Bio chem lecture 1

Overview of Carbon-Based Reactions

• The quarter will focus on carbon-based reactions in organisms, including humans.

• Emphasis on understanding how the rates of these reactions are controlled, known as metabolism.

• Metabolism consists of a simple variety of chemical reactions that become complex through their interconnections.

Key Concepts of Metabolism

• Metabolic Pathways: A series of chemical reactions where the product of one reaction becomes the reactant for the next.

• Example of complexity: Over 1,000 chemical reactions are linked in metabolic pathways seen in biological systems.

• Concentration of metabolites must remain relatively constant, which is managed by controlling the reaction rates.

Analogy of a Lake and Rivers

• Lake: Represents the concentration of a molecule (e.g., glucose) in the body.

  • When the level of the lake changes (i.e., concentration increases/decreases), it illustrates how metabolic reactions can either produce or consume that molecule.

• Rivers: Flowing in represents production (reaction rates creating glucose), while flowing out represents usage (reaction rates consuming glucose).

Regulation of Chemical Reactions

• The body can increase or decrease the rate of reactions to control metabolite concentrations.

• Example scenario: Ingesting food increases glucose in the blood, requiring the body to facilitate glucose uptake into cells.

Glucose Regulation in Action

• Blood Glucose Levels: 4 grams of glucose are in the blood at any time, with additional glucose obtained from food or synthesized by the liver.

• Consumption patterns (e.g., eating a candy bar) influence blood glucose levels and uptake into cells through regulatory pathways.

• Insulin acts like a dam, facilitating glucose entry into cells when blood glucose levels rise.

Metabolic Pathways and Reactions

• Each pathway uses specific enzymes, proteins that catalyze the reactions and regulate the metabolic process.

• Important pathways: Glycolysis, Krebs Cycle, Fatty Acid Metabolism, etc.

• Products of one reaction are usually reactants in another, highlighting the interconnectedness of metabolic processes.

Types of Pathways

• Linear Pathways: A simple sequence of reactions leading to a product from a starting molecule.

• Cyclic Pathways: Reactions that loop back, reforming the initial reactant (e.g., Krebs Cycle).

• Spiral Pathways: Similar to linear but involve a repeating process that increments or decrements molecule size (e.g., fatty acid synthesis/breakdown).

Understanding Biochemical Reactions

• Catabolism: Pathways that break down larger molecules into smaller units, releasing energy (e.g., glucose to carbon dioxide).

• Anabolism: Pathways that build larger molecules from smaller units, requiring energy (e.g., amino acids forming proteins).

• Both processes revolve around the principle that energy must be consistently input into cells to maintain function.

The Role of ATP

• Adenosine Triphosphate (ATP): The primary energy currency in cells, enabling transfer of energy for cellular processes.

• ATP comprises adenosine (a nucleotide) + three phosphates; cleavage of phosphates releases energy.

• ATP synthesis from ADP + Pi captures energy from catabolic reactions and facilitates anabolic reactions.

• ATP is constantly recycled in the body, with production matching usage in states of energy demand.

Equations for Chemical Reactions

• Key reactions in metabolism are often expressed using both standard (reactants to products) and looped arrows (denoting intermediate substances).

• Understand how to recognize reactants and products and the concept of net reactions whereby certain reactants/products cancel each other out when determining overall reactions in pathways.

Energy Changes in Reactions

• Free energy (G) indicates the energy available for work; it can either be consumed (endergonic) or released (exergonic).

• Activation energy (Ea) is the energy barrier that must be overcome for a reaction to occur.

Coupled Reactions

• In coupled reactions, an endergonic reaction (which requires energy) is paired with an exergonic reaction (which releases energy) to drive a process forward without solely relying on heat energy.

• Specific examples include the coupling of ATP hydrolysis to drive unfavorable reactions (e.g., glucose phosphorylation).

• The net reaction combines the effects of both the endergonic and exergonic processes, resulting in a reaction that can occur spontaneously in the cell.

Cellular Structures and Processes

• Cytosol: Liquid found inside cells, facilitating metabolic processes.

• Organelles: Such as mitochondria, where specific metabolic pathways occur.

• Understanding of intracellular communication and transport mechanisms is crucial for comprehending metabolic interactions in different cell types (muscle, liver, adipose).

Summary of Learning Goals

• Goals include understanding the interplay of energy transactions in biochemical pathways, types of reactions (linear, cyclic, spiral), and the mechanisms that control the rates of these reactions, especially through enzymatic regulation and hormonal responses.

• Key focus on the importance of ATP as an energy carrier in metabolic processes, and the understanding of net energy changes in reactions to highlight the efficiency and regulation of metabolic pathways.

Prepare to discuss each topic in detail, emphasizing the flow of energy and the regulation of metabolic pathways throughout the course. Look to deepen your understanding as you relate these concepts through practice problems and further readings in your information packet.