport.

Thus, the answer is primary active transport.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.