Concept 10.5: Life depends on photosynthesis Flashcards
In this chapter, we have followed photosynthesis from photons to food. The light reactions capture solar energy and use it to make ATP and transfer electrons from water to NADP+, forming
NADPH.
The Calvin cycle uses the ATP and NADPH to produce sugar from
carbon dioxide
The energy that enters the chloroplasts as sunlight becomes stored as chemical energy in
organic compounds
As for the fates of photosynthetic products, enzymes in the chloroplast and cytosol convert the G3P made in the Calvin cycle to many other
organic compounds.
In fact, the sugar made in the chloroplasts supplies the entire plant with chemical energy and carbon skeletons for the synthesis of all the
major organic molecules of plant cells.
About 50% of the organic material made by photosynthesis is consumed as fuel for
cellular respiration in plant cell mitochondria.
Technically, green cells are the only
autotrophic parts of the plant.
The rest of the plant depends on organic molecules exported from
leaves via veins
In most plants, carbohydrate is transported out of the leaves to the rest of the plant in the form of
sucrose, a disaccharide.
After arriving at nonphotosynthetic cells, the sucrose provides raw material for cellular respiration and a multitude of anabolic pathways that synthesize
proteins, lipids, and other products
A considerable amount of sugar in the form of glucose is linked together to make the ______________________(see Figure 5.6c), especially in plant cells that are still growing and maturing.
polysaccharide cellulose
Cellulose, the main ingredient of
cell walls, is the most abundant organic molecule in the plant—and probably on the surface of the planet.
Most plants and other photosynthesizers make more organic material each day than they need to use as
respiratory fuel and precursors for biosynthesis.
They stockpile the extra sugar by synthesizing starch, storing some in the chloroplasts themselves and some in storage cells of
roots, tubers, seeds, and fruits
