The Chemical Basis Of Life

Explanation
The correct answer is only electrons. Electrons are not found in the nucleus of an atom. Protons and neutrons are the subatomic particles that make up the nucleus, while electrons orbit around the nucleus in energy levels or shells.

Explanation
Calcium is a trace element found in living organisms. It plays a crucial role in various biological processes such as muscle contraction, nerve function, and blood clotting. It is also an essential component of bones and teeth, providing strength and structure. While carbon, hydrogen, oxygen, and nitrogen are also important elements in living organisms, calcium is specifically classified as a trace element due to its lower concentration in comparison to major elements like carbon, hydrogen, and oxygen.

Explanation
Organic compounds are defined as compounds that contain carbon atoms. Carbon is the key element in organic chemistry, forming the backbone of many organic molecules. It is the unique properties of carbon, such as its ability to form covalent bonds with other elements, that allow for the diverse range of organic compounds found in nature. Therefore, it can be concluded that organic compounds always contain carbon.

Explanation
Glucose and fructose are both isomers, which means they have the same molecular formula but different structural arrangements. Isomers have the same atoms but are arranged differently, resulting in different chemical properties and characteristics. In the case of glucose and fructose, they both have the same number and types of atoms (carbon, hydrogen, and oxygen), but the arrangement of these atoms differs, giving them different properties and functions.

Explanation
Prokaryotic cells lack a membrane-bound nucleus. Unlike eukaryotic cells, which have a distinct nucleus enclosed within a membrane, prokaryotic cells have their genetic material (DNA) floating freely in the cytoplasm. Prokaryotic cells include bacteria and archaea, and they are characterized by their simplicity and smaller size compared to eukaryotic cells. This lack of a nucleus allows for more efficient and rapid gene expression and adaptation to changing environments.