RuBP Carboxylase This is a part of dark reaction of photosynthesis. It catalyses the fixing of $\mathrm{CO}_2$ in $\mathrm{C}_3$ cycle.

PEPcase This is a part of photosynthesis of $\mathrm{C}_4$ plants. It catalyses the reaction of fixing of $\mathrm{CO}_2$ to form first stable product oxaloacetate. 4 carbon compound.

Pyruvate dehydrogenase It is involved in aerobic respiration and catalyses the reaction of formation of acetyl Co-A from pyruvic acid. It requires the participation of NAD and Co-enzyme-A.

Pyruvic acid $+\mathrm{Co}-\mathrm{A}+\mathrm{NAD}^{+} \xrightarrow[\text { Pyruvate dehydrogenase }]{\mathrm{Mg}^{2+}}$ Acetyl $\mathrm{Co}-\mathrm{A}+\mathrm{CO}_2+\mathrm{NADH}+\mathrm{H}^{+}$

ATPase It is a part of both respiration and photosynthesis. Both these processes uses electron transport chain and associated proton pump and ATP synthase as a key part of process. ETC uses the energy to pump hydrogen ions across a membrane.

The protons flows back through ATP synthase, driving the production of ATP.

Cytochrome Oxidase This is involved in both respiration and photosynthesis. It is an electron carrier in the electron transport chain. Hexokinase This enzyme is also involved in, respiration. In glycolysis, it catalyses the first reaction, i.e., formation of glucose -6- phosphate from glucose molecule. It uses one ATP molecule which transfers $\mathrm{PO}_4$ group to glucose molecules.

Lactate Dehydrogenase

This enzyme is involved in anaerobic respiration in bacteria Lactobacillus. Pyruvic acid formed at the end of glycolysis is converted to lactic acid by homo-fermentative lactic acid bacteria. Hydrogen from NADH molecule is transferred to pyruvate is transferred to pyruvate molecule lactic acid molecule leading formation of acid.

$\underset{\substack{\text { Pyruvic acid }}}{\mathrm{CH}_3 \mathrm{COCOOH}}+$ NADH. $\underset{\text { Dehydrogenase }}{\stackrel{\text { Lactate }}{\longrightarrow}} \underset{\text { Lactic acid }}{\mathrm{C}_3 \mathrm{H}_6 \mathrm{O}_3}+$ NAD

The old tree trunk is covered by dead woody tissue called cork. The epidermal layers of such tree get ruptured and outer cortical cells are loosely arranged. These structures are called as lenticels.

These are the sites of gases exchange and transpiration.

The following figure shows the process of glycolysis, and sites for yielding energy during glycolysis

Thus, ATP is produced during degradation of 1,3 biphosphoglyceric acid into 3-phosphoglyceric acid and during degradation of 2-phosphoenol pyruvate into pyruvic acid.

Pyruvate is synthesised in cytoplasm of the cell by the process of glycolysis. 1 molecule of glucose forms 2 molecules of pyruvate through a series of reactions. Pyruvic acid dehydrogenase catalyses the reaction in which pyruvate forms acetyl $\mathrm{Co}-\mathrm{A}$. It requires $\mathrm{NAD}^{+}$, Co-enzyme A and $\mathrm{Mg}^{2+}$ ions for its activity. The reaction is as follows

$$\text { Pyruvic acid }+\mathrm{Co}-\mathrm{A}+\mathrm{NAD}^{+} \xrightarrow[\text { Pyruvate Dehydrogenase }]{\mathrm{Mg}^{2+}} \text { Acetyl } \mathrm{Co}-\mathrm{A}+\mathrm{NADH}+\mathrm{H}^{+}+\mathrm{CO}_2 \uparrow$$

Living cells obtain energy through respiration. It is the process of generating energy in the form of ATP molecules by breaking down food molecules like glucose, fats, etc. The process starts with glycolysis which occurs in cytoplasm producing pyruvic acid. It is then converted to acetyl Co-A, which enters mitochondrial matrix. This initiates the tricarboxylic acid cycle.

This cycle is said to be amphibolic because many intermediate compounds formed in this cycle act as precursors for biosynthesis of many important biological molecules, i.e., co-enzymes, vitamins, hormones. Besides this, many molecules, i.e., fatty acids, aminoacids, co-enzymes etc, can enter this cycle directly.

Acetyl Co-A is related to synthesis and breakdown of fatty acids, steroids, carotenoids terpenes and aromatic compounds. $\alpha$-ketoglutarate and oxaloacetate are row materials for synthesis of amino acids like glutamate and aspartate and also pyrimidines and alkaloids. Succinyl forms pyrroole compunds like cytochrome and chlorophyll.

So, it is the cycle where both breakdown and synthesis reactions keep on going simultaneously. the following figure shows interrelationship among netabolic pathway showing respiration mediated break down of different organic molecule.