Biochemical Pathways Photosynthesis CHAPTER 7 Photosynthesis Autotrophs Autotrophic
Biochemical Pathways – Photosynthesis CHAPTER 7
Photosynthesis
Autotrophs Autotrophic bacteria Plants 99. 9% of all life on earth relies on photosynthesis for their energy Algae
Photosynthesis and chloroplasts l l l Photosynthesis occurs in Chloroplasts contain the pigment that captures the energy in light = Chlorophyll is found in membranous sacs called thylakoids A stack of thylakoid is called a granum (pl. grana). Grana are suspended in a fluid-filled space called the stroma.
Photosynthesis
An overview of photosynthesis l Light-capturing events – The pigment chlorophyll absorbs certain wavelengths of light and some of its electrons become excited.
An overview of photosynthesis l Light-capturing events l Light-dependent reactions – These reactions use the energy in the excited electrons to make ATP and NADPH.
An overview of photosynthesis l Light-capturing events l Light-dependent reactions l Light-independent reactions – ATP and NADPH from the light reactions are used to reduce carbon dioxide to make glucose.
Visible light spectrum l Visible light – – l Pigments are molecules that absorb light – – l Combinations of different wavelengths of light Can be seen as different colors Each pigment absorbs certain wavelengths of light The wavelengths that they do not absorb, they reflect Chlorophyll: The main photosynthetic pigment – – – Two forms; Chl a and Chl b Absorb light in the blue and red portions of the spectrum Reflect green wavelengths
Other types of pigments l Accessory pigments = Carotenoids l l l Chlorophyll + accessory pigments – l Absorb blue and green wavelengths Reflect orange and yellow Organized into photosystems that harvest the energy from many wavelengths of light When pigments absorb light – Some of their electrons become “excited”
Photosynthesis
Photosynthesis
Photosynthesis
Glyceraldehyde-3 -phosphate: The product of photosynthesis l l l Used to recycle ribulose needed in the Calvin cycle Used to make glucose Used to make the sugars needed to build ATP, DNA and RNA Can be converted into lipids Can be broken down in glycolysis Can be converted into amino acids to make proteins
Other aspects of plant metabolism l Plant cells can use the organic molecules produced in photosynthesis to make – – Fats, proteins and other carbohydrates Toxins for their protection l l – Many of these are useful medicines. Some can be used as natural insecticides. Vitamins l Molecules that we cannot make, but that we need
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