University:
Felician University
Course:
CHEM-001 | Basic Chemistry
Academic year:

2024
Views:

218

Pages:

1
Author:

CometConductor

PHOTOSynTHESIS Photosynthesis Light Spectrum Photosynthesis involves the use of light energy to synthesise organic compounds from inorganic molecules Visible light has a range of wavelengths (~ 400 – 700 nm) • Violet has the shortest wavelength, red has the longest The Visible Spectrum Light 6 CO2 + 12 H2O Carbon dioxide Water Chlorophyll C6H12O6 + 6 O2 + 6 H2O Glucose Oxygen Water 700 nm 400 nm Light Absorption Pigments are required for the conversion of light energy into chemical energy in photosynthetic organisms Chlorophyll is the main photosynthetic pigment, although other accessory pigments also exist (e.g. carotenoids) • Chlorophyll absorbs red light and blue light most effectively and reflects green light more than other colours An absorption spectrum (left) indicates the wavelengths of light absorbed by each photosynthetic pigment (e.g. chlorophyll) Photosynthetic rate Relative absorption An action spectrum (right) indicates the overall rate of photosynthetic activity at each wavelength of light carotenoid chlorophyll a chlorophyll b 500 400 600 700 600 500 400 700 Wavelength of light (nm) Wavelength of light (nm) Stages of Photosynthesis Light Dependent Reactions Light energy is converted into chemical energy • Light is absorbed by chlorophyll to produce ATP • The photolysis of water forms oxygen and hydrogen Light energy Water Oxygen Chlorophyll Hydrogen Light Independent Reactions Carbon compounds are made from the chemical energy • ATP and hydrogen are fixed with carbon dioxide • This results in the formation of organic molecules Carbon dioxide Chemical energy e– NADPH ATP NADPH ATP Carbon fixation Organic compounds Cell Processes Chromatography Limiting Factors Pigments can be separated by chromatography • Pigments are dissolved in fluid • The fluid is passed through a static material • Pigments are separated according to size When a process depends on more than one condition, the rate will be limited by the factor nearest its minimum value A retardation factor (Rf value) is calculated: Rf = distance of pigment ÷ distance of solvent Limiting factors in photosynthesis include: • Temperature (influences photosynthetic enzymes) • Light intensity (required for chlorophyll photoactivation) • Carbon dioxide concentrations (CO2 is a core substrate)