Answer:
4) Each cytochrome has an iron‑containing heme group that accepts electrons and then donates the electrons to a more electronegative substance.
Explanation:
The cytochromes are <u>proteins that contain heme prosthetic groups</u>. Cytochromes <u>undergo oxidation and reduction through loss or gain of a single electron by the iron atom in the heme of the cytochrome</u>:

The reduced form of ubiquinone (QH₂), an extraordinarily mobile transporter, transfers electrons to cytochrome reductase, a complex that contains cytochromes <em>b</em> and <em>c₁</em>, and a Fe-S center. This second complex reduces cytochrome <em>c</em>, a water-soluble membrane peripheral protein. Cytochrome <em>c</em>, like ubiquinone (Q), is a mobile electron transporter, which is transferred to cytochrome oxidase. This third complex contains the cytochromes <em>a</em>, <em>a₃</em> and two copper ions. Heme iron and a copper ion of this oxidase transfer electrons to O₂, as the last acceptor, to form water.
Each transporter "downstream" is <u>more electronegative</u><u> than its neighbor </u>"upstream"; oxygen is located in the inferior part of the chain. Thus, the <u>electrons fall in an energetic gradient</u> in the electron chain transport to a more stable localization in the <u>electronegative oxygen atom</u>.
The thing that they have in common is that they are all non metals
Answer:
Chemical energy found in the bonds between atoms
Nuclear energy found in nucleus of an atom
Electrical energy found in the flow of electrical charges
Thermal energy found when internal energy is transferred.
Answer:
Yes
Explanation:
First remember that a significant figure are basically values that contribute to the precision of a value. In any scientific notation the values are significant figures because these values stay the same. In this case we have two significant figures which is 6 and 0, you can further prove that they are significant figures by converting the notation into standard form.

Negative so move the decimal point to the left:

6 and 0 are the significant figures in this standard notation because it's precise to it's actual value which is 6.0.
To sum up, the values you have on the left side of a notation are significant figures since they will not change no matter if it's standard or scientific notation meaning it's precise.
Hope this helps.