Question

25. which of the following is a characteristic of lipids?
a) they are composed of amino acids
b) they are hydrophobic
c) they contain nitrogen
d) they are soluble in water

26. which of the following is an isotope of carbon, c - 12?
a) c - 14
b) c - 6
c) c - 40
d) c - 24

27. an isotope of an element differs from the standard form of the element in terms of the number of:
a) protons
b) electrons
c) neutrons
d) none of the above

28. which of the following is not a part of the cell theory?
a) all cells have a nucleus
b) all cells come from pre - existing cells
c) all living organisms are made of cells
d) cells are the basic unit of structure and function

Explanation:

• For question 25: Lipids are non - polar and repel water (hydrophobic). Amino acids compose proteins, lipids usually do not contain nitrogen, and they are insoluble in water.
• For question 26: Isotopes of an element have the same number of protons but different numbers of neutrons. C - 14 is an isotope of C - 12. C - 6 and C - 40 and C - 24 are not common or stable isotopes of carbon.
• For question 27: Isotopes differ in the number of neutrons while having the same number of protons and electrons (in a neutral state).
• For question 28: Prokaryotic cells do not have a nucleus. The cell theory states that all cells come from pre - existing cells, all living organisms are made of cells, and cells are the basic unit of structure and function.

Answer:

1. b) They are hydrophobic
2. a) C - 14
3. c) Neutrons
4. a) All cells have a nucleus