Which of the following controls protein and enzyme syntheses in the cytoplasm of the cell?

DNA (deoxyribonucleic acid) is the molecule that controls protein and enzyme synthesis in the cytoplasm. DNA carries the genetic code - a specific sequence of nucleotide bases (adenine, thymine, guanine, cytosine) that determines which proteins and enzymes are produced.

The process works in two main stages:

1. Transcription: In the nucleus, the relevant section of DNA unwinds and one strand serves as a template for the synthesis of messenger RNA (mRNA). The mRNA carries a complementary copy of the genetic instructions.
2. Translation: The mRNA moves out of the nucleus into the cytoplasm, where it attaches to ribosomes. Transfer RNA (tRNA) molecules bring specific amino acids to the ribosome, matching them to the codons on the mRNA. The amino acids are joined together in the correct sequence to form the protein or enzyme.

While the nucleus houses the DNA and chromosomes are the structures that DNA is packaged into, the question asks specifically what controls protein synthesis. That controlling agent is the DNA molecule itself, because it is the sequence of bases in DNA that determines which proteins are made. Chromosomes are the physical packaging of DNA, not the controlling molecule. Mitochondria have their own DNA and carry out cellular respiration, but they do not control the synthesis of proteins and enzymes in the cytoplasm of the cell.