Chemistry Pt2 Chemical Reactions
Definitions of Chemical Reactions
Reactants: The substances that interact with one another during a chemical reaction.
Products: The result of the chemical reaction, what is produced from the reactants.
Types of Chemical Reactions
Overview: Thousands of chemical reactions occur in cells continuously.
1. Decomposition Reactions
Definition: A type of reaction where a large molecule is broken down into smaller molecules.
Example: Breakdown of glycogen (a carbohydrate) into individual glucose molecules.
Chemical Bonds: The bonds between glucose molecules are broken during a decomposition reaction.
Water Requirement: Often requires water, sometimes referred to as hydrolysis.
Hydrolysis: A specific type of decomposition reaction that involves water (hydration).
Hydro refers to water; lysis refers to breakdown.
2. Synthesis Reactions
Definition: The process of combining small molecules to create larger, more complex molecules.
Example: Individual glucose molecules combine to form glycogen.
Dehydration Synthesis: A type of synthesis reaction where a water molecule is released during the formation of bonds.
Dehydration: Means loss of water.
Conceptual Difference:
Synthesis: Building larger molecules, involves creation and energy input.
Decomposition: Breaking down larger molecules into smaller components, involves energy release.
Biological Context of Reactions
Key Points:
Breakdown reactions (catabolism) and synthesis reactions (anabolism) happen simultaneously in the body.
Hormones control these processes, guiding cells to either break down (catabolism) or synthesize (anabolism) molecules.
Example of Catabolic Reaction:
When consuming starch (like spaghetti), digestion involves hydrolysis to absorb glucose.
High glucose levels can cause spikes in insulin, especially important for diabetics.
Hormonal Regulation
Catabolic Hormones: Trigger breakdown of molecules.
Anabolic Hormones: Promote synthesis of molecules, such as glycogen from glucose.
Reversible Reactions: Many reactions in the body can proceed in both directions (for example, glucose can be synthesized into glycogen and vice versa).
Role of Enzymes in Chemical Reactions
Definition of Enzymes: Biological catalysts that speed up chemical reactions by lowering the activation energy.
Activation Energy: The energy required for a reaction to occur.
Example: Enzymes allow reactions that would normally take decades to occur in seconds.
Role of Energy: In the absence of enzymes, high energy input is often needed for reactions to take place.
Specific Example:
Lactase enzyme breaks down lactose. Lack of lactase leads to difficulty in digesting dairy (lactose intolerance).
Mixtures and Their Types
Definition: Combinations of two or more substances that are not chemically bonded.
Types of Mixtures:
Suspensions:
Characteristic: Heterogeneous mixtures where particles are visible and will settle to the bottom if allowed to sit.
Example: Whole blood (red blood cells settle out).
Colloids:
Characteristic: Mixtures where particles do not settle out, and the mixture may appear opaque.
Example: Milk, mayonnaise.
Solutions:
Characteristic: Homogeneous mixtures where solute particles are dissolved in a solvent, typically clear.
Components:
Solvent: The substance in which the solute is dissolved (in biological systems, this is usually water).
Solute: The substance being dissolved (like salt or sugar).
Aqueous Solutions: A solution where the solvent is water.
Non-aqueous Solutions: Solutions that use a solvent other than water, not commonly focused on in courses.
Summary of Key Biological Reactions
Metabolic Reactions: Continuous cycle of synthesis (anabolism) and breakdown (catabolism) occurring at the cellular level.
All body cells utilize both processes to survive and function, influenced by specific hormones regulating these metabolic pathways.