Describe path of oxygen from the alveolus to the plasma membrane of a red blood cell

please could someone help me answer the following questions!Really stuck.

1)Describe path of a molecule of O2 from alveolus to the plasma membrane of red blood cell

2) Give 2 features that may be found in a prokaryotic cell that are not found in a red blood cell

3) Explain 1 advantage of a biconcave disc over a sperichal one of the same volume in transporting oxygen

Reply 1

Revenged

1) O2 diffuses into alveoli fluid... it cross membrane of alveoli and capillary... then it enters red blood cell...

2) DNA and ribosomes are in prokaryotes but are not in red blood cells

3) increased surface area