DNA is a chain of nucleotides bonded together. On that chain there are particular portions of it that the sequence of the nucleotide codes for particular proteins; this is known as a gene. In eukaryotric cells, DNA is coiled around proteins such as histones to form chromatids which when two join at the centre by a centromere to form a chromosome.
The cell membrane is semipermeable (or selectively permeable). It is made of a phospholipid bilayer, along with other various lipids, proteins, and carbohydrates.
