Chapter 5: Energy Conversion in Mitochondria and Chloroplasts

Chapter 5: Energy Conversion in Mitochondria and Chloroplasts

1. Mitochondria:

• Structure:

• Outer membrane:

• Smooth, covering the entire mitochondria.

• The main protein is porin.

• Inner membrane:

• Folded into cristae, which increase surface area.

• Contains numerous respiratory enzymes involved in the conversion of sugars and other substances into ATP (aerobic respiration).

• The number of folds varies depending on the cell’s ATP demand.

• The main impermeable membrane.

• Intermembrane space:

• Located between the outer and inner membranes.

• Allows small molecules to diffuse freely, creating a concentration similar to the cytoplasm.

• Protein content differs from the cytoplasm.

• Matrix: Contains DNA and ribosomes.

• Physiological Function:

• Synthesizes high-energy phosphate bonds, such as ATP, NADP, GTP, etc., due to enzymes on the membranes.

• The central organelle for energy exchange in the cell.

• Capable of fusion and division.

2. Chloroplasts:

• Structure:

• Spherical or ovoid, double membrane.

• Stroma: Contains DNA and ribosomes.

• Inner membrane: Not folded into cristae and doesn’t contain an electron transport chain.

• Third membrane:

• Photosynthetic system that absorbs light, electron transport chain, and ATP synthetase.

• Forms flattened, disc-shaped sacs called thylakoids.

• The thylakoid membrane creates a thylakoid interspace separate from the stroma.

• Thylakoids stack on top of each other to form grana.

• Chlorophyll is located on the thylakoid membrane, hence the green color of the grana.

• Function:

• Performs photosynthesis:

• Absorbs energy from sunlight.

• Converts that energy into high-energy molecules, ATP and NADPH.

• Releases oxygen from water.

• Performs the Calvin cycle: Uses energy from ATP and NADPH to create organic molecules from CO2.

• Synthesizes fatty acids, various amino acids, and participates in immune responses in plants.

3. Cellular Respiration:

• Definition: The metabolic process that occurs in cells to convert chemical energy from molecules into adenosine triphosphate (ATP).

• Stages:

• Glycolysis: Breakdown of glucose into pyruvate.

• Krebs cycle: Oxidation-reduction of pyruvate to release electrons.

• Electron transport chain: Utilizes released electrons to generate ATP.

4. Photosynthesis:

• Definition: The process of converting light energy into chemical energy, through cellular respiration.

• General equation:

• 6CO2 + 12H2O ? C6H12O6 + 6O2 + 6H2O

Conclusion:

Photosynthesis and cellular respiration are complementary processes that form the energy cycle in nature. The products of photosynthesis (organic matter and oxygen) are the raw materials for cellular respiration, and the products of cellular respiration (CO2 and water) are the raw materials for photosynthesis.