Tiêu đề RESPIRATION IN PLANTS(165-210)_08.02.2020.pdf ✅

NARAYANA GROUP NEET BOTANY VOL-1 CH-14 : RESPIRATION IN PLANTS 165 NARAYANA GROUP Respiration in Plants C O N T E N T S  Introduction  Do Plants Breathe?  Glycolysis  Fermentation  Aerobic Respiration  Tricarboxylic Acid Cycle  Electron Transport System (ETS) and Oxidative Phosphorylation  The Respiratory Balance Sheet  Amphibolic Pathway  Respiratory Quotient Resp iration: Exchange of gases; Cellular respiration- Glycolysis, fermentation (anaerobic), TCA cycle and Electron transport system (aerobic); Energy relations- Number of ATP molecules generated; Amphibolic pathway Respiratory quotient. NEET SYLLABUS 14

NARAYANA GROUP NEET BOTANY VOL-1 CH-14 : RESPIRATION IN PLANTS 167 NARAYANA GROUP   -oxidation of fatty acids occurs in mitochondria (or glyoxisomes in plants)  Glyoxylate cycle occurs in glyoxisomes in cooperation with mitochondria and cytosol, to convert fat into carbohydrates (sucrose) .  (ii) Protoplasmic Respiration : Where proteins are respiratory substrates.  Proteins are broken into amino acids and further they release ammonia and disintegrate into keto acids. (e.g.  – ketoglutarate) .  Protoplasmic respiration occurs during starvation and cannot continue for long, as NH3 is toxic.  A comparison of Respiration and Combustion is given below Respiration Combustion (i) It occurs inside living cells. It is a non-cellular process. (ii) Respiration is a biochemical process. Combustion is a physico-chemcial process. (iii) Energy is released in stages as chemical bonds are broken in steps. Energy is released in a single step as all chemical steps occur simultaneously. (iv) Most of the energy is trapped in ATP molecules ATP is not formed. (v) Oxidation occurs at the end of reaction (terminal oxidation) between reduced coenzyme and oxygen. The substrate is directly oxidized in combustion. (vi) A number of intermediates are formed. They are used in the synthesis of different organic compounds. No intermediates are produced in combustion. (vii) A number of enzymes are required, one for each step or reaction. Burning is a non-enzymatic process. (vii) More than 50% energy is liberated in the form of heat energy. Light is rarely produced. Energy is liberated in the form of both light and heat energy. (ix) Temperature is not allowed to rise. Temperature becomes very high. DO PLANTS BREATHE  Plants, unlike animals, have no specialised organs for gaseous exchange but they have stomata and lenticels for this purpose. There are several reasons why plants can get along without respiratory organs.  First, each plant part takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another.  Second, plants do not present great demands for gaseous exchange. Roots, stems and leaves respire at rates far lower than animals do.  Third, the distance that gases must diffuse even in large, bulky plants is not great. Each living cell in a plant is located quite close to the surface of the plant. ‘This is true for leaves’, you may ask, but what about thick, woody stems and roots?
168 168 NARAYANA GROUP CH-14 : RESPIRATION IN PLANTS NEET BOTANY VOL-1 * In stems, the ‘living’ cells are organised in thin layers inside and beneath the bark. They also have openings called lenticels. The cells in the interior are dead and provide only mechanical support. Thus, most cells of a plant have at least a part of their surface in contact with air. This is also facilitated by the loose packing of parenchyma cells in leaves, stems and roots, which provide an interconnected network of air spaces. AEROBIC AND ANAEROBIC RESPIRATION (SACHS) :  Respiration can occur with or without the involvement of oxygen. Accordingly, it is of two types, aerobic and anaerobic (Sachs, 1890) . Aerobic respiration (Gk, aer = air, bios= life) is that mode of respiration where the organic food is completely oxidised to carbon dioxide and water with oxygen functioning as terminal oxidant. About 686 kcal of energy is liberated per gram mole of glucose. Enzymes 6 6 6 686 6 12 6 2 2 2 C H O O CO H O kcal         It occurs in higher plants and animals. The organism performing aerobic respiration are called aerobes.  Anaerobic respiration (Gk. an-without , aer-air, bios-life) is that made of respiration which does not employ oxygen as ultimate oxidant. Instead, organic food is broken down incompletely. Energy is liberated due to breaking of chemical bonds. However, the amount of energy is less, 36-59 kcal (150-250 kJ) .It occurs in many prokaryotes, unicellular eukaryotes (Yeast ) , Germinating seeds etc., 2 5 2 cos Enzymes 2 6 59 / 247 6 12 6 ethanol glu e C H O C H OH CO kcal kJ    a) Facultative anaerobes: The aerobic organisms which can respire even in the absence of O2 Ex: Bacteria :- Staphylococcus spp, Streptococcus spp, Fungi :- Saccharomyce scerevisiae (yeast) b) Obligate anaerobes: Organisms which repire anaerobically only. They lack enzymes necessary for carrying out aerobic respiration Ex: Clostridium EVALUATE YOURSELF-1 1. Which process provides energy for daily activities to all organisms? (1) Photosynthesis (2) Aerobics (3) Cellular respiration (4) Combustion of sugars 2. Respiration is (1) anabolic and exergonic (2) catabolic and exergonic (3) anabolic and exergonic (4) catabolic and endergonic 3. Cellular respiration releases energy as (1) GTP (2) CTP (3) TTP (4) ATP 4. Aerobic respiration uses (1) CO2 (2) N2 (3) O2 (4) Air 5. Respiratory substrates are the organic substances which are _______ during respiration to liberate energy (1) oxidized (2) reduced (3) synthesized (4) both (1) & (2) 6. The organelle where cellular respiration takes place is the (1) nucleus (2) endoplasmic reticulum (3) ribosome (4) mitochondria 7. In addition to glucose the cell needs ______ to drive cellular respiration (1) oxygen (2) carbon dioxide (3) water (4) hydrogen