2.9 Photosynthesis

• Chlorophyll is found in the chloroplasts.
• The photosynthesis chemical formula is the opposite of respiration.
• Photosynthesis is a process where cells synthesis organic compounds (e.g. glucose) from inorganic molecules in the presence of sunlight.
• Chlorophyl absorbs all colours other than green and therefore reflects green.
• 3 pigments in chlorophyll that absorb light are carotenoid, chlorophyll a and chlorophyll b.
• Photosynthesis can only occur in plants, certain bacteria and protists.
• The word equation of photosynthesis is carbon dioxide + water --> glucose + oxygen
• Photosynthesis is anabolic.
• The visible light spectrum occurs from approximately 400 to 700nm as different wavelengths of white light from red (approx 700nm) to violet (approx 400nm).
• Blue has the smallest wavelength of light.
• Red has the longest wavelength of light.
• White is the combination of all colours in the visible light spectrum.
• Chlorophyll is responsible for light absorption in photosynthesis releasing electrons which are used to synthesise ATP.
• All chlorophyll molecules absorb the blue portion of the visible light spectrum most strongly.
• All chlorophyll molecules absorb the red portion of the visible light spectrum less strongly than blue.
• All chlorophyll molecules reflect the green portion of the visible light spectrum most strongly.
• The law of limiting factors states that when a chemical process depends on more than one essential condition being favorable, the rate of reaction will be limited by the factor that is nearest its minimum value.
• When iodine is added to starch it turns to black.
• 2.3 billion years ago, photosynthetic organisms began to saturate the environment.
• Earth's oceans initially had high levels of dissolved iron. When iron reacts with oxygen it forms iron oxide . When the iron in the ocean was completely consumed, oxygen gas began to appear in the atmosphere.
• The light dependent stage of photosynthesis converts light energy from the sun into chemical energy (APT).
• The light independent reactions in photosynthesis use chemical energy to synthesize organic compounds such as carbohydrates.
• Light dependent reactions require light.
• Light independent reactions do not require light.