T 1.01 Photosynthesis and Cellular Respiration

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All life processes are supported by the simple sugar glucose. Glucose is both the primary source of energy for these processes and an important building block for many other compounds. Plants capture light energy through their leaves and use it to convert carbon dioxide and water into glucose. The process is called ‘photosynthesis’.

Photosynthesis is the source of all of the organic compounds and most of the energy used to sustain life on Earth. Oxygen is a by-product of photosynthesis. Photosynthesis  produces most of the oxygen in our atmosphere.

Plant leaves contain pigments called chlorophyll that absorb red and blue wavelengths of light and reflect green light, which is why leaves appear green to our eyes. When a chlorophyll molecule absorbs a single photon of light, it releases a single electron that is used to drive the reactions that create glucose.

Chlorophyll is contained in organelles (structures within cells) known as chloroplasts. Inside the chloroplasts, the chlorophyll is stored in the membrane of little green pancake-like stacks known as thylakoids. The light-dependent reactions take place at the thylakoid membrane that surrounds these little pancakes. It is also here where the oxygen we breathe is created.

In this image you can see plant cells containing chloroplasts under the microscope


What Other Ingredients Do Plants Need to Produce Glucose?

Plants need carbon dioxide and water to produce glucose, which is made of carbon, hydrogen, and oxygen. 6 CO2 + 6 H2O → C6H12O6 + 6 O2. (→ = Light energy plus chlorophyll).

A plant’s roots take up water from the soil. Xylem, a woody tissue containing bundles of capillaries, transports water and minerals throughout the plant. The carbon dioxide that is needed for photosynthesis comes directly from the atmosphere. It is taken into the leaves of plants through small pores known as stomata. The stomata allow the CO₂ to diffuse into the leaf.

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