How come plants produce oxygen even though they need oxygen for respiration?

I thought plants breathe in CO2 and breathe out O2 . The teachers have been telling lies?

2 Answers
May 10, 2018

Plants need oxygen for respiration like other living organisms but green plants produce oxygen during photosynthesis.

Explanation:

Plants need oxygen for cellular respiration just like all other living organisms.

Green plants are capable of undergoing photosynthesis. Green pigment chlorophyll entraps light.

In light reaction of photosynthesis, solar energy is converted into chemical energy in form of ATP molecules and hydrolysis of #H2O# occurs and #O2# is released and #NADPH2# is produced. .

Oxygen produced during light reaction of photosynthesis is partially consumed during cellular respiration by plants and unconsumed oxygen is released in atmosphere.

Thus plants produce oxygen in presence of light. Carbon dioxide enters the plant from the atmosphere that is converted into glucose in dark reaction of photosynthesis, utilizing ATP molecules and #NADPH2# produced during light reaction. Carbon dioxide produced during respiration is used in photosynthesis and more carbon dioxide is taken in from the atmosphere.

Thus during daytime , gaseous exchange involves intake of #CO2# and exit of #O2# .

May 10, 2018

Because of photosynthesis...

Explanation:

No, your teachers are not telling you any lies! Cellular respiration, which uses oxygen and glucose, happen in all living organisms, while photosynthesis can only occur in organisms with chloroplasts, which plants have.

So, a plant will respire, but also photosynthesise at the same time! They can breathe in both oxygen and carbon dioxide gas, but they use them both for different purposes.

The respiration equation is:

#6O_2(g)+C_6H_12O_6(aq)->6CO_2(g)+6H_2O(l)+38 \ "ATP"#

The photosynthesis equation is:

#6CO_2(g)+6H_2O(l)stackrel("sunlight")stackrel("chlorophyll")->6O_2(g)+C_6H_12O_6(aq)#

Notice how the two process have almost IDENTICAL equations, just in reverse of each other.