it can't because oxygen is a gas and gas has no shape.
oxygen
Red corpuscles fit this description,
the donughnut shape of the red blood cells is specificly for the oxygen molocule. The blood comes back into the heart from the lungs in the pulmonic artery. and the oxygen molocule sits in the donoughnut hole like a seat cussion.
To optimise the surface area available for the bonding of oxygen and haemoglobin, to form oxyhaemaglobin. Individuals with sickle cell anaemia, i.e. those with red blood cells which are not disk shaped have a reduced capacity to carry oxygen in their blood.
Alveoli are the sack-shaped respiratory organs where blood picks up oxygen from the air during the process of respiration. These tiny air sacs in the lungs are surrounded by capillaries, allowing for the exchange of gases like oxygen and carbon dioxide.
Life has shaped Earth by altering its atmosphere through the release of gases like oxygen. This has influenced climate and the evolution of organisms. Earth has shaped life through geological processes like plate tectonics, which have created diverse habitats and influenced species distribution and evolution.
cardiac cells
the guard cells
There are three of these compounds. Oxygen difluoride is v-shaped. Since it's difficult to offer diagrams on answers.com let me suggest that you consult wikipedia for information about the other compounds.
As a molecule it is "V" shaped, with the oxygen atom at the vertex. In quantity, it is a fluid and so takes the shape of the container that it is in.
it is found inside red blood cells, the Lifesaver shaped ones. It is essential to oxygen processing and absorption.
Methanol has a tetrahedral shape. Oxygen by itself would have a bent shape when bonded with hydrogen and carbon