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Photosynthesis

Photosynthesis. Photosynthesis. Process by which plants and some other organisms use light energy to convert water and carbon dioxide (CO 2 ) into oxygen and carbohydrates such glucose. Takes place inside chloroplasts. FORMULA OF PHOTOSYNTHESIS. 6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2

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Photosynthesis

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  1. Photosynthesis

  2. Photosynthesis • Process by which plants and some other organisms use light energy to convert water and carbon dioxide (CO2) into oxygen and carbohydrates such glucose. • Takes place inside chloroplasts

  3. FORMULA OF PHOTOSYNTHESIS • 6 CO2 + 6 H2O  C6H12O6 + 6 O2 • Carbon dioxide + water  sugar + oxygen

  4. Photosynthesis • Needed (Reactants): • Light • Water • Carbon dioxide • Given Off (Products): • Sugars • Oxygen

  5. Autotrophs and Heterotrophs • Autotrophs – organisms that use light energy from the sun to produce food; also called producers • Examples: plants, blue-green algae, some prokaryotes • Heterotrophs – organisms that obtain energy from the foods they consume; also called consumers • Examples: animals, fungus, some prokaryotes and protists.

  6. ATP (energy) • Adenosine Triphosphate (ATP) - One of the principal chemical compounds that living things use to store and release energy

  7. ATP & NAPDH • ATP and NAPH store energy in their bonds. • ATP loses a Phosphate to become ADP, releasing energy. • NAPH loses a Hydrogen to become NADP+, releasing energy.

  8. INSIDE THE CHLOROPLAST • Thylakoids – saclike photosynthetic membranes • Grana – stacks of thylakoids • Stroma – region outside thylakoid membranes

  9. Light Absorption in the Chloroplasts • Chloroplasts in plants cells absorb light energy from the sun during the light dependent reactions • Photosynthetic cells may have thousands of chloroplasts • Chloroplasts are double membrane organelles with the an inner membrane folded into disc-shaped sacs called thylakoids

  10. Thylakoids, containing chlorophyll and other accessory pigments, are in stacks called granum (grana, plural) • Grana are connected to each other & surrounded by a gel-like material called stroma • Light-capturing pigments in the grana are organized into photosystems

  11. Pigments • Light travels as waves called photons • Wavelength is a measure of photons. • Sunlight is made of different wavelengths or colors carrying different amounts of energy • A prism separates white light into 7 colors (red, orange, yellow, green, blue, indigo, & violet) ROY G. BIV • These colors are called the visible spectrum

  12. When light strikes an object, it is absorbed, transmitted, or reflected • When all colors are absorbed, the object appears black • When all colors are reflected, the object appears white • If only one color is reflected (green), the object appears that color (e.g. Chlorophyll)

  13. Chlorophyll • Thylakoids contain a variety of pigments ( green red, orange, yellow...) • Chlorophyll a: Absorbs light mostly in the blue-violet and red regions of the visible spectrum

  14. Chlorophyll b: Absorbs light in the blue and red regions of the visible spectrum. • Chlorophyll does not absorb light well in the green region of the spectrum. • Green light is reflected by leaves, which is why plants look green. • Carotenoids are accessory pigments in the thylakoids & include yellow, orange, & red

  15. Overview of Photosynthesis   •       6CO2 + 6H2O C6H12O6 + 6O2 • Photosynthesis is not a simple one step reaction but a biochemical pathway involving many steps • This complex reaction can be broken down into two reactions: • light dependent • light independent

  16. Light-Dependent Reactions • Takes place within the thylakoid membranes • Requires: Light, Water, ADP, and NADP+ • Produce: Oxygen, ATP, and NADPH

  17. Light – Dependent Reaction: • Water is split, giving off oxygen. • This system depends on sunlight for activation energy. • Light is absorbed by chlorophyll a which "excites" the electrons in the chlorophyll molecule. • Electrons are passed through a series of carriers and ATP (energy) is produced.

  18. The Light-Independent Reactions (Calvin Cycle) • Takes place in the stroma • Requires: CO2, ATP, NADPH • Produces: Glucose, NADP+, ADP

  19. Light-Independent Reaction:    • Carbon dioxide is split, providing carbon to make sugars. • The ultimate product is glucose (C6H12O6). • While this system depends on the products from the light reactions, it does not directly require light energy. • Includes the Calvin Cycle.

  20. Calvin Cycle • ATP and NADPH are too unstable for long term energy storage, so the Calvin cycle uses their energy to produce high-energy sugars. • Uses six molecules of carbon dioxide to produce a single 6-carbon sugar molecule. • Energy for this conversion comes from ATP and high-energy electrons from NADPH.

  21. Factors Affecting Photosynthesis • Water • A shortage of water can slow or even stop photosynthesis – waxy coating on leaves helps prevent water loss. • Temperature • Photosynthesis depends on enzymes that function best between 0°C and 35°C. • Intensity of Light • Increasing light intensity increases the rate of photosynthesis...but a plant will reach a maximum rate.

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