College Physics Study Notes

Hummingbird Energy Requirement

• Hummingbirds need energy to maintain prolonged flight.

• They obtain energy from food, which is transformed through biochemical reactions.

• Their flight muscles are highly efficient in energy production. (Cory Zanker)

Aerobic Respiration

• Equation: C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + \text{energy}

• Photosynthesis reverses this process: 6CO2 + 6H2O + \text{energy} \rightarrow C6H{12}O6 + 6O2

Energy Sources in Life

• Most life forms derive energy from the sun.

• Plants use photosynthesis to capture sunlight.

• Herbivores consume plants for energy.

• Carnivores eat herbivores, and decomposers digest organic matter.

Metabolism

• Definition: The total of all chemical reactions in an organism.

• Anabolic Reactions (Anabolism):

  • Utilize energy to build complex molecules.

• Catabolic Reactions (Catabolism):

  • Release energy by breaking down complex molecules.

• Biochemical Pathways:

  • Sequential reactions where the product of one reaction is the substrate for the next.

  • Many of these steps take place in cell organelles.

Energy Concepts

• Energy defined as the capacity to do work.

• Forms of energy: mechanical, heat, sound, electric current, light, or radioactivity.

• Kinetic Energy: Energy of motion.

• Potential Energy: Stored energy.

• Heat: Common measurement of energy.

• 1 calorie = heat required to raise 1 gram of water by 1ºC.

• Distinction between calorie and Calorie (nutritional value).

Energy Flow in Organisms

• Energy flows into the biological systems from the sun.

• Photosynthetic organisms capture solar energy, converting it into potential energy in chemical bonds.

Energy Dynamics

• Activation Energy: The initial energy required for a reaction to proceed.

• Catalysts lower the activation energy needed for reactions.

Thermodynamics

• First Law of Thermodynamics:

  • Energy cannot be created or destroyed, only transformed from one form to another.

  • Total energy in the universe remains constant; energy is dissipated as heat during transformations.

• Second Law of Thermodynamics:

  • Entropy (disorder) is continuously increasing in isolated systems.

  • Energy transformations favor conversion from ordered states to more stable disordered states.

Entropy

• Definition: Measure of randomness or disorder in a system.

• General observation:

  • Gases have higher entropy than liquids, and liquids have higher entropy than solids.

Energy Transformation Examples

• Humans convert chemical energy from food into kinetic energy.

• Plants convert light energy into chemical energy.

ATP (Adenosine Triphosphate)

• ATP as the primary energy currency of cells:

  • Composed of:

  • Ribose: A 5-carbon sugar.

  • Adenine: A nitrogenous base.

  • Chain of 3 phosphates: Unstable bonds store energy.

• ADP (Adenosine Diphosphate): Contains 2 phosphates.

• AMP (Adenosine Monophosphate): Contains 1 phosphate (lowest energy form).

ATP Cycle

• ATP hydrolysis is a driving force for endergonic (energy-requiring) reactions.

• Coupled reactions yield a net -\Delta G indicating exergonic spontaneity.

• ATP is not suitable for long-term energy storage; fats and carbohydrates serve this purpose.

• Cells store only a few seconds worth of ATP.

Sodium-Potassium Pump

• Example of energy coupling:

  • Energy from exergonic ATP hydrolysis is utilized to transport sodium and potassium ions across the cell membrane.

Enzymes

• Most enzymes are proteins; some are RNA.

• The shape of enzymes allows for temporary associations between substrates without changing the enzyme.

• Example:

  • Carbonic anhydrase synthesizes 600,000 molecules of carbonic acid per second with the enzyme, in contrast to only 200 without it.

• Active Sites: Specific pockets on enzymes where substrates bind, creating an enzyme-substrate complex.

  • The precise fit lowers activation energy by applying stress to distort bonds through induced fit.

Inhibition Types

• Competitive Inhibition:

  • Competes with substrate for active site; affects initial reaction rate but not the maximal rate.

• Noncompetitive Inhibition:

  • Inhibitor binds to a different site, reducing the maximal rate of reaction.

• Allosteric Inhibition:

  • Alters enzyme's active site to reduce or prevent substrate binding.

• Allosteric Activation:

  • Enhances enzyme's affinity for substrate by modifying the active site positively.

Vitamins as Coenzymes

• Vitamins are necessary as coenzymes or precursors for enzyme functionality.

• Multivitamin supplements typically contain a mixture of essential vitamins in varying percentages.

Metabolic Pathways

• Characterized as series of reactions catalyzed by multiple enzymes.

• Feedback Inhibition:

  • Mechanism where the end product of a pathway inhibits an earlier step, regulating metabolic processes efficiently.