Cellular Respiration and Membrane Function Summary

Membrane Structure and Function

  • Membranes are fluid mosaics of lipids and proteins.
  • Exhibit: Fluid mosaic model & selective permeability

Types of Membrane Proteins

  • Transport Proteins: Facilitates ion/molecule entry/exit.
  • Enzymes: Catalyze reactions; can be grouped for sequential reactions.
  • Receptor Proteins: Bind signaling molecules; activate pathways inside.
  • Attachment Proteins: Connect to ECM and cytoskeleton; support membrane.
  • Junction Proteins: Attach adjacent cells; form intercellular junctions.
  • Glycoproteins: Serve as ID tags for cell recognition.

Transport Mechanisms

  • Passive Transport:
  • Includes diffusion (e.g., water, O2, CO2).
  • No energy required; relies on concentration gradients.
  • Osmosis: Diffusion of water across selectively permeable membranes.
  • Hypertonic: Cell shrinks.
  • Hypotonic: Cell swells.
  • Isotonic: Normal for animal cells; flaccid for plant cells.
  • Facilitated Diffusion: Uses transport proteins for polar/charged substances.

Active Transport

  • Requires ATP to move solutes against concentration gradients.
  • Example: Sodium-potassium pump (Na+/K+).
  • Exocytosis: Exports large molecules (e.g., proteins).
  • Endocytosis: Takes in large molecules;
  • Phagocytosis: Engulfing by wrapping membrane around particle.
  • Receptor-mediated Endocytosis: Uses receptors for specific solutes.

Energy and the Cell

  • Energy Types: Kinetic (motion) and potential (stored).
  • First Law of Thermodynamics: Energy cannot be created or destroyed.
  • Second Law: Entropy (disorder) increases over time.
  • Metabolism: All chemical reactions within a cell (anabolism + catabolism).

ATP - Energy Currency of Cells

  • Structure: Ribose, adenine, three phosphate groups.
  • Energy stored in phosphate bonds; breaking them releases energy.
  • ATP -> ADP + Pi releases energy for cellular work.

Enzymes

  • Enzyme shape is crucial; influenced by temperature, pH, and regulatory molecules.
  • Enzyme-substrate complex formation increases efficiency (induced fit).
  • Inhibition:
  • Competitive: Competes for active site.
  • Non-competitive: Changes enzyme shape.
  • Examples: Cyanide inhibits ATP production, ethanol competes with methanol in metabolism.