Patterns of problems
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Photosynthesis In Higher Plants

- Hit the perfect ace in exams by getting acquainted with the different ways or patterns of the questions asked for a particular concept!
Pattern: Experiments related to photosynthesis
Description: Photosynthesis is the process of preparing food in the presence of sunlight and chlorophyll. In this process, the plant uses water from the soil, carbon dioxide from the air. It occurs in green plants, certain algae, blue-green algae and bacteria. Various experiments on photosynthesis led to the discovery of photosynthesis and to prove that indeed the raw materials specified above, are required for photosynthesis.
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Pattern: Site of photosynthesis and the pigments involved
Description: Photosynthesis occurs in the chloroplast of the mesophyll cells of the leaves. The chloroplasts are double-membranous cell organelles that are comprised of stacked disc-like structures known as thylakoids. The pigment, chlorophyll, which is required for the process is present on the membrane of these thylakoids and this is where the light reaction occurs. Photosynthetic pigments capture light. In plants, chlorophyll 'a' is the main photosynthetic pigment that absorbs light and pigments like chlorophyll 'b', xanthophylls and carotenoids, which are called accessory pigments, also absorb light and transfer the energy to chlorophyll 'a'.
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Pattern: Light-dependent reactions (Light reactions)
Description: The main purpose of the light reaction is to generate organic energy molecules such as ATP and NADPH which are needed for the subsequent dark reaction. When the light falls on the plant, the chlorophyll pigment absorbs this light and electrons in it, get excited. The chlorophyll pigments which are excited, give up their electrons and to compensate for the loss of electrons, water is split to release ions, electrons and oxygen. The lost electrons enter into an electron transfer chain and then reduce to NADPH. The hydrogen ions building up inside the lumen creates a positive gradient that are used to drive hydrogen ions across ATP synthase complex to generate ATP.
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Pattern: Light-independent reaction (Dark reaction)
Description:The dark reaction of photosynthesis is not dependent on sunlight but it does not mean it does not occur in its presence. The dark reaction occurs both in the presence and absence of sunlight. This reaction occurs in the stroma of the chloroplasts. The dark reaction was first identified by Calvin. This reaction is also called by many other names such as cycle. The plants that have Calvin cycle are known as plants. The dark reaction is the actual phase where food is synthesized by the plants and it uses the energy generated by the light reactions. The main three phases of dark reaction are:
  1. Carbon fixation
  2. Reduction
  3. Regeneration
plants are different from plants. They follow hatch and slack pathway. The first stable intermediate product is a 4 carbon acid - oxaloacetate. The photosynthetic functions occur in mesophyll and bundle sheath cells.
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Pattern: Photorespiration
Description: Photorespiration is a special type of respiration that is found in plants. It occurs in the presence of sunlight. Photorespiration occurs in three organelles of the plant cells namely, chloroplast, peroxisomes, and mitochondria. It is an oxidative process where glycolate is oxidized to release carbon dioxide. Photorespiration is said to be influenced by the carbon dioxide concentration in the plant, the temperature of the atmosphere and the oxygen levels.
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Pattern: Factors affecting photosynthesis
Description: Photosynthesis is a process by which plants prepare their own food in the presence of water, chlorophyll, sunlight, and carbon dioxide. There are several factors affecting photosynthesis, its rate and efficiency. Some of the factors are: light, carbon dioxide concentration, temperature, water, oxygen. Now, the rate of photosynthesis depends on its factors affecting it which is based on Blackman's principle of limiting factors. It states that when a process is governed by more than one factor, the rate of the process is governed by that factor which is closest to its minimum value.
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