Biology Metabolic Pathways

Metabolic Pathways Overview

Redox Reactions

  • Key concepts of metabolic pathways are introduced.

Outline of Lecture Topics

  • Redox Reactions

  • Photosynthesis

  • Cellular Respiration and Fermentation

Phosphorylation

  • Definition: Adding a phosphate group to proteins to regulate cellular processes.

    • Key Steps:

      1. Target protein interacts with enzyme kinase.

      2. Protein kinase transfers ATP's terminal phosphate to substrate.

  • Commonly Phosphorylated Amino Acids: Serine, threonine, tyrosine.

Dephosphorylation

  • Definition: Removes a phosphate group from proteins.

    • Key Steps:

      1. Phosphorylated target protein interacts with enzyme phosphatase.

      2. Phosphatase catalyzes removal of phosphate.

Types of Metabolism

Catabolic Reactions

  • Definition: Break down molecules.

  • Example: Hydrolysis, breaking down disaccharides into monosaccharides.

Anabolic Reactions

  • Definition: Synthesize molecules.

  • Example: Dehydration synthesis of monosaccharides into disaccharides.

ATP Hydrolysis and Synthesis

ATP Hydrolysis

  • Definition: Breaking down ATP, a catabolic reaction.

  • Process: Water addition breaks a phosphate bond, producing ADP.

ATP Synthesis

  • Definition: Forming ATP, an anabolic reaction.

  • Location: Mitochondria and chloroplasts.

  • Process: Involves ADP and phosphate group.

Redox Reactions in Cellular Respiration

  • Definition: Electron transfer reactions; one molecule loses electrons (reducing agent), another gains them (oxidizing agent).

Nucleotides in Nucleic Acids

  • Components: Phosphate group, pentose sugar (deoxyribose in DNA, ribose in RNA), nitrogenous base.

  • Sugar Differences: Deoxyribose lacks hydroxyl group on the second carbon.

Electron Carriers

NADH

  • Forms: Reduced form (gains electrons), oxidized form NAD+.

  • Function: Coenzyme in cellular reactions.

FADH2

  • Forms: Reduced form (accepts electrons and protons), oxidized form FAD.

Photosynthesis Overview

  • Process: Sunlight energy energizes electrons to synthesize sugar molecules.

  • Electromagnetic Spectrum: Light energy measured in wavelengths; visible spectrum ranges 380nm to 750nm.

Photosynthesis Pigments

  • Primary Pigments: Chlorophyll a & b.

    • Absorption Peaks: Chlorophyll a (430, 665 nm), Chlorophyll b (453, 642 nm).

  • Secondary Pigments: Carotenoids (absorb green, reflect red/orange/yellow).

Structure of Chloroplasts

  • Components: Double membrane, thylakoids (stacked as grana), stroma (surrounding fluid).

Stages of Photosynthesis

Light-Dependent Reactions

  • Occur in thylakoid membrane; produce ATP and NADPH.

Light-Independent Reactions (Calvin Cycle)

  • Occur in stroma; utilize ATP and NADPH to synthesize GA3P from CO2.

Light-Dependent Reactions Process

  • Photo System II (PSII): Absorbs sunlight, splits water, releasing oxygen.

  • Electron Flow: Moves through thylakoid proteins, pumping hydrogen ions, creating a gradient for ATP synthesis.

Calvin Cycle Steps

  1. Carbon Fixation: CO2 combines with RuBP, producing 3-PGA.

  2. Reduction: ATP and NADPH convert 3-PGA into GA3P.

  3. Regeneration: Some GA3P forms glucose, others regenerate RuBP.

Cellular Respiration Overview

  • Equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP.

Glycolysis Overview

  • Location: Cytoplasm; processes glucose into two pyruvate and produces NADH and ATP.

Pyruvate Oxidation

  • Pyruvate enters mitochondria for aerobic respiration, releasing CO2 and forming NADH.

Krebs Cycle (Citric Acid Cycle)

  • Occurs in mitochondrial matrix; produces CO2, GTP, NADH, FADH2.

Electron Transport Chain

  • Series of proteins in the mitochondrial inner membrane transferring electrons to reduce oxygen and produce water.

ATP Synthase

  • Uses pH gradient from electron transport chain to synthesize ATP from ADP and Pi; driven by chemiosmosis.

Anaerobic Cellular Respiration

  • In absence of oxygen, NAD+ is regenerated for glycolysis through fermentation processes: lactic acid and alcohol fermentation.

Knowledge Checks

  1. What is called the addition of a phosphate group to a molecule? Answer: Phosphorylation.

  2. Glycolysis produces a net of 2 ATP and 2 NADH.

  3. Alcohol dehydrogenase produces alcohol during fermentation.

  4. The process providing energized carbon for living things is Photosynthesis.