How are photosynthesis and respiration related?

They are opposite processes. Photosynthesis uses carbon dioxide and water to make glucose and oxygen, while respiration uses glucose and oxygen to release energy, producing carbon dioxide and water as waste.

Do plants respire at night?

Yes, plants respire all the time, both day and night, to provide energy for their cells. However, they only photosynthesise during daylight hours.

What is the compensation point?

The compensation point is the specific light intensity at which the rate of photosynthesis exactly matches the rate of respiration, resulting in no net gas exchange.

What gas is produced more by plants during the day?

During the day, the rate of photosynthesis is usually higher than respiration, so there is a net production of oxygen.

Where in the cell do these processes happen?

Photosynthesis takes place in the chloroplasts, while respiration takes place in the mitochondria.

The relationship between Photosynthesis and Respiration

Remember this:

Plants make food for all other living things by photosynthesis.

Plants capture the Sun's energy and turn it into Glucose (food) - which is stored chemical energy

Without plants (photosynthesis) all animals would die.

Animals eat food to extract energy in order live and grow.

During respiration Glucose and oxygen are used up and turned back into carbon dioxide and water.

in fact respiration is the opposite of photosynthesis!

If you look at the chemical equations of these two processes, you will notice that they are the same, but in opposite directions:

PHOTOSYNTHESIS - Requires energy

CARBON DIOXIDE	+	WATER	SUNLIGHT	GLUCOSE	+	OXYGEN

			CHLOROPHYLL

RESPIRATION - releases energy

GLUCOSE	+	OXYGEN	CARBON DIOXIDE	+	WATER

RESPIRATION - eating food and using energy

PHOTOSYNTHESIS - the energy factory

During respiration energy is used to do work.	During photosynthesis energy is trapped and stored.
During respiration food is used.	Photosynthesis make food.
Carbon dioxide, water and energy are released during respiration.	Carbon dioxide, water and energy are used during photosynthesis to make food.

Diagram showing the relationship between photosynthesis and respiration.

Remember:

Respiration releases energy stored during photosynthesis

Plants also do respiration

We know that during daylight (or artificial light, except green) plants carry out photosynthesis and release OXYGEN. Like animals, plants also require energy to live and grow. This energy comes from glucose during respiration. Respiration uses oxygen and give up carbon dioxide. To demonstrate this, we can do the following:

enclosed plant

Enclosed plant, with different levels of O₂and CO₂

The graph shows that the level of oxygen rises in the daytime. This is due to photosynthesis producing more oxygen than the plant's respiration using it up. The level of oxygen falls during night due to the plant's respiration using it up and no more is being produced as there is no photosynthesis happening. The amount of oxygen rises gradually, over the period of time.

The level of CO₂ falls during day time due to photosynthesis using it up. However, it rises at night because of respiration. On the whole the level of CO₂ falls since the plant use up more CO₂ than it produces.

Fate of Glucose in side plants

Tags:Photosynthesis, Oxygen, Carbon dioxide, Respiration, Glocose, Energy, Chlorophyll