IGCSE Biology Paper-3: Specimen Questions with Answers 311 - 312 of 358

Question 311

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The cells in the leaves of plants that make glucose contain a green substance.

State the name of this green substance.

Explanation

Chlorophyll

Building-up of complex food molecules from simpler substances is called synthesis and it needs enzymes and energy to make it happen. The enzymes are present in the plant՚s cells and the energy for the first stages in the synthesis comes from sunlight. The process is, therefore, called photosynthesis ( ‘photo’ means ‘light’ ) . There is evidence to suggest that the green substance, chlorophyll, in the chloroplasts of plant cells, plays a part in photosynthesis. Chlorophyll absorbs sunlight and makes the energy from sunlight available for chemical reactions. Thus, in effect, the function of chlorophyll is to convert light energy to chemical energy. In order to keep the equation simple, glucose is shown as the food compound produced. The glucose is rapidly converted to sucrose for transport around the plant, then stored as starch or converted into other molecules.

Mesophyll is Divided

Question 312

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The cells in the leaves of plants that make glucose contain a green substance.

State the name of the cells that make glucose.

Explanation

Mesophyll is divided into two regions - Palisade tissue and spongy parenchyma. Palisade tissue is found towards upper surface. These cells have more chloroplasts and spongy parenchyma is found towards lower surface intercellular spaces are well developed between cells of spongy parenchyma. Chloroplast is the kitchen in plant cell thus produces food and mainly Glucose.

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