Bellringer 11/6• Where do trees get their mass from?

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UNIT 2 PART 4: PLANT NUTRITION

• Photosynthesis is a process where plants transform the energy from light into chemical bond energy.

• Green plants are autotrophs: they manufacture food from inorganic raw materials. A heterotroph eats food.

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Chlorophyll: A pigment

• A substance that absorbs light is called a pigment.

• Plants have green pigments, chlorophylls a & b. They look green because green light is reflected.

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• Other plant pigments include

– carotene (orange) &

–xanthophyll (yellow).

• Together, these pigments absorb the red & blue light used in photosynthesis.

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Chloroplast: Site of Photosynthesis• The chloroplasts in the

palisade & spongy cells consist of 2 membrane layers surrounding a space called the stroma.

• Within the space are the grana, made of thylakoid membranes that contain the chlorophylls and other pigments.

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Photosynthesis: The overall reaction

6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O

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•Step 1: The light-dependent reaction

•Requires light

•Light energy captured by chlorophyll is used to split water into H2 and O.

•Occurs in thylakoid membranes.

•Produces oxygen, O2.

Photosynthesis occurs in two steps:

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Photosynthesis occurs in two steps:• Step 2: the light-

independent reactions

• Do not need light, but do need some of the products of the light-dependent reactions.

• Uses CO2 (carbon fixation) to produce glucose in the Calvin cycle

• Occurs in the stroma.• Glucose is stored as

starch in leaves.

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• The rate of photosynthesis is affected by:– Light intensity

• More light

increased photosynthesis

– Temperature• Too high or low

decreased photosynthesis

– Amount of water available– Amount of minerals available

• A shortage of either water or minerals will slow or stop photosynthesis

Light intensity

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Temperature

Bellringer

• Without using your notes, write the equation for photosynthesis (either the formula or in words).

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Respiration and Photosynthesis are reverse reactions

• Respiration occurs in the cytoplasm and in mitochondria.• Converts organic molecules to inorganic

• C6H12O6 + 6O2 6CO2 + 6H20

• Releases energy from the chemical bonds in glucose, making ATP (energy)

Vs.

•Photosynthesis occurs in chloroplasts.•Converts inorganic molecules to organic

•6CO2 + 6H20 C6H12O6 + 6O2

•Stores energy from the sun in chemical bonds of glucose

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