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Photosynthesis and Cellular Respiration

• Photosynthesis and respiration are complementary processes for cycling carbon dioxide and oxygen in an ecosystem.

  • Photosynthesis:

  • Occurs in the chloroplasts of autotrophs (producers).

  • Uses:

    • Sunlight (light energy)

    • Carbon Dioxide ($CO_2$)

    • Water ($H_2O$)

  • Produces:

    • Glucose ($C<em>6H</em>{12}O_6$)

    • Oxygen ($O_2$)

  • Chemical Equation for Photosynthesis:

    • $ext{Light Energy} + 6 H<em>2O + 6 CO</em>2 <br>ightarrow C<em>6H</em>{12}O<em>6 + 6 O</em>2$

    • Enzymes are involved in this process.

  • Cellular Respiration:

  • Occurs in the mitochondria of both heterotrophs (consumers) and autotrophs (producers).

  • Burns organic molecules (glucose) with oxygen to produce:

    • Energy

    • Carbon Dioxide ($CO_2$)

    • Water ($H_2O$)

  • Chemical Equation for Cellular Respiration:

    • $C<em>6H</em>{12}O<em>6 + 6 O</em>2 <br>ightarrow 6 H<em>2O + 6 CO</em>2 + ext{Energy (ATP)}$

    • Enzymes are involved in this process.

Energy Transfer in Ecosystems

• Sunlight (radiant energy) is the initial energy source for almost all communities.

• Photosynthesis occurs in chloroplasts, where light energy converts to chemical energy.

• Respiration takes place in mitochondria, breaking down organic molecules to release energy stored by photosynthesis.

• The energy released during respiration is transported in the form of ATP (adenosine triphosphate).

ATP: Energy Carrier in Cells

1. ATP is the molecule that stores the cell’s chemical energy.

   • Chemical energy in glucose is released during cellular respiration.

   • Most of this energy is ‘lost’ as heat but some is captured for cellular use.

2. How cells utilize ATP:

   • Energy is stored and transported in the form of ATP molecules.

   • Specific enzymes release energy stored in the chemical bonds of ATP when needed for cellular work.

3. Analogy:

   • ATP functions like a rechargeable battery, where ADP (adenosine diphosphate) can bind with a free phosphate to regenerate ATP and store energy.

4. ATP-ADP Energy Cycle:

   • Visual representation of how ATP is converted to ADP and back, highlighting energy storage and release.

Pigments and Photosynthesis

• Pigments in Chloroplasts:

  • Different pigments capture different ranges of light. Key pigments include:

  • Chlorophyll a: Green

  • Chlorophyll b: Green

  • Carotene: Orange

  • Xanthophyll: Yellow

  • Anthocyanins: Red-blue

• Chlorophyll:

  • Most abundant pigment, sensitive to light changes, masking other pigments. As days shorten, chlorophyll breaks down allowing other pigments to be visible.

Monitoring Photosynthesis

• Photosynthesis can be tracked through:

  • Production of oxygen.

  • Uptake of carbon dioxide.

  • Increase in biomass.

• Factors Affecting the Rate of Photosynthesis:

  • Amount of carbon dioxide.

  • Amount of water.

  • Amount/Intensity of light.

  • Wavelength/Color of Light:

  • Blue (425-450 nm) and Red (600-700 nm) are optimal.

  • Green (495-570 nm) is least effective.

  • Temperature:

  • Affects enzyme activity involved in the reactions.

Effects of Oxygen on Energy Availability

• Aerobic Cellular Respiration:

  • Occurs in the presence of oxygen, yielding 36-38 ATP.

• Anaerobic Cellular Respiration:

  • Occurs in the absence of oxygen; produces:

  • Lactic Acid in animals.

  • Ethanol and Carbon Dioxide in yeast.

  • Low energy yield of 2 ATP in anaerobic processes.

• Human Respiratory System:

  • Specialized Red Blood Cells deliver oxygen through:

  • Inhalation of $O<em>2$ → Lungs to blood diffusion → Blood to cells diffusion → $O</em>2$ available in cells.

Leaf Anatomy and Function in Gas Exchange

• Leaf Structure for Gas Exchange:

  • Stomata: Open pores for gas exchange; regulate gas flow.

  • $O<em>2$ can diffuse out; $CO</em>2$ can diffuse in.

  • Essential for photosynthesis.

  • Transpiration: Water vapor can evaporate out.

  • Guard Cells: Control stoma opening.

Summary Diagrams

• Photosynthesis vs. Cellular Respiration:

  • Diagram: Displays interrelationships, reactants/products in each process, stages involved (e.g., Glycolysis, Krebs cycle, Electron Transport Chain).

• Leaf Cross-section and Anatomy:

  • Includes components such as Upper Epidermis, Cuticle, Spongy Mesophyll, Palisade Mesophyll, Xylem, Phloem, Lower Epidermis, Guard Cells, and Stomata.