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Cellular Respiration, Photosynthesis, & Plants. I. Cellular Respiration Cellular Respiration – the process that releases energy by breaking down glucose & other food molecules in the presence of oxygen. Equation : 6O 2 + C 6 H 12 O 6 6CO 2 + 6H 2 O + Energy
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Cellular Respiration, Photosynthesis, & Plants I. Cellular Respiration Cellular Respiration – the process that releases energy by breaking down glucose & other food molecules in the presence of oxygen. Equation : 6O2 + C6H12O6 6CO2 + 6H2O + Energy Oxygen + glucose carbon dioxide + water + Energy (Reactants) (Products) *The most common source of food energy is found in the carbohydrates that organisms eat. *Most important product of respiration is energy for life processes.
Cellular Respiration occurs in 3 steps : 1. Glycolysis – process in which 1 molecule of glucose is broken in half, producing 2 molecules of pyruvic acid, a 3-carbon compound. -End result of glycolysis is 4 ATP molecules. ATP – (adenosine triphosphate) main energy-storing molecule used by organisms. -In the absence of oxygen, glycolysis is followed by fermentation – production of ATP without oxygen (anaerobic respiration).
2 Main types of fermentation : A. Alcoholic fermentation – produces alcohol & CO2 (bread) as wastes. B. Lactic acid fermentation – produces lactic acid that builds up in muscle. -Happens when the body can’t supply enough oxygen to the tissues- muscles fatigue, ache, or burn. -The last 2 steps of cellular respiration are aerobic (need oxygen to happen). -Oxygen’s role in cellular respiration is to act as the final hydrogen (electron) acceptor in the reaction.
The Krebs Cycle 2. The Krebs cycle – process by which pyruvic acid is broken down into carbon dioxide. -The Krebs cycle generates high-energy electrons that are passed to NADH & FADH2. -The energy stored in NADH & FADH2 hydrogen bonds are transferred to ATP phosphate bonds in the electron transport chain.
Electron Transport Chain 3. Electron transport chain – series of proteins in which high-energy electrons are used to convert ADP into ATP. *Most ATP produced by cellular respiration is formed here.
II. Photosynthesis Photosynthesis – process by which plants use the energy of sunlight to convert water & carbon dioxide into carbohydrates (sugar & starches) & oxygen. Equation : (Light energy) 6CO2 + 6H2O C6H12O6 + 6O2 (Reactants) (Products) (Light energy) Carbon dioxide + water sugar + oxygen -The most important product of the reaction, glucose (an organic molecule), is used by plants to store energy for the production of ATP. No glucose = no energy for cells.
Photosynthesis happens in 2 stages : 1. Light-dependent reactions that produce oxygen, ATP, & NADPH. 2. The Calvin cycle that produces sugars (C6H12O6). -The separation of carbon from carbon dioxide (carbon fixation) occurs in the Calvin cycle. -The major photosynthetic pigment, chlorophyll is needed by plants in order to do photosynthesis. -Chlorophyll doesn’t absorb green light, it reflects it. Plants appear to be green in color but do not use the green wavelength of light for photosynthesis.