AP Inter 2nd Year Botany Notes Chapter 5 Respiration in Plants

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AP Inter 2nd Year Botany Notes 5th Lesson Respiration in Plants

→ All the energy required for life processes is obtained by oxidation of some macromolecules that we call food.

→ Only green plants and cyanobacteria can prepare their own food by the process of photosynthesis.

→ The mechanism of breakdown of food materials with in the cell to release energy and the trapping of this energy for synthesis of ATP.

→ The compounds that are oxidised during this process are known as respiratory substrates.

→ ATP acts as the energy currency of the cell.

→ Respiration is of two types a) aerobic b) an aerobic

→ Aerobic respiration occurs in the presence of O₂ in four steps.

→ Glucose is brokendown into 2 pyruvic acid molecules is called glycolysis or EMP pathway.

→ The complete oxidation of pyruvate by the step wise removal of all the hydrogen atoms, leaving 3 CO₂ molecules.

→ Pyruvate undergoes oxidative decarboxylation in the presence of pyruvic dehydrogenase then condenses with CoA to yield acetyl Co A.

→ Acetyl CoA undergoes complete oxidation and releases energy rich NADPH+H⁺ molecules through Krebs cycle.

→ NADPH+H⁺ or FADH₂ molecules oxidise and release electrons which move through ETS pathway finally reach 1/2 O₂ along with protons to form H₂O.

→ ATP synthesis can be explained by peter Mitchell, chemiosmotic hypothesis.

→ 1 Glucose on oxidises produce 36 ATP molecules.

→ In respiration both catabolism and anabolism are visible, so called amphibolic pathway.

→ The ratio of the volume of CO₂ evolved to the volume of O₂ consumed in respiration is called respiratory quotient.

→ Respiratory quotient of carbohydrates is one.

→ Respiratory quotient of fats is less than one (0.7).

→ Respiratory quotient of proteins is less than one (0.9).

→ Respiration provides energy to the plant body. It is done by the oxidation of food.

→ The compounds that are oxidised during respiration are known as respiratory substrates.

→ Glucose is the favoured substrate for respiration.

→ All the energy contained in a respiratory substrate does not release freely into the cell, but it is trapped as a chemical energy in the form of ATP.

→ The energy trapped in ATP is utilised in various energy requirements of the organism.

→ In plants respiration happens in two ways.
(i) Gaseous exchange through Stomata and Lenticels (ii) Cellular respiration

→ Cellular respiration is of two types (i) aerobic respiration (ii) anaerobic respiration.

→ Respiration in the presence of oxygen is called aerobic respiration.
Ex: Glycolysis, Kreb’s cycle.

→ Respiration in the absence of oxygen is called anaerobic respiration. Ex: Fermentation [IPE]

→ Glycolysis: [IPE]

1. Glycolysis is the first step of respiration in all living organisms.
2. It occurs in cytoplasm of cells.
3. During Glycolysis, Glucose molecules break down to release energy.
4. Glycolysis is the oxidation of one glucose molecule to form 2 molecules of pyruvic acid.

→ Kreb’s Cycle: [IPE]

1. Kreb’s cycle is a cycle of reactions used by all aerobic organisms to generate energy.
2. It takes place in mitochondria.
3. Acetyl coenzyme (CoA) is oxidised to form CO₂ and H₂O.
4. Also, ADP is converted into energy-rich ATP.

→ Cytochromes are found in cristae of mitochondria.

→ In mitochondria, protons accumulate in the intermembrane space.

→ Aerobic respiratory pathway is appropriately termed amphibolic.

→ Respiratory Quotient (RQ) Value of Tripalmitin is “0.7”.

→ In the conversion of glucose to glucose – 6 – phosphate, the first irreversible reaction of glycolysis, is catalysed by Hexokinase

→ The number of substrate level phosphorylation in one turn of citric cycle is one. [NEET-2020]