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.

Explore the concepts of energy, chemical reactions, and cellular respiration in this quiz based on Chapter 3. Understand the differences between potential and kinetic energy, and learn about the major types of chemical reactions. Test your knowledge on how these processes relate to the Laws of Thermodynamics and the role of ATP in energy transfer.