Unit 1 BIO

CELLULAR ENERGY

Encounter the Phenomenon

  • Driving Question: Why would a farmer grow lettuce in a greenhouse?

    • Use the CER (Claim, Evidence, Reasoning) chart to formulate a claim about the benefits of greenhouse cultivation for lettuce.

    • Collect evidence throughout the module to support this claim.

    • Revisit and explain your reasoning at the module's conclusion.

Lesson 1: How Organisms Obtain Energy

Focus Question

  • Question: Lettuce plants can't eat, so how do they obtain energy?

Transformation of Energy

  • Cellular activities continuously require energy to perform work:

    • Macromolecule assembly and breakdown

    • Transport of substances across cell membranes

    • Transmission of genetic instructions

  • Definition of Energy: The ability to do work.

Thermodynamics

  • Thermodynamics: The study of energy flow and transformation in the universe.

  • Laws of Thermodynamics:

    • First Law: Energy conservation; energy can convert forms but cannot be created or destroyed.

    • Example: Food energy converts to chemical energy upon ingestion and to mechanical energy when running.

    • Second Law: Energy conversion leads to usable energy loss, typically as thermal energy; also described as "entropy increases."

    • Example: Usable energy decreases at each food chain trophic level.

Autotrophs and Heterotrophs

  • Energy Sources:

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

    • Includes chemoautotrophs (use inorganic substances for energy) and photoautotrophs (use light energy).

    • Heterotrophs: Organisms that must obtain energy by consuming other organisms.

Metabolism

  • Definition: The sum of all chemical reactions in a cell.

  • Metabolic Pathways:

    • Catabolic Pathways: Release energy by breaking down larger molecules into smaller ones.

    • Anabolic Pathways: Use energy from catabolic reactions to build larger molecules from smaller ones.

  • Energy Flow: Energy transfers from one set of interacting molecules to another within these pathways.

Photosynthesis and Cellular Respiration

  • Photosynthesis: An anabolic process converting light energy into chemical energy, producing glucose from carbon dioxide and water, releasing oxygen.

  • Cellular Respiration: A catabolic process breaking down organic molecules to release energy, utilizing oxygen and producing carbon dioxide and water.

ATP: The Unit of Cellular Energy

  • Definition: Adenosine triphosphate (ATP) is a universal energy carrier in organisms.

  • Structure of ATP: Composed of adenine base, ribose sugar, and three phosphate groups.

  • Energy Release Mechanism: Energy is released when the bond between the second and third phosphate groups is broken.

    • Produces adenosine diphosphate (ADP) and a free phosphate group.

    • ATP production and hydrolysis can interconvert ATP and ADP.

Summary of Key Points

  1. Thermodynamics laws govern energy flow in organisms.

  2. Organisms produce or obtain energy from food.

  3. Cells store and release energy via catabolic and anabolic reactions.

  4. ATP breakdown releases energy for cellular activities.

Lesson 2: Photosynthesis

Focus Question

  • Question: What do lettuce plants need to survive?

Overview of Photosynthesis

  • Photosynthesis transforms energy, allowing organisms to capture and store solar energy.

  • Chemical Reaction for Photosynthesis:

    • Overall reaction: 6CO2+6H2O<br>ightarrowC6H12O6+6O26CO_2 + 6H_2O <br>ightarrow C_6H_{12}O_6 + 6O_2

  • Phases of Photosynthesis:

    • Phase One: Light-dependent reactions occur in the thylakoids, converting light energy into ATP and NADPH.

    • Phase Two: Light-independent reactions (Calvin Cycle) use ATP and NADPH to synthesize glucose.

Phase One: Light Reactions

  • Chloroplasts: Organelles where photosynthesis occurs, primarily in leaf cells.

  • Thylakoid Structure: Stacked membranes (grana) containing chlorophylls that capture light energy.

  • Pigments:

    • Chlorophylls: Absorb light energy, primarily in the violet-blue spectrum; reflect green (hence leaves appear green).

    • Carotenoids: Accessory pigments absorbing blue and green wavelengths and reflecting yellow/orange.

Electron Transport and Chemiosmosis

  • Light energy initiates water splitting in photosystem II, generating electrons, protons (H+), and oxygen.

  • Electron Transport Chain: Transports electrons, creates a proton gradient, facilitating ATP synthesis via chemiosmosis through ATP synthase.

Phase Two: The Calvin Cycle

  • Reactions:

    • Carbon fixation occurs when CO2 combines with ribulose bisphosphate (RuBP).

    • ATP and NADPH are utilized to form glucose from phosphoglycerate (PGA) and glyceraldehyde-3-phosphate (G3P).

  • Recycling RuBP: Remaining G3P regenerates RuBP to continue the cycle with the help of rubisco enzyme.

Alternative Pathways

  • C4 Pathway: Adaptation in hot, dry environments, allows for reduced water loss while still performing photosynthesis.

  • CAM Pathway: Nighttime carbon fixation in arid environments minimizes water loss.

Summary of Key Points

  1. Light energy converts into chemical energy via chloroplast pigments.

  2. Photosynthesis comprises light reactions and the Calvin cycle.

  3. ATP and NADPH formed in light reactions are crucial for synthesizing carbohydrates.

Lesson 3: Cellular Respiration

Focus Question

  • Question: How does your body get energy from eating lettuce?

Overview of Cellular Respiration

  • Cellular Respiration: A process breaking down glucose for energy, yielding ATP.

    • Reaction: C6H12O6+6O2<br>ightarrow6CO2+6H2O+extEnergyC_6H_{12}O_6 + 6O_2 <br>ightarrow 6CO_2 + 6H_2O + ext{Energy}

  • Stages of Cellular Respiration:

    • Glycolysis: Occurs in the cytoplasm, anaerobic process breaking glucose into pyruvate.

    • Krebs Cycle: Occurs in mitochondria, aerobic process where pyruvate is converted to CO2, generating NADH and ATP.

    • Electron Transport: Utilizes NADH and FADH2 to produce ATP via a series of proteins in the mitochondrial membrane, requiring oxygen.

Energy Yield

  • Total ATP Production:

    • Glycolysis: 2 ATP

    • Krebs Cycle: 2 ATP (per cycle, two cycles per glucose)

    • Electron Transport: 32 ATP

    • Total possible yield: 36 ATP (eukaryotes), 38 ATP (prokaryotes).

Anaerobic Respiration

  • Fermentation: Occurs when oxygen is lacking, producing ATP and regenerating NAD+.

    • Lactic Acid Fermentation: Converts pyruvate to lactic acid.

    • Alcohol Fermentation: Converts pyruvate to ethanol and carbon dioxide.

Interrelation of Photosynthesis and Cellular Respiration

  • Cyclical Nature: Products of photosynthesis (oxygen, glucose) are reactants of cellular respiration (and vice versa).

Summary of Key Points

  1. Cellular respiration processes involve glycolysis, Krebs cycle, and electron transport.

  2. Energy carriers like NADH and FADH2 are pivotal.

  3. Fermentation allows energy production under anaerobic conditions.

Scientific Breakthroughs

Faster Photosynthesis

  • Need for food and increased crop yields prompts research into boosting photosynthesis rates.

  • Genetic engineering modifies plants to improve photosynthesis efficiency by quickly turning off protective mechanisms when less light is available.

Conclusion

  • Scientific advances aim to enhance food supply sustainably as the global population grows.