Based on the 20 amino acids found in proteins, there are 6840 possible variations in a polymer composed of just three amino acids.
<h3>What are amino acids?</h3>
Amino acids are the molecules from which protein molecules are made from.
There are 20 common amino acids from which protein molecules are built up from.
The amino acids are joined one to another in the protein by peptide bonds.
In a polymer composed of three amino acids, the possible variations are calculated by permutation.
The possible variations are 20 permutation 3.
nPr = n!/(n - r)!
where n = 20 r = 3
nPr = 20!/(20 - 3)!
nPr = 6840
Therefore, there are 6840 possible variations in a polymer composed of just three amino acids.
Learn more about amino acids at: brainly.com/question/1302816
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.
between 5.6 and 13 cm long
