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Unit C: Section 6.1

Unit C: Section 6.1. Matter and Energy Pathways in Living Systems. Overview of Photosynthesis. The overall reaction is: 6CO 2 (g) + 6H 2 0 (l) + energy  C 6 H 12 O 6 (s) + 6O 2 (g) carbon dioxide + water + energy  glucose + oxygen

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Unit C: Section 6.1

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  1. Unit C:Section 6.1 Matter and Energy Pathways in Living Systems

  2. Overview of Photosynthesis • The overall reaction is: 6CO2 (g) + 6H20 (l) + energy  C6H12O6 (s) + 6O2(g) carbon dioxide + water + energy  glucose + oxygen • Photosynthesis occurs in the chloroplasts of green plants. The thylakoid membranes within the chloroplasts contain pigments such as cholorphyll and cartenoids that are responsible for absorbing the light energy from the sun. • The light energy is used to chemically add an electron to carbon dioxide to produce high-energy glucose molecules. The glucose molecules are then stored as carbohydrates and other sugars for future use by the plant.

  3. Overview of CellularRespiration • The overall reaction is: C6H12O6 (s) + 6O2(g)  6 CO2 (g) + 6H20 (l) + energy (ATP) glucose + oxygen  carbon dioxide + water + energy • In cellular respiration the mitochondria of the plant cells break down the carbohydrates produced by photosynthesis to generate molecules of ATP (adenosine triphosphate). • Cellular respiration releases the energy from carbohydrates or produces ATP by removing an electron from a glucose molecule (oxidation) to produce carbon dioxide and water.

  4. Mitochondria:Site of Cellular Respiration • Mitochondria like chloroplasts are also bound by two membranes. • The inner membrane, has many folds called cristae, that increase the surface area for the production of ATP. • The fluid-filled space of the inner membrane is called the matrix. The matrix contains proteins and other chemicals necessary for the break down of carbohydrates.

  5. Structure of Mitochondria

  6. ATP and Cellular Activity • ATP produced from cellular respiration supplies the energy for cellular activities. • This energy is used for: - active transport of ions and molecules across cell membranes • moving chromosomes during cell division • causing cilia and flagella to move • synthesizing compounds such as carbohydrates, proteins, fats and nucleic acids

  7. ATP and Cellular Activity • How does ATP supply energy for cellular activity? • The chemical energy of compounds is stored in their chemical bonds • Breaking the bonds releases the chemical energy • ATP has two phosphoanhydride bonds that release energy when they are broken, therefore, when the third (end) phosphate breaks off, the energy from ATP is released • The result is a free phosphate and ADP, an adenosine diphosphate molecule

  8. Metabolic Pathways • The two reactions for photosynthesis and cellular respiration can be summarized by: 6 CO2 (g) + 6H20 (l) + energy  C6H12O6 (s) + 6O2(g) and C6H12O6 (s) + 6O2(g)  6 CO2 (g) + 6H20 (l) + energy (ATP) • The two reactions appear to be opposite of each other because photosynthesis uses the products of cellular respiration as a starting point and cellular respiration uses the products of photosynthesis as its reactants. • However, these are simply the overall reactions and the processes actually consist of many more reactions to get to the final product.

  9. Metabolic Pathways • The step-by-step series of reactions that photosynthesis and cellular respiration go through to get the final products are called metabolic pathways. • In metabolic pathways, the product of one reaction becomes the starting reactant for the next reaction. • There are two types of metabolic pathways: • Anabolic pathways – synthesize larger molecules from smaller ones and require energy (Photosynthesis – Carbon dioxide to glucose) • Catabolic pathways – break down larger molecules into smaller ones and release energy (Cellular respiration – Glucose to carbon dioxide) • Metabolic pathways are catalyzed by enzymes, specialized proteins that lower the activation energy of a reaction, so the reaction proceeds more quickly.

  10. Enzymes as Catalysts Regular Reaction Effect of a Catalyst (enzyme)

  11. Oxidation and Reduction • Oxidation – when an atom or molecule loses an electron it is said to be oxidized. • Reduction – when an atom or a molecule gains an election it is said to be reduced. • Oxidation and reduction reactions take place at the same time. It one compound is oxidized another compound must be reduced. • All compounds contain more energy in their reduced form than they do in their oxidized form. • Molecules in their reduced form contain a large amount of available energy and are said to have high reducing power. • NADH is an example of a high energy molecule that is said to have high reducing power.

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