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Bellringer 11/6 Where do trees get their mass from? 7
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8 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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9 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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10 Other plant pigments include – carotene (orange) & –xanthophyll (yellow). Together, these pigments absorb the red & blue light used in photosynthesis.
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12 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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13 Photosynthesis: The overall reaction 6CO 2 + 12H 2 O C 6 H 12 O 6 + 6O 2 + 6H 2 O
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15 Step 1: The light- dependent reaction Requires light Light energy captured by chlorophyll is used to split water into H 2 and O. Occurs in thylakoid membranes. Produces oxygen, O 2. Photosynthesis occurs in two steps:
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16 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 CO 2 (carbon fixation) to produce glucose in the Calvin cycle Occurs in the stroma. Glucose is stored as starch in leaves.
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17 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 Rate of photosynthesis Temperature
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Bellringer Without using your notes, write the equation for photosynthesis (either the formula or in words). 18
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20 Respiration and Photosynthesis are reverse reactions Respiration occurs in the cytoplasm and in mitochondria. Converts organic molecules to inorganic C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 0 Releases energy from the chemical bonds in glucose, making ATP (energy) Vs. Photosynthesis occurs in chloroplasts. Converts inorganic molecules to organic 6CO 2 + 6H 2 0 C 6 H 12 O 6 + 6O 2 Stores energy from the sun in chemical bonds of glucose
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