Cellular Respiration and Cellular Transport

Overview of Cellular Respiration

  • Three major parts of cellular respiration

    • Glycolysis

    • Citric Acid Cycle

    • Oxidative Phosphorylation

Glycolysis

  • Occurs outside the mitochondria

  • Main substrate: Glucose

    • Six-carbon molecule that is broken down

  • Product: Pyruvate

    • Two three-carbon molecules created from glucose

  • Produces: 2 ATP (adenosine triphosphate)

    • ATP is the primary energy carrier in cells

Mitochondria

  • Key organelle in cellular respiration

  • Location for the citric acid cycle and oxidative phosphorylation

Citric Acid Cycle (Krebs Cycle)

  • Occurs within the mitochondria

  • Primary role:

    • Generate electrons and electron carriers (NADH and FADH2)

  • Produces:

    • Net Gain of 2 ATP

    • ATP used as energy source for cellular processes

Oxidative Phosphorylation

  • Final stage of cellular respiration

  • Divided into two components:

    1. Electron Transport Chain (ETC)

    2. Chemiosmosis

  • Major function:

    • Production of a significant amount of ATP (32-34 ATP molecules, depending on the source)

  • Occurs across the mitochondrial membrane

Total ATP Production

  • Overall, cellular respiration can yield:

    • Approximately 36 to 38 ATP molecules in total

  • ATP roles in cellular functions

    • Active processes require ATP for energy

    • Passive processes do not require ATP

Questions and Clarifications

  • Discussion on ATP production in glycolysis and citric acid cycle brought confusion regarding which produces what

    • Glycolysis: Produces ATP and pyruvate

    • Citric Acid Cycle (Krebs Cycle): Produces ATP and generates electrons

  • Clarification on glycolysis and ATP yield for experiments in lab settings

    • Each stage produces ATP, but differs in the amount and types of energy carriers

Cellular Transport Mechanisms

  • Categories of transport

    1. Passive Transport

    • No energy required

    • Molecules passively move from high to low concentration

    • Examples:

      • Simple Diffusion (small molecules directly passing through membrane)

      • Facilitated Diffusion (assisted by carrier proteins)

    1. Active Transport

    • Energy required (often from ATP)

    • Molecules move against a concentration gradient (from low to high concentration)

    • Includes mechanisms such as endocytosis (moving material into the cell) and exocytosis (moving material out of the cell)

Examples of Transport Types

  • Endocytosis

    • Types:

    • Phagocytosis: Cell 'eating' large particles

    • Pinocytosis: Cell 'drinking' fluids

    • Receptor-mediated Endocytosis: Specific binding of molecules to receptors before encapsulation and internalization

  • Exocytosis

    • Mechanism where material within vesicles is expelled from the cell by merging with the plasma membrane

Phospholipid Bilayer

  • Structure of the cell membrane

    • Composed of phospholipids (hydrophilic heads and hydrophobic tails)

    • Contains proteins facilitating transport and signaling

    • Roles of proteins and cholesterol in membrane fluidity and functionality discussed

Overview of Cell Division

  • Meiosis vs. Mitosis

Mitosis

  • Cell division producing two identical diploid daughter cells

  • Phases: Prophase, Metaphase, Anaphase, Telophase (followed by Cytokinesis)

    1. Prophase: DNA condenses, nuclear envelope degrades

    2. Metaphase: Chromosomes align in the middle

    3. Anaphase: Sister chromatids separate to opposite sides

    4. Telophase: Nuclear envelope reforms

    5. Cytokinesis: Cytoplasm divides, forming two individual cells

Meiosis

  • Two rounds of division producing four haploid cells (sex cells)

  • Key differences:

    • Involves homologous chromosomes aligning in tetrads in Prophase I

    • Results in genetic diversity through crossing over

    • Meiosis I includes Prophase I, Metaphase I, Anaphase I, Telophase I followed by Meiosis II that resembles Mitosis

  • Importance of Meiosis for reproduction and genetic variation

Crossing Over and Genetic Diversity

  • Occurs during Prophase I of Meiosis

  • Exchange of genetic material between homologous chromosomes leading to diversity in gametes

  • Importance from an evolutionary standpoint for species adaptation

Conclusion

  • Review of common questions regarding cellular processes and transport mechanisms

  • Importance of understanding both biological processes and cellular components for grasping overall cell function and integrity.

  • Discussion on uncontrolled cell division leading to cancer; genetics play an important role in susceptibility and prevention.