Bellringer 11/6 Where do trees get their mass from? 7

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.

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.

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.

13 Photosynthesis: The overall reaction 6CO H 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:

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.

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

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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