Biology Chapter on Photosynthesis and Enzymes

Key Structures and Functions

• Chloroplasts are organelles in plant cells where photosynthesis occurs. They contain thylakoids and stroma.
• Mitochondria generate ATP through cellular respiration. They have inner and outer membranes, cristae, and matrix.
• Stomata are small openings on leaves that allow gas exchange (opening during the day for CO2 intake and closing at night to conserve water).
• Vascular tissue (xylem and phloem) comprises the xylem that transports water and minerals, and the phloem that transports sugars.

Enzyme Functions

• Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.
• Competitive inhibition occurs when an inhibitor competes with the substrate for an enzyme's active site.
• Non-competitive inhibition occurs when an inhibitor binds to an enzyme at a site other than the active site, altering its function.

Facts to Memorize

• Photosynthesis equation: CO2 + H2O + light energy → C6H12O6 + O2
• Cellular respiration equation: C6H12O6 + O2 → CO2 + H2O + ATP
• Main ATP production in cellular respiration occurs in the electron transport chain (ETC).
• Chlorophyll absorbs primarily blue and red light wavelengths.

Reference Information

• Light-dependent reactions occur in the thylakoid membranes and produce ATP and NADPH.
• Light-independent reactions (Calvin cycle) occur in the stroma and produce glucose.
• Glycolysis occurs in the cytoplasm, the Krebs cycle in the mitochondrial matrix, and the ETC in the inner mitochondrial membrane.

Concept Comparisons (Photosynthesis vs Cellular Respiration)

• Photosynthesis converts light energy into chemical energy, storing it in glucose.
• Cellular Respiration breaks down glucose to release energy.
• Photosynthesis reactants: CO2, H2O, light energy.
• Cellular Respiration reactants: C6H12O6, O2
• Photosynthesis products: C6H12O6, O2
• Cellular Respiration products: CO2, H2O, ATP
• Photosynthesis location: Chloroplasts (thylakoids and stroma)
• Cellular Respiration location: Mitochondria (cytoplasm and matrix)
• Photosynthesis energy storage: Stores energy in glucose
• Cellular Respiration energy release: Energy released from glucose

Steps of Cellular Respiration

• Glycolysis: Breaks down glucose into 2 pyruvate, producing 2 ATP and 2 NADH in the cytoplasm.
• Krebs Cycle: This cycle uses acetyl CoA to produce CO2, 2 ATP, 6 NADH, and 2 FADH2 in the mitochondrial matrix.
• Electron Transport Chain (ETC): Uses O2 to produce H2O and generates 32-34 ATP in the mitochondrial membrane

Energy Yield

• Total ATP yield from one glucose molecule is approximately 36-38 ATP (2 from glycolysis, 2 from Krebs cycle, 32-34 from the ETC).
• Aerobic respiration is more efficient in energy production than anaerobic processes

Fermentation Processes

• Anaerobic respiration, in the absence of oxygen; cells generate energy through fermentation; allowing glycolysis to continue regenerating NAD⁺.

• Fermentation happens in organisms living in oxygen-poor environments or during intense exercise.

• Types of fermentation:

  • Alcoholic fermentation: 2 pyruvate → 2 ethanol and 2CO2 (yeast in brewing and baking)
  • Lactic acid fermentation: 2 pyruvate → 2 lactate (muscle cells during strenuous exercise and some bacteria)

Photosynthesis Overview

• Photosynthesis: Autotrophs convert solar energy to chemical energy stored in glucose in the chloroplasts.

• Chloroplasts contain thylakoids (stacked in grana) where chlorophyll absorbs sunlight.

  • Chlorophyll types (a and b) absorb blue and red light and reflect green.

• Two sets of reactions:

  • Light reactions (in thylakoid membranes): Water is split, oxygen is released, ATP and NADPH are produced.
  • Calvin cycle (in stroma): ATP and NADPH are used to convert carbon dioxide into glucose

Enzymes and Chemical Reactions

• Chemical reactions transform reactants into products, involving changes in chemical bonds.
• Reactants are starting materials. Products are the substances formed after the reaction.
• Spontaneous reactions release energy without external input; nonspontaneous reactions require energy.
• Activation energy is the minimum energy required for a reaction to start.
• Enzymes are biological catalysts; they accelerate reactions by lowering activation energy.
• Enzymes can be denatured by extreme conditions (high heat, extreme pH, salinity), losing their functionality.

This quiz covers key structures like chloroplasts and mitochondria, as well as their functions in photosynthesis and cellular respiration. It also explores enzyme actions, including competitive and non-competitive inhibition. Test your understanding of these fundamental biology concepts!