Cell membrane of prokaryotes and Inner mitochondria of eukaryotes
Explanation:
Electron transport chain is a part of oxidative phosphorylation which is the third step of aerobic cellular respiration in living organisms. The ETC is a complex of proteins and mobile electron carriers. It occurs when electron is being transferred from one electron carrier to another, starting from NADH and FADH2. A proton pump which is used to synthesize ATP is generated at the end.
This ETC process occurs in the cell membrane of prokaryotic cells due to the fact that they lack a membrane-bound Mitochondrion. ETC occurs in the inner membrane of the mitochondria called CRISTAE in eukaryotic cells.
There are histones in the nucleus that DNA coils around. The part of the DNA that is coiled around the histones is not accessible, and cannot be expressed in that cell. DNA that is not wrapped around a histone can be transcribed.
An organism that cannot make its own food is called a heterotroph. All animals and species of fungi, along with some types of bacteria, are heterotrophs.