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Photosynthesis & Cellular Respiration Ch. 8 & 9 All Living Things Require Energy to Survive • Photosynthesis- is the process that converts the radiant energy of sunlight into chemical energy (glucose) • Respiration-the process that releases chemical energy for use by the cell (in the form of ATP) • Autotrophs –Are plants and other organisms that make their own food –Ex. Green plants • Heterotrophs –Cannot make their own food. –Ex. animals Photosynthesis- how autotrophs produce chemical energy • 6CO2 + 6H2O chlorophyll Light energy • Carbon dioxide + Water C6H12O6 + 6O2 glucose + oxygen Respiration- breaks down glucose & release energy • C6H12O6 + 6O2 6CO2 + 6H2O + ATP energy • Respiration uses what photosynthesis makes and vice versa • Both photosynthesis & cellular respiration happen in a series of steps called biochemical pathways. The energy released in respiration is in the form of adenosine triphosphate (ATP) • An ATP molecule has 3 parts. – Adenine + Ribose = adenosine – 3 phosphate groups • A-P (AMP) = adenosine + 1 phosphate • A-P~P (ADP) = adenosine + 2 phosphate • A-P~P~P (ATP) = adenosine + 3 phosphates ~ = high energy bonds When a cell needs energy, an enzyme ATPase breaks nd the bond between the 2 & 3rd phosphate groups A-P~P~P ATP ATPase A-P~P +P + energy ADP To Add P to ADP is called Phosphorylation • The enzyme ATP synthetase has to be present for this A-P~P + P ADP + P A-P~P~P ATP ATP synthetase Photosynthesis occurs in…. • Light Reaction (occurs in light) – Energy in sunlight is trapped – O2 is released – ATP is formed – NADPH2 is formed – Occurs in the thylakoids of the chloroplast • Dark Reaction/Calvin Cycle (occurs in light or dark) – CO2 is fixed into organic compounds – ATP and NADPH2 act with CO2 C6H12O6 (glucose) – Happens in the stroma of the chloroplast Chloroplast-where photosynthesis takes place • Inner membrane = discs called thylakoids • Thylakoids are surrounded by fluid called stroma • • • • Sunlight travels in waves. Short waves have more energy than long Pigments absorb lightwaves 5 different kinds of chlorophyll (a pigment) – Chlorophyll a & b are most common (absorbs many lightwaves and reflects green. – Carotenoids also absorb lightwaves (yellow, orange, brown) •Carotenes •Xanthophylls – Phycobilins (red and blue) Respiration • Releases the energy stored in the chemical bonds of glucose. • 2 kinds of respiration • Both begin with glycolysis-occurs in cytoplasm – Breakdown of glucose into 2 pyruvic acid molecules. – Results in the production of 4 ATP molecules 2 Kinds of Respiration • Fermentationpyruvic acid is broken down without the use of oxygen • Glycolysis + fermentation = anaerobic respiration • Aerobic respiration-pyruvic acid is broken down with the use of oxygen. 2 Kinds of Fermentation • Lactic Acid– Occurs in animal cells and causes muscle fatigue • Alcoholic– Occurs in plant cells and in yeast – Produces ethyl alcohol Aerobic Respiration • Releases a lot more energy than anaerobic respiration (38 ATP’s) • C6H12O6 + 6O2 6CO2 + 6H2O + 38ATP’s • Occurs in the cell’s mitochondria Aerobic Resp. happens in a series of steps 1st-glycolysis-glucose is broken down into pyruvic acid 2nd conversion of pyruvic acid to acetyl-CoA 3rd (Krebs Cycle or Citric Acid Cycle)completes the breakdown of glucose 4th Electron transport chain- more ATP is produced • Aerobic Respiration = 38 ATP’s • Fermentation (anaerobic) = 4 ATP’s
