BIO1011 Lecture Notes - Lecture 15: Photosynthetically Active Radiation, Thylakoid, Accessory Pigment
Photosynthesis
12H20 + 6CO2 ⟶ C6H12O6 + 6O2 + 6H2O
•Life requires energy
•Most ecologies use photonic (light) energy
•Organisms that don’t use photonic energy are chemoautotrophs
•Chemoautotrophs use energy from oxidation of reduced forms of inorganic compounds
such as H2S, NH4+. They are usually bacteria
•Organisms that use light energy are photoautotrophs
-higher plants
-cyanobacteria
-algae
-photosynthetic bacteria
•The photosynthetically active radiation that can be used by plants is 400-700nm (blue-
red)
Chloroplasts
•Photosynthesis occurs in chloroplasts
•Chloroplasts contain the green pigment chlorophyll
•Found mainly in mesophyll cells
•A typical mesophyll cell has 30-40 chloroplasts
•Chloroplasts have 3 compartments:
-Stroma
-liquid that contains metabolic enzymes
-Thylakoid lumen
-discs within the chloroplast
-the lumen is the internal space inside the thylakoid
-Granum
-a stack of thylakoid membranes
Part One: Light Dependent Reaction
•Occurs in thylakoid membranes of the chloroplast
•The thylakoid membranes contain chlorophyll and other accessory pigments that absorb
light
•Chlorophyll is the green pigment
•There are two types of chlorophyll:
-chlorophyll a - CH3
-chlorophyll b - CHO
•Chlorophyll consists of a porphyrin ring. Chlorophyll a has a CH3 unit attached, where
chlorophyll b used CHO.
•Carotenoids (accessory pigments) trap blue-violet light and reflect yellow and red light.
They protect the chlorophyll from excessive light exposure
Document Summary
They are usually bacteria: organisms that use light energy are photoautotrophs. Photosynthetic bacteria: the photosynthetically active radiation that can be used by plants is 400-700nm (blue- red) Chloroplasts: photosynthesis occurs in chloroplasts, chloroplasts contain the green pigment chlorophyll, found mainly in mesophyll cells, a typical mesophyll cell has 30-40 chloroplasts, chloroplasts have 3 compartments: The lumen is the internal space inside the thylakoid. Part one: light dependent reaction: occurs in thylakoid membranes of the chloroplast, the thylakoid membranes contain chlorophyll and other accessory pigments that absorb light, chlorophyll is the green pigment, there are two types of chlorophyll: Chlorophyll b - cho: chlorophyll consists of a porphyrin ring. Chlorophyll a has a ch3 unit attached, where chlorophyll b used cho: carotenoids (accessory pigments) trap blue-violet light and re ect yellow and red light. Light excites chloroplasts and this excitement is passed around the chloroplasts until it reaches the reaction centre, or p680.