The best possible explanation is that the 20 amino acids serve as a signal (peptide) sequence that directs the
forming polypeptides to the endoplasmic reticulum, where they are
cleaved off during processing.
Answer:
The correct aswer is crystal size.
Explanation:
Cooling rate affects to the size of the crystal formed by cooling a molten material. A fast cooling produces small crystals whereas slow cooling produces large crystals. At a slow cooling rate, crystals have more time to grow and therefore they are larger than those are formed at a fast cooling rate.
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.
This is an organ that served a purpose in the distant ancestor of an organism, but is not longer pertinent in the presently existing, recently evolved, organisms.
Vastus medialis, vastus lateralis, vastus intermedius, and the rectus femoris.
