Answer:
- Oxygen
- The body cells
- Producing energy
Explanation:
We breathe in oxygen from the external environment. Oxygen passes into our lungs and is passed into the blood capilaries. Here it is carried to all the cells throughout the body.
It diffuses into the cells and is necessary for the final stages of energy production by aerobic respiration. Therefore, it is necessary for powering all cellular processes.
DNA is replicated during the “S” phase (synthesis).
Against their concentration gradient means its active transport.
Diffusion is with the concentration gradient.
Osmosis is the movement of water.
Every cell of the organism has the same DNA sequence and same genes. However, not all genes are expressed in every single cell at the same time. Only those genes necessary for a specialised function of a specialised cell are expressed in the specialised cell. For example, skin cells have some different proteins than nerve cells. Genes responsible for those "skin proteins" are activated in skin cells and are turned off in nerve cells.
At the smallest level of organization, the DNA wraps itself around small globular proteins called histones. Complexes of histones and DNA form nucleosomes, which appear as "beads" on the DNA strand. Chromatin refers to the decondensed DNA that has not formed separate chromosomes.
