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SURFACE AREA AND ITS IMPACT ON BIOLOGY

Chloroplast













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WHAT IS A CHLOROPLAST ? 

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Chloroplasts are specialized organelles found in all higher plant cells. These organelles contain the plant cell's chlorophyll, hence provide the green color. They have a double outer membrane. Within the stroma are other membrane structures - the thylakoids and grana (singular = granum) where photosynthesis takes place.































HOW DOES SURFACE AREA IMPACT PHOTOSYNTHESIS ? 

 

 

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The chloroplast is the organelle where photosynthesis occurs in photosynthetic eukaryotes. The organelle is surrounded by a double membrane. Inside the inner membrane is a complex mix of enzymes and water. This is called stroma and is important as the site of the Calvin cycle.

Embedded in the stroma is a complex network of stacked sacs. Each stack is called a granum and each of the flattened sacs which make up the granum is called a thylakoid. Each thylakoid has a series of photosystems and associated proteins. The photosystems contain chlorophyll and other pigments and all these associated structures in the thylakoid membrane are the site for the light reactions in which light energy is converted to chemical energy needed for the Calvin cycle.

 

 

 WHAT IS THE CALVIN CYCLE ?

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The Calvin cycle is a metabolic pathway found in the stroma of the chloroplast in which carbon enters in the form of CO2 and leaves in the form of sugar. The cycle spends ATP as an energy source and consumes NADPH2 as reducing power for adding high energy electrons to make the sugar. There are three phases of the cycle.

 

*** In phase 1 (Carbon Fixation), CO2 is incorporated into a five-carbon sugar named ribulose bisphosphate (RuBP).

 

*** In phase 2 (Reduction), ATP and NADPH2 from the light reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-phosphate, the three-carbon carbohydrate precursor to glucose and other sugars.

 

*** In phase 3 (Regeneration), more ATP is used to convert some of the pool of glyceraldehyde 3-phosphate back to RuBP, the acceptor for CO2, thereby completing the cycle.

 

For every three molecules of CO2 that enter the cycle, the net output is one molecule of glyceraldehyde 3-phosphate (G3P).

 

 

HOW DOES SURFACE AREA IMPACTS CHLOROPLAST ?

Like in mitochondria surface area is of great significance in chloroplast because it increases the rate of a chemical reaction that produces sugar (glucose). This is the reason for which chloroplast has a very large surface area of the membranes inside compared to the size of the organelle it self.