Respiration In Plants-Quick Revision

1

Cellular respiration

Cellular respiration is the exchange of gases (oxygen and carbon dioxide) between blood and cells or within the cell. It is the biochemical pathway to release energy.

2

Respiration in plants

1. The plants respire with the help of small pores which are present on the leaf.
2. These pores are known as stomata which help in gaseous exchange.
3. Roots also have small pores which help in absorption.

3

Respiration in plants

Just like animals, plants also respire (take in oxygen and release out carbon dioxide). They use oxygen for the breakdown of food and releases energy. It can be represented by an equation as:
Glucose (food) + Oxygen → Carbon dioxide + Water + Energy.

1. The intake of oxygen and release of carbon dioxide is through different routes in different parts of the plants.
In leaves and stem, exchange of gases takes place through stomata (guarded pores). 
2. In stems with bark, exchange of gases take place through the lenticels.
3. Root cells take the air (through diffusion) in the soil spaces. 
4. The oxygen in the air is then utilized for breaking down glucose to release energy and carbon dioxide.
5. Respiration in most plants occurs under dark conditions (no light).

4

Photosynthesis and respiration

The difference between photosynthesis and respiration are as follows:

Photosynthesis	Respiration
1.Occurs only in the presence of chlorophyll	Occurs in all living cells
2. Occurs only in the presence of light	Occurs at all time
3. Uses carbon dioxide and water	Uses oxygen and glucose
4. Oxygen is released as an end product	Carbon dioxide is released as end product
5. Light energy is converted into chemical energy and stored	Chemical energy is partly converted into heat and partly into useful energy for various activities
6. Results in gain of dry mass	Results in loss of dry mass
7. Glucose is manufactured	Glucose is broken down
8. Anabolic process, resulting in building up of carbohydrate molecule	Catabolic process, resulting in breakup of carbohydrate molecule

5

Krebs cycle

Krebs cycle is the series of chemical reaction to produce energy. It is used by all aerobic living organisms. It was discovered by the Hans Krebs.

1. It is the process of oxidation of activated acetyl-CoA.
2. It occurs in the matrix of the mitochondria.
3. It is the ten stepped enzymatic pathway.
4. As its first product is citric acid or citrate, it is also called as citric acid cycle.
5. This pathway needs oxygen and releases lots of energy.
6. In this process, two acetyl residues liberate two ATP or GTP through substrate level phosphorylation.
7. It is connected with the oxidative phosphorylation.
8. It produces ATP, NADH, FADH2​, CO2​, and H2​O

6

Respiratory quotient

Respiratory quotient is the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed in respiration over a period of time. Its value can be one, zero and more or less than one.
RQ = volume ofO2​ absorbedvolume ofCO2​ evolved​
Importance of RQ

• It helps to determine respiratory substrate.
• It helps to know the type of respiration performed.

7

RQ of respiratory materials

The respiratory quotient can be calculated for any respiratory substrate e.g., carbohydrate, fats and proteins. 

For example: RQ of carbohydrate.

The respiratory quotient for carbohydrate metabolism can be demonstrated by the chemical equation for oxidation of glucose:

C6​H12​O6​ + 6 O2​ ——–> 6 CO2​+ 6 H2​O

Because the gas exchange in this reaction is equal, the respiratory quotient for carbohydrates is: 

RQ = 6 CO2​ / 6 O2​ = 1.0