Answer:
An oxygen atom is what is found on the periodic table. The Oxygen atom is made of 8 proton, 8 electrons and generally 8 neutrons.The oxygen molecule is made of two oxygen atoms that have formed a double bond with each other and share valence electrons.
Explanation:
 
        
             
        
        
        
Answer:
Explanation:
There are two types of respiration:
1.	Aerobic respiration  
2.	Anaerobic respiration
Aerobic respiration
It is the breakdown of glucose molecule in the presence of oxygen to yield large amount of energy. Water and carbon dioxide are also produced as a byproduct.
Glucose + oxygen → carbon dioxide + water + 38ATP
Anaerobic Respiration
It is the breakdown of glucose molecule in the absence of oxygen and produce small amount of energy. Alcohol or lactic acid and carbon dioxide are also produced as byproducts.  
Glucose→ lactic acid/alcohol + 2ATP + carbon dioxide
This process use respiratory electron transport chain as electron acceptor instead of oxygen. It is mostly occur in prokaryotes. Its main advantage is that it produce energy (ATP) very quickly as compared to aerobic respiration
 
        
             
        
        
        
The organism would not have to find a partner in order to reproduce.
 
        
                    
             
        
        
        
Out of the following given choices;
a. they increase the amount of energy transferred from the
lungs to the blood
b. they increase the flexibility of the lungs as they expand
during inhalation
c. they increase the volume of the lungs, allowing more
oxygen to be inhaled
d. they increase the surface area of the lungs, allowing the
efficient gas exchange
The answer is D. Due to their microscopic nature, they are numerous in the lungs and are also circular-shaped so as to increase the surface area for gaseous exchange.
Other characteristics of alveoli that increase gas exchange are that they thinned-walled (with only a layer of cells) and moist.