RB

Cellular Respiration and Photosynthesis

Glycolysis and its Products

  • Glycolysis breaks down carbohydrates, specifically glucose.

  • The final product of glycolysis is pyruvate.

Pathways Dependent on Oxygen Availability

  • In the presence of oxygen:

    • The process moves forward to produce Acetyl CoA (acetyl coenzyme A).

  • In the absence of enough oxygen:

    • The process results in fermentation, leading to the production of:

      • Lactic acid (in animals).

      • Ethanol (in yeasts).

Cellular Respiration Locations

  • Glycolysis occurs in the cytosol.

  • The citric acid cycle occurs in the mitochondria:

    • Acetyl CoA is transported into the mitochondria to enter the citric acid cycle.

Citric Acid Cycle Functions

  • The citric acid cycle's primary goal is to oxidize Acetyl CoA:

    • This process involves harvesting electrons in the form of NADH and FADH₂.

Electron Transport Chain

  • The electron transport chain (ETC) is also located in the mitochondria:

    • NADH from the citric acid cycle enters at complex I.

    • FADH₂ from the citric acid cycle enters at complex II.

    • From complexes I and II, electrons are transferred to complex III via a carrier (coenzyme Q).

Proton Gradient Creation

  • The movement of electrons through the complexes pumps protons (H⁺ ions) from the matrix into the intermembrane space:

    • This creates a proton gradient as protons accumulate in the intermembrane space.

  • The higher concentration of protons in the intermembrane space compared to the matrix generates a proton motive force.

ATP Production Mechanism

  • The concentration gradient of protons is utilized to synthesize ATP:

    • ATP is formed by adding a phosphate group to ADP using the energy from the proton flow.

  • The process described involves:

    • "Taking running water and using a dam":

      • Water backs up, creating pressure, which is then released (like the flow of protons), generating energy to convert ADP + P into ATP.

Energy Sources

  • The energy harvested from food ultimately comes from the sun:

    • Plants convert sunlight into chemical energy during photosynthesis, which is stored in the bonds of glucose.

Test Preparations

  • Understanding the electron transport chain and its role in forming a proton gradient is critical for the test.

  • Familiarity with NADH and FADH₂ as electron carriers is emphasized:

    • Students are encouraged to study the material in advance of the test.

Uncouplers of Oxidative Phosphorylation

  • An example is presented about a weight-loss drug that disrupts oxidative phosphorylation:

    • This disrupts electron flow, affecting the proton gradient and leading to heat production.

  • Importance of oxygen is reiterated:

    • Without oxygen, Acetyl CoA should not proceed into the electron transport chain.

Photosynthesis Overview

  • Photosynthesis comprises two main types of reactions:

    • Light reactions (convert light energy into chemical energy).

    • Dark reactions (Calvin cycle, synthesize sugar from CO₂).

  • Light reactions require water, produce oxygen, and generate ATP and NADPH.

Symbiotic Relationships in Ecosystems

  • Unique capabilities of plants:

    • Conversion of inorganic CO₂ into organic sugars is highlighted:

    • This process is what allows plants to be self-sustaining (autotrophic).

  • Explanation of energy cycles:

    • Plants utilize sunlight and water while animals consume organic materials and exhale CO₂.

Importance of Photosynthesis

  • Essential for life as it converts light energy into chemical energy:

    • Plants absorb sunlight in their leaves through chlorophyll, creating biomass.

    • Oxygen produced through photosynthesis is critical for respiration in living organisms.

Definitions

  • Autotrophs: Organisms that produce their own food (e.g., plants).

  • Heterotrophs: Organisms that consume other organisms for energy.

Photosynthesis Mechanism

  • Chloroplasts are the site of photosynthesis within plant cells:

    • Chlorophyll absorbs light energy; it is reflected as green because it does not absorb green wavelengths effectively.

  • The Calvin cycle uses ATP and NADPH to convert CO₂ into glucose.

Electromagnetic Spectrum and Light Absorption

  • Light behaves as both waves and particles (photons), influencing energy usage in photosynthesis.

  • Important terms:

    • Wavelength: The distance between successive crests of a wave.

  • Types of electromagnetic radiation and their significance include:

    • Gamma rays, X-rays, ultraviolet rays, visible light, infrared, microwaves, and radio waves.

Pigments in Photosynthesis

  • Chlorophyll and its role in absorbing light:

    • Green chlorophyll reflects green light while absorbing other wavelengths for photosynthesis.

  • Discussion of spectrophotometers:

    • Tools that measure absorption spectra, assessing how different colors absorb light.

Conclusion

  • Review of the relationship between light and pigment absorption in photosynthesis is emphasized prior to taking tests.