BIOLOGY 3 Marks Question

Assumptions for obtaining ATP molecules:
(i) This process starts from glycolysis and ends with Krebs' cycle and ETS. Therefore, it is a sequential, well-organised functional path in which one substrate is formed from another.
(ii) NADH produced during the glycolysis process enters the mitochondria, where it is phosphorylated.
(iii) Only glucose is used in respiration. No other alternative substrate enters any intermediate step in respiration.
(iv) None of the intermediates in the respiratory tract are used in the formation of other compounds.
In fact, all the paths work together. The substrate keeps coming in and out of the path as per requirement. ATP can be used as per requirement. The rate of action of enzymes is controlled by various factors. Respiration is a useful activity for life. Energy is stored and extracted continuously in the living system.

Difference between Glycolysis and Fermentation

Glycolysis	Fermentation
(i) This process occurs in both Aerobic respiration and Anaerobic respiration.	(i) Partial disintegration of glucose occurs in this.
(ii) It occurs in the cytoplasm. In this, when pyruvic acid is formed from glucose molecule, pure 2 molecules of ATP are formed.	(ii) This process also takes place in the cytoplasm and during the formation of pyruvic acid from glucose, pure 2 molecules of ATP are formed.
(iii) Sugar gets partially oxidised to form two molecules of pyruvic acid.	(iii) In fermentation, the oxidation of NADH to NAD+ is slow.

During the oxidation process inside the cell, the entire energy present in the respiratory substrate is not released simultaneously in the cell. It is released in the form of slow stepwise reactions controlled by enzymes, which store chemical energy in the form of ATP. It is worth noting that the energy released by oxidation in Biology-Class 11 respiration is not directly used but it is used in the synthesis of ATP and whenever this energy is needed, it gets broken down and provides energy. For this reason, ATP acts as energy currency for the cell. The energy stored in ATP is used in various energy-essential processes of living organisms. The organic substances produced during respiration serve as precursors for the synthesis of other molecules in the cell.

Amphibolic path : Because the respiratory pathway is involved in both anabolism and catabolism it is called amphibolic path.
Difference between Respiration and Photosynthesis

Respiration	Photosynthesis
1. This is a disruptive action.	1. It is a creative activity.
2. It is present in every cell of living beings.	2. Occurs only in chlorophyll cells.
3. It happens continuously in both light and darkness.	3. Occurs only in the presence of light.
4. In this, O2 is absorbed and CO2 is released.	4. When CO2 is taken in, O2 is released.
5. Weight decreases.	5. Weight increases.
6. Food disintegrates.	6. Food is manufactured.

Alcohol, CO₂ and energy C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 28 Kcal Energy
Importance of respiration : Respiration plays an important role in the life of plants which are as follows:
1. This releases energy which is used in metabolic activities necessary for plant life.
2. Regulation of energy is produced as per the requirement of all activities.
3. Due to this, insoluble food substances are converted into soluble forms.
4. This releases CO₂ which is used in photosynthesis.
5. The Krebs cycle is a general pathway for the oxidative breakdown of carbohydrates, fatty acids, and amino acids.
6. It activates various meristematic tissues of plants.