Biology Chapter 3: Energy and Reactions

Chapter 3: Energy, Chemical Reactions, and Cellular Respiration

• This chapter covers energy, chemical reactions, and cellular respiration.
• Learning objectives include comparing and contrasting potential and kinetic energy and their relation to the Laws of Thermodynamics.
• Learning objectives also include explaining the three major types of chemical reactions (synthesis, decomposition, and oxidation-reduction).
• Learning objectives also detail how reactions are categorized (anabolic, catabolic, endergonic, exergonic, reversible, irreversible).

Energy

• All living organisms need energy.
• Energy is required for muscle power, blood pumping, nutrient absorption, gas exchange, synthesizing new molecules, and establishing cellular ion concentrations.

Energy and ATP

• Glucose is broken down through metabolic pathways (cellular respiration).
• This process forms ATP, the "energy currency" of cells.
• ATP is a nucleotide composed of a nitrogenous base (adenine), a ribose sugar, and three phosphate groups.
• Covalent bonds between the last two phosphate groups store energy.
• Energy is released when these bonds are broken.

Energy and ATP (Continued)

• ATP formation (endergonic reaction) requires energy input. Breaking down fuel molecules, like glucose provides this energy.
• ATP splitting (exergonic reaction) releases energy, used for cellular processes like body movement.

Energy

• Energy is the ability to do work.
• Two main types of energy are potential energy (stored energy) and kinetic energy (energy of motion).
• Potential energy can be converted into kinetic energy and vice versa.
• Kinetic energy is the movement of ions, molecules, etc. across a membrane.
• Potential energy can be stored in concentration gradients.

Chemical Energy

• Chemical energy is a form of potential energy.
• It is stored in the chemical bonds of molecules.
• Energy is released when these bonds are broken.
• Examples of molecules that store chemical energy include triglycerides, glucose and ATP.
• Chemical energy powers body processes like movement and synthesis.

Kinetic Energy

• Kinetic energy includes electrical energy (ion movement), mechanical energy (muscle contractions), sound energy (vibration), radiant energy (light), and heat energy (molecular motion).

Laws of Thermodynamics

• Thermodynamics is the study of energy transformations.
• The first law states that energy cannot be created or destroyed, but can change form.
• The second law states that some energy is lost as heat during transformations.

Chemical Equations

• Chemical equations describe chemical reactions and show what reactants form what products.
• Reactants are the starting materials, products are the end results.
• Chemical reactions involve breaking and forming bonds.

Classification of Chemical Reactions

• Chemical reactions are categorized based on changes in chemical structure, chemical energy, and reversibility.

Classification of Chemical Reactions (Continued)

• Three main types of chemical reactions based on structure: synthesis, decomposition, and exchange reactions.

Synthesis Reaction

• Two or more structures combine to form a larger structure.
• An example in the body is dehydration synthesis, which builds dipeptides from amino acids.
• Anabolism encompasses all synthesis reactions in the body.

Decomposition Reaction

• A large molecule breaks down into smaller structures.
• An example is hydrolysis, where sucrose breaks down into glucose and fructose.
• Catabolism includes all decomposition reactions in the body.

Exchange Reaction

• Groups are exchanged between two structures.
• It has components of both decomposition and synthesis.
• Formation of ATP in muscle tissue is an example of an exchange reaction.

Oxidation-Reduction (Redox) Reaction

• Redox reactions involve the transfer of electrons between structures.
• Oxidation involves loss of electrons, reduction involves gain of electrons.
• Reactions always occur simultaneously.
• An example is NAD+ to NADH, where NAD+ is reduced to NADH as it gains electrons.

Classification of Chemical Reactions (Continued)

• Two categories related to energy: exergonic reactions and endergonic reactions.
• Exergonic reactions release energy, while endergonic reactions require energy input.

Exergonic and Endergonic Reactions (Continued)

• In exergonic reactions, reactants have more energy than the products, and energy is released.
• In endergonic reactions, reactants have less energy than products, and energy is absorbed.
• Examples illustrated in graphs that show potential energy change across a reaction.
• Exergonic reactions often relate to decomposition, while endergonic relate to synthesis of molecules

Reversible Reactions

• These reactions proceed in both forward and reverse directions, characterized by no net change in concentration of reactants and products.
• These reactions reach a state of equilibrium.
• Key example: Carbonic Acid reaction, converting between carbon dioxide and bicarbonate.

Important Note:

• The diagrams illustrate the processes and the relationships between components.