Photosynthesis Notes PDF

## Properties and Functions of Cells ### Nutrition * The process whereby living organisms obtain and utilise materials from the external environment for metabolic activities such as growth, excretion, and reproduction. ### Metabolism * Refers to all the chemical processes associated with living...

## Properties and Functions of Cells ### Nutrition * The process whereby living organisms obtain and utilise materials from the external environment for metabolic activities such as growth, excretion, and reproduction. ### Metabolism * Refers to all the chemical processes associated with living organisms. It is divided into two: catabolism and anabolism. ### Autotrophic Mode of Nutrition #### Types of Nutrition 1. **Phototrophic** * Phototrophic mode of nutrition is categorized into two: * Photosynthetic * Chemosynthetic * **Photosynthetic:** In this form, green plants manufacture their own food from simple inorganic substances using sunlight as an external source of energy. * $6CO_2 + 6H_2O \xrightarrow{sunlight, chlorophyll} C_6H_{12}O_6 + 6O_2$ * **Chemosynthetic nutrition:** This involves the manufacture of food from simple inorganic substances such as carbon dioxide, water, and hydrogen sulfide using energy released during chemical reactions. * $12H_2S + 6CO_2 \xrightarrow{chemical\ energy} C_6H_{12}O_6 + 12S + 6H_2O$ 2. **Heterotrophic** #### Mechanism of Photosynthesis * The process of photosynthesis is divided into two: 1. Light reaction 2. Dark reaction ##### Light reaction * This occurs in light (grana) of the chloroplast. * It is divided into four steps: * **Step 1:** Chlorophyll becomes energized after absorption of sunlight. * **Step 2:** Photolysis of water: The energy absorbed by the chlorophyll is used to split water molecules into hydrogen ions ($H^+$) and hydroxyl ions ($OH^-$). * **Step 3:** Hydrogen is transferred by NADP (Nicotinamide Adenine Dinucleotide Phosphate). The hydrogen atom released during photolysis of water is picked up by NADP. This is to prevent the escape of hydrogen atoms from the cell or the combining with oxygen to form water. * **Step 4:** Formation of ATP (Adenosine Triphosphate). Chloroplast contains ADP (Adenosine Diphosphate) which is an energy carrier. The extra energy not used up in the splitting of water molecules is released to RDP to form ATP, which is used in the dark reaction. ##### Dark reaction * This reaction does not require light. Carbon dioxide is released by combining with two atoms of H provided by NADPH to form sugars after undergoing a series of stepwise reactions. * The energy needed for the formation of sugar is provided by ATP from light reactions. * The reaction takes place in the stroma of the chloroplast. #### Materials Needed for Photosynthesis 1. Water 2. Light energy 3. Chlorophyll 4. Stable temperature 5. Carbon dioxide 6. Oxygen