Essential amino acids are amino acids that must be supplied to one's body by their diet because they cannot be synthesized from scratch.
Answer:
Pacemaker cells are located in the <u>sinoatrial node.</u>
Contractile cells are located in the <u>Heart</u>
Explanation:
Answer:
In the n=1 energy level, the atom has 2 electrons
Explanation:
Electrons orbit the nucleus of an atom in multiple rings (energy levels). The first ring of the electron can only hold 2 electrons. After that, electrons are added to the second ring. Excluding the first ring, all other rings can hold a maximum of 8 electrons.
For example, Oxygen is an atom with 6 electrons. The first energy level contains 2 electrons, and the second energy level contains 4 electrons. The second energy level has room for up to 4 more electrons.
In your example of an atom with 15 electrons, there would be 2 electrons in the first ring, 8 electrons in the second ring, and 5 electrons in the third and final ring.
To summarize, all atoms have a first energy level containing 2 electrons, and all other energy levels can contain 8 electrons. This is true no matter the number of electrons.
