Overview of Cellular Transport

• Focus on how cells move molecules and how they drive chemical reactions.

• Main processes: photosynthesis (food creation in plant cells) and cellular respiration (energy production in all cells).

Molecular Movement in Cells

• Constant challenge of moving substances (water, oxygen, nutrients, waste).

• Types of molecules moved: hormones, nutrients, chemicals.

Passive Transport

• Definition: Movement of molecules without energy input.

• Main Types of Passive Transport:

  • Simple Diffusion: Small/uncharged molecules pass directly through cell membrane (e.g., oxygen, carbon dioxide).

  • Facilitated Diffusion: Larger/charged molecules (e.g., glucose, ions) require protein channels to cross the membrane.

  • Osmosis: Facilitated diffusion of water; water moves from high solute potential to low solute potential.

    • Key Concepts:

      • Pure water has a solute potential of 0 megapascal.

      • As solutes are added, solute potential decreases (more negative), reducing water concentration.

Concentration Gradients

• Molecules move from areas of high concentration to low concentration (down the gradient).

• If no gradient, no net diffusion occurs.

Active Transport

• Definition: Movement of substances against their concentration gradient, requiring energy (ATP).

• Always involves protein transporters.

• Key concept: ATP is the energy currency of the cell.

Types of Energy in Biological Systems

• Potential Energy: Stored energy; examples include chemical energy in bonds (e.g., fuels like gasoline).

• Kinetic Energy: Energy of movement; transforms through chemical reactions in the body.

• Energy Transformation: Energy is converted through chemical reactions but is not created or destroyed (Law of Conservation).

Role of ATP

• Synthesized from ADP and phosphate via energy from breaking down macromolecules.

• Energy released from ATP when the bond between phosphate ions is broken during hydrolysis.

• Used by cells for various processes (e.g., transports, muscle movement).

Enzymes

• Enzymes act as catalysts for chemical reactions, lowering energy barriers.

• Active Site: Specific area on enzyme where reactants (substrates) bind and undergo reaction.

• Enzyme Action:

  • Enzyme-Substrate Complex: Formed when substrate binds to enzyme.

  • Hydrolysis: Breaking of bonds with the help of enzymes.

  • Dehydration Synthesis: Enzymes help form bonds between substrates.

Enzyme Regulation

• Enzymes are affected by environmental conditions (pH, temperature, salt concentration).

• Denaturation: Loss of enzyme shape leads to loss of function.

• Specificity: Enzymes react with specific substrates only.

• Inhibitors: Molecules that can bind to enzymes and prevent substrate binding (observed in toxins, drugs).

Metabolism

• Definition: All chemical reactions in a cell; often sequential linked pathways.

• Examples: Photosynthesis and Cellular Respiration.

• Metabolic pathways consist of reactants transforming into products through multiple steps, regulated by various enzymes.

Key Points on Homeostasis and Regulation

• Homeostasis affects enzyme efficiency; conditions too outside optimal range hinder function.

• Body maintains temperature around 98.6°F (37°C) for optimal enzyme activity.

• Enzymes can operate best at differing pHs depending on their function (e.g., enzymes in stomach vs. blood).

Conclusion

• The transport of molecules and the functioning of enzymes are vital for cellular processes, contributing to the overall homeostasis and energy management within organisms.